TWI762290B - Interval Pressurization Combination Method for Power Modules with Multiple Power Components - Google Patents

Abstract

A spacer pressure bonding method for a power module with a plurality of power elements, comprising the following steps: disposing a plurality of power elements on a first ceramic substrate at intervals, and disposing a metal spacer block on each power element respectively, wherein the metal spacers The direction of the block away from the first ceramic substrate is defined as a setting surface; a second ceramic substrate provided with a nano-silver layer is covered to the setting surface, and the setting height exceeds the power between the first and second ceramic substrates detachably. The sum of components and metal spacer blocks is lower than the power components and metal spacer blocks plus the thickness of the nano-silver layer. The silver layer is melted into a thin silver layer and is electrically connected with the metal spacer, and is cooled and solidified.

Description

Interval Pressurization Combination Method for Power Modules with Multiple Power Components

The present invention relates to a method for making a power module with a plurality of power elements.

In today's increasingly serious global warming, with the rising awareness of environmental protection, governments around the world have also introduced many green energy subsidy policies in transportation in recent years, making more and more consumers choose electric vehicles to replace the traditional fossil fuels. Powered vehicles, such as replacing conventional cars with electric vehicles and replacing two-stroke locomotives with electric scooters. These electric vehicles all rely on high-power electric motors to provide power. Therefore, the market demand for high-power power modules has grown, and major suppliers have also rushed to invest in capital and research and development to improve production line yield and output. In addition, light source devices such as high-brightness LEDs or LDs are constantly being introduced, resulting in a continuous increase in the energy consumption of the power supply devices. Power modules with high power and high heat dissipation are also required for effective support.

Due to the high energy consumption of high-power power modules, it is inevitable that a part of the energy will be converted into heat energy; at the same time as the miniaturization of electronic devices, high-power components will be accompanied by higher heat in a smaller space, so How to remove excess heat energy and maintain the stability of the operating environment becomes critical. In order to solve the problem of heat dissipation, the most commonly adopted solution is to use ceramic material as the insulating material layer of the circuit substrate. The most common ceramic material is the Direct Bonded Copper (DBC) substrate made of aluminum oxide (Aluminum Oxide, Al ₂ O ₃ ). Under the crystal structure, there are 20 to 27W/mK. Other common ceramic material substrates include aluminum nitride (AlN), beryllium oxide (BeO) and silicon carbide (SiC). Therefore, ceramic substrates have become the first choice for high-power power module substrates.

However, the ceramic substrate has the problem of warping and deformation, which may be tolerated in small size, but when the size of the substrate is larger, the severity of warping deformation is more obvious, resulting in uneven top surface of the substrate, a piece of 5 to 6 cm The ceramic substrate may be bent by about 0.2mm. Compared with the wafer with a height of only about 0.2mm, the impact should not be underestimated. Especially when the current of the power module needs to reach hundreds of amperes or even hundreds of amperes, it is often not enough for a single high-power component, and multiple high-power components need to be arranged in parallel on the same ceramic substrate plane to form a power supply. module.

Therefore, for ceramic substrates whose length and width are more than a few centimeters, the problems of uneven height and unevenness caused by warpage and deformation will affect the overall component packaging and even performance. Especially for high-power power modules that require double-sided contact with ceramic substrates for heat dissipation, it is difficult to keep each high-power power module chip connected to the double-sided ceramic substrates in an excellent conductive state. Unfortunately, if a wafer that can pass 200A is taken as an example, when the conduction state is not perfect, it may cause high resistance due to high heat generation when the current passes, causing the actual current to be reduced to only 100A, especially for processing large For the current power module chip, any slight poor contact may cause great damage to the chip, and the remaining conductive chips have to bear a larger load current, so ensure that each power module chip can be well conductively connected to the substrate is very important, and is the problem that the present invention seeks to solve.

In order to solve the above problems, some researchers have proposed to use nano-silver paste as the adhesive material, and heat it during the installation process to vaporize the doping in the original nano-silver paste and become pure molten silver, although the thickness will be greatly reduced. , but can take advantage of the pads and wafers on the ceramic board A sterling silver connection is formed between the input and output electrodes. However, the inventor's actual test found that there is no problem in using this technology on a single chip, but when a chip containing six or more power components is to be mounted, since the ceramic substrate must have a sufficient area, warpage It is unavoidable that the thickness of the nano-silver paste is greatly reduced during the heat treatment, and the limited thickness of the power element chip itself makes the problem of the inevitable warpage of the ceramic substrate in the thickness direction more and more serious and difficult to solve, even before heating and welding. , the power components will be damaged by impact due to inaccurate distance estimation, and the product yield and output efficiency will be significantly affected.

One object of the present invention is to provide a method for manufacturing a high-power power module, which can reduce the risk of damage due to collision between the ceramic substrate and the power element, and improve the manufacturing yield by using appropriate molds.

Another object of the present invention is to provide a method for producing a power supply module with a plurality of power components, using the mold as a high guarantee to avoid poor contact between the nano-silver paste on the ceramic substrate and the power components, resulting in conductive defects in the finished product, improving The reliability of the completed power module.

Another object of the present invention is to provide a method for ensuring the conductive connection between individual power components and the double-sided ceramic substrate.

In order to achieve the above-mentioned object, the present invention discloses a space-pressing bonding method for a power supply module with a plurality of power elements, including the following steps: a) disposing a plurality of power elements on a first ceramic substrate at intervals, wherein each of the aforementioned power elements There is a pair of input and output electrodes respectively located on the top surface and the bottom surface, and a pad circuit layer is formed on the first ceramic substrate, which is respectively used to conduct the input and output electrodes of the bottom surface of the power element, and on the top surface of each of the power components. A corresponding metal spacer block is respectively set on the input and output electrodes, wherein the metal spacer block is far away from the first ceramic base The plate direction is defined as a setting surface; b) a second ceramic substrate provided with a layer of nano-silver layer is covered with the connecting surface of the nano-silver layer to the above-mentioned setting surface, so that the above-mentioned setting surface of the above-mentioned metal spacer block is Pressing into the nano-silver layer respectively, wherein, in a separable manner, between the first ceramic substrate and the second ceramic substrate, the height exceeds the sum of the power element and the metal spacer block, and is lower than the power The element and the above-mentioned metal spacer blocks are combined with a plurality of spacer mold spacers of the thickness of the above-mentioned nano-silver layer to ensure that the above-mentioned metal spacer blocks can penetrate into the above-mentioned nano-silver layer, and will not directly touch the above-mentioned second ceramic substrate and cause damage; c ) Pressing and heating and melting the nano-silver layers in the direction perpendicular to the first and second ceramic substrates so that the nano-silver layers are respectively melted into thin silver layers and conductively bonded to the metal spacers respectively, and cooled. Then, the above-mentioned silver layer is cured.

Before heating and soldering, due to the existence of spacer mold spacers, no matter how the ceramic substrate is warped, it can ensure that the power components and metal spacers can be smoothly inserted into the nano-silver paste on the second ceramic substrate without direct impact The second ceramic substrate; thereby avoiding the risk of damage to the chip or ceramic substrate of the power element due to mechanical force during processing, and on the other hand, it is ensured that the metal spacer can be pressed into the nano-silver paste without fail There are unreachable issues.

The nano-silver paste has special melting characteristics. After melting at 200 degrees Celsius, the dopant in it is vaporized. On the one hand, the nano-silver paste is melted into liquid pure silver, and the overall height is reduced to about one-third of the original height. During the heating process, pressure is applied to the upper and lower sides, so that the warpage of the ceramic substrate is partially corrected by the external force, the thickness error is reduced, and the fluidity of the molten sterling silver can ensure that the second ceramic substrate pads and metal spacers that have been contacted All can achieve conductive connection due to the surface tension of silver. Even if the thickness of the nano-silver layer is reduced when heated and finally cooled to become a silver layer, an excellent conductive connection will still be formed after cooling, and the second ceramic substrate is tightly conductively bonded to the metal. spacer block. Thanks to the method thus invented, it is possible to ensure that the individual power components and the double-sided ceramic substrate are insulated from each other. The best conductive connection, especially when the power module requires a large size, for example, when trying to produce a power module with an overall length and width of more than 5 to 6 cm, the problem of warping and deformation of the ceramic substrate on both sides of the power element can be solved.

1, 1': the first ceramic substrate

11: Pad circuit layer

13': The first ceramic substrate part

14': first dielectric material substrate

2, 2': power components

21: Underside

22: Top surface

211, 221: In and out electrodes

3, 3': metal spacer block

31, 31': set face

4, 4': the second ceramic substrate

41: Nano silver layer

42, 42': sterling silver layer

43': The second ceramic substrate part

44': Second Dielectric Material Substrate

411: Connection surface

5, 5': spacer die spacer

81~86: Steps

FIG. 1 is a flow chart of a method of spaced pressure bonding of a power module with a plurality of power elements according to the present invention.

2 to 6 are schematic structural side views of different steps of the first preferred embodiment of the present invention.

FIG. 7 is a schematic side view of the structure of the second preferred embodiment of the present invention.

The foregoing and other technical contents, features and effects of the present invention will be clearly presented in the following detailed description of the preferred embodiments with reference to the drawings; in addition, in each embodiment, the same elements will be represented by similar label representation.

The first preferred embodiment of the spaced pressure bonding method of the power supply module with a plurality of power elements of the present invention is shown in FIG. 1 , first, in step 81 as shown in FIG. 2 , the plurality of power elements 2 are respectively arranged on the pads of a first ceramic substrate 1 On the plurality of pads corresponding to the circuit layer 11 , wherein each power element 2 includes a bottom surface 21 , an input and output electrode 211 on the bottom surface 21 and soldered on the pad circuit layer 11 , a top surface 22 , and an input and output electrode 221 on the top surface 22 Then in step 82, a metal spacer 3, which is exemplified as copper-plated silver, is respectively set on the inlet and outlet electrodes 221 of the top surface 22 of the power element 2. Because the above-mentioned first ceramic substrate 1 is warped, the surface is uneven, so that the above-mentioned first ceramic substrate 1 is warped. The installed power elements 2 have different levels, and the upper surface of the metal spacer 3 in the direction away from the first ceramic substrate 1 also forms a setting surface 31 with different levels.

Step 83 , as shown in FIG. 3 , a second ceramic substrate 4 is covered with a nano-silver layer 41 , wherein the above-mentioned nano-silver layer 41 is about 600 μm in this example, but it can be changed according to the actual operation and need not be limited to The thickness is fixed; then, under the first ceramic substrate 1 and above the second ceramic substrate 4, a pressurizing device (not shown) is respectively set to pressurize relatively, in order to prevent the second ceramic substrate 4 and the nano-silver layer 41 from pressing Approaching the first ceramic substrate 1 excessively presses the power element 2 to cause damage. In this example, in step 84 as shown in FIG. A plurality of spacer die spacers 5 are detachably arranged between or around the individual power elements 2, wherein the height of the spacer mold spacers 5 exceeds the sum of the power element 2 and the metal spacer block 3, and is lower than the power element 2 and the metal spacer. The spacer block 3 is added with the thickness of the nano-silver layer 41 to form a plurality of spacers that can limit the closest distance between the first ceramic substrate 1 and the second ceramic substrate 4 .

As shown in FIG. 5 , at this time, the connection surface 411 of the second ceramic substrate 4 with the nano-silver layer 41 is covered and abuts the setting surface 31 . Since the nano-silver layer 41 itself has a little flexibility, the above-mentioned When the nano-silver layer 41 contacts the above-mentioned setting surface 31 of the above-mentioned metal spacer block 3, it will be inserted by the metal spacer block 3 as shown in FIG. Absorb the warpage of the first ceramic substrate 1 and the second ceramic substrate 4 at a maximum of about 200 μm, and there will be no gaps due to lack of contact, and no metal spacers will hit the second ceramic substrate 4 to cause cracks or micro-gap. The slight height difference between the setting surface 31 and the second ceramic substrate 4 caused by the warpage of the first ceramic substrate 1 and the second ceramic substrate 4 is completely compensated.

As shown in FIG. 6 , as shown in step 85, pressurizing and heating the nano-silver layer 41 in the direction perpendicular to the first ceramic substrate 1 and the second ceramic substrate 4, forcing the nano-silver layer 41 to be heated to vaporize the dopant When the nano-silver layer begins to melt to form a pure silver layer 42 with a smaller thickness, due to the original It has been in contact with the above-mentioned setting surface 31 and the above-mentioned second ceramic substrate 4 up and down respectively. Therefore, under the influence of surface tension, the silver interposed therebetween will be effectively conductively bonded to the above-mentioned metal spacer 3 and the above-mentioned second ceramic substrate 4 respectively. Even if the thickness of the nano-silver layer 41 is reduced to the pure silver layer 42 after heating, it can still ensure excellent conductive connection between each power element and the pads on the second ceramic substrate above; finally, the pure silver layer 42 is cooled in step 86 , solidify and remove the above-mentioned spacer mold spacer 5 .

Due to the height design of the spacer mold spacer block 5, on the one hand, the first ceramic substrate 1 and the second ceramic substrate 4 are restricted from being too close, resulting in damage to the metal spacer block 3 and the power element 2 due to the impact force, which makes the good quality of the machining process. On the other hand, the height of the spacer mold spacer block 5 can ensure that even if there is warpage of the ceramic substrate, the metal spacer block 3 can still be firmly inserted into the nano-silver layer 41, and there will be no poor contact and cause future The reliability of poor conductivity during use is improved, thereby achieving the above-mentioned object of the present invention.

Of course, as can be easily understood by those skilled in the art, the first ceramic substrate and the second ceramic substrate here are not limited to a single complete ceramic substrate, because the ceramic substrate has good heat resistance and thermal conductivity, but the structure cannot Therefore, some people in the industry have proposed a thermoelectric separation substrate in which a ceramic substrate is embedded with a dielectric material substrate, so that high heat generation such as power components are arranged on the ceramic substrate, and more complex such as control circuits are arranged in FR-4, etc. On the dielectric material multilayer circuit board, a structure in which complex control circuits and high heat dissipation circuits of high-power components coexist and the advantages of both coexist is achieved.

Therefore, as shown in the second preferred embodiment of the present invention in FIG. 7 , the same parts as those of the previous preferred embodiment will not be repeated here, and similar elements are also given similar names and numbers, and only the differences are described. In this example, before step 81, a previous step of manufacturing the first ceramic substrate 1' is further included, and the first ceramic substrate portion is embedded in the position of the first dielectric material substrate 14' corresponding to the power element 2' 13'; similarly, before step 83, it further includes a previous step of manufacturing the second ceramic substrate 4', inlaying the second ceramic substrate portion 43' in the position of the second dielectric material substrate 44' corresponding to the power element 2', and The position of the second ceramic substrate portion 43 ′ corresponding to the power element 2 ′ is covered with a nano-silver layer, so that in step 84 the nano-silver layer covers and abuts the setting surface 31 ′, and is abutted by the spacer mold spacer 5 ′. Finally, step 85 pressurizes and heats and melts the nano-silver layer in the direction perpendicular to the first ceramic substrate 1 ′ and the second ceramic substrate 4 ′ to form a pure silver layer 42 ′ with a smaller thickness, so that the metal spacer 3 ′ and the above-mentioned The second ceramic substrate portion 43' of the second ceramic substrate 4' is conductively bonded.

However, the above are only the preferred embodiments of the present invention, which cannot limit the scope of the present invention. Any simple equivalent changes and modifications made according to the scope of the patent application of the present invention and the contents of the description of the invention should be It still falls within the scope of the patent of the present invention.

1: The first ceramic substrate

11: Pad circuit layer

2: Power components

3: Metal spacer block

31: Set face

4: Second ceramic substrate

41: Nano silver layer

5: Spacer die spacer

Claims (4)

A spaced and pressurized bonding method for a power supply module with a plurality of power elements, comprising the following steps: a) disposing a plurality of power elements on a first ceramic substrate at intervals, wherein each of the aforementioned power elements has a pair of respectively located on the top surface and the The input and output electrodes on the bottom surface, and a pad circuit layer is formed on the first ceramic substrate, which are respectively used to conduct electricity and combine the input and output electrodes on the bottom surface of the power element, and a corresponding pair of input and output electrodes on the top surface of each of the power components is respectively provided. A metal spacer, wherein the direction of the metal spacer away from the first ceramic substrate is defined as a setting surface; b) a second ceramic substrate provided with a nano-silver layer is covered with the connecting surface having the nano-silver layer to the above-mentioned setting surface, so that the above-mentioned setting surfaces of the above-mentioned metal spacers are respectively pressed into the above-mentioned nano-silver layer, wherein, in a separable manner, between the first ceramic substrate and the second ceramic substrate, the setting height exceeds the above-mentioned The sum of the power element and the metal spacer block, and a plurality of spacer mold spacers that are lower than the thickness of the power element and the metal spacer block plus the nano-silver layer thickness, to ensure that the metal spacer block can penetrate into the nano-silver layer, and Will not directly touch the second ceramic substrate and cause damage; c) pressurize and heat the nano-silver layer in the direction perpendicular to the first and second ceramic substrates, so that the nano-silver layer is respectively melted into thinner silver The layer is electrically connected to the metal spacer block, and is cooled to solidify the nano-silver layer. The method for spacer and pressure bonding of a power supply module with a plurality of power elements as described in the first claim, wherein step a further includes a sub-step a3 of silver-plating the surface of the metal spacer block. As described in item 1 of the scope of the patent application, a spacer and pressure bonding method for a power supply module with a plurality of power elements, wherein before step a, it further comprises a method of embedding a ceramic substrate in the circuit substrate part to form a Step d of the first ceramic substrate. A method for spaced and pressurized bonding of a power supply module with a plurality of power components as described in the first item of the scope of the application, wherein before step b, it further comprises a second ceramic substrate formed by embedding a ceramic substrate on the circuit substrate and covered with a nano-silver Layer step e.

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