Welding method of bottom-plate-free IGBT (insulated gate bipolar transistor) module

Abstract

The invention discloses a welding method for a bottom-plate-free IGBT (Insulated Gate Bipolar Translator) module, which comprises the following steps of: after pins are inserted into a clamp by equipment, directly tinning the upper end surfaces of metal pins, covering a DBC (Direct Bonding Copper) substrate on the metal pins, and directly feeding the DBC substrate into a heating cavity of a tunnel furnace for heating without turning over; gas in the heating cavity heats solder paste through the hollowed-out opening reserved in the bottom plate of the welding unit of the clamp, welding of a module without a bottom plate is carried out, the dislocation influence caused by overturning is reduced, a DBC substrate cannot be polluted and oxidized by adopting a gas heating mode in the welding process, the hollowed-out design of the welding unit of the clamp is beneficial for improving the heat convection heating effect, and the welding quality of the DBC substrate is improved. The base plate-free IGBT module is fully and uniformly heated, the welding consistency is good, the tin adhesion phenomenon and the pseudo soldering phenomenon between the terminals can be avoided, the operation is simple and efficient, and the welding is accurate and reliable.

Description

Technical Field

[0001] This invention relates to IGBT (Insulated Gate Bipolar Transistor) modules, and more particularly to a method for soldering a baseboard-less IGBT module. Background Technology

[0002] like Figure 1 As shown, the baseless IGBT module includes an IGBT chip 39, a DBC (direct bonding copper ceramic) substrate 31, a metal pin 33, an aluminum wire 38, and a housing 4; the IGBT chip 39 and the metal pin 33 are soldered onto the conductive copper layer on the front side of the DBC substrate 31.

[0003] The common soldering method for baseless IGBT modules is vacuum furnace soldering. A vacuum furnace is a device that heats in a vacuum environment. It is connected to a high-vacuum pump system via pipes within a sealed furnace chamber, which is enclosed by a metal casing or a quartz glass cover. The heating system within the furnace chamber can be directly heated by an electric resistance wire (such as a tungsten wire) or by high-frequency induction heating. During the reflow soldering process, the back of the DBC substrate 31 is placed on a carrier. Metal pins 33, inserted into the positioning holes of the fixture, are pressed vertically downwards onto the conductive copper solder joints on the front side of the pre-coated solder paste DBC substrate 31. During the reflow operation, the fixture needs to be flipped along with the DBC substrate 31 and the carrier. This flipping process can easily cause misalignment of the metal pins 33. Furthermore, because the metal pins 33 are extremely lightweight, some pins may get caught in the positioning holes of the fixture during the reflow operation. Additionally, the back of the DBC substrate 31 is prone to contamination and oxidation due to contact heating after soldering. Moreover, when the spacing between the metal pins 33 is small, solder bridging may occur between some pins. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a welding method for IGBT modules without a base plate, which does not cause DBC substrate contamination and oxidation, has good welding consistency, is simple and efficient to operate, and is accurate and reliable to weld.

[0005] To solve the above-mentioned technical problems, the present invention provides a welding method for a baseless IGBT module, which includes the following steps;

[0006] S1. Prepare fixture 1, wherein the fixture has at least one welding unit;

[0007] The welding unit is a groove formed by the bottom plate and the side wall;

[0008] The lateral dimension of the inner side of the groove is consistent with the outline of the DBC substrate 31 of the IGBT module.

[0009] The bottom plate 11 of the groove has multiple positioning holes 12 corresponding to the area of ​​the conductive copper layer solder joint on the front side of the DBC substrate 31.

[0010] The bottom plate 11 of the groove is hollowed out in the area on the front of the DBC substrate 31 where there are no solder joints;

[0011] S2. Insert a metal pin 33 into the corresponding positioning hole 12 of the bottom plate 11 of the groove with the opening facing upward in the welding unit, and apply solder paste directly to the upper end of the metal pin 33.

[0012] S3. Place the DBC substrate 31 at the top of the groove and press the DBC substrate 31 so that its front side abuts against the upper end of the metal pin 33, thus completing the assembly of the welding unit of the DBC substrate 31, the metal pin 33 and the fixture 1.

[0013] S4. Keeping the fixture 1 in the lower position and the DBC substrate 31 in the upper position, the fixture 1, which is assembled with the DBC substrate 31 and the metal pin 33, is sent into the heating chamber of the tunnel furnace for heating to melt the solder paste and perform soldering of the conductive copper layer solder joints on the front side of the DBC substrate 31 of the bottomless IGBT module to the metal pin 33.

[0014] Preferably, the heating chamber heats the fixture 1, which is assembled with the DBC substrate 31 and metal pins 33, simultaneously from above and below through gas thermal convection.

[0015] Preferably, the tunnel furnace is a tunnel-type nitrogen vacuum furnace.

[0016] Preferably, the tunnel furnace further includes a cooling chamber;

[0017] In step S4, the fixture 1, which is assembled with DBC substrate 31 and metal pins 33, is sent into the heating chamber of the tunnel furnace to heat and melt the solder paste. Then it is sent into the cooling chamber to cool the DBC substrate 31 to room temperature and then transferred to the next process.

[0018] Preferably, the cooling chamber adopts a hybrid mode of air cooling and water cooling to cool the DBC substrate 31 to room temperature.

[0019] Preferably, the tunnel furnace further includes a vacuum chamber;

[0020] In step S4, the fixture 1, which is assembled with DBC substrate 31 and metal pins 33, is sent into the heating chamber of the tunnel furnace to heat and melt the solder paste. Then it is sent into the vacuum chamber to remove air bubbles in the solder paste and reduce air bubbles and voids in the solder paste. Then it is sent into the cooling chamber to cool the DBC substrate 31 to room temperature and then transferred to the next process.

[0021] Preferably, the tunnel furnace is equipped with at least two real-time flux recovery devices in the heating chamber to recover flux residues left in the heating chamber when the solder paste melts.

[0022] Preferably, the bottom surface of the fixture 1 has at least three support columns 10.

[0023] The welding method for the bottomless IGBT module of the present invention allows for direct soldering of the metal pins 33 directly on the upper surface of the metal pins 33 after the device inserts the pins using the fixture 1 without flipping, ensuring control of the amount of solder paste on the small welding surface. After soldering, the DBC substrate 31 is placed on the metal pins 33 and directly fed into the heating chamber of the tunnel oven without flipping. The gas in the heating chamber heats the solder paste through the pre-reserved cutout on the bottom plate of the welding unit of the fixture 1, melting the solder paste. The bottomless IGBT module is welded in the tunnel oven using an inverted welding method (DBC on top, terminals on the bottom), reducing the misalignment caused by flipping. The gas heating method during welding does not cause contamination or oxidation of the DBC substrate 31. The cutout design of the welding unit of the fixture 1 is conducive to improving the heat convection heating effect, ensuring that the bottomless IGBT module is fully and evenly heated, resulting in good welding consistency and avoiding solder adhesion and cold solder joints between terminals. The operation is simple and efficient, the welding is accurate and reliable, and the production efficiency is improved. Attached Figure Description

[0024] To more clearly illustrate the technical solution of the present invention, the accompanying drawings used in the present invention will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0025] Figure 1 This is a schematic diagram of a baseless IGBT module structure;

[0026] Figure 2 This is a schematic diagram of the assembly of a DBC substrate, metal pins, and fixture in an embodiment of the welding method for a baseless IGBT module of the present invention.

[0027] Figure 3 This is a flowchart of an embodiment of the welding method for the bottomless IGBT module of the present invention.

[0028] Explanation of reference numerals in the attached figures:

[0029] 39 IGBT chip; 31 DBC substrate; 33 metal pin; 38 aluminum wire; 4 housing; 1 clamp; 11 base plate; 12 positioning hole; 10 support column. Detailed Implementation

[0030] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0031] Example 1

[0032] A soldering method for a base-plate-less IGBT module is as follows: Figure 3 As shown, it includes the following steps;

[0033] S1. Prepare fixture 1, wherein the fixture has at least one welding unit;

[0034] The welding unit is a groove formed by the bottom plate and the side wall;

[0035] The lateral dimension of the inner side of the groove is consistent with the outline of the DBC (direct bonding copper ceramic) substrate 31 of the IGBT module.

[0036] The bottom plate 11 of the groove has multiple positioning holes 12 corresponding to the area of ​​the conductive copper layer solder joint on the front side of the DBC substrate 31.

[0037] The bottom plate 11 of the groove is hollowed out in the area on the front of the DBC substrate 31 where there are no solder joints;

[0038] S2. Insert a metal pin 33 (used as a power terminal and signal terminal) into the corresponding positioning hole 12 of the bottom plate 11 of the groove with the opening facing upward in the soldering unit, and apply solder paste directly to the upper end of the metal pin 33.

[0039] S3. Place the DBC substrate 31 at the top of the groove, press the DBC substrate 31 so that its front side abuts against the upper end of the metal pin 33, completing the assembly of the DBC substrate 31, metal pin 33, and the welding unit of the fixture 1. Figure 2 As shown;

[0040] S4. Keeping the fixture 1 in the lower position and the DBC substrate 31 in the upper position, the fixture 1, which is assembled with the DBC substrate 31 and the metal pin 33, is sent into the heating chamber of the tunnel furnace for heating to melt the solder paste and perform soldering of the conductive copper layer solder joints on the front side of the DBC substrate 31 of the bottomless IGBT module to the metal pin 33.

[0041] Preferably, the heating chamber heats the fixture 1, which is assembled with the DBC substrate 31 and metal pins 33, simultaneously from above and below through gas thermal convection.

[0042] Preferably, the tunnel furnace is a tunnel-type nitrogen vacuum furnace.

[0043] The soldering method for the bottomless IGBT module in Example 1 involves the fixture 1 directly applying solder to the upper surface of the metal pin 33 after the pin insertion is completed by the equipment, without flipping it, ensuring control of the amount of solder paste on the small soldering surface. After soldering, the DBC substrate 31 is placed on the metal pin 33 and directly sent into the heating chamber of the tunnel oven without flipping. The gas in the heating chamber heats the solder paste through the pre-reserved cutout on the bottom plate of the soldering unit of the fixture 1, melting the solder paste. The bottomless IGBT module is soldered in the tunnel oven using an inverted (DBC on top, terminals on the bottom) soldering method, reducing the misalignment caused by flipping. The gas heating method during soldering does not cause contamination or oxidation of the DBC substrate 31. The cutout design of the soldering unit of the fixture 1 is conducive to improving the heat convection heating effect, so that the bottomless IGBT module is fully and evenly heated, resulting in good soldering consistency and avoiding solder adhesion and cold solder joints between terminals. The operation is simple and efficient, the soldering is accurate and reliable, and the production efficiency is improved.

[0044] Example 2

[0045] The welding method for a bottomless IGBT module in Embodiment 1 includes a tunnel furnace that further comprises a cooling chamber;

[0046] In step S4, the fixture 1, which is assembled with DBC substrate 31 and metal pins 33, is sent into the heating chamber of the tunnel furnace to heat and melt the solder paste. Then it is sent into the cooling chamber to cool the DBC substrate 31 to room temperature and then transferred to the next process.

[0047] Preferably, the cooling chamber adopts a hybrid mode of air cooling and water cooling to cool the DBC substrate 31 to room temperature.

[0048] Example 3

[0049] The welding method for the bottomless IGBT module in Example 2, wherein the tunnel furnace further includes a vacuum chamber;

[0050] In step S4, the fixture 1, which is assembled with DBC substrate 31 and metal pins 33, is sent into the heating chamber of the tunnel furnace to heat and melt the solder paste. Then it is sent into the vacuum chamber to remove air bubbles in the solder paste and reduce air bubbles and voids in the solder paste. Then it is sent into the cooling chamber to cool the DBC substrate 31 to room temperature and then transferred to the next process.

[0051] Example 4

[0052] The welding method for the bottomless IGBT module in Example 2 is provided with at least two flux real-time recovery devices in the heating chamber of the tunnel furnace, which are used to recover the flux residue in the heating chamber when the solder paste is heated and melted.

[0053] The soldering method for the baseless IGBT module in Example 4 can improve flux recovery capability and reduce flux residue.

[0054] Example 5

[0055] The welding method for the bottomless IGBT module in Example 1 has at least three support columns 10 formed on the bottom surface of the fixture 1.

[0056] The welding method for the bottomless IGBT module in Example 5 involves the fixture 1 being mounted on a carrier inside the tunnel furnace heating chamber via the support columns 10 on the bottom surface. This reduces contact heating and helps improve the heat distribution consistency of the bottomless IGBT module.

[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A soldering method of a no-submount IGBT module, characterized by, It comprises the following steps: S1. Prepare a clamp (1) formed with at least one welding unit; The welding unit is a groove formed by a bottom plate and a side wall; The transverse dimension of the inside of the groove is consistent with the profile of the DBC substrate (31) of the IGBT module; The bottom plate (11) of the groove corresponds to the area of the soldering point of the front conductive copper layer of the DBC substrate (31) and is formed with a plurality of positioning holes (12); The bottom plate (11) of the groove is hollowed out corresponding to the area without soldering point on the front of the DBC substrate (31); S2. Insert a metal needle (33) into the corresponding positioning hole (12) of the bottom plate (11) of the groove with the opening of the welding unit facing upwards, and directly point the tin paste on the upper end of the metal needle (33); S3. Place the DBC substrate (31) at the top of the groove, press the DBC substrate (31) so that the front surface abuts against the upper end of the metal needle (33), and complete the assembly of the DBC substrate (31), the metal needle (33) and the welding unit of the clamp (1); S4. Keep the clamp (1) in the state that the lower DBC substrate (31) is on top, and send the clamp (1) assembled with the DBC substrate (31) and the metal needle (33) into the heating cavity of the tunnel furnace for heating, so that the tin paste is melted, and the soldering of the soldering point of the front conductive copper layer of the DBC substrate (31) of the bottom plate-free IGBT module and the metal needle (33) is carried out.

2. The welding method of the bottom plate-free IGBT module according to claim 1, characterized in that, The heating cavity simultaneously heats the clamp (1) assembled with the DBC substrate (31) and the metal needle (33) from above and below through the heat transfer mode of gas thermal convection.

3. The welding method of the bottom plate-free IGBT module according to claim 1, characterized in that, The tunnel furnace is a tunnel type nitrogen vacuum furnace.

4. The welding method of the bottom plate-free IGBT module according to claim 1, characterized in that, The tunnel furnace further comprises a cooling cavity; In step S4, after the tin paste is melted by sending the clamp (1) assembled with the DBC substrate (31) and the metal needle (33) into the heating cavity of the tunnel furnace, the DBC substrate (31) is cooled to room temperature by being sent into the cooling cavity, and then the next process is transferred.

5. The welding method of the bottom plate-free IGBT module according to claim 4, characterized in that, The cooling cavity adopts a mixed mode of air cooling and water cooling to cool the DBC substrate (31) to room temperature.

6. The welding method of the bottom plate-free IGBT module according to claim 4, characterized in that, The tunnel furnace further comprises a vacuum cavity; In step S4, after the tin paste is melted by sending the clamp (1) assembled with the DBC substrate (31) and the metal needle (33) into the heating cavity of the tunnel furnace, the DBC substrate (31) is cooled to room temperature by being sent into the cooling cavity, and then the next process is transferred.

7. The welding method of the bottom plate-free IGBT module according to claim 1, characterized in that, At least two real-time flux recycling devices are arranged in the heating cavity of the tunnel furnace to recycle the flux residue in the heating cavity when the tin paste is heated and melted.

8. The soldering method of a no-submount IGBT module according to claim 1, characterized by, The fixture 1 is formed with at least three support columns (10) on the bottom surface.

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