CN113560724B

CN113560724B - Laser welding method for copper sheet of power battery

Info

Publication number: CN113560724B
Application number: CN202110935671.7A
Authority: CN
Inventors: 张长明; ***; 唐成华; 凌小康; 章恒
Original assignee: SHENZHEN BOMIN ELECTRONIC CO Ltd
Current assignee: SHENZHEN BOMIN ELECTRONIC CO Ltd
Priority date: 2021-08-16
Filing date: 2021-08-16
Publication date: 2023-05-23
Anticipated expiration: 2041-08-16
Also published as: CN113560724A

Abstract

The invention discloses a method for laser welding of a power battery copper sheet, which comprises the steps of manufacturing a power battery PCB; and correspondingly fixing the power battery PCB and the galvanized copper sheet to be welded in a prefabricated tooling jig, and performing laser welding. The invention provides a method for laser welding of a power battery copper sheet, provides preparation of materials and tools during laser welding, performance of a machine and requirements on laser welding quality, and provides welding spot arrangement and production parameters of laser welding.

Description

Laser welding method for copper sheet of power battery

Technical Field

The invention belongs to the technical field of laser welding, and particularly relates to a method for laser welding of a power battery copper sheet.

Background

Laser is another important invention after nuclear, computer, semiconductor for the 20 th century. Atomic light is excited, so the name "laser": electrons in atoms absorb energy and then transition from a low energy level to a high energy level, and when the electrons fall back from the high energy level to the low energy level, the released energy is emitted in the form of photons. The attracted (excited) photon beam (laser) has high uniformity of photon optical characteristics. Compared with a common light source, the laser has good monochromaticity, high brightness and good directivity. Laser applications are very wide and include laser marking, laser welding, laser cutting, fiber optic communication, laser ranging, laser radar, laser weapon, laser record, laser vision correction, laser beauty treatment, laser scanning, laser mosquito killer, LIF nondestructive detection technology, and the like.

The application of laser in PCB from laser drilling in HDI at the beginning of 21 st century to laser cutting of metal base in the embedding technology in recent years is said to be more and more widely applied in PCB. The traditional welding mode of the power battery copper sheet has smaller tensile capacity and faster heat conduction of the copper-based position, which is not beneficial to the traditional welding mode; the steel is manufactured by adopting tapping and threading modes, and the tensile capacity meets the requirements, but the production efficiency is extremely low, the degree of automation is extremely poor, and the time effect of mass production is limited. In view of this, the application of laser welding of copper sheets in power cells to PCBs has been at a very open corner.

Disclosure of Invention

The invention aims to provide a method for laser welding of a power battery copper sheet, which aims to solve the problems in the prior art in the background art. In order to achieve the above purpose, the invention adopts the following technical scheme:

a method for laser welding a power battery copper sheet, comprising:

manufacturing a power battery PCB;

and correspondingly fixing the power battery PCB and the galvanized copper sheet to be welded in a prefabricated tooling jig, and performing laser welding.

Further, the manufacturing of the power battery PCB includes: cutting, transferring an inner layer pattern, laminating, drilling, plating copper, transferring the pattern, etching, welding characters, forming, correspondingly manufacturing a power battery PCB, and performing depth control milling on a position on the PCB which is not contacted with the welding spring piece.

Further, a slot for fixing the power battery PCB and a pressing device for fixing the galvanized copper sheet to be welded are arranged in the tooling jig.

Further, the laser welding includes:

placing the power battery PCB in a slot of a tooling jig, fixing a galvanized copper sheet to be welded through the pressing device, positioning the galvanized copper sheet to be welded above the slot, and adjusting the pressing device to enable the galvanized copper sheet to be welded to correspond to a position to be welded on the power battery PCB;

and (3) adjusting the laser point focus, welding copper sheets in a transverse three-row mode, and keeping the welding spot spacing to be 0.4-0.5mm.

Further, the solder joint size, solder joint pitch, and board appearance were visually inspected after soldering.

Further, connecting the welded galvanized copper sheet with a fixture, respectively pulling the copper sheets at two sides, and measuring the pull-off force value of the copper sheets and the PCB, if the pull-off force value is larger than 200N, judging that the pull-off force test is qualified.

Further, the thickness of the galvanized copper sheet is 0.3mm plus or minus 0.015mm, and the dimensional tolerance of the length, the width, the bending position and the like is plus or minus 0.1mm.

Further, the power of the equipment corresponding to the laser welding is 600-1500W.

Further, the size of the depth control milling is that the position of the shrapnel to be welded is vacated and reduced by 0.1mm, and the depth control milling depth is required to be 0.5mm plus or minus 0.1mm.

Compared with the prior art, the method has the following advantages:

the invention provides a method for laser welding of a power battery copper sheet, provides preparation of materials and tools during laser welding, performance of a machine and requirements on laser welding quality, and provides welding spot arrangement and production parameters of laser welding. .

Drawings

FIG. 1 is a schematic diagram of the structure of the present invention;

FIG. 2 is a schematic view of a vertical row of welds of the present invention;

FIG. 3 is a schematic view of a transverse arrangement of welding spots according to the present invention;

FIG. 4 is a schematic diagram of an S-shaped solder joint pattern according to the present invention;

FIG. 5 is a schematic diagram showing the relationship between penetration and tensile testing in accordance with the present invention;

Detailed Description

The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. The specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. All other embodiments, which can be made by one of ordinary skill in the art without undue burden on the person of ordinary skill in the art based on embodiments of the present invention, are within the scope of the present invention.

The present invention provides a method of laser welding a power cell copper sheet as shown in figures 1-4,

requirements of laser welding on raw materials

The PCB1 to be welded by laser is required to be additionally provided with a depth control milling flow after being molded, the depth control milling is carried out on the position which is not contacted with the welding shrapnel, the size of the depth control milling is referred to the position which is free of the shrapnel to be welded and is reduced by more than 0.1mm, and the depth control milling is required to be 0.5mm+0.1mm/-0mm. After depth control milling is completed, small steps are formed at the positions to be welded and the positions without welding, then surface treatment of nickel-gold is performed, so that the adhesion between the welding elastic sheet 2 and the welding spot of the PCB1 is ensured, the positions to be welded of the PCB1 are required to be flat, and the bonding force of the nickel-gold layer is good. The galvanized copper sheet 2 is clean and flat, and has the thickness of 0.3mm plus or minus 0.015mm, and the dimensional tolerance of plus or minus 0.1mm of length, width, bending position and the like.

Quality requirements of laser welding

Appearance inspection: after laser welding, the size of the welding spots, the spacing of the welding spots and the appearance of the plate are checked visually, no welding slag and black stains exist after laser welding, the solder mask layer of the PCB1 at the back of the welding spots is undamaged, and the galvanized copper sheet 2 is free from knocked and bent. And the groove direction of the galvanized copper sheet 2 is upwards placed after laser welding.

And (3) tensile force test: the galvanized copper sheet 2 is connected with the fixture, punching, fixture or welding is adopted, the direction shown by the picture is used as a reference, the left copper sheet is pulled towards the left side, the right copper sheet is pulled towards the right side, the pull-out force values of the copper sheets and the PCB are respectively measured, if the pull-out force value is larger than 200N, the copper sheets are not dropped, the experiment is stopped, and the pull-out test is judged to be qualified.

The equipment requirements are as follows:

tool fixture 3, laser welding is to weld under a steady state, improves laser welding's machining efficiency, improves whole accurate degree to adapt to various types of PCB welding, just need a suitable mould, the fixed PCB of mould fluting, and have press type device fixed galvanized copper sheet of waiting welded, reach laser welding's at every turn uniformity and accuracy.

The performance of mechanical equipment, the power of laser welding equipment is 600-1500W, the specific use parameters of the machine model are MGL-BEVMZ-3P4S-3704100 and are shown in table 1;

table 1 parameter table of laser welding apparatus

Focal length mm	Power w	Pulse width ms	Frequency Hz	Welding speed mm/s	Welding length mm
						250	800	10	10	4.0	2.5

Copper sheet welding method

Placing the PCB1 on the tool, placing the copper sheet upwards in the groove, pressing the tool, adjusting the laser spot to focus, and welding the direction: the welding effect of different welding directions is confirmed, the test is carried out in the horizontal row, the vertical row and the S-shaped direction, and the horizontal row can only weld two rows under the influence of the welding position;

the three welding modes are respectively subjected to tensile test, the tensile test of the vertical row and the S-shaped welding is similar to 150-200N from the result of the tensile test, the result of the horizontal row tensile test is poor, and the space for further improving the tensile force is not provided for the S-shaped welding, so that the vertical row welding mode is selected, and DOE experiments are carried out from the influence factors such as the number of welding rows, the number of welding points, the welding length and the like, so that the optimal welding mode is obtained.

The influence factors are respectively set as the number of welding rows (2 rows and 3 rows), the number of welding points (6, 7, 8 and 9), the welding length (5.0 mm, 4.5mm and 4.0 mm), and the three factors are configured at different levels, as shown in Table 2:

TABLE 2 design of influence factors related to each other

It is explained here that the horizontal factor of the welding length is selected, the total width of the galvanized shrapnel is 5.5mm, if the welding length is implemented according to 5.5mm, the stress position is only the first row, the two latter rows cannot be stressed, the tensile force test effect is poor, so that the horizontal factor of 0.5mm below 5.5mm is selected, 25 sets are manufactured by orthogonal experiment full factor experimental design each scheme, and the tensile force test standard is improved to 220N to confirm the bad quantity, as shown in table 3:

TABLE 3 orthogonal experimental design and experimental results of related influencing factors

From the above, the tensile test result of welding 3 rows is obviously better than the tensile test result of welding 2 rows, and is influenced by the welding position, so that only 3 rows can be welded at most. The welding spot number is obvious, and the welding spot number is better at 7-8. The welding length is shown as the shorter length, the better the tensile force effect is, the tensile force born by the 1 st row is more easily transferred to the 2 nd row and the 3 rd row due to the shorter length, so that the tensile force test result is increased, the welding length does not find the optimal factor, and a shorter welding length experiment can be further carried out to confirm the optimal welding length.

And (3) selecting welding lengths of 3.5mm, 3.0mm and 2.5mm again for experiments, confirming that the welding length is optimal when the welding length is 3.0mm, and the experimental 25set tensile test results are all above 220N, so that the quality requirements of tensile test 200N can be completely met, the tensile test effect and tensile test equipment are as shown in figure 1, welding slices and welding point penetration slices are confirmed, and the penetration is more than or equal to 0.3 mm.

Influence of penetration on tensile force

As shown in FIG. 5, the number of welding rows, the number of welding points and the welding length are studied and analyzed before, and in the customer standard, the requirement of the customer on the penetration is not less than 0.3mm, and the main view is as follows: to prove whether this is true, three rows of data are made of 7 points transversely arranged when the welding length is 3.0mm, the penetration is controlled by different laser energy, and the tensile force at different penetration is tested. From the test results, the penetration is not deeper and better, but reaches the strongest tensile force at more than 0.35mm, and then gradually descends, which can be interpreted as that the penetration can bear the tensile force and the thickness of the galvanized copper sheet is related, when the penetration is larger than the thickness of the copper sheet, the tensile force reaches the top point, the welding contact surface of laser welding is not increased any more when the penetration is excessive, the bearable tensile force is not increased any more, and the rationality of the requirements of customers on the penetration is further verified.

Finally, it should be noted that: the foregoing description of the preferred embodiments of the present invention is not intended to limit the invention, but rather, although the invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described, or equivalents may be substituted for elements thereof, and any modifications, equivalents, improvements or changes may be made without departing from the spirit and principles of the invention.

Claims

1. A method for laser welding a power battery copper sheet, comprising: firstly, carrying out depth control milling on a position, which is not contacted with a welding spring piece, on a PCB to be welded by laser, wherein the depth control milling is carried out by taking the position of the welding spring piece as reference, and reducing the size by more than 0.1mm, the depth control milling is required to be 0.5mm plus or minus 0.1mm, a small step is formed between the position to be welded and the position which is not required to be welded after the depth control milling is completed, and then, carrying out surface treatment of nickel-plated gold, so as to ensure the adhesiveness between the welding spring piece and a welding point of the PCB, wherein the welding spring piece is a galvanized copper sheet, the thickness is 0.3mm plus or minus 0.015mm, and the dimensional tolerance of the long, wide and bending positions is plus or minus 0.1mm; the method comprises the steps of adopting a die to slot and fix a PCB, utilizing a pressing device to fix a galvanized copper sheet to be welded, welding the galvanized copper sheet with a welding spot of the PCB through laser welding equipment, visually checking the size of the welding spot, the distance between the welding spots and the appearance of a plate after laser welding, ensuring that a welding slag and black stains are avoided after laser welding, ensuring that a PCB solder mask on the back of the welding spot is intact and undamaged, ensuring that the galvanized copper sheet is free from collision and bending, and ensuring that a groove of the galvanized copper sheet is upwards placed after laser welding; and then connecting the galvanized copper sheet with a clamp, pulling the left copper sheet towards the left side, pulling the right copper sheet towards the right side, respectively measuring pull-off force values of the copper sheets and the PCB, and if the pull-off force value is more than 200N, stopping the experiment and judging that the pull-off test is qualified.