JPH0258295A - Manufacture of base material for printed circuit board - Google Patents

Abstract

PURPOSE:To obtain a base material for printed circuit boards having a good adhesive property to an insulating resin surface film, especially a heat resisting adhesive property under a hygroscopic condition, by performing a mechanical surface roughening process to the surface of an Al or Al-alloy plate and a DC electrolytic process in an electrolytic solution composed principally of nitric acid after the plate is subjected to a chemical etching process. CONSTITUTION:The surface of an Al or Al-alloy plate is roughened within a roughness range of 1-15mum Rmax by performing a mechanical surface roughening process to the surface, and then, a DC electrolytic process is performed to the plate by dipping the plate in an electrolytic solution composed principally of nitric acid after the plate is subjected to a chemical etching process of an etching depth of 0.5-6mum. For example, the surface of the Al plate which is made of the H24 material specified in JIS A1100 and has a thickness of 1mm is processed to have surface roughness of 6.4mum Rmax by performing an air blasting process by using abrasives of corundum #220 and an injection pressure of 3kg/cm<2>. Then the chemical etching process is performed to an etching depth of 0.5mum by using an aqueous solution heated to 40 deg.C end containing 10wt.% of NaOH. After etching, the plate is subjected to the DC electrolytic process by dipping the plate in an aqueous solution heated to 60 deg.C and containing 10wt.% of nitric acid for 5 minutes under 10V.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method of manufacturing a base material for a printed circuit board used in various electronic and electrical devices, and in particular to a method for manufacturing a base material for a printed circuit board using aluminum or an aluminum alloy. It is about the method.

As is well known in the art, printed circuit boards are made by forming an insulating resin layer made of epoxy resin, polyimide #4 resin, etc. on a plate-shaped base material made of metal, resin, ceramics, etc., and then forming a circuit on top of this. A conductive thin film such as copper foil is formed for formation.

In recent years, with the high-density packaging of FC, LSI, etc., there has been a stronger demand than ever for substrates for printed circuit boards to have excellent heat dissipation properties. As for the material, aluminum or aluminum alloy is used because it has good thermal conductivity, excellent heat dissipation, good workability, can withstand deformation such as bending, and has excellent electromagnetic shielding properties. It has become so.

By the way, it is necessary for the base material for a printed circuit board to have good adhesion to the insulating resin layer formed thereon. If this adhesion is poor, defects such as blistering or peeling may occur during soldering to mount ICs, LSIs, etc. on circuits, or peeling of the coating may occur during the etching process for forming circuit patterns, resulting in poor insulation. This may cause inconveniences such as decreased sexual ability. However, aluminum and its alloys generally do not have good adhesion to resins, and particularly have poor heat-resistant adhesion under moisture absorption. Therefore, when using aluminum or aluminum alloy for printed circuit boards,
In order to improve the adhesion with the insulating resin layer, it was necessary to perform a surface treatment on the surface of the aluminum or aluminum alloy plate in advance.

Conventionally, the following surface treatments have been performed on aluminum or aluminum alloy plates for printed circuit boards to improve adhesion to resin.

A: Perform mechanical surface roughening treatment.

B: After mechanical roughening treatment, chromic acid treatment is performed.

C: Anodizing treatment is performed after chemical etching treatment.

D: After R mechanical surface roughening treatment, an amino-based silane coupling solvent is applied.

E: A crosslinked polyolefin resin layer is provided.

F: Anodized film is provided.

G: Perform alkali etching.

Problems to be Solved by the Invention Although the conventional methods described above can improve the adhesion between aluminum or aluminum alloy plates and resin to some extent, they are still insufficient for use as printed circuit boards, especially in moisture-absorbing conditions. Therefore, there is a strong desire to develop a method that can reliably and sufficiently improve heat-resistant adhesion with resins.

On the other hand, when a conductive aluminum or aluminum alloy plate is used as a base material for a printed circuit board,
It is necessary to ensure that the surface treatment of the base material does not adversely affect the electrical insulation properties of the insulating resin film, but among the methods described above, the method of mechanically roughening the surface If the unevenness of the rear surface is too large, insulation #ff
1. Locally thin portions may occur in the film, resulting in loss of electrical insulation.

This invention was made against the background of the above circumstances, and is basically insulating! The object of the present invention is to provide a method for producing a substrate for a printed circuit board made of aluminum or an aluminum alloy, which has excellent adhesion to the M resin film, especially heat-resistant adhesion under humidity.

A second object of the present invention is to combine v! with insulating resin! P.I.
Provided is a method for manufacturing a base material for a printed circuit board made of aluminum or an aluminum alloy that has excellent appetability, especially heat-resistant adhesion under the condition, and at the same time does not impair the electrical insulation properties of the insulating resin layer. The purpose is to

Means to Solve the Problem An effective method for improving the adhesion of aluminum plates with resin is to electrolytically treat them in an electrolytic solution containing nitric acid as the main component to form minute pores (micropores). A possible method is to form it on the surface of an aluminum plate. In this case, it is expected that the resin will penetrate into the micropores and the IW properties with the resin will improve due to the so-called anchor effect.

However, according to detailed experiments conducted by the present inventors, it is difficult to achieve sufficient adhesion simply by electrolytic treatment in a nitric acid electrolytic bath. 2
! l! It has been found that it is extremely effective to perform appropriate mechanical surface roughening treatment and chemical etching treatment in that order prior to the treatment to sufficiently improve adhesion. On the other hand, if emphasis is placed on electrical insulation as well as improved adhesion with the resin, the b1 mechanical shaving treatment described above may be omitted, and an appropriate chemical etching treatment may be performed prior to the electrolytic treatment in a nitric acid electrolytic bath. It has been found that it is effective to improve the adhesion with the resin without impairing the electrical insulation properties.

Therefore, the first invention of this application is to mechanically roughen the surface of an aluminum plate or aluminum alloy plate to produce a base material for a printed circuit board so that Rmax falls within the range of 1 to 15 IJa. It is characterized in that it is roughened, then chemically etched to an etching depth of 0.5 to 6 μm, and then subjected to direct current electrolytic treatment in an electrolytic solution containing nitric acid as a main component.

In addition, the second invention of this application is that when manufacturing a base material for a printed circuit board, the surface of an aluminum plate or aluminum alloy plate is subjected to a chemical etching treatment to an etching depth of 0.5 to 10 mm, and then etched with nitric acid. It is characterized by direct current electrolytic treatment in an electrolytic solution containing as a main component.

In the method of the first invention, an aluminum plate or aluminum alloy plate (hereinafter collectively referred to as A1 plate) that has been finished to a predetermined thickness is first subjected to mechanical roughening 51! ! to administer. By roughening the surface in this way, the surface area of the A1 plate increases and the contact area with the resin increases, and when the resin is coated, an anchor effect occurs in the resin, improving the adhesion of the resin. This mechanical surface roughening treatment is 9831! It is necessary to perform this so that the roughness of the subsequent surface is within the range of 1 to 15 degrees in terms of Rmax. R
If Rmax is less than 1, the effect of improving the adhesion with the resin due to surface roughening cannot be obtained, while if Rmax exceeds 15, the adhesion with the resin will be improved, but the unevenness will be too large.
There is a risk that the insulating resin layer will be thin, resulting in poor insulation. Therefore, by mechanically roughening the surface so that Rmax falls within the range of 1 to 15 C, it is possible to improve the adhesion with the resin without impairing the electrical insulation. Note that as a specific method for this mechanical surface roughening treatment, any of air blasting, ball polishing, brush polishing, honing, etc. may be applied, but air blasting is preferable in consideration of productivity.

1 After the mechanical roughening treatment, the A1 plate is subjected to a chemical etching treatment. By performing this chemical etching treatment, the surface treatment layer, polishing debris, etc. generated by the mechanical roughening treatment are removed. If chemical etching treatment is not performed, the surface treatment layer and polishing debris of the A1 plate are difficult to wet with the resin, so that the resin is likely to have coating defects and voids, which may cause blisters in the wood 1117 layer. Furthermore, unless chemical etching is performed before electrolytic treatment, the bores formed during electrolysis will be non-uniform and uniform adhesion will not be achieved.

Therefore, in order to achieve uniform and excellent adhesion with the resin layer, it is necessary to perform chemical etching treatment before electrolytic treatment.

The etching depth (etching depth) in this 98 chemical etching process must be within the range of 0.5 to 6 etchings. If the field is less than 0.5, the above-mentioned effects cannot be obtained,
On the other hand, if the number of peaks exceeds 6, the tips of the unevenness formed by the mechanical roughening process will become rounded, or the fine unevenness will disappear, reducing the density of the unevenness, which will reduce the adhesion of the resin layer. The force-improving effect will be reduced. Note that this chemical etching is normally desirably alkaline etching using NaOH or KOH, etc., and the etching time may be set so as to obtain the etching duration as described above, but preferably the solution temperature is 30 to 30 ℃. 70℃, concentration 1~20w
t%, the time is about 1 to 120 seconds.

Note that after the above-mentioned chemical etching treatment, a desmut treatment for removing smut (dissolved residue) may be performed using hydrochloric acid, sulfuric acid, or the like.

Next, a direct current electrolytic treatment is performed in an electrolytic solution containing nitric acid as a main component. By this DC electrolytic treatment, micropores with an average diameter of about 1 to 10 mm are formed on the surface of the A1 plate. Therefore, in the resin coating process, the resin penetrates into these micropores, creating a strong anchoring effect, and the synergistic effect with the above-mentioned mechanical roughening effect and chemical etching effect causes the resin to adhere tightly. The properties, especially the adhesion to heat-resistant resins, are significantly improved. Here, if hydrochloric acid, sulfuric acid, oxalic acid, chromic acid, etc. are used as the electrolyte, micropores are not formed, or even if they are formed, the micropore diameter is small and the resin does not penetrate deeply, so the above-mentioned problem occurs. No effect is obtained. On the other hand, when alternating current electrolysis is used, smut containing AI(OH>2 as a main component) adheres to the micropores during electrolysis, inhibiting improvement in resin adhesion.

Therefore, the electrolytic treatment must be direct current electrolysis in an electrolytic solution containing nitric acid as a main component.

Note that a small amount of an inorganic acid such as hydrochloric acid, TiA acid, or phosphoric acid may be added to the nitric acid electrolytic solution used in this electrolytic treatment. However, the amount added is preferably less than 0.11%. 0.
If it exceeds 1 wt%, the shape of the bore may collapse and the adhesion of the resin may deteriorate. Also, the concentration of the electrolytic solution is 0.
It is preferably about 5 to iowt%.

If the concentration is less than 0.5%, the number of bores formed per unit area is small, so a sufficient adhesion improvement effect cannot be obtained;
If it exceeds t%, the film may be so dissolved that a bore may not be formed. The bath temperature during electrolytic treatment is 30-7
0°C is preferred. If the temperature exceeds 70°C, ♂ disintegration will be severe and a bore will not be formed, and if it is below 30°C, the liquid resistance will increase and high voltage will be required, making it unsuitable for actual operation. .

Furthermore, it is desirable that the electrolytic voltage be 30V or less. If the voltage exceeds 30V, the melting will be intense, and local dissolution may be uneven or coarse bores may be formed, which is not suitable. Also, the electrolysis time is 1~
It takes about 20 seconds. If it takes less than 1 second, a sufficient number of bores will not be formed and the effect of improving resin adhesion will not be achieved.
On the other hand, if it exceeds 20 seconds, the bore diameter becomes too large, which is inappropriate.

As described above, in the method of the first invention, mechanical surface roughening treatment, chemical etching treatment, and direct current electrolysis in a vII acid bath are performed in that order, thereby achieving excellent adhesion to the resin. can be obtained.

In other words, the relatively large irregularities caused by the mechanical surface roughening q8 process are superimposed with the fine bores caused by direct current electrolysis in the nitric acid bath, resulting in a large anchoring effect. Since the bore is formed uniformly by keeping the holes in place, the anchoring effect due to the bore formation acts uniformly, and chemical etching ff1yJ! This improves wetting with the resin layer, and these act synergistically to provide uniform and sufficient adhesion.

On the other hand, the method of the second invention places emphasis on electrical insulation as well as adhesion with the resin. After performing an etching process, direct current electrolysis is performed in an electrolytic solution containing nitric acid as the main component.

In the method of the second invention, the surface treatment layer, oxide film, etc. produced during rolling of the A1 plate are removed by the first chemical etching treatment. If chemical etching is not performed, the surface treatment layer and oxide film of the A1 plate will not easily blend with the resin, which will easily cause coating gaps and voids in the resin, which will cause blisters in the resin layer and reduce the density of the resin. causing delinquents.

In addition, if chemical etching is not performed before electrolytic treatment, the bores formed during electrolysis will be uneven and will not have uniform adhesion. Therefore, in order to obtain uniform and excellent adhesion with the resin layer, It is necessary to perform chemical etching treatment before electrolytic treatment.In this chemical etching treatment, the etching depth is 0.
．． It must be within the range of 5 to 10 square meters. 0.5a11
If the etching depth is less than 10mm, the above-mentioned effect will not be achieved, and on the other hand, if the etching depth is 10m, the surface treatment layer and oxide film will be sufficiently removed, so it is not necessary to etch the thickness exceeding 10mm.

As for the chemical etching treatment, as in the case of the first invention, it is usually sufficient to use alkaline etching using NaOH or KOH, and the etching time may be determined so as to obtain an etching duration, but preferably WR lagoon is used. is 30-70℃, concentration is 1-20wt%,
The time required for 98 treatments is approximately 1 to 120 seconds. Note that after this chemical etching treatment, desmutting treatment may be performed using hydrochloric acid, sulfuric acid, etc. to remove undissolved residue, as in the case of the first invention.

After the chemical etching treatment, as in the case of the first invention, direct current electrolysis treatment is performed in an electrolytic solution containing nitric acid as a main component.

Through this DC electrolytic treatment, the surface of the Al plate has an average diameter of 1
Micropores perpendicular to the plate surface are formed at ~10 excitations. Since these bores have a larger diameter than those formed by anodizing, the resin easily penetrates into these micropores during the resin coating process, resulting in a strong anchoring effect, which improves the adhesion of the resin, especially Heat-resistant resin adhesion is significantly improved. Also, unlike the irregularities caused by mechanical surface roughening, only recesses are formed on the surface of the original board, so there is no thin part of the insulating resin, which has a negative impact on electrical insulation. There is no risk of damage. Here, if hydrochloric acid, sulfuric acid, oxalic acid, chromic acid, etc. are used as the electrolyte, micropores are not formed, or even if they are formed, the micropore diameter is small and the resin does not penetrate deeply, so the above-mentioned problem occurs. No effect is obtained. On the other hand, when AC electrolysis is used, smut mainly composed of AI(0t()2) is generated in the micropores during electrolysis.
It inhibits the improvement of the richness of IfA fat.

Therefore, the electrolytic treatment must be direct current electrolysis in an electrolytic solution containing nitric acid as a main component.

Furthermore, the nitric acid used in this electrolytic treatment is In the electrolytic solution, as in the case of the first invention, hydrochloric acid, [! 2. A small amount of less than 0.1% of an inorganic acid such as 'lA acid may be added. Further, the concentration of the electrolytic solution is 0.5 to 1 as in the case of the first invention.
It is preferably about 0 wt%, and the bath temperature during the electrolytic treatment is also preferably 30 to 70°C, as in the case of the first invention. Moreover, the electrolytic voltage is preferably 20V or less.

If it exceeds 20 V, local dissolution non-uniformity and coarse bore formation are likely to occur, which is inappropriate. Further, the electrolysis time is about 1 to 20 seconds. If the time is less than 1 second, a sufficient number of bores will not be formed and the effect of improving resin adhesion will not be obtained;
If the time exceeds 0 seconds, the bores will connect with each other and a convex portion will be formed, resulting in a thin portion of the insulating resin layer, which may adversely affect the electrical insulation, and is therefore inappropriate.

As described above, in the method of the second invention, by performing the chemical etching treatment and the DC electrolysis in a nitric acid bath in that order, the electrical insulation properties of the insulating resin layer are not impaired, and the resin is bonded to the insulating resin layer. Excellent adhesion can be obtained. In other words, the anchoring effect of the resin is obtained by the fine bores created by direct current electrolysis in a nitric acid bath, and because the bores are formed uniformly by chemical etching treatment before the electrolytic treatment, the anchoring effect due to bore formation is improved. acts uniformly, and the chemical etching treatment also improves wetting with the resin layer, and these act synergistically to provide uniform and sufficient adhesion, and there is no need for mechanical surface roughening treatment. Therefore, unevenness caused by surface roughening treatment does not adversely affect electrical insulation.

Examples First, Examples 1 and 2 according to the first invention and Comparative Examples 1 to 3 will be shown.

[Example 1, Example 2] A plate with a thickness of 11i made of JIS A1100-H24 material
For the first sample, air blasting was performed as mechanical surface roughening treatment. Morundum #220 is used as the abrasive in this air blasting process, and its injection pressure is 3k (
+/ci. Surface roughness after air blasting (R
nax) are shown in Table 1. Then 10wt% at 40℃
Chemical etching treatment was performed using an aqueous NaOH solution. The etching child at this time is 0.5 trend. after that,
Direct current electrolysis treatment was performed using a 10 wt % nitric acid aqueous solution at 60°C. The electrolytic treatment conditions are shown in Table 1.

[Comparative Example 1] About 2 similar A1 plates were subjected to air blasting as n-mechanical surface roughening treatment in the same manner as described above.

The conditions for this air blasting treatment are the same as in Examples 1 and 2. Note that chemical etching treatment and electrolytic treatment were not performed.

[Comparative Example 2] The same A1 tentative as above was subjected to air blasting as a mechanical surface roughening treatment in the same manner as above.

The conditions for this air blasting treatment are the same as in Examples 1 and 2. Then, as in Example 1.2, 10
Etching fi 0.5 using wt% NaOH aqueous solution
74 chemical etching treatments were performed. Note that no electrolytic treatment was performed.

[Comparative Example 3, Comparative Example 4] The same A1 plate as described above was subjected to air blasting as a mechanical surface roughening treatment in the same manner as described above.

The conditions for this air blasting treatment are the same as in Examples 1 and 2. Next, direct current electrolytic treatment was performed immediately without chemical etching treatment. This electrolytic treatment was carried out under the electrolytic conditions shown in Table 1 using a 6 wt % f14 acid aqueous solution at 60° C., as in Example 1.2.

[Performance Evaluation 1] The above Examples 1.2 and Comparative Examples 1 to 4! a! ! Jl
A 40# thick epoxy resin was applied as an insulating resin layer to the surface of each A1 plate, and a 35°C thick electrolytic copper foil was pasted on top of the insulating resin layer.
Cooked under heat and pressure for 0min. Then 55in x 2511
Cut into i size, heat resistant 1! ! This was used as an appetizing test piece.

For each test piece, 121℃ x 1 in an autoclave.
After absorbing moisture for 6 hours, it was floated on a solder bath at 260°C. Thereafter, the copper foil was peeled off, and the heat-resistant adhesion of the A1 plate to the resin was evaluated based on the exposed area of aluminum. The results are shown in Table 1. The adhesion evaluation is ○ when the exposed area of aluminum is 0%, and △ when the exposed area of aluminum is more than 0% and less than 50%.
, cases of 50% or more are indicated by ×.

Table 1 As shown in Table 1, an example of the first invention in which shot blasting as mechanical surface roughening treatment, chemical etching treatment, and DC electrolysis treatment in a nitric acid electrolytic bath were performed in that order. According to the above, it is clear that an A1 substrate for a printed circuit board having extremely excellent heat-resistant adhesion to an insulating resin layer can be obtained.

Next, Examples 3 to 5 and Comparative Examples 5 and 6 according to the second invention will be shown.

[Examples 3 to 5] A1 plate similar to that used in Example 1.2 was heated at 40°C.
A chemical etching process was performed using a 10W [% Na OH* solution]. The amount of chemical etching at this time is shown in Table 1. Next, direct current electrolysis was performed using a 2 wt % nitric acid aqueous solution. The electrolytic bath temperature at this time was as shown in Table 2, the electrolytic time was 2 seconds, and the electrolytic voltage was 5 .mu.m.

[Comparative Example 5] Direct current electrolysis using a 21% nitric acid aqueous solution was performed on an A1 plate similar to the above without chemical etching. The electrolytic bath temperature at this time was as shown in Table 2, the electrolytic time was 2 seconds, and the electrolytic voltage was 5 .mu.m.

[Comparative Example 6] Regarding the same AI board as above, 10 wt% NaO at 40°C
A chemical etching process was performed using a H aqueous solution.

The amount of chemical etching at this time is shown in Table 2.

Note that no electrolytic treatment was performed.

[Performance Evaluation 2] Four layers of epoxy resin were applied as an insulating resin layer to the surface of each A1 plate treated in Examples 3 to 5 and Comparative Examples 5 and 6.
Coat it to a thickness of 0IJIn, paste a 35cm thick electrolytic copper foil on top, and press it at 165℃ x 901cm.
It was cooked under heat and pressure. Thereafter, it was cut into a size of 55ux and 25nra to obtain a heat-resistant adhesion test piece.

Each test piece was hung at 121°C in an autoclave.
After absorbing moisture for 6 hours, it was floated on a solder bath at 260°C. Thereafter, the copper foil was peeled off, and the heat-resistant adhesion of the Ai plate to the resin was evaluated based on the exposed area of aluminum. Regarding electrical insulation, the withstand voltage was investigated according to JIS C64131. The results are shown in Table 2.

Obtainable.

Table 2 Effects of the Invention As is clear from the above examples, according to the method of the first invention, aluminum or aluminum alloy has excellent adhesion to the insulating resin layer, especially heat-resistant adhesion under moisture absorption. It is possible to obtain a base material for a printed circuit board made of.

Further, according to the method of the second invention, a printed circuit board made of aluminum or aluminum alloy that has excellent heat-resistant adhesion with the insulating resin layer i layer and does not impair the electrical insulation properties of the insulating resin layer. A base material for use can be obtained.

As shown in Table 2, according to the embodiment of the second invention in which chemical etching treatment and direct current electrolysis treatment in a nitric acid electrolytic bath were performed in that order, the heat-resistant adhesion to the insulating resin layer was good and the insulation Applicant: Sky Aluminum Co., Ltd. for A1 board for printed circuit boards that does not impair the electrical insulation properties of the resin layer

Claims (2)

[Claims] (1) Rmax is 1 to 15 μm by mechanically roughening the surface of the aluminum plate or aluminum alloy plate.
rough surface within the range of , then etching depth 0.5 to 6
1. A method for manufacturing a base material for a printed circuit board, which comprises performing a chemical etching treatment of micrometers, followed by direct current electrolysis treatment in an electrolytic solution containing nitric acid as a main component. (2) Printing characterized by chemically etching the surface of an aluminum plate or aluminum alloy plate to an etching depth of 0.5 to 10 μm, and then subjecting it to direct current electrolytic treatment in an electrolytic solution containing nitric acid as the main component. A method for manufacturing a base material for a circuit board.