JPS60241291A - Method of producing printed circuit board - 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] [Technical Field of the Invention] The present invention relates to a method C for manufacturing a printed wiring board, and more specifically,
Improvement of a method for manufacturing printed wiring boards using a semi-additive method in which conductor circuits are formed using a combination of electroless steel plating and electrolytic copper plating using adhesive-coated laminates as starting materials (Related:).

[Technical background of the invention and its problems]

The currently mainstream method for manufacturing printed wiring boards is the so-called subtractive method.

This method is often modified depending on the purpose of use of the printed wiring board, but in all cases an extremely complicated force method is adopted, resulting in high manufacturing costs and extremely high material loss. It has the disadvantage of being large. For example, regarding the copper through-hole method, which is a typical example of the subtractive method, this method:
The process of drilling holes for through holes, ■ The process of forming a thin electroless steel plating film on the surface of the laminate and the inner wall of the through holes to make all surfaces of the laminate electrically conductive, ■ Electrolytic copper plating (4) Applying a photosensitive film to the front and back surfaces of the laminate after electrolytic plating. , After exposing the original image to ultraviolet rays in a pattern, it is developed and a resist film is left over the necessary circuit parts and through-holes. ■ The steel is immersed in an etching solution so that there is no resist film and the copper plating film is exposed. The process consists of a series of steps: 1. removing the resist film by etching; and 2. removing the resist film.

There are two other methods with slightly different processes from this copper through-hole method, but both involve extremely complicated processes and inevitably increase production costs.

Moreover, in the electrolytic plating process, a thick copper plating film is deposited even on non-circuit parts that do not require copper plating film, and then it is removed by etching, which results in a huge amount of etching, which saves resources. From this point of view, this was extremely inconvenient.

On the other hand, in contrast to the above-mentioned subtractive method (2), a printed wiring board manufacturing method using an additive method has recently been attracting attention. This method uses an insulating substrate as a starting material, and the necessary circuit parts including through holes are coated with chemical copper plating. It is a method of forming conductive circuits by simply creating a conductive circuit, and has the advantage of being able to manufacture printed wiring boards at low cost because the process is simple.Also, since etching is often required, there is less material loss and it is excellent from the perspective of resource conservation. There is.

However, in this additive method, since the conductive circuit portion is formed only by chemical copper plating, the deposited copper film is required to have excellent mechanical properties, especially spreadability. Currently used chemical steel plating solutions that meet these requirements have a deposition rate of 1 to 3 μm.
/ hr, and in order to deposit a predetermined copper film thickness (approximately 35 μm), C2 had drawbacks such as a long time of 12 to 35 hours, and a decrease in work efficiency.

In order to solve the above drawbacks, various chemical copper plating solutions have been developed with the aim of improving the deposition rate and mechanical properties, but all of these solutions have a high solution temperature and high pH. This reduced the adhesion between the adhesive layer provided on the front and back sides of the laminate and the deposited copper film, resulting in new drawbacks such as a decrease in peel strength and soldering heat resistance.

[Purpose of the invention]

Therefore, the present invention provides a printed wiring board using a semi-additive method that uses electric steel plating in combination to improve reliability, excellent adhesion between the copper film and the substrate, and to form a copper film of a predetermined thickness in a short time. The purpose is to provide a manufacturing method.

[Summary of the invention]

The method of the present invention includes (a) adhesive application, drying, (b) through-hole drilling, (C) hydrophilization, activation, (DL electroless copper plating, (e) plating resist printing, (f) electricity In a method for producing a printed wiring board comprising the steps of copper plating, (g) plating resist removing IJ, and (hl soft etching), the tonally decomposed copper plating bath contains a copper salt, a ring agent, a PH adjuster, and
Ethylenediaminetetraacetic acid and N as complexing agents.

containing a mixture of N,Nl,N'-tetrakis-(2-hydroxypropyl)ethylenediamine, and containing at least 1a of a sulfur-containing compound, a nonionic surfactant, and an α,α'-dipyridyl or phenanthroline derivative. It is characterized by this.

The method of the present invention will be explained below in order of steps.

First, in the (al process), an adhesive-coated laminate is formed.

Adhesives constituting adhesive-backed laminates are broadly classified into those containing diene-based synthetic rubber and those not containing diene-based synthetic rubber.

Examples of adhesives containing diene-based synthetic rubber include butadiene polymer, butadiene-acrylontrile copolymer, imprene rubber, chloroprene rubber, and acryloft 1.
1-butadiene-styrene copolymer, or a mixture of two or more of these, or a thermosetting resin such as epoxy resin or phenol resin, or silica gel, zirconium silicate, or silicic acid that serves as a reinforcing agent. Materials containing appropriate amounts of magnesium and the like can be spun. However, when adhesives containing these diene-based synthetic rubbers are used, high adhesion can be obtained for circuit layers that are important for printed wiring boards.

In addition, examples of adhesives that do not contain diene-based synthetic rubber include epoxy resins such as bisphenol-type epoxy resins, Novo2-type epoxy resins, and alicyclic epoxy resins, or those made by appropriately blending inorganic fillers with these epoxy resins. Things can be mentioned. When such an epoxy resin adhesive is used, a printed wiring board having excellent electrical properties can be finally obtained.

Among these adhesives, examples of adhesives containing diene-based synthetic rubber include those having the compositions shown in Table 1.

Table 1 In order to form an adhesive-backed laminate according to the present invention, for example, a method of applying an adhesive solution as shown in Table 1 onto the laminate and letting it dry, or a method of temporarily applying an adhesive solution as shown in Table 1, or temporarily After forming an adhesive layer on the transfer film and overlapping it with the prepreg constituting the IDT Jrl board so that the surface of the adhesive contacts the surface of the prepreg, the adhesive layer and the laminate are bonded together under heat and pressure conditions. Examples include a method of integrating.

(b) The step is to drill holes in the adhesive-coated laminate thus obtained at predetermined positions and holes for forming through balls that penetrate through the surface thereof, using, for example, a drill or punching means. , (b) End the process.

(The C1 process is a process in which the surface of the adhesive is roughened and at the same time made hydrophilic, so that the electroless plating film described later is firmly and closely layered with the laminate through the surface of the adhesive. In step (b), the adhesive-coated laminate obtained in step (b) is immersed in an aqueous solution containing an oxidizing agent.

Examples of oxidizing agents include chromic anhydride, chromate,
Permanganate or a mixed system of chromic acid-sulfuric acid, chromic acid-sulfuric acid-phosphoric acid, etc. is suitable.

In this step, the adhesive-coated laminate may be treated with dimethylformamide or the like to swell the adhesive layer, if necessary, prior to immersion in the oxidizing agent solution.

This method provides strong adhesion to the plated film, especially when an adhesive that does not contain a diene-based synthetic comb is used. An example of the composition of the oxidizing agent solution is shown in Table S52.

Table 2 A laminate with a roughened adhesive surface is immersed in a catalytic solution containing a metal or metal oxide that has a catalytic effect on an electroless copper plating bath, and all surfaces are coated with the metal or metal oxide. This is the process of adsorbing metal oxides.

There are two main methods for imparting bicatalytic action to the surface of the laminate; one is to bring the surface of the adhesive into contact with a colloidal solution composed of palladium chloride and tin chloride in an acidic state. The other one was first immersed in a tin chloride solution as shown in Table 3 (2) to adsorb tin chloride on the adhesive surface, then further removed (as shown in Table 2). This is a method in which palladium and palladium chloride are adsorbed in a two-step operation by contacting with a palladium chloride solution.

Table 3 Table 4 In this (C-) step C, the plating catalyst is adsorbed on all the adhesive surfaces including the holes for the through holes,
At this stage, electroless plating is ready to start on all surfaces.

(d) The laminate processed in the above steps (al to (e))
In the step, the steel plate according to the present invention is immersed in an electroless steel plating bath to form a copper plating film on the through-hole portion and surface. Prior to this electroless copper plating, it is preferable to immerse the laminate in an acid or alkaline solution to activate the catalyzed portion.

The electroless copper plating bath according to the present invention includes a copper salt, a reducing agent,
Contains a mixture of ethylenediaminetetraacetic acid and N,N,N',N'-(2-hydroxypropyl)ethylenediamine as a pH adjuster and a complexing agent, and also contains a sulfur-containing compound, a nonionic surfactant, and α, It is characterized by containing at least 1 amount of α'-dipyridyl or phenanthroline derivative.

As the copper salt, the reducing agent, and the pH adjuster in the chemical steel plating solution of the present invention, compounds that have been conventionally used in the preparation of chemical steel plating solutions can be used.

The complexing agent according to the present invention C2, N , N , N/, N
The amount of the mixture of '-tetrakis(2-hydroxypropyl)ethylenediamine and ethylenediaminetetraacetic acid added is usually 1 to 10 times the mole of the copper salt, preferably 1.1 to 2
It is set in the double molar range. If the same molar amount is used, the second problem is that the copper salt will become copper hydroxide and precipitate in the alkaline copper plating solution, and if it exceeds 10 times the molar amount, the effect of adding the complexing agent will be reduced. It is economically unfavorable because it becomes saturated. The mixing ratio is usually 1=4 to 4:1. Preferably, it is set in the range of 2:3 to 3:2.

If N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine is used alone, the mechanical properties, peel strength, and soldering heat resistance of the deposited copper film will deteriorate; When used alone, the precipitation rate decreases, resulting in a decrease in work efficiency.

Examples of the sulfur-containing compound according to the present invention include inorganic sulfur compounds such as sodium sulfide, potassium sulfide, and silver sulfide; 2-mercaptobenzothiazole, 2-mercaptobenzimidazole, 1-allyl-2-thiourea, l-
Phenyl-2-thiourea, ethylenethiourea Z, 1.3-
dimethylthiourine≠, 1,3-diethylthiourine, l, 3
- MAm yellow compounds such as dibutylthiourea, dodecylmercaptan, and n-octadecylmercaptan. The amount of these additions is usually 0. O1~10rl/J
, preferably set in the range of 0.1 to 5 mf'/l. If it is less than o, o imy/l, the stability will not improve much, and if it exceeds lQmf/r, the precipitation rate will be extremely reduced, leading to a decrease in work efficiency.

The amount of nonionic surfactant added to the plating bath according to the present invention is preferably in the range of 30 mr/l to 20 f/l. If the amount added is outside this range, the mechanical properties, peel strength, and soldering heat resistance of the resulting copper-plated film will deteriorate.

Zenatroline derivatives used in the present invention include, for example, l,10-phenanthroline, 2,9-dimethylphenanthroline, 2,9-dimethyl-4,7-cyphenylphenanthroline, 2,9-dimethyl-4,7
-cyhydroxyphenanthroline, 2,3,8.9-dibenzo-4,7-dimethyl-5,6-cyhydroxyphenanthroline, and the like.

Further, the amount of α,α'-dipyridyl or phenanthroline derivative added to plating bath C is preferably in the range of 2 to 50 mv/l.3. If it is outside this range, the mechanical properties, peel strength, and soldering heat resistance of the copper-plated film will deteriorate, as in the case of nonionic surfactants.

Further, in the electroless copper plating bath according to the present invention, it is preferable that the temperature is 0 or more and the PI-I is in the range of 11.7 to 12.8, and each condition is within this range. If it comes off, the mechanical properties of the copper plating film, peel strength,
Solder heat resistance and stability decrease.

(The EL process is a process in which a plating resist film is formed on the surface of the adhesive other than the area where the conductor circuit is to be formed, and this process is used to prevent copper plating from depositing on this area in the electrolytic copper plating process described later. This is the process of applying

The resist film is a strong film that does not elute from the plating bath, and is formed by applying an epoxy resin or the like by screen printing and curing it by heat treatment or ultraviolet irradiation treatment. In addition to this printing method, it is also possible to use a photographic method in which a so-called photosensitive film is placed on the surface of the adhesive (thus, a resist film is formed on the non-circuit portions).

Step (f) is a step of growing a copper film to a desired thickness by electrolytic copper plating on the necessary electrical pattern parts including the hole walls.

Step (g) is a step of peeling off the tinted resist applied in step (e).

(The hl process is a process in which the copper plating film formed on the non-circuit parts of the laminate in the dl process is removed by immersion in a copper etching solution F2.

As described above, it is possible to produce a printed wiring board with sufficient reliability in terms of strength, peel strength, solder heat resistance, etc. in a short period of time.

[Embodiments of the invention]

EXAMPLE An adhesive was applied to both the front and back surfaces of a paper epoxy laminate (EPL, manufactured by Toshiba Chemical ■, trade name) having a thickness of 1.6 mm so that the dry film thickness was 40 μm.

Thereafter, it was immersed in an oxidizing agent solution for 50 minutes to etch the adhesive surface so that the plating film was completely adhered to it.

Subsequently, the surface was catalyzed by immersion in a tin(II) chloride solution and a palladium chloride solution. Next, 1~ shown in Table 5
5, 70"Q, PH
A copper plating film with a thickness of 2 to 5 μm was formed under the conditions of 12.3, and then copper was deposited to a thickness of about 1 μm by electrolytic copper plating to prepare a test piece.

(Left below) Regarding this test piece, Japanese Industrial Standards (JIS C6481)
.

An adhesion test and a solder heat resistance test were conducted according to the copper-clad laminate test method for printed circuits. The results obtained and the precipitation rate are shown in Table 6.

Table 6 As shown in Table 6, C2, N of Example 1, N,
N'.

When he'-teto2kis(2-hydroxypropyl)ethylenediamine was used alone, the precipitation rate was fast, but the peel strength and soldering heat resistance/I were low. If there is,
It has excellent peeling strength and soldering heat resistance, but the deposition rate is slow and it takes a long time to deposit a predetermined paulownia 11 thickness.

In contrast, the present invention (=Such Examples 2 to 4) has a fast precipitation rate and is also excellent in peel strength and soldering heat resistance. This makes it possible to manufacture printed wiring boards with excellent quality in a short period of time.

〔Effect of the invention〕

According to the method of the present invention, a printed wiring board with excellent peel strength, soldering heat resistance, etc., and high circuit reliability can be manufactured using an adhesive-coated laminate as a starting material. In addition, the method of the present invention is a method for manufacturing printed wiring boards that is extremely advantageous from the viewpoint of saving capital compared to the conventional subtractive method, and its industrial value is great.

Representative patent attorney Kensuke Norichika (and one other person)

Claims (3)

[Claims] (1) (Step of attaching an adhesive to the Al laminate and drilling holes for forming through balls that communicate with the shells on the front and back surfaces of the laminate, (C) Roughening the surface of the adhesive Then, the gold or metal oxide is applied to all surfaces by immersing it in a melting solution containing a metal or metal oxide that simultaneously becomes C dihydrophilic and has a catalytic effect on the electroless steel plating bath. (d) The laminate is immersed in an electroless steel plating bath to form a thin electroless steel plating film on the surface of the laminate and the inner wall of the through hole to make all surfaces of the laminate electrically conductive. (Step of forming a plating resist film on the adhesive surface of the area other than the part where the ELL horizontal laminate conductor circuit is to be formed. (g) Peeling off the plating resist film, <111 (accumulation &r
A method for producing a printed wiring board comprising the step of removing the etched film formed on the non-circuit portion of the board by immersing it in a copper etching solution, wherein the electroless copper plating bath contains a copper salt, a ring agent, Ethylenediaminetetraic acid ffl:N as a PH adjuster and complexing agent. N, N/, N/-tetrakis-(2-hydroxypropyl) containing a mixture of diamines, and at least one of a sulfur-containing compound, a nonionic surfactant, and an α, α′-dipyridyl or phenanthroline derivative. A method for manufacturing a printed wiring board, characterized in that it contains. (2) Chemistry [Concentration in plating solution is 0.01 to 10rng]
/ 1 sulfur-containing compound and nonionic surfactant 3Q
mg/l to 2 Dg/'l and 2 to 50 r of at least one α, α'-dipyridyl or phenanthroline derivative.
n? The method for manufacturing a printed wiring board according to claim 1, wherein the printed wiring board contains: /l. (3) The electroless copper plating bath has a temperature of i50'o or higher and a pH of 11.7 to 2.8.
A method for manufacturing a printed wiring board as described in Section 1.