JPH0951151A - Circuit board for power module and manufacturing method thereof - Google Patents

Abstract

(57) [Abstract] (Corrected) [PROBLEMS] To prevent warpage and cracking of a ceramic substrate by absorbing thermal deformation, to reduce the size and to make it relatively light. A circuit made of a plastic porous metal is formed on a ceramic substrate made of Al ₂ O ₃ or AlN. If necessary, a thin metal plate 14 made of Al or Cu forming a circuit is bonded to the ceramic substrate,
A plastic porous metal is laminated thereon. The manufacturing method is a step of applying a slurry containing a metal powder on a ceramic substrate so as to form a predetermined circuit pattern, drying and foaming, and applying a slurry on a foam layer with the same pattern as the circuit pattern, drying and foaming. It is preferable that the step and the laminated foam layer are fired to form a circuit made of a plastic porous metal on the ceramic substrate. The plastic porous metal is filled or impregnated with silicone grease or the like.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power module circuit board for supplying power and a method for manufacturing the same.

[0002]

2. Description of the Related Art Heretofore, as a circuit board for a power module of this type, there has been known one in which a circuit board made of Cu or Al is adhered to a ceramic substrate. In this bonding method, a method of directly laminating and bonding a ceramic substrate and a circuit board has been proposed. As a method for directly laminating and bonding the ceramic substrate and the circuit substrate, Al ₂ O ₃ and Cu are used.
In the case where the ceramic substrate and the circuit board are overlapped with each other, a load of 0.5 to 2 kgf / c is applied to them.
The so-called DBC method (Direct Bonding Copper method) in which m ² is added and heated to 1065 ° C. in an N ₂ atmosphere, or Ag-Cu-Ti brazing material foil is sandwiched between a ceramic substrate and a circuit substrate. Load 0.5 to 2 kgf / cm
There is a so-called active metal method in which ² is added and heated to 800 to 900 ° C. in a vacuum.

[0003]

However, although the circuit board can be adhered to the ceramic board by the above-mentioned method of directly laminating and adhering, since the ceramic board and the circuit board have different thermal expansion coefficients, the power module board is warped. There is a problem that the ceramic substrate may be cracked due to the heat cycle. Especially when trying to increase the cross-sectional area of the circuit board in order to increase the current density, the deformation force due to the heat of the circuit board may exceed the strength of the ceramic board and the ceramic board may be damaged in the case of a relatively thin ceramic board. It was Increasing the thickness of the ceramic substrate to eliminate these points causes an increase in mass and an increase in shape,
Further, there is a problem that the heat dissipation property is deteriorated due to the increase of the thermal resistance value.
An object of the present invention is to provide a power module circuit board that absorbs thermal deformation and prevents warpage and cracking of the ceramic board, and a method for manufacturing the same. Another object of the present invention is to provide a circuit board for a power module and a method for manufacturing the same, in which the ceramic board can be made thin to be small in size and can be made relatively lightweight.

[0004]

The invention according to claim 1 is
As shown in FIG. 1, it is a power module circuit board in which a circuit made of a plastic porous metal 17 is formed on a ceramic substrate 13 made of an Al ₂ O ₃ or AlN sintered body.
In the invention according to claim 2, as shown in FIG. 2, a metal thin plate 14 made of Al or Cu forming a circuit is bonded onto a ceramic substrate 13 made of an Al ₂ O ₃ or AlN sintered body to form a metal thin plate 14. A circuit board for a power module, on which a plastic porous metal 17 is laminated. Metal thin plate is Cu
The plate or Al plate is formed by press molding or etching to form a circuit. The metal thin plate has a thickness of 0.05 to 0.20 mm, and a load of 0.5 to 2 kgf / is applied to the metal substrate 14 and the metal thin plate 14 with a foil of Al-Si brazing material as a brazing material sandwiched therebetween. The thin metal plate 14 is bonded to the ceramic substrate 13 by adding cm ² and heating to 600 to 650 ° C. in a vacuum.

The invention according to claim 3 is a circuit board for a power module, as shown in FIG. 3, in which a circuit made of a plastic porous metal 17 is surrounded by a silicone gel 18. The invention according to claim 4 is a circuit board for a power module, in which a circuit made of a plastic porous metal 17 is filled or impregnated with silicone grease, silicone oil, or epoxy resin.

According to the invention of claim 5, (a) the average particle size is 5
A metal powder composed of Cu, Al or Ag having a size of 100 μm
A metal powder-containing slurry containing a water-soluble resin binder, a water-insoluble hydrocarbon-based organic solvent, a surfactant, a plasticizer, and water is placed on a ceramic substrate 13 made of an Al ₂ O ₃ or AlN sintered body. A step of applying and drying to form a predetermined circuit pattern, and foaming; (b) a step of applying a slurry on the foam layer by the same pattern as the circuit pattern and drying and foaming; and (c) laminated foaming. And a step of firing the layer to form a circuit made of the plastic porous metal 17 on the ceramic substrate 13, a method of manufacturing a circuit board for a power module.

In the plastic porous metal of Cu, Cu powder having an average particle diameter of 5 to 100 μm is used as the metal powder, and in the plastic porous metal of Al, the average particle diameter of 5 to 100 μm as the metal powder.
A mixture of Al powder of m and Cu powder having an average particle size of 5 to 100 μm is used, and Ag plastic powder having an average particle size of 5 to 100 μm is used as the metal powder in the plastic porous metal of Ag. As the water-soluble resin binder, methyl cellulose, hydroxypropyl methyl cellulose, hydroxyethyl methyl cellulose, carboxymethyl cellulose ammonium, ethyl cellulose or the like is used, and as the water-insoluble hydrocarbon organic solvent, neopentane, hexane, isohexane,
Heptane or the like is used. Further, a commercially available kitchen neutral synthetic detergent (for example, 28% mixed aqueous solution of alkyl glucoside and polyoxyethylene alkyl ether) is used as the surfactant, and ethylene glycol is used as the plasticizer.
Polyhydric alcohols such as polyethylene glycol and glycerin, fats and oils such as sardine oil, rapeseed oil and olive oil, ethers such as petroleum ether, diethyl phthalate, diN-butyl phthalate, diethylhexyl phthalate and di-N-phthalate.
Esters such as octyl are used.

In the step of drying and foaming the metal powder-containing slurry, the metal powder-containing slurry is applied in an amount of 5-1.
Hold at 00 ° C. for 0.25 to 4 hours to volatilize and foam the plasticizer in the slurry, and at 30 to 6 at 50 to 200 ° C.
The slurry is held for 0 minutes and dried to form a thin plate-like porous molded body. In the step of firing the foamed layer, the porous molded body is sintered together with the ceramic substrate in a predetermined atmosphere for 500 to 10 times.
The porous molded body is heated at 60 ° C. for 0.5 to 4 hours and held to form a thin plate-shaped porous sintered body having a skeleton structure and a porosity of 90 to 93% and a thickness of 0.5 to 5 mm.

The invention according to claim 6 is a power module in which a metal thin plate 14 made of Al or Cu having the same pattern as a circuit pattern is pre-bonded to the ceramic substrate 13 in the step (a) through a brazing material. It is a manufacturing method of a circuit board for use. By adhering the metal thin plate in advance, the application of the metal powder-containing slurry is facilitated. The invention according to claim 7 is a method for manufacturing a circuit board for a power module, wherein the step (b) is repeated a plurality of times. By applying the slurry a plurality of times and drying it, the thickness of the plastic porous metal can be increased and the current density can be increased.

The invention according to claim 8 is a method for producing a circuit board for a power module, further comprising a circuit comprising a plastic porous metal 17 surrounded by silicone gel after the step (c). The invention according to claim 9 is a method for manufacturing a circuit board for a power module, which further comprises, after the step (c), a step of filling or impregnating a circuit composed of the plastic porous metal 17 with silicone grease, silicone oil or epoxy resin. is there. Silicone gel 18 with plastic porous metal 17
The heat dissipation characteristics can be improved by enclosing the circuit made of, or by filling or impregnating with silicone grease, silicone oil, or epoxy resin.

[0011]

Operation: Circuit board 1 for power module shown in FIG.
At 0, even if the thermal expansion coefficient of the ceramic substrate 13 and the circuit made of the plastic porous metal 17 are different, the plastic porous metal 17 that is the circuit absorbs the thermal deformation, so that the ceramic substrate 13 is not warped or cracked. It can be prevented from occurring. In addition, plastic porous metal 17 with silicone grease,
By filling or impregnating with a silicone oil or an epoxy resin, or by impregnating them with each other at the time of use, the thermal conductivity of the plastic porous metal 17 is improved, so that the heat dissipation characteristics are not impaired.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described in detail with reference to the drawings. <Embodiment 1> As shown in FIG. 1, a power module circuit board 10 includes a circuit made of a plastic porous metal 17 on a surface of a ceramic substrate 13 and having a coefficient of thermal expansion different from that of the ceramic substrate 13. A ceramic substrate 13
Ceramic material with 96% l ₂ O ₃ content has length, width and thickness of 30 mm, 70 mm and 0.635 m, respectively.
It was formed in a rectangular thin plate shape of m. Plastic porous metal 17
80 g of Cu powder having an average particle size of 40 μm and a water-soluble methylcellulose resin binder 2.5
g, glycerin 5 g, surfactant 0.5 g, water 2
It was prepared by kneading with 0 g for 30 minutes, then adding 1 g of hexane and kneading for 3 minutes.

A slurry containing metal powder was applied to the surface of the ceramic substrate 13 in a predetermined thickness to form a predetermined circuit pattern. In this state, the temperature is kept at 40 ° C. for 30 minutes to evaporate hexane in the slurry to foam,
The slurry was held at a temperature of 90 ° C. for 40 minutes and dried to form a foam layer composed of a thin plate-like porous molded body. A metal powder-containing slurry was further applied to the surface of this foam layer so as to have the same circuit pattern with a predetermined thickness, and dried again under the same conditions to form a foam layer made of a thin plate-shaped porous molded body. Such an operation was repeated 3 times to obtain a foamed layer laminated in 3 layers. Next, this laminated foam layer was heated to 500 ° C. in air for 0.5 hours and held together with the ceramic substrate, and then heated to 1030 ° C. in hydrogen for 1 hour and held to form the laminated foam layer into a skeleton structure. Porosity having 92-95
%, And a plate-like porous sintered body having a thickness of 4.5 mm. Further, this porous sintered body is rolled together with a ceramic substrate to make the thickness of the porous sintered body 1.5 mm, so that the plastic porous metal 1 having a porosity of 30% can be obtained from the slurry containing metal powder.
A circuit consisting of 7 was formed. The pores of the plastic porous metal 17 were filled with silicone grease from the side surface of the metal 17. Thus, the power module circuit board 10 was obtained.

<Embodiment 2> Although not shown, a metal powder-containing slurry, which is a plastic porous metal, is mixed with A having an average particle size of 40 μm.
100 g of powder, 2.5 g of water-soluble methyl cellulose resin binder, 5 g of glycerin, and 0.5 g of surfactant
And 20 g of water are kneaded for 30 minutes, and then 1 g of hexane
It was prepared by adding and kneading for 3 minutes. This metal powder-containing slurry was applied to the same ceramic substrate as in Example 1 so as to have a predetermined circuit pattern with a predetermined thickness and kept at a temperature of 40 ° C. for 30 minutes to volatilize hexane in the slurry to foam. After that, the temperature was maintained at 90 ° C. for 40 minutes and drying was performed to form the foamed layer of the above-mentioned slurry into a thin plate-shaped porous molded body. A metal powder-containing slurry was further applied to the surface of this foam layer so as to have the same circuit pattern with a predetermined thickness, and dried again under the same conditions to form a foam layer made of a thin plate-shaped porous molded body. Such an operation was repeated 3 times to obtain a foamed layer laminated in 3 layers. Next, this laminated foam layer is put together with a ceramic substrate in air at 900
The laminated foam layer was made into a thin plate-like porous sintered body having a skeleton structure and a porosity of 90 to 93% and a thickness of 4.5 mm, by heating and holding at 3 ° C. for 3 hours. Further, by rolling this porous sintered body together with a ceramic substrate and making the thickness of the porous sintered body 1.5 mm, a circuit made of a plastic porous metal having a porosity of 30% is formed from a slurry containing metal powder. Formed.

<Embodiment 3> Although not shown, a metal powder-containing slurry, which is a plastic porous metal, is mixed with A having an average particle size of 25 μm.
50 g of 1 powder, 1.2 g of Cu powder having an average particle size of 9 μm, 2.5 g of a water-soluble methylcellulose resin binder, 5 g of glycerin, 0.5 g of a surfactant, and 20 g of water, 30 g.
After kneading for 1 minute, 1 g of hexane was added and kneading was continued for 3 minutes to prepare. This metal powder-containing slurry was applied to the same ceramic substrate as in Example 1 so as to form a predetermined circuit pattern, and the temperature was maintained at 40 ° C. for 30 minutes to volatilize hexane in the slurry to foam and then The slurry was held at 90 ° C. for 40 minutes and dried to form a foam layer made of the thin plate-like porous molded body. A metal powder-containing slurry was further applied to the surface of this foam layer so as to have the same circuit pattern with a predetermined thickness, and dried again under the same conditions to form a foam layer made of a thin plate-shaped porous molded body.
Such an operation was repeated 3 times to obtain a foamed layer laminated in 3 layers. Next, the laminated foam layer is heated together with the ceramic substrate at 600 ° C. in a vacuum for 1 hour and held, and the laminated foam layer has a skeleton structure and a porosity of 93 to 96%.
It was a thin plate-like porous sintered body having a thickness of 4.5 mm. Further, by rolling this porous sintered body together with a ceramic substrate to make the thickness of the porous sintered body 1.5 mm, a circuit made of a plastic porous metal having a porosity of 30% is formed from a slurry containing metal powder. did.

<Embodiment 4> As shown in FIG. 2, in the power module circuit board 40 of this example, a metal made of Al having a thickness of 0.1 mm and having the same pattern as the circuit pattern on the surface of the ceramic substrate 13. Thin plate 14 is Al-Si
Preliminarily adhered with a brazing material, and then the third embodiment is placed on the thin metal plate.
A plastic porous metal 17 composed of a three-layer thin plate-shaped porous molded body identical to the above was molded. That is, the ceramic substrate 13
A circuit made of the plastic porous metal described in Example 3 was formed on the surface of each of them through the metal thin plate 14 made of Al. <Examples 5 to 7> Although not shown, in Examples 5 to 7, a metal thin plate made of Cu having a thickness of 0.1 mm and having the same pattern as the circuit pattern on the surface of the ceramic substrate is DBC.
Pre-bonded by the method of Example 1-3 on the thin metal plate.
A plastic porous metal composed of three layers of thin plate-like porous molded bodies, which are respectively the same as the above, was molded. That is, the surface of the ceramic substrate has the same pattern as the circuit pattern, and Cu
Loaded with a thin metal plate consisting of
f / cm ² was added, and the mixture was heated to 1065 ° C. in an N ₂ atmosphere for adhesion, and circuits formed of the plastic porous metal described in each of Examples 1 to 3 were formed on the surface. <Examples 8 to 14> Although not shown, Examples 8 to 14 have the same configurations as Examples 1 to 7, respectively, except that the ceramic substrate is made of AlN. However,
The ceramic substrate was previously oxidized at 1300 ° C. and an Al ₂ O ₃ layer was formed on the surface of the ceramic substrate with an optimum thickness.

<Comparative Example 1> Although not shown, a thickness of 0.5 m having the same current density as that of the plastic porous metal of Example 1
Comparative Example 1 was a circuit board for a power module, in which a circuit board made of Cu of m was adhered to a ceramic board made of an Al ₂ O ₃ sintered body. That is, the power module circuit board includes circuit boards directly bonded to the upper surface of the ceramic board by the DBC method. <Comparative Example 2> Although not shown, a circuit board made of Al and having the same current density as that of the plastic porous metal of Example 1 and having a thickness of 0.7 mm was adhered onto a ceramic substrate made of an Al ₂ O ₃ sintered body. The power module circuit board having the above-described configuration was used as Comparative Example 2. That is, a circuit board for a power module is such that a foil of Al—Si brazing material, which is a brazing material, is sandwiched between a ceramic substrate and a circuit board made of Al and a load of 0.
5 ~ 2kgf / cm ² added, 600 ~ 650 in vacuum
The circuit board is laminated and adhered to the ceramic board by being heated to ℃. Table 1 shows the contents of Examples 1 to 16 and Comparative Examples 1 and 2.

[0018]

[Table 1]

<Comparative Test and Evaluation> The circuit boards for power modules of Examples 1 to 14 and Comparative Examples 1 and 2 were -40 ° C.
The thermal resistance and the cracking of the ceramic substrate after the temperature cycle of 0 cycle (no temperature cycle was given), 10 cycles and 50 cycles under the temperature cycle condition of ˜125 ° C. were examined, respectively. The thermal resistance R _th (° C) is
Although not shown, a heat radiation fin of 70 × 30 mm and a fin height of 35 mm is attached to the back of the circuit board with grease, and two rectangular heating elements of 15 mm both vertically and horizontally are arranged on the circuit.
The ambient air temperature T _a (° C.) and the temperature T _j (° C.) of the heating element when the heating element was heated at 10 W and adhered via b-Sn solder were measured and determined from the equation. R _th = (T _j −T _a ) / 10 ... Further, the cracking ratio C _r (%) of the ceramic substrate is obtained by etching the circuit made of the plastic porous metal from the ceramic substrate and peeling it off, and the circuit is laminated and adhered by a microscope. Perimeter crack length L _c (mm) and total circuit length L before etching
_a (mm) was measured and calculated from the formula. C _r = (L _c / L _a ) × 100 ... The results are shown in Table 2.

[0020]

[Table 2]

As is clear from Table 2, it was found that the cracking rate of the example was significantly lower than that of the conventional example.
It was also found that the thermal resistance of the example was better than that of the comparative example at 50 cycles.

[0022]

As described above, according to the present invention, since the circuit made of the plastic porous metal is formed on the ceramic substrate, the plastic porous metal absorbs the thermal deformation and warps or cracks of the ceramic substrate. It can be prevented. Further, since the plastic porous metal absorbs thermal deformation, the ceramic substrate can be made thin, and the power module circuit substrate can be made small and relatively lightweight. Further, the plastic porous metal is a porous sintered body of Cu, Al or Ag having a porosity of 20 to 50%, and the plastic porous metal is filled or impregnated with silicone grease, silicone oil or epoxy resin, or used. At this time, by impregnating these with each other, the heat radiation characteristic from the circuit made of the plastic porous metal to the ceramic substrate is not impaired.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a power module circuit board according to a first embodiment of the present invention.

FIG. 2 is a sectional view corresponding to FIG. 1, showing a fourth embodiment of the present invention.

FIG. 3 is a cross-sectional view corresponding to FIG. 1 showing its usage state.

[Explanation of symbols]

 10,40 Power module circuit board 13 Ceramic board 14 Metal thin plate 17 Plastic porous metal

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Masafumi Hatsuka 1-297 Kitabukurocho, Omiya City, Saitama Prefecture Mitsubishi Materials Research Institute

Claims (9)

[Claims] 1. A circuit board for a power module in which a circuit made of a plastic porous metal (17) is formed on a ceramic substrate (13) made of an Al ₂ O ₃ or AlN sintered body. 2. A thin metal plate (14) made of Al or Cu forming a circuit is adhered onto a ceramic substrate (13) made of a sintered Al ₂ O ₃ or AlN, and plasticity is provided on the thin metal plate (14). A circuit board for power modules in which porous metal (17) is laminated. 3. The circuit board for a power module according to claim 1, wherein the circuit made of a plastic porous metal (17) is surrounded by a silicone gel (18). 4. The circuit board for a power module according to claim 1, wherein the circuit made of the plastic porous metal (17) is filled or impregnated with silicone grease, silicone oil or epoxy resin. 5. (a) Cu having an average particle size of 5 to 100 μm,
A metal powder-containing slurry containing a metal powder made of Al or Ag, a water-soluble resin binder, a water-insoluble hydrocarbon organic solvent, a surfactant, a plasticizer, and water is burned with Al ₂ O ₃ or AlN. Applying a predetermined circuit pattern on a ceramic substrate (13) made of a bonded body, and drying and foaming; (b) applying the slurry on the foamed layer in the same pattern as the circuit pattern. A method for producing a circuit board for a power module, which includes a step of drying and foaming, and (c) a step of firing the laminated foamed layer to form a circuit made of a plastic porous metal on the ceramic substrate (13). . 6. The thin metal plate (14) made of Al or Cu having the same pattern as the circuit pattern is previously adhered to the ceramic substrate (13) in the step (a) through a brazing material. Manufacturing method of circuit board for power module. 7. The method for manufacturing a circuit board for a power module according to claim 5, wherein the step (b) is repeated a plurality of times. 8. A plastic porous metal (1) is further added after the step (c).
8. The method for manufacturing a circuit board for a power module according to claim 5, wherein the circuit consisting of 7) is surrounded by silicone gel. 9. A plastic porous metal (1) is further added after the step (c).
8. The method for manufacturing a circuit board for a power module according to claim 5, further comprising the step of filling or impregnating the circuit consisting of 7) with silicone grease, silicone oil or epoxy resin.