Power module and method for diffusion welding of signal terminals

Abstract

The invention provides a signal terminal diffusion welding power module and method, and a copper-clad ceramic substrate. The copper-clad ceramic substrate comprises a substrate and a conductive metal layer on the substrate. The signal terminal is welded on the conductive metal layer of the copper-clad ceramic substrate through a welding layer; wherein the welding layer is formed when the copper-clad ceramic substrate and the signal terminal are welded through a transient liquid phase sintering soldering lug; the transient liquid phase sintering soldering lug is of a three-layer structure including a solder layer, a metal layer and a solder layer. And the module has a higher working temperature.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor technology, and in particular to a power module and a method for diffusion welding of signal terminals. Background Art

[0002] A power module is an electronic component that packages power semiconductor devices together for easy use. With the rapid development of semiconductor technology, power modules have also gained an increasingly large market and are widely used in new energy, automobiles, photovoltaics, rail transportation and other fields. Faced with a variety of usage scenarios and harsh operating environments, the reliability requirements of power modules are increasing. The signal terminal is a bridge connecting the client circuit board and the internal signal of the module. The quality of its connection directly affects the normal use of the module.

[0003] In the process of welding the signal terminal to the copper-clad ceramic substrate of the commonly used power module, the welding materials used mainly include tin-antimony, tin-silver, tin-silver-copper and other alloys, and their melting points range from 200-260°C. Affected by the material of the solder, it cannot be used at higher operating temperatures. In the production process of conventional power modules, multi-step welding is often required. The lower melting point temperature causes the solder under the signal terminal to melt again in the subsequent two-step welding process. After the solder melts again, it is necessary to consider whether the signal terminal will shift or have a cold solder joint. It is necessary to add a fixture to position it to prevent it from shifting or having a cold solder joint. Since there are semiconductor chips, signal terminals, power terminals, bonding wires, etc. on the DBC, the layout is relatively compact, which brings great difficulties to the design of the fixture. Summary of the invention

[0004] Based on the above records, the present invention provides a power module and method for diffusion welding of signal terminals, which solves the technical problems in the prior art that power module welding is difficult to adapt to high temperature operation.

[0005] A power module with diffusion welding of signal terminals, comprising:

[0006] A copper-clad ceramic substrate, comprising a substrate and a conductive metal layer on the substrate;

[0007] The signal terminal is welded on the conductive metal layer of the copper-clad ceramic substrate through the welding layer;

[0008] Wherein, the welding layer is formed when the copper-clad ceramic substrate and the signal terminal are welded by transient liquid phase sintering welding sheet;

[0009] The transient liquid phase sintering solder sheet has a three-layer structure of solder layer-metal layer-solder layer.

[0010] Furthermore, it also includes a semiconductor chip, which is welded on the conductive metal layer of the copper-clad ceramic substrate through a welding layer.

[0011] Furthermore, it also includes bonding metal wires, which are welded to the conductive metal layer of the copper-clad ceramic substrate through the welding layer.

[0012] Furthermore, the material of the solder layer of the transient liquid phase sintering solder sheet is one of tin-antimony alloy, tin-silver alloy, and tin-silver-copper alloy.

[0013] Furthermore, the metal layer of the transient liquid phase sintering solder sheet is made of pure copper.

[0014] Furthermore, the thickness of the solder layer of the transient liquid phase sintering solder sheet is not greater than 0.05 μm.

[0015] Furthermore, the signal terminal is made of metal or a metal-based composite material.

[0016] A method for diffusion welding of signal terminals, used to form a power module with diffusion welding of signal terminals, comprising:

[0017] Step A1, placing a transient liquid phase sintering welding sheet at the position where the signal terminal is welded on the copper-clad ceramic substrate;

[0018] Step A2, assembling the signal terminal and the metal fixture and then mounting them on the transient liquid phase sintering solder sheet on the copper-clad ceramic substrate;

[0019] Step A3, after the signal terminals are fixed on the copper-clad ceramic substrate, the substrate enters a vacuum reflow furnace and is heated to perform formic acid reduction activation;

[0020] Step A4, continue to raise the temperature until the solder layer of the transient liquid phase sintering solder sheet melts, and maintain the temperature for a preset time so that the soldering interface is completely converted into an intermetallic compound;

[0021] Step A5, then gradually cool to room temperature.

[0022] Furthermore, in step A1, a transient liquid phase sintering solder sheet is placed at the position where the semiconductor chip is soldered on the copper-clad ceramic substrate;

[0023] In step A2, the semiconductor chip is also placed on the corresponding transient liquid phase sintering solder pad on the copper clad ceramic substrate.

[0024] Furthermore, in step A1, a transient liquid phase sintering solder sheet is placed at the position where the bonding metal wire is welded on the copper-clad ceramic substrate;

[0025] In step A2, bonding metal wires are also placed on corresponding transient liquid phase sintering pads on the copper clad ceramic substrate.

[0026] The beneficial technical effect of the present invention is that the present invention uses a transient liquid phase sintering solder sheet to weld the signal terminal to a copper-clad ceramic substrate. After welding, the transient liquid phase sintering solder sheet forms a welding layer with an intermetallic compound, which makes welding easier, has higher welding stability and reliability, and can adapt to higher operating temperatures. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1-Figure 2 It is a schematic structural diagram of a power module with diffusion welding of signal terminals according to the present invention;

[0028] Figure 3 The present invention is a flowchart of the steps of a signal terminal diffusion welding method.

[0029] in,

[0030] 1-signal terminal;

[0031] 2-bonding metal wires;

[0032] 3- Semiconductor chips;

[0033] 4-Copper clad ceramic substrate;

[0034] 5-conductive metal layer;

[0035] 6- Welding layer. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0038] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but they are not intended to limit the present invention.

[0039] See also Figure 1 and Figure 2 The present invention provides a power module with diffusion-welded signal terminals, comprising:

[0040] A copper-clad ceramic substrate (4), comprising a substrate and a conductive metal layer (5) on the substrate;

[0041] A signal terminal (1) is welded to a conductive metal layer (5) of a copper-clad ceramic substrate (4) via a welding layer (6);

[0042] The welding layer (6) is formed by welding the copper-clad ceramic substrate (4) and the signal terminal (1) through a transient liquid phase sintering welding sheet;

[0043] The transient liquid phase sintering solder sheet has a three-layer structure of solder layer-metal layer-solder layer.

[0044] The solder layer is usually composed of a low melting point alloy to facilitate the formation of the liquid phase in the initial stage. The middle metal layer is made of materials with strong high temperature resistance. During the welding process, the solder layers on both sides first melt into the liquid phase, and then diffuse with the middle metal layer at the atomic level. Over time, the elements in the liquid solder gradually diffuse into the solid metal layer, and the liquid component continues to decrease until it is completely solidified, eventually forming a uniform and dense bonding layer, namely the intermetallic compound. This process allows the formed joint to withstand higher operating temperatures without failure.

[0045] The present invention uses a transient liquid phase sintering welding sheet to weld the signal terminal on the copper-clad ceramic substrate. After welding, the transient liquid phase sintering welding sheet forms a welding layer with an intermetallic compound, which makes welding simpler, has higher welding stability and reliability, and can adapt to higher operating temperatures.

[0046] A metal fixture is used to fix the signal terminals on the copper-clad ceramic substrate.

[0047] Specifically, the welding is performed in a vacuum reflow furnace.

[0048] Furthermore, it also comprises a semiconductor chip (3), wherein the semiconductor chip (3) is welded on the conductive metal layer (5) of the copper-clad ceramic substrate (4) via a welding layer (6).

[0049] Specifically, the semiconductor chip (3) includes an IGBT chip and a diode chip.

[0050] Furthermore, it also includes a bonding metal wire (2), wherein the bonding metal wire (2) is welded to the conductive metal layer (5) of the copper-clad ceramic substrate (4) through a welding layer (6).

[0051] Specifically, the conductive metal layer (5) is a copper layer. The bonding metal wire (2), the signal terminal (1), and the semiconductor chip (3) are all welded to the conductive metal layer (5) of the copper-clad ceramic substrate (4) via a welding layer (6).

[0052] Furthermore, the material of the solder layer of the transient liquid phase sintering solder sheet is one of tin-antimony alloy, tin-silver alloy, and tin-silver-copper alloy.

[0053] Furthermore, the metal layer of the transient liquid phase sintering solder sheet is made of pure copper.

[0054] Furthermore, the thickness of the solder layer of the transient liquid phase sintering solder sheet is not greater than 0.05 μm.

[0055] Specifically, the total thickness of the transient liquid phase sintering welding sheet is 0.03-0.2 mm.

[0056] Furthermore, the signal terminal (1) is made of metal or a metal-based composite material.

[0057] Specifically, the signal terminal (1) includes an upright portion, a bent portion, and a buffer structure portion, such as Figure 2 As shown.

[0058] See also Figure 3 The present invention also provides a method for diffusion welding of signal terminals, which is used to form the aforementioned power module with diffusion welding of signal terminals, comprising:

[0059] Step A1, placing a transient liquid phase sintering welding sheet at the position where the signal terminal is welded on the copper-clad ceramic substrate;

[0060] Step A2, assembling the signal terminal and the metal fixture and then mounting them on the transient liquid phase sintering solder sheet on the copper-clad ceramic substrate;

[0061] Step A3, after the signal terminals are fixed on the copper-clad ceramic substrate, the substrate enters a vacuum reflow furnace and is heated to perform formic acid reduction activation;

[0062] Step A4, continue to raise the temperature until the solder layer of the transient liquid phase sintering solder sheet melts, and maintain the temperature for a preset time so that the soldering interface is completely converted into an intermetallic compound;

[0063] Step A5, then gradually cool to room temperature.

[0064] The present invention uses a transient liquid phase sintering welding sheet to weld the signal terminal on the copper-clad ceramic substrate. After welding, the transient liquid phase sintering welding sheet forms a welding layer with an intermetallic compound, which makes welding simpler, has higher welding stability and reliability, and can adapt to higher operating temperatures.

[0065] Using formic acid (HCOOH) as a reducing agent at a certain temperature to remove the oxide layer or other impurities on the welding surface makes the welding surface purer and more active, which is conducive to the subsequent bonding between the solder and the substrate. This activation process can enhance the wettability of the solder and promote good metallurgical bonding.

[0066] Furthermore, in step A1, a transient liquid phase sintering solder sheet is placed at the position where the semiconductor chip is soldered on the copper-clad ceramic substrate;

[0067] In step A2, the semiconductor chip is also placed on the corresponding transient liquid phase sintering solder pad on the copper clad ceramic substrate.

[0068] Furthermore, in step A1, a transient liquid phase sintering solder sheet is placed at the position where the bonding metal wire is welded on the copper-clad ceramic substrate;

[0069] In step A2, bonding metal wires are also placed on corresponding transient liquid phase sintering pads on the copper clad ceramic substrate.

[0070] Specifically, the conductive metal layer is a copper layer. The bonding metal wires, signal terminals, and semiconductor chips are all welded to the conductive metal layer of the copper-clad ceramic substrate through the welding layer, thereby improving the operating temperature tolerance of the power module.

[0071] The above are only preferred embodiments of the present invention, and are not intended to limit the implementation methods and protection scope of the present invention. Those skilled in the art should be aware that all solutions obtained by equivalent substitutions and obvious changes made using the description and illustrations of the present invention should be included in the protection scope of the present invention.

Claims

1. A power module with diffusion soldered signal terminals, characterized in that: include: A copper-clad ceramic substrate, comprising a substrate and a conductive metal layer on the substrate; A signal terminal is welded on the conductive metal layer of the copper-clad ceramic substrate through a welding layer; Wherein, the welding layer is formed when the copper-clad ceramic substrate and the signal terminal are welded by a transient liquid phase sintering welding sheet; The transient liquid phase sintering solder sheet has a three-layer structure of solder layer-metal layer-solder layer.

2. A power module with diffusion soldered signal terminals as claimed in claim 1, characterized in that: It also includes a semiconductor chip, which is welded on the conductive metal layer of the copper-clad ceramic substrate through the welding layer.

3. A power module with diffusion soldered signal terminals as claimed in claim 1, characterized in that: It also includes a bonding metal wire, which is welded on the conductive metal layer of the copper-clad ceramic substrate through the welding layer.

4. A power module with diffusion soldered signal terminals as claimed in claim 1, characterized in that: The material of the solder layer of the transient liquid phase sintering solder sheet is one of tin-antimony alloy, tin-silver alloy and tin-silver-copper alloy.

5. A power module with diffusion soldered signal terminals as claimed in claim 1, characterized in that: The metal layer of the transient liquid phase sintering welding sheet is made of pure copper.

6. A power module with diffusion soldered signal terminals as claimed in claim 1, characterized in that: The thickness of the solder layer of the transient liquid phase sintering solder sheet is not higher than 0.05 μm.

7. A power module with diffusion soldered signal terminals as claimed in claim 1, characterized in that: The signal terminal is made of metal or metal-based composite material.

8. A method for diffusion welding of a signal terminal, characterized in that: A power module for forming a signal terminal diffusion welded as claimed in any one of claims 1 to 7, comprising: Step A1, placing a transient liquid phase sintering welding sheet at the position where the signal terminal of the copper-clad ceramic substrate is welded; Step A2, assembling the signal terminal and the metal fixture and installing them on the transient liquid phase sintering welding sheet on the copper-clad ceramic substrate; Step A3, the copper-clad ceramic substrate is fixed with the signal terminal and then placed into a vacuum reflow furnace, where the temperature is raised to perform formic acid reduction activation; Step A4, continue to raise the temperature until the solder layer of the transient liquid phase sintering solder sheet melts, and maintain the temperature for a preset time so that the welding interface is completely converted into an intermetallic compound; Step A5, then gradually cool to room temperature.

9. A method for diffusion welding of a power module signal terminal as claimed in claim 8, characterized in that: In the step A1, the transient liquid phase sintering welding sheet is also placed at the position where the semiconductor chip is welded on the copper-clad ceramic substrate; In the step A2, the semiconductor chip is also placed on the corresponding transient liquid phase sintering solder pad on the copper-clad ceramic substrate.

10. A method for diffusion welding of signal terminals of a power module according to claim 8, characterized in that: In the step A1, the transient liquid phase sintering welding sheet is also placed at the position where the bonding metal wire is welded on the copper-clad ceramic substrate; In the step A2, the bonding metal wire is also placed on the corresponding transient liquid phase sintering solder pad on the copper-clad ceramic substrate.

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