WO2022058311A1 - Electronic module and method for connecting several conductors to a substrate - Google Patents

Electronic module and method for connecting several conductors to a substrate Download PDF

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Publication number
WO2022058311A1
WO2022058311A1 PCT/EP2021/075243 EP2021075243W WO2022058311A1 WO 2022058311 A1 WO2022058311 A1 WO 2022058311A1 EP 2021075243 W EP2021075243 W EP 2021075243W WO 2022058311 A1 WO2022058311 A1 WO 2022058311A1
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WO
WIPO (PCT)
Prior art keywords
connection pad
substrate
conductor
conductors
welding process
Prior art date
Application number
PCT/EP2021/075243
Other languages
French (fr)
Inventor
Robert Woehl
Frederic Möß
Original Assignee
Danfoss Silicon Power Gmbh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Danfoss Silicon Power Gmbh filed Critical Danfoss Silicon Power Gmbh
Publication of WO2022058311A1 publication Critical patent/WO2022058311A1/en

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L23/00—Details of semiconductor or other solid state devices
    • H01L23/48—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor
    • H01L23/488—Arrangements for conducting electric current to or from the solid state body in operation, e.g. leads, terminal arrangements ; Selection of materials therefor consisting of soldered or bonded constructions
    • H01L23/498—Leads, i.e. metallisations or lead-frames on insulating substrates, e.g. chip carriers
    • H01L23/49811—Additional leads joined to the metallisation on the insulating substrate, e.g. pins, bumps, wires, flat leads
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/48—Manufacture or treatment of parts, e.g. containers, prior to assembly of the devices, using processes not provided for in a single one of the subgroups H01L21/06 - H01L21/326
    • H01L21/4814—Conductive parts
    • H01L21/4846—Leads on or in insulating or insulated substrates, e.g. metallisation
    • H01L21/4853—Connection or disconnection of other leads to or from a metallisation, e.g. pins, wires, bumps

Definitions

  • the present invention relates to an electronic module comprising two or more conductors each comprising a connection pad attached to a substrate by means of a welding process.
  • the invention also relates to a method for connecting two or more conductors to a substrate.
  • the power terminals are typically attached onto the substrate by means of a soldering process.
  • the soldering process is, however, time-consuming and costly.
  • the lead frames take up a lot of space in the soldering oven. Accordingly, the throughput of the soldering process is rather low.
  • Ultrasonic welding is one of the favoured techniques for attaching terminals onto a substrate. Ultrasonic welding typically requires more space than available on the substrate of power electronic modules. In these cases, it is not possible to use ultrasonic welding for attaching terminals onto the substrates.
  • the method according to the invention is a method for connecting two or more conductors to a substrate, wherein each conductor comprises a connection pad, wherein the method comprises the steps of: a) placing a first connection pad of a first conductor in a first position and placing a second connection pad of a second conductor in a second position, in which the first connection pad of the first conductor is arranged between the second connection pad of the second conductor and the substrate and b) carrying out a welding process, in which the second connection pad of the second conductor, the first connection pad of the first conductor are welded to each other and to the substrate.
  • the two or more conductors are metal conductors.
  • the conductors are copper terminals.
  • the substrate may be a power electronic substrate.
  • the substrate is an insulated metal substrate. In one embodiment, the substrate is a direct bonded copper (DBC) substrate. In another embodiment, the substrate is an active metal brazed (AMB) substrate.
  • DBC direct bonded copper
  • AMB active metal brazed
  • connection pad comprises a connection pad.
  • the connection pad is shaped and configured to be attached to the substrate by means of a welding process. It may be an advantage that the connection pad comprises a planar contact surface for providing a good contact between the connection pad and the substrate (that typically is flat).
  • connection pads When placing a first connection pad of a first conductor in a first position and placing a second connection pad of a second conductor in a second position, in which the first connection pad of the first conductor is arranged between the second connection pad of the second conductor and the substrate the connection pads are ready to be attached to the substrate in a single welding operation.
  • the welding process can be carried out in such a manner that the second connection pad of the second conductor and the first connection pad of the first conductor are welded to each other and to the substrate in a single welding step. Accordingly, the welding time and the required space on the substrate can be reduced.
  • the method comprises the step of providing the connection pads at the distal end of the conductors.
  • the connection pads at the distal end of the conductors.
  • ultrasonic welding is one of the preferred techniques for attaching conductors to a substrate.
  • the ultrasonic welding process is a torsion welding process. This type of ultrasonic welding technique allows the joining of the connection pads with substrate without significant deformation of the joining partners.
  • the head motion is rotational rather than linear.
  • the tool that creates ultrasonic vibrations is typically referred to as a sonotrode.
  • the sonotrode is moved in a manner in which the amplitude is circumferential.
  • the ultrasonic vibration process is a process, in which the ultrasonic vibrations are created by using a sonotrode.
  • the sonotrode comprises a stack of piezoelectric transducers attached to a tapering metal rod (e.g. titanium, aluminium or steel). Since a sonotrode delivers energy directly to the welding contact area with limited diffraction, the vibrations will not damage any surrounding electronic components.
  • the method comprises an additional step, in which one or more additional connection pads of one or more additional conductors are placed on the top of the second connection pad of the second conductor before the welding process is carried out.
  • the attachment takes up less space on the substrate since the same contact area is used to attach the connection pads to the substrate.
  • connection pads of the conductors may also be an advantage if only the connection pads of the conductors overlap when viewed along an axis which is orthogonal to the plane of the connection pads. In this embodiment, it is only the connection pads themselves that overlap each other, and not other portions of the conductors. In this manner, all portions of the conductors which overlap each other are in close proximity with other conductors and are thus utilised for creating the welded connection.
  • the electronic module according to the invention comprises two or more conductors each comprising a connection pad that are attached to a substrate, wherein: a) a first connection pad of a first conductor is placed in a first position and a second connection pad of a second conductor is placed in a second position, in which the first connection pad of the first conductor is arranged between the second connection pad of the second conductor and the substrate and b) the second connection pad of the second conductor, the first connection pad of the first conductor are welded to each other and to the substrate by means of a welding process.
  • the conductors are metal conductors.
  • the conductors are copper terminals.
  • the substrate may be a power electronic substrate. It may be an advantage that the substrate is an insulated metal substrate. In one embodiment, the substrate is a DBC substrate. In another embodiment, the substrate is an active metal brazed (AMB) substrate.
  • AMB active metal brazed
  • connection pad that is configured and shaped to be attached to the substrate by means of a welding process.
  • the connection pad may preferably comprise a planar contact surface in order to providing a good contact between the connection pad and the substrate that typically is flat.
  • connection pad is plate-shaped, wherein the top surface of the connection pad extends parallel to bottom surface of the connection pad.
  • connection pads are provided at the distal end of the conductors.
  • the connection pads are provided at the distal end of the conductors.
  • connection pad extends in extension of the adjacent portion of the conductor.
  • the electronic module comprises one or more additional connection pads of one or more additional conductors, wherein the additional connection pads are placed on the top of the second connection pad of the second conductor, wherein the connection pads of all the conductors are welded to each other and to the substrate by means of a welding process.
  • the additional connection pads are placed on the top of the second connection pad of the second conductor, wherein the connection pads of all the conductors are welded to each other and to the substrate by means of a welding process.
  • the attachment takes up less space since the same contact area may be used to attach the connection pads to the substrate.
  • the welding process is ultrasonic welding.
  • the ultrasonic welding process is a torsion welding process.
  • the ultrasonic welding process is a process carried out in a manner, in which the ultrasonic vibrations are created by using a sonotrode.
  • connection pads of the conductors overlap when viewed along an axis which is orthogonal to the plane of the connection pads. In this embodiment, it is only the connection pads themselves that overlap each other, and not other portions of the conductors. In this manner, all portions of the conductors which overlap each other are in close proximity with other conductors and are thus utilised for creating the welded connection.
  • Fig. 1 shows a perspective view of a metal terminal having three conductors that have been attached to a substrate by using the method according to the invention
  • Fig. 2 shows a perspective view of a metal terminal having two conductors being attached to a substrate by using the method according to the invention
  • Fig. 3A shows a connection pad of a first conductor that is placed on a substrate
  • Fig. 3B shows the substrate shown in Fig. 3A in a configuration, in which a connection pad of a second conductor is placed on the top of the connection pad of the first connector;
  • Fig. 3C shows the substrate shown in Fig. 3B in a configuration, in which a connection pad of a third conductor is placed on the top of the second connection pad;
  • Fig. 4 shows how the ultrasonic welding process can be carried out by using a sonotrode and Fig. 5 shows a the inventive method as a flowchart.
  • FIG. 1 a perspective view of a metal terminal 2 having a first conductor 4, a second conductor 4' and a third conductor 4" that have been attached to a substrate 6 by using the method according to the invention is illustrated in Fig. 1.
  • the substrate 6 comprises a flat portion, onto which a planar connection pad of the third conductor 4" is attached.
  • the substrate 6 and the connection pads of the three conductors 4, 4', 4" extend along the plane spanned by the X axis and the Y axis indicated in Fig. 1.
  • the pads of conductors 4, 4', 4" are stacked on the top of each other. It can be seen that the connection pad of the midmost conductor 4' is sandwiched between the connection pad of the first conductor 4 and the connection pad of the third conductor 4".
  • the pads are attached to the substrate 6 by means of an ultrasonic welding process, preferably a torsion welding process by using a sonotrode (as shown in Fig. 4).
  • Fig. 2 illustrates a perspective view of a metal terminal 2 having two conductors 4, 4' being attached to a substrate 6 by using the method according to the invention.
  • the terminal 2 comprises a flat portion.
  • a first conductor 4 and a second conductor 4' are separated from each other and extend in extension of said flat portion.
  • the proximal portion of the conductors 4, 4' extend parallel to each other.
  • the distal portion of the conductors 4, 4' comprises a connection pad 8, 8' having a flat portion that extends parallel to the plane spanned by the X axis and the Y axis indicated.
  • the connection pad 8 of the first conductor 4 is placed on the top of the connection pad 8' of the second conductor 4'.
  • the substrate 6 extends along the plane spanned by the X axis and the Y axis.
  • the required electrical connection between the terminal 2 and the substrate 6 can be accomplished by using the method according to the invention and carrying out a welding process, in which the second connection pad 8' of the second conductor 4', the first connection pad 8 of the first conductor 4 are welded to each other and to the substrate 6.
  • the welding process is preferably an ultrasonic welding process, such as the torsion welding process shown in and explained with reference to Fig. 4.
  • Fig. 3A illustrates a connection pad 8 of a first conductor 4 that is placed on a substrate 8.
  • the substrate 6 is planar and extends along the Y axis.
  • the first conductor 4 comprises a proximal portion that extends along the Y axis and an intermediate portion that extends along the Z axis.
  • the distal portion of the conductor 4 is formed as the connection pad 8 that is configured and shaped to be attached to the substrate by using an ultrasonic welding process.
  • Fig. 3B illustrates the substrate 6 shown in Fig. 3A in a configuration, in which a connection pad 8' of a second conductor 4' is placed on the top of the connection pad 8 of the first connector 4.
  • the second conductor 4' comprises a proximal portion that extends along the Y axis and an intermediate portion that extends along the Z axis.
  • the distal portion of the second conductor 4' is formed as a connection pad 8' that is configured to be attached to the top of the connection pad 8 of the first connector 4 by using an ultrasonic welding process.
  • Fig. 3C illustrates the substrate 6 shown in Fig.
  • connection pad 8' of a third conductor 4' is placed on the top of the connection pad 8' of the second connector 4'.
  • the distal portion of the third conductor 4" is formed as a connection pad 8" that is designed to be fixed to the top of the connection pad 8' of the second connector 4' by using an ultrasonic welding process.
  • Fig. 4 illustrates how the ultrasonic welding process can be carried out by using a sonotrode 10.
  • a connection pad 8 of a first connector 4 and a connection pad 8' of a second connector 4' is placed on a substrate 6 like the one illustrated in Fig. 3B.
  • a sonotrode 10 comprising a stack of piezoelectric transducers (not shown) attached to a tapering rod.
  • the distal portion sonotrode 10 is brought into contact with the top surface of the connection pad 8' of the second connector 4'.
  • the longitudinal axis of the sonotrode 10 extends parallel with the normal axis (Z axis) of the substrate 6.
  • the first conductor 4 comprises a proximal portion that extends along the Y axis and an intermediate portion that extends along the Z axis.
  • the second conductor 4' comprises a proximal portion that extends along the Y axis and an intermediate portion that extends along the Z axis.
  • connection pads 8, 8' and the portion of the substrate 6 to which the connection pads 8, 8' are attached are plate-formed and extend along the Y axis.
  • the height (thickness) height H2 of the connection pad 8' of the second connector 4' equals the height Hi of the connection pad 8 of the first connector 4.
  • the height H 3 of the substrate 6 corresponds to the height Hi, H 2 of any of the connection pads 8, 8'. It is, however, possible to apply a substrate having another height H 3 .
  • the height H 2 of the connection pad 8' of the second connector 4' differs from the height Hi of the connection pad 8 of the first connector 4.
  • the length Li of the contact surface between the connection pad 8' of the second connector 4' and the connection pad 8 of the first connector 4 is larger than the height Hi, H 2 of any of the connection pads 8, 8'.
  • the length L 2 of the contact surface between the connection pad 8 of the first connector 4 and the substrate 6 is larger than the height Hi, H 2 of any of the connection pads 8, 8'. In fact, the length L 2 of the contact surface between the connection pad 8 of the first connector 4 and the substrate 6 is larger than the length Li of the contact surface between the connection pad 8' of the second connector 4' and the connection pad 8 of the first connector 4.
  • Fig. 5 illustrates the inventive method as a flowchart.
  • the method starts 100 by obtaining a substrate 6 and two or more conductors 4, 4', 4" wherein each conductor 4, 4', 4" comprises a connection pad 8, 8'.
  • a first connection pad 8 of a first conductor 4 is placed in a first position and a second connection pad 8' of a second conductor 4' is placed in a second position, so that the first connection pad 8 of the first conductor 4 is arranged between the second connection pad 8' of the second conductor 4' and the substrate 6.
  • a welding process is carried out in which the second connection pad 8' of the second conductor 4', the first connection pad 8 of the first conductor 4 are welded to each other and to the substrate 6.
  • step 103 The method is then completed as step 103.
  • step 104 which may be provided between step 101 and 102, one or more additional connection pads 8, 8' of one or more additional conductors 4" may be placed on the top of the second connection pad 8' of the second conductor 4' before the welding process is carried out.

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Ceramic Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Pressure Welding/Diffusion-Bonding (AREA)
  • Connections Effected By Soldering, Adhesion, Or Permanent Deformation (AREA)

Abstract

A method for connecting two or more conductors with connection pads to a substrate, comprising the steps of: placing a first connection pad of a first conductor and a second connection pad of a second conductor such that the first connection pad is arranged between the second connection pad and the substrate and subsequently carrying out a welding process, in which the second connection pad and the first connection pad are welded to each other and to the substrate.

Description

Electronic Module and Method for Connecting Several Conductors to a Substrate
Field of invention
The present invention relates to an electronic module comprising two or more conductors each comprising a connection pad attached to a substrate by means of a welding process. The invention also relates to a method for connecting two or more conductors to a substrate.
Prior art
When producing power electronic modules provided with power terminals, the power terminals are typically attached onto the substrate by means of a soldering process. The soldering process is, however, time-consuming and costly. Moreover, for modules having lead frames, the lead frames take up a lot of space in the soldering oven. Accordingly, the throughput of the soldering process is rather low.
Ultrasonic welding is one of the favoured techniques for attaching terminals onto a substrate. Ultrasonic welding typically requires more space than available on the substrate of power electronic modules. In these cases, it is not possible to use ultrasonic welding for attaching terminals onto the substrates.
Thus, is would be desirable to have an electronic module, enabling the use of ultrasonic welding for attaching the terminals onto the substrate.
It is an object of the present invention to provide an electronic module and a method for producing an electronic module, wherein ultrasonic welding can be used for attaching the terminals onto the substrate.
Summary of the invention
The object of the present invention can be achieved by a method as defined in claim 1 and by an electronic module having the features as defined in claim 7. Preferred embodiments are defined in the dependent subclaims, explained in the following description and illustrated in the accompanying drawings.
The method according to the invention is a method for connecting two or more conductors to a substrate, wherein each conductor comprises a connection pad, wherein the method comprises the steps of: a) placing a first connection pad of a first conductor in a first position and placing a second connection pad of a second conductor in a second position, in which the first connection pad of the first conductor is arranged between the second connection pad of the second conductor and the substrate and b) carrying out a welding process, in which the second connection pad of the second conductor, the first connection pad of the first conductor are welded to each other and to the substrate.
Hereby, it is possible to provide a method for producing an electronic module, wherein ultrasonic welding is used for attaching the terminals onto the substrate. Accordingly, the production time and the production costs can be reduced. Furthermore, it is possible to provide a more compact design because the terminals have a reduced contact area and thus take up less space on the substrate.
In one embodiment, the two or more conductors are metal conductors.
In a preferred embodiment, the conductors are copper terminals.
The substrate may be a power electronic substrate.
In one embodiment, the substrate is an insulated metal substrate. In one embodiment, the substrate is a direct bonded copper (DBC) substrate. In another embodiment, the substrate is an active metal brazed (AMB) substrate.
Each conductor comprises a connection pad. The connection pad is shaped and configured to be attached to the substrate by means of a welding process. It may be an advantage that the connection pad comprises a planar contact surface for providing a good contact between the connection pad and the substrate (that typically is flat).
When placing a first connection pad of a first conductor in a first position and placing a second connection pad of a second conductor in a second position, in which the first connection pad of the first conductor is arranged between the second connection pad of the second conductor and the substrate the connection pads are ready to be attached to the substrate in a single welding operation.
The welding process can be carried out in such a manner that the second connection pad of the second conductor and the first connection pad of the first conductor are welded to each other and to the substrate in a single welding step. Accordingly, the welding time and the required space on the substrate can be reduced.
In one embodiment, the method comprises the step of providing the connection pads at the distal end of the conductors. Hereby, it is possible to minimise the size of the conductors. Accordingly, the overall size of the electronic module can be minimised.
It may be an advantage that the welding process is carried out by using ultrasonic welding. Ultrasonic welding is one of the preferred techniques for attaching conductors to a substrate. In one embodiment, the ultrasonic welding process is a torsion welding process. This type of ultrasonic welding technique allows the joining of the connection pads with substrate without significant deformation of the joining partners. In ultrasonic torsion welding the head motion is rotational rather than linear. The tool that creates ultrasonic vibrations is typically referred to as a sonotrode. In ultrasonic torsion welding the sonotrode is moved in a manner in which the amplitude is circumferential.
It may be advantageous that the ultrasonic vibration process is a process, in which the ultrasonic vibrations are created by using a sonotrode. In one embodiment, the sonotrode comprises a stack of piezoelectric transducers attached to a tapering metal rod (e.g. titanium, aluminium or steel). Since a sonotrode delivers energy directly to the welding contact area with limited diffraction, the vibrations will not damage any surrounding electronic components.
It may be an advantage that the method comprises an additional step, in which one or more additional connection pads of one or more additional conductors are placed on the top of the second connection pad of the second conductor before the welding process is carried out. Hereby, it is possible to join three or more connection pads to the substrate within a single process step. Moreover, the attachment takes up less space on the substrate since the same contact area is used to attach the connection pads to the substrate.
In may also be an advantage if only the connection pads of the conductors overlap when viewed along an axis which is orthogonal to the plane of the connection pads. In this embodiment, it is only the connection pads themselves that overlap each other, and not other portions of the conductors. In this manner, all portions of the conductors which overlap each other are in close proximity with other conductors and are thus utilised for creating the welded connection.
The electronic module according to the invention comprises two or more conductors each comprising a connection pad that are attached to a substrate, wherein: a) a first connection pad of a first conductor is placed in a first position and a second connection pad of a second conductor is placed in a second position, in which the first connection pad of the first conductor is arranged between the second connection pad of the second conductor and the substrate and b) the second connection pad of the second conductor, the first connection pad of the first conductor are welded to each other and to the substrate by means of a welding process.
Hereby, it is possible to provide an electronic module, in which ultrasonic welding is applied for attaching the terminals onto the substrate. Accordingly, the production time and the production costs can be reduced. Furthermore, it is possible to provide a more compact design because the terminals take up less space on the substrate.
It may be an advantage that the conductors are metal conductors.
In a preferred embodiment, the conductors are copper terminals.
The substrate may be a power electronic substrate. It may be an advantage that the substrate is an insulated metal substrate. In one embodiment, the substrate is a DBC substrate. In another embodiment, the substrate is an active metal brazed (AMB) substrate.
Each conductor comprises a connection pad that is configured and shaped to be attached to the substrate by means of a welding process. The connection pad may preferably comprise a planar contact surface in order to providing a good contact between the connection pad and the substrate that typically is flat.
In a preferred embodiment, the connection pad is plate-shaped, wherein the top surface of the connection pad extends parallel to bottom surface of the connection pad.
It may be an advantage that the connection pads are provided at the distal end of the conductors. Hereby, it is possible to minimise the size of the conductors so that the overall size of the electronic module can be minimised.
In a preferred embodiment, the connection pad extends in extension of the adjacent portion of the conductor.
It may be advantageous that the electronic module comprises one or more additional connection pads of one or more additional conductors, wherein the additional connection pads are placed on the top of the second connection pad of the second conductor, wherein the connection pads of all the conductors are welded to each other and to the substrate by means of a welding process. Hereby, it is possible to join three or more connection pads to the substrate within a single process step. Moreover, the attachment takes up less space since the same contact area may be used to attach the connection pads to the substrate.
It may be an advantage that the welding process is ultrasonic welding.
In one embodiment, the ultrasonic welding process is a torsion welding process.
In a preferred embodiment, the ultrasonic welding process, is a process carried out in a manner, in which the ultrasonic vibrations are created by using a sonotrode.
In another preferred embodiment, only the connection pads of the conductors overlap when viewed along an axis which is orthogonal to the plane of the connection pads. In this embodiment, it is only the connection pads themselves that overlap each other, and not other portions of the conductors. In this manner, all portions of the conductors which overlap each other are in close proximity with other conductors and are thus utilised for creating the welded connection.
Description of the Drawings
The invention will become more fully understood from the detailed description given herein below. The accompanying drawings are given by way of illustration only, and thus, they are not limitative of the present invention. In the accompanying drawings:
Fig. 1 shows a perspective view of a metal terminal having three conductors that have been attached to a substrate by using the method according to the invention;
Fig. 2 shows a perspective view of a metal terminal having two conductors being attached to a substrate by using the method according to the invention;
Fig. 3A shows a connection pad of a first conductor that is placed on a substrate;
Fig. 3B shows the substrate shown in Fig. 3A in a configuration, in which a connection pad of a second conductor is placed on the top of the connection pad of the first connector;
Fig. 3C shows the substrate shown in Fig. 3B in a configuration, in which a connection pad of a third conductor is placed on the top of the second connection pad;
Fig. 4 shows how the ultrasonic welding process can be carried out by using a sonotrode and Fig. 5 shows a the inventive method as a flowchart.
Detailed description of the invention
Referring now in detail to the drawings for the purpose of illustrating preferred embodiments of the present invention, a perspective view of a metal terminal 2 having a first conductor 4, a second conductor 4' and a third conductor 4" that have been attached to a substrate 6 by using the method according to the invention is illustrated in Fig. 1.
The substrate 6 comprises a flat portion, onto which a planar connection pad of the third conductor 4" is attached. The substrate 6 and the connection pads of the three conductors 4, 4', 4" extend along the plane spanned by the X axis and the Y axis indicated in Fig. 1. The pads of conductors 4, 4', 4" are stacked on the top of each other. It can be seen that the connection pad of the midmost conductor 4' is sandwiched between the connection pad of the first conductor 4 and the connection pad of the third conductor 4". In order to establish the required electrical connection between the terminal 2 and the substrate 6, the pads are attached to the substrate 6 by means of an ultrasonic welding process, preferably a torsion welding process by using a sonotrode (as shown in Fig. 4).
Fig. 2 illustrates a perspective view of a metal terminal 2 having two conductors 4, 4' being attached to a substrate 6 by using the method according to the invention. The terminal 2 comprises a flat portion. A first conductor 4 and a second conductor 4' are separated from each other and extend in extension of said flat portion. The proximal portion of the conductors 4, 4' extend parallel to each other. The distal portion of the conductors 4, 4', however, comprises a connection pad 8, 8' having a flat portion that extends parallel to the plane spanned by the X axis and the Y axis indicated. The connection pad 8 of the first conductor 4 is placed on the top of the connection pad 8' of the second conductor 4'. Like the connection pads 8, 8', the substrate 6 extends along the plane spanned by the X axis and the Y axis.
The required electrical connection between the terminal 2 and the substrate 6 can be accomplished by using the method according to the invention and carrying out a welding process, in which the second connection pad 8' of the second conductor 4', the first connection pad 8 of the first conductor 4 are welded to each other and to the substrate 6.
The welding process is preferably an ultrasonic welding process, such as the torsion welding process shown in and explained with reference to Fig. 4.
Fig. 3A illustrates a connection pad 8 of a first conductor 4 that is placed on a substrate 8. The substrate 6 is planar and extends along the Y axis. The first conductor 4 comprises a proximal portion that extends along the Y axis and an intermediate portion that extends along the Z axis. The distal portion of the conductor 4 is formed as the connection pad 8 that is configured and shaped to be attached to the substrate by using an ultrasonic welding process.
Fig. 3B illustrates the substrate 6 shown in Fig. 3A in a configuration, in which a connection pad 8' of a second conductor 4' is placed on the top of the connection pad 8 of the first connector 4. The second conductor 4' comprises a proximal portion that extends along the Y axis and an intermediate portion that extends along the Z axis. The distal portion of the second conductor 4' is formed as a connection pad 8' that is configured to be attached to the top of the connection pad 8 of the first connector 4 by using an ultrasonic welding process. Fig. 3C illustrates the substrate 6 shown in Fig. 3B in a configuration, in which a third connection pad 8' of a third conductor 4' is placed on the top of the connection pad 8' of the second connector 4'. The distal portion of the third conductor 4" is formed as a connection pad 8" that is designed to be fixed to the top of the connection pad 8' of the second connector 4' by using an ultrasonic welding process.
Fig. 4 illustrates how the ultrasonic welding process can be carried out by using a sonotrode 10. A connection pad 8 of a first connector 4 and a connection pad 8' of a second connector 4' is placed on a substrate 6 like the one illustrated in Fig. 3B. A sonotrode 10 comprising a stack of piezoelectric transducers (not shown) attached to a tapering rod.
The distal portion sonotrode 10 is brought into contact with the top surface of the connection pad 8' of the second connector 4'. The longitudinal axis of the sonotrode 10 extends parallel with the normal axis (Z axis) of the substrate 6. The first conductor 4 comprises a proximal portion that extends along the Y axis and an intermediate portion that extends along the Z axis. Likewise, the second conductor 4' comprises a proximal portion that extends along the Y axis and an intermediate portion that extends along the Z axis.
The connection pads 8, 8' and the portion of the substrate 6 to which the connection pads 8, 8' are attached, are plate-formed and extend along the Y axis.
It is an advantage that the sonotrode delivers energy directly to the welding contact area with limited diffraction. Due to this, the vibrations will not damage any surrounding electronic components placed on the substrate 6. Accordingly, the use of a sonotrode to carry out the welding process seems to be very appealing is advantageous. The height (thickness) height H2 of the connection pad 8' of the second connector 4' equals the height Hi of the connection pad 8 of the first connector 4. The height H3 of the substrate 6 corresponds to the height Hi, H2 of any of the connection pads 8, 8'. It is, however, possible to apply a substrate having another height H3.
In one embodiment, the height H2 of the connection pad 8' of the second connector 4' differs from the height Hi of the connection pad 8 of the first connector 4.
It can be seen that the length Li of the contact surface between the connection pad 8' of the second connector 4' and the connection pad 8 of the first connector 4 is larger than the height Hi, H2 of any of the connection pads 8, 8'.
The length L2 of the contact surface between the connection pad 8 of the first connector 4 and the substrate 6 is larger than the height Hi, H2 of any of the connection pads 8, 8'. In fact, the length L2 of the contact surface between the connection pad 8 of the first connector 4 and the substrate 6 is larger than the length Li of the contact surface between the connection pad 8' of the second connector 4' and the connection pad 8 of the first connector 4.
Fig. 5 illustrates the inventive method as a flowchart.
The method starts 100 by obtaining a substrate 6 and two or more conductors 4, 4', 4" wherein each conductor 4, 4', 4" comprises a connection pad 8, 8'.
At step 101, a first connection pad 8 of a first conductor 4 is placed in a first position and a second connection pad 8' of a second conductor 4' is placed in a second position, so that the first connection pad 8 of the first conductor 4 is arranged between the second connection pad 8' of the second conductor 4' and the substrate 6.
At step 102, a welding process is carried out in which the second connection pad 8' of the second conductor 4', the first connection pad 8 of the first conductor 4 are welded to each other and to the substrate 6.
The method is then completed as step 103.
In an optional step 104, which may be provided between step 101 and 102, one or more additional connection pads 8, 8' of one or more additional conductors 4" may be placed on the top of the second connection pad 8' of the second conductor 4' before the welding process is carried out.
List of reference numerals
2 Metal terminal
4, 4', 4" Conductor
6 Substrate
8, 8' Connection pad
10 Welding device
100, 101, Steps in the inventive
103, 104 connection method
X, Y, Z Axis
Hi, H2, H3 Height (thickness)
LI, L2 Length

Claims

Claims
1. A method for connecting two or more conductors (4, 4', 4") to a substrate (6), wherein each conductor (4, 4', 4") comprises a connection pad (8, 8'), wherein the method comprises the steps of: a) placing a first connection pad (8) of a first conductor (4) in a first position and placing a second connection pad (8') of a second conductor (4') in a second position, in which the first connection pad (8) of the first conductor (4) is arranged between the second connection pad (8') of the second conductor (4') and the substrate (6) and b) carrying out a welding process, in which the second connection pad (8') of the second conductor (4'), the first connection pad (8) of the first conductor (4) are welded to each other and to the substrate (6).
2. A method according to claim 1, characterised in that the method comprises the step of providing the connection pads (8, 8') at the distal end of the conductors (4, 4', 4").
3. A method according to claim 1 or 2, characterised in that the welding process is carried out by using ultrasonic welding.
4. A method according to claim 3, characterised in that the ultrasonic welding process is a torsion welding process.
5. A method according to claim 3 or 4, characterised in that the ultrasonic welding process is a process, in which ultrasonic vibrations are created by using a sonotrode (10).
6. A method according to one of the preceding claims, characterised in that the method comprises an additional step, in which one or more additional connection pads (8, 8') of one or more additional conductors (4") are placed on the top of the second connection pad (8') of the second conductor (4') before the welding process is carried out.
7. A method according to one of the preceding claims, characterised in that only the connection pads (8, 8') of the conductors (4, 4', 4") overlap when viewed along an axis (Z) which is orthogonal to the plane of the connection pads (8, 8').
8. An electronic module comprising two or more conductors (4, 4', 4") each comprising a connection pad (8, 8') that are attached to a substrate (6), characterised in that: a) a first connection pad (8) of a first conductor (4) is placed in a first position and a second connection pad (8') of a second conductor (4') is placed in a second position, in which the first connection pad (8) of the first conductor (4) is arranged between the second connection pad (8') of the second conductor (4') and the substrate (6) and b) the second connection pad (8') of the second conductor (4'), the first connection pad (8) of the first conductor (4) are welded to each other and to the substrate (6) by means of a welding process.
9. An electronic module according to claim 8, characterised in that the connection pads (8, 8') are provided at the distal end of the conductors (4, 4', 4").
10. An electronic module according to one of the claims 8-9, characterised in that the electronic module comprises one or more additional connection pads (8, 8') of one or more additional conductors (4"), wherein the additional connection pads (8, 8') are placed on the top of the second connection pad (8') of the second conductor (4'), wherein the connection pads (8) of all the conductors (4) are welded to each other and to the substrate (6) by means of a welding process. 16
11. An electronic module according to one of the claims 8-10, characterised in that the welding process is ultrasonic welding.
12. An electronic module according to one of the claims 8-11, characterised in that the ultrasonic welding process is a torsion welding process.
13. An electronic module according to one of the claims 8-12, characterised in that the ultrasonic welding process, is a process in which ultrasonic vibrations are created by using a sonotrode (10).
14. An electronic module according to one of the claims 8-13, characterised in that only the connection pads (8, 8') of the conductors (4, 4', 4") overlap when viewed along an axis (Z) which is orthogonal to the plane of the connection pads (8, 8').
PCT/EP2021/075243 2020-09-16 2021-09-14 Electronic module and method for connecting several conductors to a substrate WO2022058311A1 (en)

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JP2812104B2 (en) 1992-10-26 1998-10-22 松下電器産業株式会社 Ultrasonic wire bonding equipment
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US4004726A (en) * 1974-12-23 1977-01-25 Western Electric Company, Inc. Bonding of leads
US20170086313A1 (en) * 2014-05-19 2017-03-23 Robert Bosch Gmbh Electronic Control Module, in Particular for Gear Mechanism Control, with Electrical Components Which Are Welded to Press Contacts
US20180242454A1 (en) * 2017-02-22 2018-08-23 Lg Chem, Ltd. Printed circuit board and a method of bonding electrode lead of battery to printed circuit board
US20190115704A1 (en) * 2017-10-13 2019-04-18 Kulicke and Soffa Indsutries,Inc. Conductive terminals, busbars, and methods of preparing the same, and methods of assembling related power

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