CN109298309B - Method for monitoring IGBT solder layer in real time - Google Patents
Method for monitoring IGBT solder layer in real time Download PDFInfo
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Abstract
IGBT solder layer state real-time monitoring device and method based on temperature gradient. The device comprises a power supply module, a temperature sensor module, an ADC module, an MCU module and an information display module; the temperature sensor module is connected with the ADC module, the ADC module is connected with the MCU module, and the MCU module is connected with the information display module. The invention also discloses a method for monitoring the solder layer in real time by using the IGBT solder layer state real-time monitoring device based on the temperature gradient. The method positions the aging type and position of the solder layer through the symbols of the elements in the variable matrix of the temperature gradient matrix and the heat conduction angle, has simple realization, high detection precision and better real-time performance, is not influenced by the change of the environmental temperature, and can detect the conditions of cavities and cracks of the solder layer on line.
Description
Technical Field
The invention relates to a method for monitoring an IGBT (insulated gate bipolar transistor) solder layer in real time, in particular to real-time diagnosis of sizes and positions of cavities and cracks of the solder layer of an Insulated Gate Bipolar Transistor (IGBT), which is mainly applied to the technical field of power IGBT reliability.
Background
The Insulated Gate Bipolar Transistor (IGBT) combines the advantages of a field effect transistor (MOSFET) and a Bipolar Junction Transistor (BJT), has the characteristics of simple driving, low loss, high voltage resistance and the like, is widely applied to the fields of new energy, high-speed rail aerospace and the like, and requires higher reliability in a plurality of occasions where the IGBT is applied.
In recent years, with the popularization of IGBT use, the reliability of IGBTs has become more and more important. IGBT aging failure has been demonstrated to be one of the primary failure modes of its failure under temperature cycling. When the power module operates stably, the device basically keeps thermal stability, and the fluctuation of junction temperature is small. However, the operating environment of the present IGBT is increasingly severe, and the power fluctuation thereof is increased, resulting in increased junction temperature fluctuation. An IGBT is a power device stacked by seven layers of materials, and a solder layer is the weakest link. Thermal stresses exist between the layers due to the different coefficients of thermal expansion between the different layers, which can cause mechanical damage between the layers. The fluctuation of the junction temperature causes an increase in thermal stress, accelerating the aging of the solder layer.
The invention provides a method for evaluating thermal reliability of IGBT air-to-temperature based on a three-dimensional model, which is invented by 'a method for analyzing the influence of cavities on thermal reliability of IGBT based on three-dimensional modeling', and has the application number of 201510037099.7 and the publication number of 104573266A. The application number is 201510657533.1, and the publication number is 105242189A < IGBT health state monitoring method based on collector-emitter saturation voltage drop and solder layer voidage > invents an IGBT health state estimation method based on emitter saturation voltage drop and solder layer voidage, and can realize IGBT solder layer health diagnosis by measuring emitter saturation voltage drop. In the above methods, the health state of the solder layer cannot be monitored in real time.
Disclosure of Invention
The invention aims to solve the problem of overcoming the defects of the prior art and provides a method for monitoring the solder layer of the IGBT in real time, so that the cracks and cavities of the solder layer of the IGBT device can be effectively monitored in real time, and the accuracy is high.
The technical scheme adopted for solving the problems is as follows:
and (3) monitoring the IGBT solder layer in real time by using a temperature gradient-based IGBT solder layer state real-time monitoring device.
The IGBT welding flux layer state real-time monitoring device based on the temperature gradient comprises a power supply module, a temperature sensor module, an ADC module, an MCU module and an information display module;
the power supply module is used for supplying power to the temperature sensor module, the ADC module, the MCU module and the information display module. The power supply module comprises a 5V direct-current voltage module and a 3.3V direct-current voltage module, the 5V direct-current voltage module supplies power to the information display module and the temperature sensor module, and the 3.3V direct-current voltage module supplies power to the MCU module and the ADC module;
the temperature sensor module is connected with the ADC module, the ADC module is connected with the MCU module, and the MCU module is connected with the information display module;
the temperature sensor module measures the temperature of the IGBT device substrate; the temperature sensor module is used for acquiring temperature information (the acquired temperature information can be the temperature of a key information node of the IGBT device substrate), the ADC module is used for acquiring analog signals, and the analog signals are processed by the ADC module and converted into digital signals to be transmitted to the MCU module; the MCU module processes the digital signals transmitted by the ADC module, judges the state of the solder layer and transmits the state of the solder layer (namely the area and the position of a crack and the area and the position of a cavity) to the information display module for real-time display; and the information display module receives the state information of the solder layer transmitted by the MCU module and displays the state information in real time.
The ADC module has multi-channel temperature acquisition capacity, and the MCU module controls the sampling sequence and the channels by controlling the ADC module. The ADC module collects data of the temperature sensor module in real time by receiving an instruction sent by the MCU module.
Further, the temperature sensor module comprises at least two thermistors for measuring the temperature of the key node of the IGBT device substrate. In the invention, the temperature sensor module comprises 16 thermistors. Without loss of generality, the thermistor selects a negative temperature coefficient resistor with the model number of AYN-MF55-104F-3950F B-1500-28, the temperature measurement range is-30 ℃ to 105 ℃, and the measurement of the substrate temperature at different environmental temperatures is met.
Further, the ADC module is preferably a 16-channel 12-bit ADC module with a sampling frequency of 20 Hz. Without loss of generality, the ADC module may be built in to an MCU module, such as an MCU chip TMS320F28235 with an ADC module built in, with a built-in (sample-and-hold) S/H12-bit ADC core analog input, with 16 dedicated ADC channels.
Furthermore, a state distinguishing module and a state display warning module are arranged in the MCU module. Without loss of generality, the MCU module can be selected from a DSP with the model number TMS320F 28235.
Furthermore, the thermistors of the temperature sensor module are uniformly distributed on the upper surface of the IGBT device substrate and can be uniformly distributed on key nodes of the IGBT device substrate.
Further, the information display module comprises an LED liquid crystal screen and an LED warning lamp, and the LED liquid crystal screen and the LED warning lamp are connected with the MCU module. Without loss of generality, the LED liquid crystal screen is 12864, and the model is KS0108 LCD; the LED warning lamp selects a light emitting diode.
The method for monitoring the IGBT solder layer in real time comprises the following steps:
step (1), starting an ADC module and an MCU module for initialization, and introducing a matrix form [ T ] of an initial temperature correction value into the MCU module0]Setting a sampling time interval delta t and a temperature gradient matrix change threshold value delta of the ADC module through the MCU module, and recording the position of each thermistor on a substrate of the IGBT device, the height from a solder layer to the substrate and the area of the whole solder layer by the MCU module;
step (2), when the IGBT device does not work, the MCU module sends a sampling instruction to the ADC module, the ADC module receives the sampling instruction, the ADC module collects temperature signals from the temperature sensor module, performs analog-to-digital conversion on the collected temperature signals and then transmits the temperature signals to the MCU module, the MCU module performs wavelet filtering processing on the temperature signals transmitted from the ADC module and then compares the temperature signals with the indoor temperature, if the two temperatures are consistent, normal working sampling can be performed, and the step (3) is carried out; if not, adjusting the sampling algorithm in the ADC module through the MCU until the temperature sampled by the ADC module and transmitted to the MCU module is consistent with the indoor temperature, and then turning to the step (3);
the sampling algorithm in the ADC module is adjusted into the existing mature technology through the MCU;
step (3), when the IGBT device works, the MCU module sends a sampling instruction to the ADC module, the ADC module receives the sampling instruction, the ADC module collects temperature signals from the temperature sensor module, performs wavelet filtering processing on the collected temperature signals and then transmits the temperature signals to the MCU module, and the step (4) is carried out;
step (4), calculating a temperature gradient matrix [ dT]＝[T]-[T0]，[T]In the form of a matrix of the measured temperatures of all thermistors at the current sampling time, [ T0]A matrix form representing an initial value of temperature correction; when the IGBT device works, if the sampling times of the ADC module are more than two times, calculating a temperature gradient matrix [ dT]When is in [ T ]0]Replacing the temperature measurement matrix form by all thermistors at the last sampling time of the current sampling time; obtaining a temperature gradient matrix [ dT]Then, the step (5) is carried out;
calculating the temperatureDegree gradient matrix [ dT]＝[T]-[T0]The specific method comprises the following steps: for each thermistor on the IGBT device, subtracting the temperature value at the last sampling time from the sampling temperature obtained at the current sampling time (when the IGBT device works, for the first sampling of the ADC module, the temperature value at the last sampling time is replaced by the temperature correction initial value) to obtain the temperature gradient of each thermistor, and jointly forming a temperature gradient matrix by the temperature gradients of all the thermistors obtained at the current sampling time according to the distribution mode of the temperature gradients on the IGBT device.
If 16 thermistors are arranged on the IGBT device, when the 16 thermistors are distributed in 4 rows and 4 columns, for each thermistor, subtracting the temperature value at the last sampling time from the sampling temperature obtained at the current sampling time (when the IGBT device works, for the first sampling of the ADC module, the temperature value at the last sampling time is replaced with the initial temperature correction value) to obtain the temperature gradient of each thermistor, and combining the temperature gradients of the 16 thermistors obtained at the current sampling time according to the distribution mode of the temperature gradients on the IGBT device (i.e., the distribution mode of 4 rows and 4 columns) to form a 4 × 4 temperature gradient matrix, where each thermistor corresponds to one element in the temperature gradient matrix (e.g., the thermistor at the 1 st row and 1 st column on the IGBT device corresponds to the element at the 1 st row and the 1 st column in the temperature gradient matrix).
Step (5), calculating the variation of the temperature gradient matrix
Δ t is the sampling time interval; calculating to obtain the variation [ Delta dT ] of the temperature gradient matrix]Then, turning to the step (6);
if 16 thermistors are arranged on the IGBT device, and 16 thermistors are distributed in 4 rows and 4 columns, as described above, the temperature gradient matrix [ dT ] is a 4 × 4 matrix, the variation matrix [ Δ dT ] of the temperature gradient matrix is also a 4 × 4 matrix, and each thermistor corresponds to an element in the variation matrix [ Δ dT ] of the temperature gradient matrix (e.g., the thermistor in the 1 st row and the 1 st column on the IGBT device corresponds to an element in the 1 st row and the 1 st column in the variation matrix [ Δ dT ] of the temperature gradient matrix).
Step (6), comparing the absolute value of each element in the variation matrix [ Delta dT ] of the temperature gradient matrix with a preset temperature gradient matrix variation threshold value delta, and turning to step (7) when the element in the variation matrix [ Delta dT ] of the temperature gradient matrix is larger than the preset temperature gradient matrix variation threshold value delta; when the absolute values of all elements in the variation matrix [ Delta dT ] of the temperature gradient matrix are less than or equal to the preset temperature gradient matrix variation threshold value delta, returning to the step (3) and re-sampling;
if 16 thermistors are arranged on the IGBT device, and the 16 thermistors are distributed in 4 rows and 4 columns, each element in a variation matrix [ Delta dT ] (which is a 4-4 matrix) of the temperature gradient matrix is compared with a preset temperature gradient matrix variation threshold value Delta.
Step (7), when the temperature of one thermistor changes, the temperature of the adjacent thermistor also changes correspondingly, and the signs of all elements in the variation matrix [ Delta dT ] of the temperature gradient matrix are judged; when cracks appear on a solder layer of the IGBT device, the temperature of a chip of the IGBT device is gathered at the edge of the cracks when the chip of the IGBT device transfers heat to a substrate of the IGBT device through the solder layer (the heat conduction angle is 45 degrees), the cracks on the solder layer form a rectangle on the substrate after being amplified through heat conduction, at the moment, the temperature variation of a thermistor in the rectangle on the substrate is a positive value, elements in a variation matrix [ [ Delta dT ] of a temperature gradient matrix corresponding to the thermistor in the rectangle on the substrate are also positive values, and the shape enclosed by the positive values in the variation matrix [ [ Delta dT ] of the temperature gradient matrix is also a rectangle; when a cavity appears in a solder layer of the IGBT device, a chip of the IGBT device transfers heat to a substrate of the IGBT device through the solder layer (the heat conduction angle is 45 degrees), the cavity on the solder layer forms a circle on the substrate after heat conduction amplification, at the moment, the temperature variation of a thermistor in the circle on the substrate is a negative value, elements in a variation matrix [ Delta dT ] of a temperature gradient matrix corresponding to the thermistor in a ring on the substrate are also negative values, and the shape enclosed by the negative value elements in the variation matrix [ Delta dT ] of the temperature gradient matrix is also a circle;
if a rectangular region composed of positive-value elements exists in the variation matrix [ Delta dT ] of the temperature gradient matrix, determining that cracks exist on the solder layer of the IGBT device, forming a rectangle on the substrate of the IGBT device by the thermistor corresponding to the positive-value elements forming the rectangular region, obtaining the central position, the length and the width of the rectangle on the substrate of the IGBT device by the MCU, obtaining the length of the crack on the solder layer as the length of the rectangle on the substrate-the height from the solder layer to the substrate x 2 because the heat conduction angle is 45 degrees, obtaining the width of the crack on the solder layer as the width from the rectangle on the substrate-the height from the solder layer to the substrate x 2, obtaining the central point of the rectangle on the substrate, which is the central point of the crack on the solder layer in an orthographic projection manner, drawing the rectangle on the solder layer by taking the central point of the obtained crack as the center, and obtaining the length and the width of the crack, the long edge of the rectangle drawn on the solder layer is parallel to the long edge of the rectangle on the substrate, the short edge of the rectangle drawn on the solder layer is parallel to the short edge of the rectangle on the substrate, the area of the rectangle drawn on the solder layer is the area of the crack, and the position of the rectangle drawn on the solder layer is the position of the crack; the MCU module calculates the percentage of the area of the crack in the whole solder layer area to obtain the health state of the solder layer affected by the crack; the MCU module transmits the area and position data of the cracks and the health state of the solder layer affected by the cracks to the display module for displaying and alarming;
if a circular area formed by negative elements exists in a variable matrix [ delta dT ] of the temperature gradient matrix, determining that a cavity exists on a solder layer of the IGBT device, and a thermistor corresponding to the negative elements forming the circular area also encloses a circle on a substrate of the IGBT device; the MCU module calculates the percentage of the area of the cavity in the whole solder layer area to obtain the health state of the solder layer affected by the cavity; the MCU module transmits the area and position data of the holes and the health state of the solder layer affected by the holes to the display module for displaying and alarming;
after the step (7) is finished, switching to a step (8);
and (8) ending.
Further, the step (6) is completed in a state discrimination module in the MCU module, and the step (7) is completed in a state display alarm module in the MCU module.
Further, in the step (7), the specific method for calculating the percentage of the area of the cavity in the entire solder layer by the MCU module to obtain the health state of the solder layer affected by the cavity includes:
when the percentage of the area of the cavity to the area of the whole solder layer is more than or equal to 20 percent, the health state of the solder layer affected by the cavity is a dangerous state, and the whole IGBT device needs to be replaced;
when the area of the cavity with the volume of more than or equal to 10 percent accounts for less than 20 percent of the area of the whole solder layer, the healthy state of the solder layer affected by the cavity is an unhealthy state, and a user can select whether to replace the whole IGBT device according to actual needs;
when the area of the cavity with the volume of 5 percent or more accounts for less than 10 percent of the area of the whole solder layer, the health state of the solder layer affected by the cavity is a sub-health state, and a user can select whether to replace the whole IGBT device according to actual needs;
when the percentage of the area of the cavity in the whole solder layer is less than 5%, the health state of the solder layer affected by the cavity is obtained as a health state, and the whole IGBT device does not need to be replaced.
Further, in the step (7), the specific method for calculating the percentage of the area of the crack in the whole solder layer by the MCU module to obtain the health state of the solder layer affected by the crack includes:
when the percentage of the area of the cracks in the whole solder layer is more than or equal to 10%, the health state of the solder layer affected by the cracks is a dangerous state, and the whole IGBT device needs to be replaced;
when the area of the crack is more than or equal to 5% and less than 10% of the area of the whole solder layer, the healthy state of the solder layer affected by the crack is obtained to be an unhealthy state, and a user can select whether to replace the whole IGBT device according to actual needs;
when the area of the crack is more than 0% and less than 5% of the area of the whole solder layer, the health state of the solder layer affected by the crack is obtained as a sub-health state, and a user can select whether to replace the whole IGBT device according to actual needs;
when the percentage of the area of the crack to the area of the entire solder layer is 0%, it is found that the healthy state of the solder layer affected by the crack is a healthy state, and it is not necessary to consider replacing the entire IGBT device.
The thermistor matrix group can divide the substrate into different areas, and when each area is a rectangular area surrounded by four temperature sensors, the 16 sensors can be divided into 9 areas in total. The MCU module selects an ADC module of the DSP and is provided with 16 sampling channels, and if the requirement on the measured accurate value is high, the number of the temperature sensors and the number of the ADC channels can be increased.
Compared with the prior art, the invention has the following advantages:
(1) the temperature measurement of the invention is carried out at the substrate of the IGBT, and the online detection can be realized.
(2) The invention can realize the analysis of the health state of the solder layer by MCU signal processing, can effectively identify the cavities and cracks of the solder layer and the sizes thereof by the symbols and the heat conduction angles of the elements in the variable quantity matrix of the temperature gradient matrix, and position the cavities and the cracks, and evaluate the device in real time, thereby avoiding causing great influence on the system;
(3) the crack measurement is irrelevant to the environment temperature and only relevant to the temperature gradient measurement error, the accuracy is higher, the real-time performance is better, and the on-line detection of the cavity and the crack condition of the solder layer can be realized.
Drawings
FIG. 1 is an overall schematic diagram of a temperature gradient-based IGBT solder layer state real-time monitoring device;
FIG. 2 is a schematic structural diagram of a temperature sensor module;
FIG. 3 is a schematic diagram of the connection between the ADC module and the MCU module;
FIG. 4 is a schematic diagram of the connection between the MUC module and the information display module;
FIG. 5 is a schematic diagram of the arrangement of temperature sensitive resistors on the substrate of the IGBT device;
fig. 6 is a flowchart of a method for real-time monitoring of an IGBT solder layer.
Detailed Description
The invention is further illustrated by the following figures and examples.
The IGBT chip is a heating source of the power device, the heat conduction of the IGBT chip is transferred from the chip to the substrate U06 through the solder layer, and the IGBT chip has a certain heat conduction angle which is generally 45 degrees. When the solder layer is defective, the temperature gradient of the layers below the chip changes. And the size of the defects of the solder layer has a linear relation with the change of the temperature.
And (3) monitoring the IGBT solder layer in real time by using a temperature gradient-based IGBT solder layer state real-time monitoring device.
Referring to fig. 1, the device for monitoring the state of the solder layer of the IGBT in real time based on the temperature gradient comprises a power supply module U01, a temperature sensor module U02, an ADC module U03, an MCU module U04 and an information display module U05;
the power supply module U01 is used for supplying power to the MCU module U04, the thermocouple module U02, the ADC module U03 and the display module U05, the power supply module U01 adopts 5V direct current voltage and 3.3V direct current voltage for supplying power, the 5V direct current voltage supplies power to the information display module U05 and the thermocouple module U02, and the 3.3V direct current voltage supplies power to the MCU module U04 and the ADC module U03;
the temperature sensor module U02 is connected with the ADC module U03, the ADC module U03 is connected with the MCU module U04, and the MCU module U04 is connected with the information display module U05;
the temperature sensor module U02 measures the temperature of the IGBT device substrate U06; the MCU module U04 sends a sampling instruction to the ADC module U03, the ADC module U03 receives the sampling instruction, the ADC module U03 collects temperature information from the temperature sensor module (the collected temperature information can be the temperature of a key information node of the IGBT device substrate), the temperature information collected by the ADC module U03 is an analog signal, and the ADC module U03 processes the collected analog signal, converts the analog signal into a digital signal and transmits the digital signal to the MCU module U04; the MCU module U04 processes the digital signals transmitted by the ADC module U03, judges the state of the solder layer (namely the area and position of a crack and the area and position of a cavity), and transmits the state of the solder layer to the display module U05 for real-time display; the display module U05 receives the solder layer state information transmitted by the MCU module U04 and displays the information in real time.
The ADC module has a multi-channel temperature acquisition capability. The MCU module controls the sampling sequence and the channel of the thermocouple module U02 by controlling the ADC module. The ADC module U03 collects data of the temperature sensor module U02 in real time by receiving instructions sent by the MCU module U04.
Referring to fig. 2, the thermocouple module U02 includes 16 thermistors U021. The 16 thermistors U021 of the temperature sensor module are uniformly arranged on the upper surface of the IGBT device substrate (see fig. 5), and may be uniformly arranged on the key nodes of the IGBT device substrate. Without loss of generality, the thermistor is Negative Temperature Coefficient (NTC) resistor with model number of AYN-MF55-104F-3950FB-1500-28 #.
Referring to fig. 3, the ADC module U03 in the device for real-time monitoring of solder layer is a 12-bit ADC module with 16 channels, and the ADC module built in the MCU is selected here without loss of generality.
Referring to fig. 3, a state discrimination module U041 and a state display alarm module U042 are arranged in the MCU module of the solder layer real-time monitoring apparatus. Without loss of generality, the MCU module can be selected from a DSP with the model number TMS320F 28235.
Referring to fig. 4, the information display module U05 includes an LED liquid crystal screen U051 and an LED warning light U052, both of which are connected to the MCU module U04. Without loss of generality, the LED liquid crystal screen U051 adopts a 12864 liquid crystal screen with the model of KS0108 LCD; the LED alarm lamp selects a light emitting diode.
The method for monitoring the IGBT solder layer in real time comprises the following steps:
step (1), starting an ADC module U03 and an MCU moduleThe U04 is initialized, and a matrix form T of initial temperature correction values is introduced into the MCU module U040]Setting a sampling time interval delta t and a temperature gradient matrix change threshold value delta of the ADC module U03 by the MCU module U04, and recording the position of each thermistor U021 on a substrate U06 of the IGBT device, the height from a solder layer to the substrate U06 and the area of the whole solder layer by the MCU module U04;
step (2), when the IGBT device does not work, the MCU module U04 sends a sampling instruction to the ADC module U03, the ADC module U03 receives the sampling instruction, the ADC module U03 collects temperature signals from the temperature sensor module U02, performs analog-to-digital conversion on the collected temperature signals and transmits the temperature signals to the MCU module U04, the MCU module U04 performs wavelet filtering on the temperature signals transmitted from the ADC module U03 and compares the temperature signals with the indoor temperature, if the two temperatures are consistent, normal working sampling can be performed, and the step (3) is carried out; if the temperature of the sample is inconsistent with the indoor temperature, the sampling algorithm in the ADC module U03 is adjusted through the MCU module U04 until the temperature sampled by the ADC module U03 and transmitted to the MCU module U04 is consistent with the indoor temperature, and then the step (3) is carried out;
the sampling algorithm in the ADC module U03 is adjusted to be the existing mature technology through the MCU module U04;
step (3), when the IGBT device works, the MCU module U04 sends a sampling instruction to the ADC module U03, the ADC module U03 receives the sampling instruction, the ADC module U03 collects temperature signals from the temperature sensor module U02, performs wavelet filtering on the collected temperature signals and then transmits the temperature signals to the MCU module U04, and the step (4) is carried out;
step (4), calculating a temperature gradient matrix [ dT]＝[T]-[T0]，[T]In the form of a matrix of the measured temperatures of all thermistors U021 at the current sampling moment, [ T0]A matrix form representing an initial value of temperature correction; when the IGBT device works, if the sampling times of the ADC module U03 are more than two times, calculating a temperature gradient matrix [ dT]When is in [ T ]0]Replacing the temperature measurement matrix form by all thermistors at the last sampling time of the current sampling time; obtaining a temperature gradient matrix [ dT]Then, the step (5) is carried out;
calculating a temperature gradient matrix [ dT]＝[T]-[T0]The specific method is: for each thermistor U021 on the IGBT device, subtracting the temperature value at the last sampling time from the sampling temperature obtained at the current sampling time (when the IGBT device works, for the first sampling of the ADC module, the temperature value at the last sampling time is replaced by the temperature correction initial value) to obtain the temperature gradient of each thermistor, and jointly forming a temperature gradient matrix by the temperature gradients of all the thermistors U021 obtained at the current sampling time according to the distribution mode of the temperature gradients on the IGBT device.
If 16 thermistors U021 are arranged on the IGBT device, and 16 thermistors U021 are distributed in 4 rows and 4 columns, for each thermistor U021, the temperature value at the previous sampling time is subtracted from the sampling temperature obtained at the current sampling time (when the IGBT device operates, the temperature value at the previous sampling time is replaced by a temperature correction initial value for the first sampling of the ADC module) to obtain the temperature gradient of each thermistor U021, the temperature gradients of the 16 thermistors U021 obtained at the current sampling time jointly form a 4 × 4 temperature gradient matrix according to the distribution mode of the temperature gradients on the IGBT device (i.e., the distribution mode of 4 rows and 4 columns), and each thermistor U021 corresponds to one element in the temperature gradient matrix (e.g., the thermistor at the 1 st row and the 1 st column on the IGBT device corresponds to the element at the 1 st row and the 1 st column in the temperature gradient matrix).
Step (5), calculating the variation of the temperature gradient matrix
Δ t is the sampling time interval; calculating to obtain the variation [ Delta dT ] of the temperature gradient matrix]Then, turning to the step (6);
if 16 thermistors U021 are provided on the IGBT device, and 16 thermistors U021 are distributed in 4 rows and 4 columns, as described above, the temperature gradient matrix [ dT ] is a 4 × 4 matrix, the variation matrix [ Δ dT ] of the temperature gradient matrix is also a 4 × 4 matrix, and each thermistor U021 also corresponds to an element in the variation matrix [ Δ dT ] of the temperature gradient matrix (e.g., the thermistor in the 1 st row and the 1 st column on the IGBT device corresponds to an element in the 1 st row and the 1 st column in the variation matrix [ Δ dT ] of the temperature gradient matrix).
Step (6), comparing the absolute value of each element in the variation matrix [ Delta dT ] of the temperature gradient matrix with a preset temperature gradient matrix variation threshold value delta, and turning to step (7) when the element in the variation matrix [ Delta dT ] of the temperature gradient matrix is larger than the preset temperature gradient matrix variation threshold value delta; when the absolute values of all elements in the variation matrix [ Delta dT ] of the temperature gradient matrix are less than or equal to the preset temperature gradient matrix variation threshold value delta, returning to the step (3) and re-sampling;
if 16 thermistors U021 are arranged on the IGBT device, and 16 thermistors U021 are distributed in 4 rows and 4 columns, each element in the variation matrix [. DELTA.dT ] (which is a 4 x 4 matrix) of the temperature gradient matrix is compared with a preset temperature gradient matrix variation threshold value δ.
Step (7), when the temperature of one thermistor U021 changes, the temperature of the adjacent thermistor U021 also changes correspondingly, and the signs of all elements in the variation matrix [ Delta dT ] of the temperature gradient matrix are judged; when cracks appear on the solder layer of the IGBT device, the temperature of a chip of the IGBT device is gathered at the edge of the cracks when the chip of the IGBT device transfers heat to a substrate of the IGBT device through the solder layer (the heat conduction angle is 45 ℃), the cracks on the solder layer form a rectangle on the substrate U06 after being amplified through heat conduction, at the moment, the temperature variation of the thermistor in the rectangle on the substrate U06 is a positive value, elements in a variation matrix [ Delta dT ] of a temperature gradient matrix corresponding to the thermistor in the rectangle on the substrate U06 are also positive values, and the shape enclosed by the positive elements in the variation matrix [ Delta dT ] of the temperature gradient matrix is also a rectangle; when a cavity appears in a solder layer of the IGBT device, a chip of the IGBT device transfers heat to an IGBT device substrate U06 (the heat conduction angle is 45 degrees) through the solder layer, the cavity on the solder layer forms a circle on the substrate after heat conduction amplification, at the moment, the temperature variation of a thermistor in the circle on the substrate is a negative value, elements in a variation matrix [ [ Delta ] dT ] of a temperature gradient matrix corresponding to the thermistor in a ring on the substrate U06 are also negative values, and the shape enclosed by the negative value elements in the variation matrix [ [ Delta ] dT ] of the temperature gradient matrix is also circular;
if a rectangular region composed of positive-value elements exists in the variation matrix [ Delta dT ] of the temperature gradient matrix, determining that a crack exists on the solder layer of the IGBT device, and the thermistor corresponding to the positive-value elements composing the rectangular region also encloses a rectangle on the substrate U06 of the IGBT device, obtaining the central position, the length and the width of the rectangle on the substrate U06 of the IGBT device through the MCU module U04, wherein the length of the crack on the solder layer is equal to the length of the rectangle on the substrate-the height from the solder layer to the substrate x 2, the width of the crack on the solder layer is equal to the width of the rectangle on the substrate-the height from the solder layer to the substrate x 2, the point where the central point of the rectangle on the substrate is projected on the solder layer is the central point of the crack on the solder layer, and drawing a rectangle on the solder layer by taking the obtained central point of the crack as the center, the long edge of the rectangle drawn on the solder layer is parallel to the long edge of the rectangle on the substrate, the short edge of the rectangle drawn on the solder layer is parallel to the short edge of the rectangle on the substrate, the area of the rectangle drawn on the solder layer is the area of the crack, and the position of the rectangle drawn on the solder layer is the position of the crack; the MCU 04 calculates the percentage of the area of the crack in the whole solder layer area to obtain the health state of the solder layer affected by the crack; the MCU module U04 transmits the area and position data of the cracks and the health state of the solder layer affected by the cracks to the display module for displaying and alarming;
if a circular area formed by negative elements exists in the variable matrix [ delta dT ] of the temperature gradient matrix, determining that a cavity exists on a solder layer of the IGBT device, and a thermistor corresponding to the negative elements forming the circular area also encloses a circle on a substrate of the IGBT device, and obtaining the central position and the radius of the circle on the substrate of the IGBT device through an MCU module U04, wherein the radius of the cavity on the solder layer is equal to the radius of the circle on the substrate-the height from the solder layer to the substrate because the heat conduction angle is 45 degrees, the point of the orthographic projection of the central point of the circle on the substrate on the solder layer is the central point of the cavity on the solder layer, and the radius of the cavity is drawn on the solder layer by taking the central point of the obtained cavity as the center; the MCU 04 calculates the percentage of the area of the cavity in the whole solder layer area to obtain the health state of the solder layer affected by the cavity; the MCU module U04 transmits the area and position data of the holes and the health state of the solder layer affected by the holes to the display module for displaying and alarming;
after the step (7) is finished, switching to a step (8);
and (8) ending.
The step (6) is completed in a state judging module in the MCU module U04, and the step (7) is completed in a state display alarm module in the MCU module U04.
In the step (7), the specific method for calculating the percentage of the area of the cavity in the whole solder layer area by the MCU module U04 to obtain the health state of the solder layer affected by the cavity is as follows:
when the percentage of the area of the cavity to the area of the whole solder layer is more than or equal to 20 percent, the health state of the solder layer affected by the cavity is a dangerous state, and the whole IGBT device needs to be replaced;
when the area of the cavity with the volume of more than or equal to 10 percent accounts for less than 20 percent of the area of the whole solder layer, the healthy state of the solder layer affected by the cavity is an unhealthy state, and a user can select whether to replace the whole IGBT device according to actual needs;
when the area of the cavity with the volume of 5 percent or more accounts for less than 10 percent of the area of the whole solder layer, the health state of the solder layer affected by the cavity is a sub-health state, and a user can select whether to replace the whole IGBT device according to actual needs;
when the percentage of the area of the cavity in the whole solder layer is less than 5%, the health state of the solder layer affected by the cavity is obtained as a health state, and the whole IGBT device does not need to be replaced.
Further, in the step (7), the MCU module U04 calculates the percentage of the area of the crack in the entire solder layer area, and the specific method for obtaining the health status of the solder layer affected by the crack is as follows:
when the percentage of the area of the cracks in the whole solder layer is more than or equal to 10%, the health state of the solder layer affected by the cracks is a dangerous state, and the whole IGBT device needs to be replaced;
when the area of the crack is more than or equal to 5% and less than 10% of the area of the whole solder layer, the healthy state of the solder layer affected by the crack is obtained to be an unhealthy state, and a user can select whether to replace the whole IGBT device according to actual needs;
when the area of the crack is more than 0% and less than 5% of the area of the whole solder layer, the health state of the solder layer affected by the crack is obtained as a sub-health state, and a user can select whether to replace the whole IGBT device according to actual needs;
when the percentage of the area of the crack to the area of the entire solder layer is 0%, it is found that the healthy state of the solder layer affected by the crack is a healthy state, and it is not necessary to consider replacing the entire IGBT device.
It is to be noted that, in this document, relational terms such as up and down are used solely to distinguish one entity or operation from another entity or operation without necessarily requiring or implying any actual such relationship or order between such entities or operations. Also, the terms "comprises," "comprising," or other variations are intended to cover non-exclusive inclusions.
The above description is only for the preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. The method for monitoring the IGBT solder layer in real time uses a temperature gradient-based IGBT solder layer state real-time monitoring device to monitor the IGBT solder layer in real time,
the IGBT welding flux layer state real-time monitoring device based on the temperature gradient comprises a power supply module, a temperature sensor module, an ADC module, an MCU module and an information display module;
the power supply module is used for supplying power to the temperature sensor module, the ADC module, the MCU module and the information display module;
the temperature sensor module is connected with the ADC module, the ADC module is connected with the MCU module, and the MCU module is connected with the information display module;
the temperature sensor module measures the temperature of the IGBT device substrate; the temperature sensor module is used for acquiring temperature information, the MCU module sends a sampling instruction to the ADC module, the ADC module receives the sampling instruction, the ADC module acquires the temperature information from the temperature sensor module, the temperature information acquired by the ADC module is an analog signal, and the ADC module processes the acquired analog signal, converts the analog signal into a digital signal and transmits the digital signal to the MCU module; the MCU module processes the digital signals transmitted by the ADC module, judges the state of the solder layer, and transmits the state of the solder layer, namely the area and position of a crack and the area and position of a cavity to the information display module for real-time display; the information display module receives the state information of the solder layer transmitted by the MCU module and displays the state information in real time;
the temperature sensor module comprises at least two thermistors, and the thermistors of the temperature sensor module are uniformly arranged on the upper surface of the IGBT device substrate;
the method for monitoring the IGBT solder layer in real time is characterized by comprising the following steps of:
step (1), starting an ADC module and an MCU module for initialization, and introducing a matrix form [ T ] of an initial temperature correction value into the MCU module0]Setting a sampling time interval delta t and a temperature gradient matrix change threshold value delta of the ADC module through the MCU module, and recording the position of each thermistor on a substrate of the IGBT device, the height from a solder layer to the substrate and the area of the whole solder layer by the MCU module;
step (2), when the IGBT device does not work, the MCU module sends a sampling instruction to the ADC module, the ADC module receives the sampling instruction, the ADC module collects temperature signals from the temperature sensor module, performs analog-to-digital conversion on the collected temperature signals and then transmits the temperature signals to the MCU module, the MCU module performs wavelet filtering processing on the temperature signals transmitted from the ADC module and then compares the temperature signals with the indoor temperature, if the two temperatures are consistent, normal working sampling can be performed, and the step (3) is carried out; if not, adjusting the sampling algorithm in the ADC module through the MCU until the temperature sampled by the ADC module and transmitted to the MCU module is consistent with the indoor temperature, and then turning to the step (3);
step (3), when the IGBT device works, the MCU module sends a sampling instruction to the ADC module, the ADC module receives the sampling instruction, the ADC module collects temperature signals from the temperature sensor module, performs wavelet filtering processing on the collected temperature signals and then transmits the temperature signals to the MCU module, and the step (4) is carried out;
step (4), calculating a temperature gradient matrix [ dT]＝[T]-[T0]，[T]In the form of a matrix of the measured temperatures of all thermistors at the current sampling time, [ T0]A matrix form representing an initial value of temperature correction; when the IGBT device works, if the sampling times of the ADC module are more than two times, calculating a temperature gradient matrix [ dT]When is in [ T ]0]Replacing the temperature measurement matrix form by all thermistors at the last sampling time of the current sampling time; obtaining a temperature gradient matrix [ dT]Then, the step (5) is carried out;
calculating a temperature gradient matrix [ dT]＝[T]-[T0]The specific method comprises the following steps: for each thermistor on the IGBT device, subtracting the temperature value at the last sampling time from the sampling temperature obtained at the current sampling time to obtain the temperature gradient of each thermistor, substituting the temperature value at the last sampling time with the temperature correction initial value for the first sampling of the ADC module when the IGBT device works, and forming a temperature gradient matrix by the temperature gradients of all the thermistors obtained at the current sampling time according to the distribution mode of the temperature gradients on the IGBT device;
step (5), calculating the variation of the temperature gradient matrix
Δ t is the sampling time interval; calculating to obtain the variation [ Delta dT ] of the temperature gradient matrix]Then, turning to the step (6);
step (6), comparing the absolute value of each element in the variation matrix [ Delta dT ] of the temperature gradient matrix with a preset temperature gradient matrix variation threshold value delta, and turning to step (7) when the element in the variation matrix [ Delta dT ] of the temperature gradient matrix is larger than the preset temperature gradient matrix variation threshold value delta; when the absolute values of all elements in the variation matrix [ Delta dT ] of the temperature gradient matrix are less than or equal to the preset temperature gradient matrix variation threshold value delta, returning to the step (3) and re-sampling;
step (7), when the temperature of one thermistor changes, the temperature of the adjacent thermistor also changes correspondingly, and the signs of all elements in the variation matrix [ Delta dT ] of the temperature gradient matrix are judged; when the solder layer of the IGBT device cracks, the temperature of a chip of the IGBT device is gathered at the edge of the crack when the chip of the IGBT device transfers heat to the substrate of the IGBT device through the solder layer, the heat conduction angle during heat transfer is 45 degrees, the crack on the solder layer forms a rectangle on the substrate after heat conduction amplification, at the moment, the temperature variation of the thermistor in the rectangle on the substrate is a positive value, the element in the variation matrix [ [ Delta dT ] of the temperature gradient matrix corresponding to the thermistor in the rectangle on the substrate is a positive value, and the shape enclosed by the positive value element in the variation matrix [ [ Delta dT ] of the temperature gradient matrix is also a rectangle; when a cavity appears in a solder layer of the IGBT device, a chip of the IGBT device transfers heat to a substrate of the IGBT device through the solder layer, the cavity on the solder layer forms a circle on the substrate after being amplified by heat conduction, the heat conduction angle during heat conduction is 45 degrees, at the moment, the temperature variation of a thermistor in the circle on the substrate is a negative value, elements in a variation matrix [ Delta dT ] of a temperature gradient matrix corresponding to the thermistor in a ring on the substrate are also negative values, and the shape enclosed by the negative value elements in the variation matrix [ Delta dT ] of the temperature gradient matrix is also circular;
if a rectangular region composed of positive-value elements exists in the variation matrix [ Delta dT ] of the temperature gradient matrix, determining that cracks exist on the solder layer of the IGBT device, forming a rectangle on the substrate of the IGBT device by the thermistor corresponding to the positive-value elements forming the rectangular region, obtaining the central position, the length and the width of the rectangle on the substrate of the IGBT device by the MCU, obtaining the length of the crack on the solder layer as the length of the rectangle on the substrate-the height from the solder layer to the substrate x 2 because the heat conduction angle is 45 degrees, obtaining the width of the crack on the solder layer as the width from the rectangle on the substrate-the height from the solder layer to the substrate x 2, obtaining the central point of the rectangle on the substrate, which is the central point of the crack on the solder layer in an orthographic projection manner, drawing the rectangle on the solder layer by taking the central point of the obtained crack as the center, and obtaining the length and the width of the crack, the long edge of the rectangle drawn on the solder layer is parallel to the long edge of the rectangle on the substrate, the short edge of the rectangle drawn on the solder layer is parallel to the short edge of the rectangle on the substrate, the area of the rectangle drawn on the solder layer is the area of the crack, and the position of the rectangle drawn on the solder layer is the position of the crack; the MCU module calculates the percentage of the area of the crack in the whole solder layer area to obtain the health state of the solder layer affected by the crack; the MCU module transmits the area and position data of the cracks and the health state of the solder layer affected by the cracks to the display module for displaying and alarming;
if a circular area formed by negative elements exists in a variable matrix [ delta dT ] of the temperature gradient matrix, determining that a cavity exists on a solder layer of the IGBT device, and a thermistor corresponding to the negative elements forming the circular area also encloses a circle on a substrate of the IGBT device; the MCU module calculates the percentage of the area of the cavity in the whole solder layer area to obtain the health state of the solder layer affected by the cavity; the MCU module transmits the area and position data of the holes and the health state of the solder layer affected by the holes to the display module for displaying and alarming;
after the step (7) is finished, switching to a step (8);
and (8) ending.
2. The method for monitoring the IGBT solder layer in real time according to claim 1, wherein the information display module comprises an LED liquid crystal screen and an LED warning lamp, and the LED liquid crystal screen and the LED warning lamp are both connected with the MCU module.
3. The method for monitoring the IGBT solder layer in real time according to claim 1, wherein in the step (7), the MCU module calculates the percentage of the area of the voids to the area of the whole solder layer, and the specific method for obtaining the health status of the solder layer affected by the voids is as follows:
when the percentage of the area of the cavity to the area of the whole solder layer is more than or equal to 20 percent, the health state of the solder layer affected by the cavity is a dangerous state, and the whole IGBT device needs to be replaced;
when the area of the cavity with the volume of more than or equal to 10 percent accounts for less than 20 percent of the area of the whole solder layer, the healthy state of the solder layer affected by the cavity is an unhealthy state, and a user selects whether to replace the whole IGBT device according to actual needs;
when the area of the cavity with the volume of 5 percent or more accounts for less than 10 percent of the area of the whole solder layer, the health state of the solder layer affected by the cavity is a sub-health state, and a user selects whether to replace the whole IGBT device according to actual needs;
when the percentage of the area of the cavity in the whole solder layer is less than 5%, the health state of the solder layer affected by the cavity is obtained as a health state, and the whole IGBT device does not need to be replaced.
4. The method for monitoring the IGBT solder layer in real time according to claim 1, wherein in the step (7), the MCU module calculates the percentage of the area of the crack to the area of the whole solder layer, and the specific method for obtaining the health state of the solder layer affected by the crack is as follows:
when the percentage of the area of the cracks in the whole solder layer is more than or equal to 10%, the health state of the solder layer affected by the cracks is a dangerous state, and the whole IGBT device needs to be replaced;
when the area of the crack is more than or equal to 5% and less than 10% of the area of the whole solder layer, the healthy state of the solder layer affected by the crack is obtained to be an unhealthy state, and a user selects whether to replace the whole IGBT device according to actual needs;
when the area of the crack is more than 0% and less than 5% of the area of the whole solder layer, the health state of the solder layer affected by the crack is obtained as a sub-health state, and a user selects whether to replace the whole IGBT device according to actual needs;
when the percentage of the area of the crack to the area of the entire solder layer is 0%, it is found that the healthy state of the solder layer affected by the crack is a healthy state, and it is not necessary to consider replacing the entire IGBT device.
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