JPH0297686A - Production of enameled substrate - Google Patents

Abstract

PURPOSE:To obtain an enameled substrate having high adhesive strength between the enamel coat and metal core by forming an oxide coating film on a metal core of an Fe-Ni alloy, immersing the core in a slurry contg. dispersed frit having a specified compsn., electrodepositing the frit and carrying out calcining. CONSTITUTION:An oxide coating film of 100Angstrom -5mum thickness is formed on a metal core consisting of Fe and 35-50wt.% Ni. The core is immersed in a slurry prepd. by dispersing frit contg. BaO, SiO2, MgO and B2O3 in an org. solvent and the frit is electrodeposited on the core by electrophoresis. Calcining is then carried out at a high temp. The resulting enamel coat bonds firmly to the surface of the metal core through the oxide coating film having satisfactory adhesion and an enameled substrate having superior adhesion and a low coefft. of thermal expansion is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for manufacturing a printed circuit board in which the surface of a metal substrate is enameled.

<Conventional technology> Enamel substrates are particularly easy to increase in size, are less expensive than ceramic substrates, are easier to process and mold, and have better heat dissipation than ordinary ceramic substrates (alumina). Since then, it has been used in various fields in recent years.

Conventional enamel substrates are made by coating the surface of a metal core such as iron, copper, or aluminum with crystalline glass or the like, and then printing and firing a metal glaze resistor to form a circuit pattern.

<Problems to be solved by the invention> However, when an IC package with a semiconductor element is mounted on the surface of such a conventional enamel substrate, or a bare IC chip is directly mounted, the metal core Because the coefficients of thermal expansion of the materials used, such as iron, aluminum, and copper, are large, the solder joints with the IC package and the IC chip itself may peel or crack due to thermal stress caused by heating and cooling. It was inevitable.

Therefore, in order to solve the problem caused by the difference in thermal expansion coefficient (α), an IC package or a ``bare IC'' is attached to the metal core.
Attempts have been made to use a Pe--Ni alloy with a small α that matches the α of the C chip.

However, since such Fe-Ni alloys have excellent high-temperature oxidation resistance, they have a problem in that strong adhesion cannot be obtained between the enamel coating layer and the metal core at the firing temperature.

Therefore, as a method to eliminate this drawback, attempts have been made to roughen the surface by pickling or blasting to improve adhesion. However, this method requires a lot of effort due to pickling and blasting, and also has the problem that the smoothness of the metal core may be lost, and large substrates are likely to warp.

The present invention provides a method for manufacturing an enamel substrate that solves the problems of the conventional techniques.

<Means for Solving the Problems> In order to solve the above-mentioned problems, the present inventors have conducted intensive research and found that F has excellent high-temperature oxidation resistance and has a small coefficient of thermal expansion.
An oxide film of 100 Å to 5 μm is provided in advance on the metal core of the e-Ni alloy, and it is coated with BaO, SiO2MgO, B, O.
By immersing a frit of crystallized glass containing . The present invention was completed based on the discovery that an enamel substrate with strong adhesion can be obtained.

Function> The metal core used in the present invention has excellent high-temperature oxidation properties, and
Pe-Ni (35-50
It is an alloy with a composition of
Generally, such a method of adjusting the atmosphere has the problem of high cost, so a method of forming the oxide film in the atmosphere to a thickness of 100 Å to IO μm is usually preferably used.

Here, the reason why the thickness of the oxide film is limited to 100 Å to 5 μm is that if there are fewer than 100 people, the effect of improving adhesion will be weak;
This is because if it exceeds this, floating rust is likely to occur, and on the contrary, adhesion is reduced and peeling is likely to occur.

The oxide film formed in this way to a thickness of 100 Å to 5 μm on the surface of the Fe-Ni (35 to 50% by weight) metal core has excellent adhesion to the metal core of the base material, and can be used as a substitute. As BaO, SiO2, MgO.

B, 0. When electrophoretic electrodeposition is performed by immersing a crystallized glass containing a mixture in a slurry dispersed in an organic solvent such as iso-propanol, uniform electrodeposition can be achieved without causing any electrodeposition problems.

In addition, by firing the object to be coated after electrodeposition using the usual method, a strong bond can be obtained between the coated material and the enamel coating layer through the highly adhesive oxide film formed on the surface of the metal core. , an enamel substrate with excellent adhesion and a small coefficient of thermal expansion can be obtained.

<Example> The content of the present invention will be specifically explained below with reference to Examples.

Using a metal core made of an Fe-Ni alloy having a composition of Examples 1 to 4 shown in Table 1 with a small coefficient of thermal expansion,
Heating to 0°C, Fe, 10. The surface was oxidized so that the thickness of the oxide film was assumed to be 200 Å to 3 μm.

Next, electrodeposition was performed in a slurry in which BaO-Mg0-BzOs-SiOx-based crystallized glass frits (maximum particle size of 30 μm or less) were dispersed to a thickness of about 200.17 m after firing, and no rough skin was observed. A coating layer with a smooth surface was obtained. Next, this was fired in a continuous furnace at a maximum temperature of 850°C, and an enameled substrate with a smooth surface without surface defects was obtained.

We conducted an electrodeposition test on these according to JIS R4301, and after mounting the IC package, we tested them at -55℃~
A thermal cycle test was conducted 1,000 times in a temperature range of 150°C to check for cracks in the joints. Table 1 summarizes these results and the results of examining the thermal expansion coefficients before and after the formation of the enamel layer. Separately, for comparison, oxide films were formed on the metal cores of Comparative Examples 1 to 4 in Table 1 below 100 Å and above 5 μm, which are outside the appropriate range of the present invention, and then electrodeposited in the same manner as in the examples. After firing, the obtained substrate was evaluated for characteristics in the same manner as in the examples. The results obtained are shown in Table 1.

As is clear from these results, in Examples 1 to 4 of the present invention, the metal core with a small coefficient of thermal expansion had a thickness of 200 Å to 3 μm.
An oxide film of BaO-MgO-820 is provided on this surface.
, 1-3i02 series crystallized glass frit is electrodeposited and fired, and the substrate has excellent adhesion and a small overall coefficient of thermal expansion, so even when an IC package is mounted on it, the IC package will shrink due to heat cycles. It can be seen that there are no problems such as cracking or peeling of the solder joints.

On the other hand, when the thickness of the oxide film is 100 Å or less as in Comparative Examples 2 and 4, or when the appropriate thickness is 5 Å as in Comparative Example 1.3,
It can be seen that sufficient adhesion cannot be obtained when the oxide film is formed to a thickness of μm or more.

<Effects of the Invention> As detailed above, according to the method of the present invention, BaO can be deposited on a metal core with a low expansion coefficient and excellent high-temperature oxidation properties using an extremely simple method without causing any electrodeposition problems.

Since it is possible to form a coating layer of crystallized glass containing MgO, Bz(h, SiO□) with excellent adhesion, it is possible to mount an IC package on a substrate or use it by directly mounting an IC chip. It is extremely useful.

Agent Patent Attorney Mamoru Takeuchi

Claims (1)

[Claims] (1) After providing an oxide film with a thickness of 100 Å to 5 μm on the surface of a metal core made of Fe-Ni (35 to 50% by weight),
A method for manufacturing an enamel substrate, which comprises immersing a frit of crystallized glass containing BaO, SiO_2, MgO, and B_2O_3 in a slurry in which the frit is dispersed, electrodepositing it by electrophoretic electrodeposition, and firing it.