JPH0249547B2 - PURINTOHAISENBANNOSEIZOHOHO - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a method for manufacturing a printed wiring board that is suitably employed when manufacturing a printed wiring board by a part-time additive method. BACKGROUND ART Conventionally, the mainstream method for manufacturing printed circuit boards has been the subtract method, which is a method in which a desired conductive pattern is formed by etching away unnecessary copper using a copper-clad laminate as a material. However, due to the rapid advancement of electronic devices in recent years, the demand for printed circuit boards has increased rapidly, and the required characteristics have diversified.
In particular, improvements in economic efficiency and reliability are desired. As a method to solve these problems, the additive method, which uses a laminate as a material and selectively forms only the necessary conductive patterns at any thickness by plating, is attracting attention, unlike the conventional subtract method. ing. This additive method is considered to be extremely advantageous when high density is desired, as it can greatly shorten the processing steps and prevent the reduction in circuit width due to etching, which is a disadvantage of the subtract method. Currently, there are three known methods for manufacturing printed wiring boards using additive methods: full additive method, semi-additive method, and partially additive method. Among these methods, the full additive method forms all patterns and through holes by electroless copper plating, and is the method that can simplify the process the most and has the most expectations in the future. In addition to various problems with substrates, adhesives, printing inks, plating liquids, etc., there are problems with the use of expensive special substrates, pollution caused by surface roughening liquids, and problems with the adhesion between the substrate and circuit parts. There are still many disadvantages compared to those based on copper-clad laminates, considering the cost of the adhesive used and the cost of the adhesive used. On the other hand, in the semi-additive method, electroless copper plating is applied to the entire surface of the substrate as a conductor for pattern electroplating, and after pattern electroplating, the electroless copper plating film on the non-pattern areas is dissolved and removed. Although it has advantages such as easy densification and easy control of plating solution, it cannot be expected to greatly simplify the process, and there are problems with pollution due to surface roughening solution and problems with adhesion between the base material and the circuit part. The same problems as the fully additive method remain. On the other hand, the part-additive method is a printed wiring board manufacturing method that has recently attracted particular attention as a method that can overcome the drawbacks of both the subtract method and the additive method. In this method, a pattern is formed by etching a copper-clad laminate, and only the through holes are plated with electroless copper.In a specific example, through holes are first formed in the copper-clad laminate by drilling, punching, etc. Thereafter, a catalyst layer for depositing copper from an electroless copper plating solution is formed on the through-hole walls, and then an etching resist film is formed on the surface of the copper-clad laminate by a method such as a printing method or a dry film lamination method. Next, the copper-clad laminate is etched to form a pattern by dissolving the copper in non-resist areas, and after peeling off the etching resist film, resist printing is performed on areas other than lands, through-holes, and necessary circuit areas. moon·
A solder resist film is formed, and finally electroless copper plating is performed to form an electroless copper plating film on the through-hole wall. Problems to be Solved by the Invention However, according to the studies of the present inventors, when a printed wiring board is manufactured according to the process of the above-mentioned part-time additive method, through-holes such as blowholes, through-hole defects, and non-plating occur. Poor plating often occurred. The reason for this is that the adhesion of the catalyst to the through-hole walls is not strong, so the processes after the formation of the catalyst layer, that is, the formation process of the etching resist film, the etching (pattern formation) process, the peeling process of the etching resist film, the plating/solder resist During the film formation process, and after the substrate is immersed in an electroless copper plating solution, copper is deposited on the entire surface of the through-hole wall, and during the time (take time) until it is completely covered with copper, the catalyst layer is inactivated or It is presumed that this is because the copper is dissolved and there are areas on the through-hole walls where copper does not precipitate. In order to prevent poor through-hole plating due to deactivation or dissolution of the catalyst layer, the catalyst layer is protected by electroless nickel plating after formation of the catalyst layer, or by filling holes with a resist. It is possible to reactivate the catalyst layer after plating/solder resist film formation, or to perform strike electroless copper plating (high activity, low physical properties) before applying thick electroless copper plating to the through-hole wall. Although these methods have been proposed, they have the problem of increasing the number of steps and complicating them. Therefore, when manufacturing printed wiring boards using the part-additive method, it is possible to easily and reliably prevent through-hole plating defects and perform electroless copper plating without unnecessarily complicating the process. A method was requested. The present invention was developed in view of the above circumstances, and it is possible to perform electroless copper plating while reliably preventing through-hole plating defects, and furthermore, it can perform electroless copper plating by following the process of the normal part-triadive method as it is. An object of the present invention is to provide a method for manufacturing a printed wiring board that can perform the following steps. Means for Solving the Problems In order to achieve the above object, the present invention forms through holes in a copper-clad laminate, forms a catalyst layer for electroless copper plating on the walls of the through holes, and then etches the surface of the laminate. A resist film is formed, then copper in non-resist areas is dissolved and removed, the etching resist film is peeled off to form a copper pattern area, and then a plating resist film is formed, leaving land areas, through holes, and necessary circuit areas. In the method for manufacturing a printed wiring board, the laminated board is immersed in an electroless copper plating solution to form an electroless copper plating film on the through-hole wall after forming the etching resist film. It is designed to add an agent. That is, the present inventors found that although alkaline aqueous solutions such as sodium carbonate and sodium hydroxide are often used to strip etching resist films, this kind of stripping solution inactivates the catalyst layer, which causes throughhole plating. Anticipating that this might lead to defects, we conducted various studies on stripping solutions and found that sodium hypophosphite, sodium borohydride,
It has been discovered that when a reducing agent such as dimethylamine borane is added to the stripping solution, throughhole plating defects such as throughhole defects due to deactivation of the catalyst layer are reliably prevented, and electroless copper plating can be performed reliably inside the throughholes. However, the present invention has been completed. The present invention will be explained in more detail below. In the method for manufacturing a printed wiring board according to the present invention, first, through holes are formed by drilling or punching in a copper-clad laminate in which copper foil is laminated on one or both sides of a base material such as a paper-reinforced epoxy board or a paper-reinforced phenol board. . Next, a catalyst layer for electroless copper plating is formed on the through-hole wall. The method for forming this catalyst layer can be any conventional method and is not particularly limited. For example, the laminate is immersed in a mixed solution of palladium salt and stannous salt, and then immersed in an acid or alkaline solution. Suitable methods include a method in which metal palladium nuclei are attached to the through-hole wall by immersion, and a method in which the laminate is immersed in a sensitizing liquid such as an acidic stannous chloride solution, and then immersed in an activating liquid such as a palladium chloride solution. Can be adopted. After forming the catalyst layer in this manner, an etching resist film for pattern formation is formed on the surface of the copper-clad laminate. The method for forming this etching resist film may also be a conventional method, such as a printing method using printing ink or a method using a dry film. Next, the laminate on which the etching resist film has been formed is etched, and the copper in the non-resist areas is dissolved and removed. Here, as the etching solution, dichlorochloride
Commonly used etching solutions such as copper solution, ferric chloride solution, ammonium persulfate solution, ammonia alkaline thickener solution, and ammonia alkaline copper solution are used, and copper etching is performed by spraying, dipping, etc. can be done. After etching, the etching resist film is peeled off to form a copper pattern. In this case, the etching resist film stripping solution may be a solvent-based stripping solution such as methylene chloride depending on the type of the etching resist film. An alkaline semi-solvent type stripping solution containing a solvent such as , butylcellosolve, or triethanolamine, or an alkaline aqueous solution type stripping solution based on an alkali such as sodium carbonate or sodium hydroxide can be used. Among these, alkaline aqueous solutions are preferably used from the viewpoint of cost, working environment, etc. Note that these stripping solutions can be used to strip the etching resist film under the conditions under which they are normally used. For example, in the case of an alkaline aqueous solution, spraying or dipping can be performed at room temperature or at an appropriate temperature (35 to 65 degrees Celsius). The etching resist film can be dissolved and removed by a method or the like. Here, in the present invention, a reducing agent is added to the etching resist stripping solution, and by stripping the etching resist film using the stripping solution to which the reducing agent has been added, it is possible to remove the etching resist film during through-hole plating. Through-hole plating defects such as through-hole defects are reliably avoided, and good through-hole plating is made possible. In this case, it is preferable to use an alkaline aqueous solution as the stripping solution for the purpose of the present invention. Reducing agents to be added to this stripping solution include hypophosphorous acid and its salts such as sodium hypophosphite, borohydrides such as sodium borohydride and potassium borohydride, dimethylamine borane, diethylamine borane, etc. Amine borane compounds and the like are preferably used. The concentration of these reducing agents added is 0.01 to 0.6.
The amount can be set to 0.1 mol/mole or less, and even a small amount is sufficiently effective. After the etching resist film is peeled off as described above, a plating resist film is formed leaving the land portions, through holes, and necessary circuit portions.
In this case, the plating resist film (which usually also serves as a solder resist) can be formed by an appropriate method such as printing with epoxy solder resist ink or using a photographic photo solder resist. Finally, the laminate is immersed in an electroless copper plating solution to form an electroless copper plating film on the through-hole walls. In this case, as the electroless copper plating solution, one for thick coating with high physical properties is suitably used. Such electroless copper plating solution is not particularly limited, but for example, divalent copper salts such as copper sulfate (copper ion concentration
0.01 to 1 mol/), reducing agents such as formaldehyde (reducing agent concentration 0.02 to 1 mol/), ethylenediamines such as ethylenediaminetetraacetic acid, tetrahydroxypropylethylenediamine, N-hydroxyethylethylenediaminetriacetic acid, and salts thereof, and 2 such as diethylenetriaminetriacetic acid, diethylenetriaminepentaacetic acid, nitrilotriacetic acid, cyclohexylenediaminetetraacetic acid, citric acid, tartaric acid, and salts thereof.
A complexing agent that complexes valent copper ions (the concentration of the complexing agent is 2
The main component is copper ion (equimolar or more), and if necessary, stabilizers such as pyridyl, cyanide, thiocyanate, etc., compounds that form addition products with formaldehyde such as glycine, sodium hydroxide. A bath containing a PH regulator such as phthalate can be used. The plating conditions are appropriately selected depending on the composition of the plating solution used, etc., but the thickness of the electroless copper plating film on the through-hole wall is 25~25cm.
The thickness is preferably 30 μm. After forming an electroless copper plating film on the through-hole wall as described above, heat treatment (120~
200℃), rust prevention treatment, solder coating, etc. Effects of the Invention According to the method for manufacturing a printed wiring board of the present invention,
After forming through holes in the copper-clad laminate and forming a catalyst layer for electroless copper plating on the walls of the through holes,
An etching resist film is formed on the surface of the laminate, then copper in non-resist areas is dissolved and removed, the etching resist film is peeled off to form a copper pattern area, and then land areas, through holes, and necessary circuit areas are removed. In the method for manufacturing a printed wiring board, the laminate is immersed in an electroless copper plating solution to form an electroless copper plating film on the through-hole walls after forming a plating resist film on the through-hole walls. By using a stripping solution to which a reducing agent is added, poor through-hole plating due to deactivation of the catalyst layer can be effectively prevented. EXAMPLES Hereinafter, the present invention will be specifically explained with reference to Examples. Example: Copper-clad laminate with copper foil laminated on both sides of paper-reinforced epoxy board (thickness 1.6 mm) (NEMA standard FR-3)
was cut into 13 x 17 cm pieces, and 100 through holes with a diameter of 0.8 mm were formed by drilling. Next, a catalyst layer (palladium core) was formed on the through-hole wall by the following steps. 1 Immersion in catalytic solution PdCl ₂ 0.5 g / SnCl ₂ 25 g / HCl 350 ml / Room temperature, 5 minute immersion 2 Water washing 3 Activation treatment HCl 50 ml / Room temperature, 5 minute immersion 4 Water washing 5 Drying 80℃, 15 minutes After formation of catalyst layer , pattern printing was performed using an alkali-removable etching resist to form an etching resist film, and then CuCl ₂ mol/,
Using an etching solution containing 0.01 mole of CuCl and 3 mole of HCl, the copper in the non-resist area was removed by etching at a temperature of 55° C. using a spray etching device. Next, the etching resist film was removed by using an alkaline aqueous stripping solution having the composition shown below and under the following conditions. Stripping solution composition NaOH 4.0% by weight Reducing agent shown in Table 1 0.01 mol / Stripping condition Temperature 40°C Time 5 minutes After that, by using epoxy solder resist ink on parts other than lands, through holes and necessary circuit parts, A plating resist film was formed, and then immersed in an electroless copper plating solution having the following composition, and plating was performed under the following conditions. Electroless copper plating solution composition and plating conditions CuSO ₄・5H ₂ O 0.04 mol / Formaldehyde (37%) 0.3 〃 EDTA・4Na 0.1 〃 NaCN 5ppm PH (adjusted with NaOH) 12.2 Plating temperature 30℃ Plating time 15 After plating, the presence or absence of plating defects in the through holes was observed using a stereomicroscope. The results are shown in Table 1.

【table】

[Table] From the results shown in Table 1, it was confirmed that through-hole plating defects could be reliably avoided by adding a reducing agent to the etching resist film stripping solution.

Claims (1)

[Scope of Claims] 1. After forming through holes in a copper-clad laminate and forming a catalyst layer for electroless copper plating deposition on the walls of the through holes, an etching resist film is formed on the surface of the laminate, and then a non-resist area is formed. After dissolving and removing the copper, the etching resist film is peeled off to form a copper pattern, and then a plating resist film is formed leaving land parts, through holes and necessary circuit parts, and then this laminate is electrolessly processed. In the method for producing a printed wiring board, which forms an electroless copper plating film on the through-hole wall by immersing the board in a copper plating solution, the etching resist is removed using a stripping solution for the etching resist film to which a reducing agent is added. A method for manufacturing a printed wiring board, characterized by peeling off a film. 2. The method according to claim 1, wherein the stripping solution is an alkaline aqueous solution, and a reducing agent is added thereto. 3. Claim 1 in which one or more types selected from hypophosphorous acid and its salts, borohydrides, and amine borane compounds are used as reducing agents.
or the method described in paragraph 2.