JPS6083399A - Multilayer printed circuit board and method of producing same - 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 Application of the Invention] The present invention is directed to improving the adhesion between a circuit conductor and a resin in a multilayer printed circuit board having a plurality of conductor layers constituting a circuit network on the surface and inside. The present invention relates to a multilayer printed circuit board with improved reliability and a method for manufacturing the same.

[Background of the invention]

Conventionally, when bonding this type of circuit board, the copper foil used for the intermediate layer has been a double-sided roughened foil whose surface in contact with the adhesive prepreg has been roughened to the same roughness as the matte surface (back surface of the copper foil). A method of supplementing the adhesion between the prepregs on the circuit copper foil by using copper oxide or by forming a film of cuprous oxide or cupric oxide is used.

However, double-sided roughened copper foil is more expensive than ordinary single-sided roughened copper foil.

Recently, chemical copper plating films have been increasingly used as circuit conductors in place of the electrolytic copper foils described above due to considerations such as pattern accuracy and economical efficiency.

In the case of chemical copper plating films, the major difference from conventionally used copper foils (electrolytic copper foils, rolled copper foils) is that they generate an extremely large amount of hydrogen gas when heated. Therefore, when each circuit board is bonded in layers under heat and pressure via prepreg, a part of the cuprous oxide or cupric oxide film formed on the surface of the copper foil is reduced by hydrogen due to the heat. The inventors of the present invention found through their studies that the adhesive force between the circuit surface and the prepreg decreases because the prepreg returns to its original state. - This point will be explained in detail using the attached Figure 1. Figure 1 is a schematic diagram of the multilayer adhesion process and the outer i-circuit conductor formation process in the case of manufacturing an example of a multilayer printed circuit board, and (°) indicates each stage before multilayer bonding. Placement of parts! Figure (b) shows a multilayer printed circuit board. In No. 1 and 1, the code 1 means the outer layer circuit board, 2 means the inner layer circuit board, 5 means chemical copper, 4 means copper oxide coating, 5 means prepreg, 6 means outer layer circuit copper, and 7 means through hole plating film. do.

However, in the prior art, it has been found that in the multilayer bonding process, a portion of the copper oxide film 4 is reduced and returned to the original copper, resulting in a decrease in adhesive strength as described above.

[Purpose of the invention]

An object of the present invention is to provide a multilayer printed circuit board with improved interlayer adhesion and reliability of a multilayer printed circuit board having a chemical copper plating film, and a method for manufacturing the same.

[Summary of the Invention] □ To summarize the present invention, the first invention of the present invention is a machine relating to a multilayer printed circuit board, which comprises a chemical copper plating coating as at least a part of the circuit conductor of the inner layer printed circuit board. A multilayer printed circuit board using the present invention is characterized in that the circuit board is subjected to dehydrogenation treatment during its manufacturing process.

Further, a second invention of the present invention relates to a method for manufacturing a multilayer printed circuit board according to the first invention, wherein the hydrogen content in the chemical copper plating film component is reduced to 50% before multilayer adhesion.
It is characterized by performing dehydrogenation treatment to reduce the hydrogen content to ppm or less.

As mentioned above, the present inventors have found that the presence of hydrogen is disadvantageous during multilayer bonding, particularly that the presence of hydrogen in excess of a certain amount is undesirable.

Examples of dehydrogenation treatment include treatment in an oxidizing atmosphere at normal pressure or reduced pressure, treatment using a hydrogen adsorbent, and the like.

However, as a result of various studies, the inventors of the present invention have found that heat treatment under normal pressure is optimal in terms of ease of treatment, influence on post-treatment, dehydrogenation effect, etc.

Furthermore, as a result of examining the allowable amount of residual hydrogen, including the timing of dehydrogenation treatment, the inventors found that when using a chemical copper plating film as an inner layer circuit conductor, If a cuprous oxide or cupric oxide coating is formed after the hydrogen gas in the chemical copper plating film is expelled to 50 ppm or less by heat treatment, the decrease in adhesive strength after multilayer adhesion as in conventional methods is avoided. I found out that it disappears.

Furthermore, it has been found that performing the above heat treatment after forming a cuprous oxide or cupric oxide coating on the chemical copper plating surface and before bonding has some effect.

The heat treatment performed in the present invention is carried out around 10'01::, which is usually performed after chemical copper plating (1 to 2 hours at D temperature & heat treatment, so that the amount of residual hydrogen in the chemical copper plating film exceeds 50 ppm. , No effect at all.The heating temperature is 110℃~
It is effective in the range of 300°C, but preferably 120-200°C.
It was found that a temperature range of 60°C was best. On the other hand, at low temperatures, it is difficult for hydrogen gas to be sufficiently discharged from the copper coating, so an extremely long heating time is required, resulting in poor workability.

Furthermore, if the heat treatment temperature is too high, the copper coating will be oxidized and physical properties will deteriorate.

In the present invention, the hydrogen content in the copper coating is 30 ppm.
When the temperature exceeds 100%, a part of the oxide film in contact with the prepreg on the copper film is reduced by the hydrogen gas generated in the film due to heating during multilayer adhesion and returns to the original copper, making it difficult to bond with the prepreg. Power decreases. In other words, the target is 0, 6
kg/c! In order to obtain adhesive strength of n or more, 30
It needs to be less than ppm.

The amount of hydrogen in the copper foil was measured by heating and melting the copper foil (approximately 1500° C.) in an inert gas atmosphere and measuring the amount of hydrogen generated. The measuring equipment used was Kokusai Denkisha '4'! It is "Nitromat".

[Embodiments of the invention]

Next, the present invention will be explained in more detail with reference to Examples, but the present invention is not limited thereto.

The chemical copper plating method used in the present invention is as shown below.

A method: Full additive method (A method developed by Hitachi, Ltd.)
The method used the chemical copper plating solution used in the P'-11 method), and the plating pretreatment and temperature conditions were all the same. (Refer to %'i' Publication No. 56-27594) Method B: Pre-plating treatment using the chemical copper plating solution used in the fully additive method (CC-4 method) carried out by Hitachi Chemical. All conditions such as temperature and so on were the same.

Example 1 A hole of φ050 for interlayer connection was drilled in a polyimide copper-clad laminate (MOL-■-67.02 washing thickness, manufactured by Hitachi Chemical Co., Ltd.) with ultra-thin copper foil of 9 μm thick laminated on both sides. After that, a chemical copper plating film (thickness 35 μm) was applied to the entire surface by method A.
m) was formed.

At this time, the hydrogen content in the chemical steel plating film was 55 ppm.
Met. Thereafter, it was heat-treated in a constant temperature bath at 200° C. for 1 hour. It was confirmed that the hydrogen content in the chemical copper plating film after heat treatment was reduced to 15 ppm. After this, a circuit was formed by etching. Then, it was degreased and surface roughened by immersion in ammonium persulfate aqueous solution g (zoor/4) at home temperature for 30 seconds. )
, in an aqueous solution of sodium chlorite (502/l), 7
After processing at 0 to 80°C for 120 seconds, it was dried at 100°C for about 1 hour to form an oxide film.Next, each inner layer circuit board created as described above was coated with polyimide prepreg (G Multi-layer bonding was carried out using A-67N°, 0.1 field thickness, manufactured by Hitachi Chemical Co., Ltd.). The heating conditions at this time were 130 to 170°C for 90 minutes, and the pressure was 26 kg/l, I.

Finally, after drilling through holes and plating, a circuit conductor for the outer layer was formed to create a multilayer printed circuit board with 12 conductor layers.

Example 2 Example 1 except that the above method B was used as the chemical copper plating method
A multilayer printed circuit board was created in exactly the same manner as above. However, the hydrogen content in the chemical copper plating film before heat treatment is 1
1', 5 ppm, but after heat treatment at 200° C. for 1 hour, it was confirmed that it was 28 ppm.

Example 3 Epoxy-based -MOL-60 as double-sided copper-clad laminate
A multilayer printed circuit board was prepared in exactly the same manner as in Example 1, except that GFA-608N (manufactured by Hitachi Chemical Industries, Ltd.), also an epoxy type, was used as the multilayer adhesive prepreg. However, the heat treatment of the chemical copper plating film was performed at 170° C. for 120 minutes. The amount of hydrogen is 25
ppm.

Example 4 Surface roughening treatment using cupric chloride (40 r/l), hydrochloric acid (
The treatment was carried out at 45°C for 50 seconds in an aqueous solution of
t/l), copper sulfate (sr/l), ammonia (1p/4
') in an aqueous solution at 70 to 80°C for about 120 seconds,
A multilayer printed board was produced in exactly the same manner as in Example 3 except that the oxide film formation treatment was performed. The amount of hydrogen in the chemical copper gloss coating was <25 ppm, the same as in Example 3.

Example 5 A multilayer printed board was produced in exactly the same manner as in Example 1, except that the heat treatment after chemical copper plating was performed after the oxide film was formed. Note that the amount of hydrogen was the same as in Example 1 (15 pp'm).

Fruit Example 6 A multilayer printed circuit board was produced in exactly the same manner as in Example 6, except that the heat treatment conditions for the chemical steel plating film were 50° C. and the filtration time. The hydrogen content in the chemical copper plating film after the heat treatment was 18 ppm.

Example 7 A multilayer printed circuit board was produced in exactly the same manner as in Example 1, except that the chemical copper plating film was formed in a pattern. However, in this case, after the heat treatment, the ultra-thin copper film other than the pattern area was removed by etching. Heating conditions are 190℃
, 60 minutes. In addition, chemical copper plating coat 5 after heat treatment
The hydrogen content in the film was 20 ppm.

Comparative Examples 1 to 3 Multilayer printed circuit boards were prepared in the same manner as in Examples 1 to 3 except that the heat treatment of the steel plating film was not performed.

The properties of the chemical copper plating films obtained in each of the above Examples and Comparative Examples are summarized in Table 1.

Table 1 In Table 1, the adhesive strength between the inner layer copper and the prepreg was measured by cutting out the inner layer copper (from the surface) and measuring the peeling strength of the inner layer steel between the inner layer copper and the prepreg.

Hydrochloric acid seepage during through-hole plating pretreatment was observed by cutting a cross section after through-hole plating. □ Soldering heat resistance was determined by floating a test piece in a solder bath at 260°C and measuring the time until blistering occurred.

〔Effect of the invention〕

As is clear from the above description, the multilayer printed circuit board manufactured according to the present invention has excellent adhesive strength, acid resistance, and heat resistance, and is extremely reliable.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a multilayer bonding process and a multilayer circuit conductor forming process in the case of manufacturing an example of a multilayer printed circuit board. □ 1: Circuit board for outer layer, 2: Circuit board for inner layer, 3: Chemical copper, 4
Copper dioxide coating, 5: prepreg, 6: outer layer circuit copper, 7
: Through-hole plating membrane patent applicant: Hitachi, Ltd. □ Agent: Hiroshi Nakamoto Figure 1

Claims (1)

[Claims] 1. A multilayer printed circuit board using a chemical copper plating film as at least a part of the circuit conductor of the inner layer printed circuit board, wherein the circuit board is subjected to dehydrogenation treatment during its manufacturing process. A multilayer printed circuit board characterized by its solidity. 2. In a method for manufacturing a multilayer printed circuit board using chemical copper plating 1 as at least a part of the circuit conductor of the inner layer printed circuit board, hydrogen content in the chemical steel plating fatigue film component is removed before multilayer bonding. 5 of a multilayer printed circuit board characterized by performing a dehydrogenation treatment to reduce the amount of hydrogen to 30 ppm or less, the dehydrogenation treatment is performed after the formation of a copper oxide film after the formation of a copper plated film. A method for manufacturing a self-mounted multilayer printed circuit board according to claim 2, including heating at 110° C. or higher before or after the treatment.