Laser soldering process for IGBT module substrate

Abstract

The application discloses a kind of laser resistance welding processes of IGBT module substrate, including IGBT mainboard and DBC substrate;The IGBT mainboard is obtained by laser slotting resistance welding slot, and the resistance welding slot is formed by laser heating oxidation in the metal component of IGBT mainboard;The DBC substrate is fixed on the IGBT mainboard by welding;When welding, solder flow is guided and prevented from overflowing by resistance welding slot, to avoid solder overflow or accumulation and then affect insulation performance, improve welding quality.The present application can prevent the accumulation and overflow of solder during IGBT welding, and improve the IGBT welding quality.

Description

Technical Field

[0001] This invention relates to the field of electronic technology, and in particular to a laser resist soldering process for IGBT module substrates. Background Technology

[0002] With the rapid economic development and technological advancements in various regions, IGBT modules are modular semiconductor products that are packaged by IGBT (Insulated Gate Bipolar Transistor) chips and FWD (Freewheeling Diode) chips through a specific circuit bridge. The packaged IGBT modules are directly applied to equipment such as frequency converters and UPS uninterruptible power supplies.

[0003] In the process of packaging IGBT chips into modules, ceramic copper-clad laminates (DBC boards) are generally used to achieve properties such as insulation, thermal conductivity, welding, and electrical conductivity. DBC consists of a ceramic substrate, a bonding adhesive layer, and a conductive layer. It refers to a special process method in which copper foil is directly bonded to the surface of an alumina or aluminum nitride ceramic substrate at high temperature. It has high thermal conductivity, high adhesion strength, excellent solderability, and excellent electrical insulation properties.

[0004] The product structure can be referenced from a ceramic copper-clad laminate device for IGBT power module packaging disclosed in publication number CN201821488564.4. This device includes a heat sink base, a DBC board, a bridge, IGBT chips, FWD chips, and aluminum wires. The DBC board is positioned above the heat sink base, with a first region on its inner side, a second region fixed inside, and a third region on its inner side. The bridge is fixed inside the third region. A solder mask frame is located inside the DBC board, and a fourth region is also located inside. This DBC board device for IGBT power module packaging includes IGBT chips, and the connection between the third region of the DBC board and the IGBT chips and FWD chips is soldering. Since solder is generated during chip soldering, if the solder is not properly channeled, it will accumulate and affect the chip. Summary of the Invention

[0005] The purpose of this invention is to provide a laser solder resist process for IGBT module substrates. This invention can prevent solder accumulation and overflow during IGBT soldering, thereby improving the IGBT soldering quality.

[0006] The technical solution of the present invention is a laser solder resist process for an IGBT module substrate, comprising an IGBT main board and a DBC substrate; the IGBT main board is laser-grooved to obtain a solder resist groove, which is formed by laser heating and oxidation of the metal components in the IGBT main board;

[0007] The DBC substrate is fixed to the IGBT motherboard by welding. During welding, the solder flows through the solder resist tank for guidance and spill prevention, avoiding solder overflow or accumulation that could affect insulation performance and improve welding quality.

[0008] In the laser solder resist process of the IGBT module substrate described above, the solder resist grooves are connected end to end.

[0009] In the aforementioned laser solder resist process for the IGBT module substrate, the solder resist groove is frame-shaped.

[0010] The aforementioned laser solder resist process for the IGBT module substrate involves forming the solder resist groove by laser heating and oxidation of nickel and copper in the IGBT motherboard.

[0011] In the aforementioned laser solder resist process for the IGBT module substrate, the IGBT main board is also covered with an isolation layer, the outline of which overlaps vertically with the outline of the IGBT main board.

[0012] In the aforementioned laser solder resist process for IGBT module substrates, the material of the isolation layer is solder resist ink.

[0013] In the aforementioned laser solder resist process for the IGBT module substrate, solder resist is printed on the isolation layer, and the space formed by the solder resist matches the protected circuit or IGBT chip.

[0014] The aforementioned laser solder resist process for the IGBT module substrate includes a first solder layer, an insulating layer, and a second solder layer. The first solder layer is soldered onto the motherboard, the insulating layer is attached to the first solder layer, and the second solder layer is attached to the insulating layer. The insulating layer is used to protect the IGBT chip and circuitry soldered onto the second solder layer.

[0015] In the aforementioned laser solder resist process for the IGBT module substrate, during the laser grooving process, the laser power is 30W, the frequency is 40kHz, the scanning speed is 1200mm / s, the horizontal spacing of the laser spot is 30μm, and the radius of the laser spot is 30μm. First, the first laser spot impacts and heats the IGBT motherboard, causing oxidation and roughening of the metal surface structure. Then, the front part of the second laser spot covers the oxidized and roughened part of the first laser spot, undergoing a second impact and heating to form a secondary roughened structure that covers the first roughened structure, thus forming a nano-flocculent double-layer roughened structure. The rear part of the second laser spot continues to oxidize and roughen the metal surface structure of the IGBT motherboard, and the impact and heating process is repeated by the next laser spot until the grooving is completed.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] 1. This invention creates a solder resist groove on the IGBT motherboard using laser grooving. During the soldering process between the IGBT motherboard and the DBC substrate, the solder flow is guided and prevented from overflowing through the solder resist groove, avoiding solder spillage or accumulation that could affect insulation performance and improving soldering quality. Simultaneously, the solder resist groove is formed by the oxidation of metal components in the IGBT motherboard through laser heating. Its metal oxide ensures that the solder resist groove is not easily soldered to the solder, thus improving solder resistance and guaranteeing soldering quality.

[0018] 2. The solder resist of this invention can protect circuit components during soldering, preventing damage and avoiding oxidation that occurs during soldering, thus preventing weld cracks and ensuring soldering quality. Furthermore, the solder resist can improve the high-temperature resistance of chips and circuit boards, extending their lifespan. Additionally, this invention effectively isolates the chip from the IGBT motherboard through the insulating layer within the DBC substrate, improving insulation performance.

[0019] 3. The present invention further optimizes the laser processing process. The first laser spot impacts and heats the IGBT motherboard, causing oxidation and roughening of the metal surface structure of the IGBT motherboard. Then, the front part of the second laser spot covers the part oxidized and roughened by the first laser spot, and a second impact and heating are performed to form a secondary roughened structure that covers the first roughened structure, thereby forming a nano-floc double-layer roughened structure. This nano-floc double-layer roughened structure has good contact performance and adhesion, and can absorb solder into the solder resist seam constructed by the nano-floc double-layer roughened structure, thereby improving the solder resist seam's ability to prevent overflow. Attached Figure Description

[0020] Figure 1 This is a schematic diagram of the structure of the IGBT motherboard and DBC substrate in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the IGBT motherboard in an embodiment of the present invention;

[0022] Figure 3 This is a schematic diagram of the solder resist groove in this embodiment;

[0023] Figure 4 This is a schematic diagram of laser spot processing;

[0024] Figure 5 An optical microscope image of the oxidized and roughened portion of the first laser spot;

[0025] Figure 6 This is an optical microscope image of the secondary roughened structure.

[0026] The present invention will be further described below with reference to the accompanying drawings and embodiments, but this should not be construed as limiting the present invention.

[0027] Example: A laser solder resist process for an IGBT module substrate, such as... Figure 1-3 As shown, it includes an IGBT motherboard 101 and a DBC substrate 104; the IGBT motherboard 101 is laser-grooved to obtain a solder resist groove, which is formed by the oxidation of metal components in the IGBT motherboard by laser heating, and the first and last ends of the solder resist groove are connected to form a frame shape, forming a solder resist frame groove 101a. There can be one or more solder resist frame grooves 101a, and two are provided in this embodiment.

[0028] The DBC base 104 board is fixed to the IGBT main board by welding. During welding, the solder flows through the solder resist groove to prevent overflow and avoid solder overflow or accumulation, which would affect the insulation performance and improve the welding quality.

[0029] Furthermore, the IGBT motherboard is also covered with an isolation layer 102, which is attached to the upper surface of the motherboard 101. This isolation layer 102 is solder resist ink (a material that prevents circuit board pads or pins from being soldered, composed of resin (acrylic resin), solvent (alcohol), and common curing agent (photocuring agent), and is commercially available). The outline of the isolation layer 102 overlaps vertically with the outline of the motherboard 101, completely covering the motherboard 101. Solder resist 103 is provided on the isolation layer. The solder resist 103 is green solder resist, printed on the upper surface of the isolation layer 102 by screen printing or pad printing. The space formed by the solder resist matches the protected circuit or IGBT chip. In this embodiment, the solder resist 103 is L-shaped, with four in a group, corresponding to the four corners of the IGBT motherboard.

[0030] Furthermore, the DBC substrate 104 includes a first solder layer, an insulating layer, and a second solder layer; the first solder layer is soldered onto the motherboard 101 and is a copper plate; the insulating layer is attached to the first solder layer and is a ceramic plate, which serves as insulation to protect the chip and circuit board soldered to the second solder layer; the second solder layer is attached to the insulating layer and is a copper plate.

[0031] In this embodiment, during the laser grooving process, the laser power is 30W, the frequency is 40kHz, the scanning speed is 1200mm / s, the horizontal spacing of the laser spot is 30μm, and the radius of the laser spot is 30μm. Figure 4As shown, the process begins by impacting and heating the IGBT motherboard with a first laser spot, causing oxidation and roughening of the metal surface. Then, the front portion of a second laser spot covers the oxidized and roughened portion of the first laser spot, undergoing a second impact and heating process to form a secondary roughened structure that covers the first roughened structure, thus creating a nano-flocculent double-layer roughened structure. The rear portion of the second laser spot then continues to oxidize and roughen the metal surface of the IGBT motherboard, and the impact and heating process is repeated with a subsequent laser spot until the grooving is complete. It should be noted that the width of the solder mask groove can be adjusted based on the number of grooving operations performed by the laser spot. Figure 4 The width of the medium-resistance welding bath is 90 μm. Furthermore, the applicant used an optical microscope to observe the oxidation and roughening of the first laser spot and the secondary roughening structure, the results of which are as follows: Figure 5 and Figure 6 As shown. From Figure 5 It can be seen that the first laser spot oxidation and roughening section has a large number of pits and spikes, indicating that the laser spot oxidation of the IGBT motherboard forms a good roughening structure. Figure 6 It can be seen that the secondary roughening structure has more pits and spikes, which indicates that the secondary impact and heating of the laser spot can form a better rough structure, which is a nano-floc double-layer rough structure. This rough structure has good contact performance and adhesion, and can absorb solder into the solder resist seam, thereby improving the solder resist seam's ability to prevent overflow.

[0032] In summary, this invention can prevent solder buildup and overflow during IGBT soldering, thereby improving the IGBT soldering quality.

[0033] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A laser resist soldering process for an IGBT module substrate, characterized in that: It includes an IGBT motherboard and a DBC substrate; the IGBT motherboard is laser-grooved to obtain a solder resist groove, which is formed by laser heating and oxidation of the metal components in the IGBT motherboard; The DBC substrate is fixed to the IGBT motherboard by welding. During welding, the solder flows through the solder resist tank for guidance and spill prevention, avoiding solder overflow or accumulation that could affect insulation performance and improve welding quality. During the laser grooving process, the laser power is 30W, the frequency is 40kHz, the scanning speed is 1200mm / s, the horizontal spacing of the laser spot is 30μm, and the radius of the laser spot is 30μm. Thus, the first laser spot is used to impact and heat the IGBT motherboard, causing the metal surface structure of the IGBT motherboard to be oxidized and roughened. Then, the front part of the second laser spot covers the part oxidized and roughened by the first laser spot, and performs a second impact and heating to form a secondary roughened structure that covers the first roughened structure, thereby forming a nano-flocculent double-layer roughened structure. Then, the rear part of the second laser spot continues to oxidize and roughen the metal surface structure of the IGBT motherboard. The impact and heating process is repeated by the next laser spot until the grooving is completed. The solder mask groove is formed by laser heating and oxidation of nickel and copper in the IGBT motherboard.

2. The laser resist soldering process for the IGBT module substrate according to claim 1, characterized in that: The solder resist grooves are connected end to end.

3. The laser resist soldering process for the IGBT module substrate according to claim 2, characterized in that: The solder resist groove is frame-shaped.

4. The laser resist soldering process for the IGBT module substrate according to claim 1, characterized in that: The IGBT motherboard is also covered with an isolation layer, the outline of which overlaps vertically with the outline of the IGBT motherboard.

5. The laser resist soldering process for the IGBT module substrate according to claim 4, characterized in that: The material of the isolation layer is solder resist ink.

6. The laser resist soldering process for the IGBT module substrate according to claim 4, characterized in that: The isolation layer is printed with solder resist, and the space formed by the solder resist matches the protected circuit or IGBT chip.

7. The laser resist soldering process for the IGBT module substrate according to claim 1, characterized in that: The DBC substrate includes a first solder layer, an insulating layer, and a second solder layer; the first solder layer is soldered onto the motherboard, the insulating layer is attached to the first solder layer, and the second solder layer is attached to the insulating layer. The insulating layer is used to protect the IGBT chip and circuits soldered onto the second solder layer.

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