JPS63254031A - Manufacture of circuit substrate - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to the manufacture of circuit boards, and more particularly to a method of manufacturing a circuit board by bonding a conductive metal plate to a ceramic substrate.

(Prior art and problems to be solved) Conventionally, in the production of circuit boards such as hybrid integrated circuit boards called so-called hybrid boards, the surface is generally made by metallizing a ceramic board such as alumina. A method of forming a metal layer has been adopted. For example, a metal paste such as Mo is printed on both sides of a ceramic substrate, dried and fired to form a metallized layer, a Ni plating layer is formed on top of that, and after dehydrogenation treatment, a copper plate or N
There is a method that involves a multi-step process of joining i-plated copper plates with solder.

On the other hand, a method of bonding metal plates such as copper plates thinner than the substrate thickness to both sides of a ceramic substrate by oxidation (Japanese Unexamined Patent Publication No. 121890/1989) is also being researched to manufacture substrates for semiconductor modules. This method has the advantage of preventing warping and board cracking compared to methods that bond metal plates only on one side.

However, in any of the above methods, there is a problem in that the joint between the ceramic substrate and the conductive metal plate peels off during a thermal cycle process such as subsequent heat treatment, resulting in poor thermal shock resistance.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a circuit board that can eliminate the drawbacks of the prior art described above and improve the heat shock resistance of the joint between a ceramic substrate and a conductive metal plate.

(Means for Solving the Problems) In order to achieve the above object, 1. In view of the fact that conventional methods employ means such as soldering or oxidation, the inventors have worked diligently to find a new joining method. As a result of repeated research, it was discovered that this is possible by using an adhesive with a specific physical structure.

That is, in manufacturing a circuit board in which a circuit is formed on a ceramic substrate, the method for manufacturing a circuit board according to the present invention includes applying an adhesive material made of a composite powder mechanically interlocked and bonded by a mechanical alloying method onto the ceramic substrate. This method is characterized in that after a conductive metal plate is attached using the metal plate, the surface of the metal plate is subjected to a peening treatment.

The present invention will be explained in detail below based on examples.

First, the ceramic substrate may be made of the same material as in the past, and ceramic materials such as alumina (A (1203)), aluminum nitride (AμN), silicon carbide (SiC), etc. are used.

When bonding a conductive metal plate to the surface or one surface of this ceramic substrate, heat bonding is performed using an adhesive described below. The conductive metal plates to be joined may be made of an appropriate material depending on the purpose, such as a copper plate or copper foil, a stainless steel plate, or an aluminum plate. For example, when bonding a copper plate as a heat sink, a certain amount of thickness is required to function as a heat sink and to be able to follow changes in thermal expansion, and the thickness of a ceramic substrate is usually 0.
．． The plate thickness (e.g., 2 mm) is greater than the thickness of the plate (1 mm to 1 mm).

In addition, in the case of copper foil, it is possible to follow changes in thermal expansion, but
On the other hand, if the thickness becomes too thick, the adhesive components will diffuse toward the copper foil side and cause deterioration of the surface layer, so it is preferable to use an arbitrary thickness within a range that does not cause diffusion.

As an adhesive, it is necessary to use a composite powder that is mechanically interlocked and bonded using a mechanical alloying method.For example, the component system may be a composite metal powder, or a composite powder containing metal powder and non-metal powder. There are things like
It is preferable to use it in the form of a paste.

Specific examples of the adhesive are shown below.

(1) 10% of at least one of Cu and Ni
~60% (weight%, the same applies hereinafter), T1, Nb and Zr
A paste-like product in which a composite powder containing 10 to 80% of at least one of the above and the remainder substantially consisting of Ag is dispersed in an organic solvent.

The bonding temperature is preferably 600 to 900°C.

(2) 10% of at least one of Cu and Ni
-60%, at least one of Ti, Nb, and Zr at 7-90%, at least one of rare earth elements (including Y) at 5 ppm-3%, and the remainder is substantially A.
A paste-like product in which a composite powder having a composition of g is dispersed in an organic solvent. This adhesive is particularly suitable when using SiC as the substrate material. Bonding temperature is 600-900℃
is preferred.

(3) In the adhesive material of (1) or (2) above, 5 μm
An adhesive containing 1 to 10% of any one of the following AQ, 03, Mo, and Sio2. This adhesive is alumina,
It is also suitable for substrates made of various ceramic materials such as aluminum nitride and SiC. Bonding temperature is 830-900℃
is preferred.

(4) At least one of Ti, Zr and Nb: 15-25%, Ni: 5-15%, Ag: 35-45
%, Cu: 25-35%, and Si: 1-7%, which is made into a paste by dispersing it in an organic solvent. This adhesive is suitable when using SiC as the substrate material. The bonding temperature is preferably 750 to 950°C.
Yes.

(5) At least one of Ti, Zr and Nb: 10-20%, Ni: 5-10%, Cu: 18-28
%, Si: 2 to 10%, SiC: 10 to 30%, and the balance is Ag. This adhesive is particularly suitable when using SiC as the ceramic substrate material. The bonding temperature is preferably 750 to 950°C.

All of the above adhesives are printed on the surface of the ceramic substrate and the surface of the conductive metal plate, dried and degreased, and then under appropriate bonding conditions, such as applying a load of 1 to 10 kg/cm2 and reducing the pressure to 1 O-3 Torr or less. The bonding may be carried out by heating and bonding at the above-mentioned heating temperature under or in an inert atmosphere.

Note that the above adhesive can also be used in the form of powder, sheet, or the like.

After joining or forming a circuit, the surface of the conductive metal plate is subjected to peening treatment. The peening treatment may be carried out under the conditions normally used, and examples include air blasting treatment and the like. Through this treatment, compressive stress is applied to the metal plate, so even if tensile stress in the contraction direction is applied to the metal plate during the thermal cycle process, the compressive stress is canceled out and the residual stress is relaxed or evenly distributed. This prevents the joint from peeling off or the board from cracking.

Next, examples of the present invention will be shown.

(Example) As a raw material powder, powders having the components shown in Table 1 were prepared and blended (parts by weight).

In addition, in the case of Ti-Cu-Ag adhesive in the same table, sponge titanium powder (classified to -20 μm) 20 parts silver powder (average particle size 1.6 μm) 40 parts copper powder (average particle size 1 .5 μm) 40 copies were prepared.

In addition, in the case of a Ti-Ag-Cu-Ni-8L-SiC adhesive, 16 parts of sponge titanium powder (classified to -20 μm), 32 parts of silver powder (average particle size of 1.6 μm), and 8 parts of carbonyl nickel powder are used. Silicon powder 6 parts SiC fine powder
I have prepared 14 copies.

As a pretreatment, these were mixed and crushed for 5 hours using a crusher to obtain a composite powder. After mixing and grinding, Fisher sub-
The average particle size was measured with a sieve sizer and found to be 1.3 μm in all cases.

Next, a vehicle was added to this mixed and pulverized product in the following ratio, and the mixture was pre-kneaded for 5 hours using a grinder. The purpose of pre-kneading is to improve dispersibility by activating the powder surface and bringing it into contact with the vehicle.

The above mixed pulverized product 80 parts by weight Ethylcellulose 1.5N Texanol
16.7 #Surfactant 1.8
After the preliminary mixing was completed, main mixing was performed using a three-roll mill to obtain a paste-like adhesive material.

Next, 9 with dimensions of approximately 2.5 mm opening x 0.635 nv + t.
6% An, ○, substrate, A12N substrate and SiC substrate,
A copper plate with a 25 mm opening and a thickness (111 m) shown in the same table and 5
The above paste was printed on one entire surface of each US304 board by a screen printer using a 200-mesh, bias tension, emulsion-thickness screen of 45 μm.

After printing, it was dried at 120°C for 30 minutes and degreased at 600'C in a nitrogen stream for 20 minutes.

Next, using the combinations shown in Table 1, metal plates were stacked on both sides of the substrates in a nitrogen stream at 850° C. so as to form a sandwich structure with the substrates at the center, and they were bonded together by heating.

After bonding, the cut samples were subjected to a thermal cycle test. In this test, the bonded sample was mounted as it was on a thermal cycle testing device, and one cycle was -55°C for 30 minutes and +150'C for 30 minutes, and the number of cycles until the board was destroyed was checked.

In addition, the above-mentioned thermal sancle test was also conducted on samples whose metal plate surfaces were subjected to peening treatment after bonding.

In addition, for the peening treatment, alumina (product name A-
40 morundum) #8o, pressure 3 kg/cm
Air blast treatment was performed in step 2. The above test results are also listed in Table 1.

As is clear from the table, the circuit boards that were not subjected to peening treatment peeled off after almost 5 cycles, whereas the circuit boards according to the examples of the present invention that were subjected to peening treatment did not peel off until after 50 cycles. It showed remarkable thermal shock resistance. Furthermore, it can be seen that the present invention example can be applied to bonding ceramic substrates and conductive metal plates made of any material.

Note that the peeling mode was such that the substrate cracked at the center in all cases.

[Blank 1 (Effects of the Invention) As detailed above, according to the present invention, an adhesive made of composite powder having a specific physical structure is used when bonding a conductive metal plate to a ceramic substrate. Therefore, peeling or cracking of the circuit board can be effectively prevented even if the circuit board is repeatedly subjected to severe thermal history.

Claims (1)

[Claims] When manufacturing a circuit board that forms a circuit on a ceramic substrate, a conductive metal plate is attached to the ceramic substrate using an adhesive made of a composite powder that is mechanically interlocked and bonded by a mechanical alloying method. A method for manufacturing a circuit board, characterized by subjecting the surface of a metal plate to peening treatment.