JPS60195988A - Method of forming through hole circuit - 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 The present invention relates to an improved method of manufacturing high reliability through-hole circuits. Conventionally, in the manufacturing method of thick film conductors, a resist is provided on a thin metal plate in areas other than the circuit area, electrolytic plating is performed to form a conductor in the circuit area, and then the obtained conductor is applied to the thin metal plate as an insulating layer. After pasting the conductor on the outside, a hole for the through hole was made, the thin metal plate was etched away, and electrolytic plating was performed again on the conductor to form the through hole using only electrolytic plating. However, electrolytic plating alone is dependent on the thickness of the insulating layer, and when the insulating layer is thick, there is a drawback that some depressions occur on the inner wall of the through hole.

The present invention solves the above problems by performing electroless plating to form a conductor on the inner wall of the through hole, and then performing electrolytic plating.

That is, after a gold plate with a conductor provided by electrolytic plating is bonded to both sides of an insulating layer with the metal thin plate facing outward, holes for through holes are drilled, and then activated for electroless plating. Highly reliable, characterized by pre-treatment with a liquid, followed by electroless plating → thin metal plate removal → electrolytic plating, or thin metal plate removal → electroless plating → electrolytic plating to make through-hole connections. The present invention provides a method for uniformly forming through holes.

The thin metal plate used in the present invention may be any material as long as it is a conductor and can be etched, but it is preferably one that has etching characteristics different from those of electroplated conductors; in this case, the thin metal plate can be etched. During removal, the electrolytically plated conductor is not etched, allowing highly accurate thin metal plate etching. Appropriate for this,
These include aluminum, tin, and zinc. In addition, the JyX thickness is 7 to 500 μm, particularly 5 to 200 μm, and even 70 μm.
A preferable range is 700 μm. If the film thickness is 78 m or less, it is difficult to handle and the plating film thickness tends to be uneven. Further, if the film thickness is 5θθμm or more, it takes time to remove the film by etching, and productivity decreases.

In the present invention, the resist may be formed on parts other than the circuit part by screen printing or gravure printing, but it is also possible to form the resist through an exposure and development process using a photoresist that can easily form a fine pattern. I can do it. As photoresists, negative types such as Eastman Kodak's KPR, KOR, KPL%KTFR, Tokyo Ohka Co.'s TPR, 0MR81, Fuji Pharmaceutical's FAR, and Eastman Kodak's KADR,
There are positive types such as AZ-1350 manufactured by V-Pub Co., Ltd. 17), but those with excellent plating resistance are preferred, and negative types are particularly preferably used. A dry film resist can also be used. The thicker the film, the more useful it will be in preventing the plating from thickening, but if it is too thick, it will be impossible to obtain a fine pattern.
4 m is preferred. If the distance is 0.14 m or less, pinholes are likely to occur.

As for the type of electrolytic plating, copper is preferable from the viewpoint of conductivity and economy, but any metal such as silver, gold, or nickel may be used. The type of plating solution is silver cyanide bath for silver plating,
For gold plating, acidic or neutral alkaline baths can be used, and for chive-kel plating, nickel sulfate baths, sulfur amino acid nickel baths, etc. can be used.

Examples of copper electrolytic plating include cyanide copper plating, birophosphate steel plating, copper sulfate plating, and borofluoride steel plating. Electrolytic plating can be carried out under normal conditions, but
When selectively plating in the thickness direction or using aluminum, zinc, or tin on a thin gold plate, metal elution may occur in the plating solution when the pH is too high or the plating is too thin. Koruen Mei, 17 Reki liquid is in the neutral range, pH 4t
It is preferable to use one of ~IO1 and especially ~3~. In the case of copper metal plates, monopyrophosphate steel plating 11 is preferred.

The electrolytic plating process can be carried out in the usual way, but if the metal is
1) When using aluminum, tin, lead, the film thickness θ, 3 is initially applied at a current density of θ, θs −, 2 h/dvri, preferably θ, 7 to /, 2 A/dm. ~/
Electrolytic plating is performed at θ μm, preferably 1 μm, 1-1 μm.

Current density = 2A/drr? If the metal layer is more than that, the plating time will be longer and the productivity will be lower. If the film thickness is less than 0.3 'Jim', sufficient adhesion cannot be obtained, and plating is then carried out at a higher current density than in the pre-plating process until the desired film thickness is reached. The density is preferably 3 A/dm' or more, particularly j''' A/dd or more, and more preferably J'A/dm' or more, and increasing the cathode current density suppresses thickening in the width direction. The higher the cathode current density, the better, and pulse plating is also preferably used. The upper limit of cathode current density is determined by burnout.

1. The method of the present invention can be used in places with low wiring density, but it is practical for use with 3, 4 or more wiring lines. Suitable for wiring in the main hall and beyond.

Furthermore, the present invention has a conductive pattern whose space factor is more than jOS, especially 7.
It is suitable when θ is greater than or equal to θ.

In addition, as an insulating layer, polyimide, polyamideimide,
It is also possible to use a substrate made of polyester, polyparabanic acid, epoxy (2) resin, phenolic resin, alkyd resin, or a composite thereof and attach it with an adhesive, or it is possible to apply a face without using a substrate and attach it with an adhesive. You can also match them. Alternatively, the adhesive may be directly applied and bonded as is. The film thickness is not particularly limited, but preferably j-20
θμm especially 10~/! θμm is preferred. If the thickness of the insulating layer is less than 58 m, the mechanical strength will be insufficient, and in some cases, the insulation between the front and back conductor patterns will deteriorate.

When the thickness of the insulating layer is 200 μm or more, the conductor space factor decreases.

Next, the through-holes may be formed by any method as long as no particles or debris are generated and the conductor layer around the holes does not peel off from the insulating layer, such as using a drill or punch.

In the activation process for electroless plating, a normal activator for electroless plating is used, but when the metal sheet is aluminum, zinc, or tin, a normal activator cannot be used and The bath should be kept in a neutral region with a pH of 4 to 1 to prevent the metal thin plate from eluting and significantly deteriorating the bath, or from eluting all the metal thin plates and activating parts other than the conductor of the circuit.
0, especially those that can be controlled to pH = j to s, j are used.

Things that can be used for this include palladium organic complexes.For example, the activating liquid is Schering's Activator Neogant 834, and the reducing liquid is Schering's Glueducer Neogant (WA), sulfuric acid, etc. It can be used after adjusting the pH with an acid.

In addition, pre-treatment for activation treatment includes a degreasing process using a surface activator to remove dirt from the thin metal plate or the inner wall of the through hole, and a process on the rough surface to improve the adhesion of metal deposited by electroless plating. Therefore, it is better to provide a soft etching process consisting of an aqueous ammonium persulfate solution.

As for the type of electroless plating, copper is preferable from the viewpoint of conductivity and economy, but any metal such as nickel, trowel, or ring conductor may be used. If the metal sheet is aluminum, zinc, or tin,
If the process of metal thin plate removal → electroless plating is used, a normal electroless plating solution can be used, but in the case of electroless plating → metal style thin plate removal process, the pH is in the neutral range, pH = Q ~ IO.
Electroless plating solution must be used. For example, in the case of nickel, Schumer 8 manufactured by Nippon Kanigen Co., Ltd.
-680 etc.

As a method for removing the metal thin plate by etching, a method is used in which the used gold fil# plate is etched by spraying or dipping using a solution that electrolyzes the plate. Money@
When aluminum, tin, or zinc is used as the thin plate,
Although it is preferable not to etch the electrolytically plated conductor, for example, to etch it with an alkaline aqueous solution, it is also possible to etch it with an acidic aqueous solution such as diluted hydrochloric acid. - Also, in order to remove dirt on the conductor after etching the thin metal plate, it is preferable to immerse it in dilute nitric acid as a post-treatment.

EXAMPLES In order to further clarify aspects of the present invention, examples will be described below, but the present invention is not limited to the following examples, and various modifications can be made.

Example/ On a thin aluminum plate with a film thickness of <10 μm, a negative type V-syst “Microresist 7471” manufactured by Eastman Kodak was applied.
After drying 10csIJ, apply it to the ridge where the film thickness becomes jam,
It was prebaked, exposed to light using a high pressure mercury lamp through a circuit pattern mask, developed using a special developer and rinse solution, and postbaked to form a resist in areas other than the circuit portion.

Next, using a biroline plating solution manufactured by Bershoku Murayama Co., Ltd., and using a thin aluminum plate as a cathode, the current density was initially Q,
j After coating with A7'd- to an average film thickness of 2 μm,
The current density was increased to /A/dd, and copper with a total thickness of /θθμm was formed in the circuit portion. Thereafter, a phenolic resin-nitrile rubber adhesive [XA364-4J manufactured by Bostic Co., Ltd.] was applied to both sides of the polyimide film "Kapton" manufactured by DuPont (film thickness, 2 μffI) so that the film thickness after drying was 59 m. The above electrolytically plated material is pasted on both sides of the insulating substrate with the thin aluminum plate facing outside under heat and pressure at 750°C for 3θ minutes, and then holes are drilled into the through-hole formation areas with θ and 7θ holes. I opened it. Already 9 after that
Activation treatment was performed using Schuling's activating liquid activator Neogant 834 and reducing liquid reducer Neogant (WA), which had been adjusted to 4 times, and then the aluminum thin plate was treated with 36-fold diluted hydrochloric acid in water for 2 hours. It was removed by etching with a diluted solution. After that, electroless plating (MK-430 manufactured by Muromachi Kagaku Co., Ltd.) was performed, and then using a rophosphate steel plating solution manufactured by CCCC Bershoku Co., Ltd., the current density ♂A/d-
Steel plating was performed with a film thickness of lθθμm (wiring tank thickness: Yumoto/W). After plating, we measured the electrical resistance between the front and back patterns through the through holes, and each through hole was 5m.
It was less than Ω. Further, no depression was observed on the inner wall of the through hole.

Example 1 A negative type resist "Microresist 747" manufactured by Eastman Kodatsu Co., Ltd.
-110cst J was dried, applied to a film thickness of 5 μm, prebaked, exposed to a high pressure mercury lamp through a circuit pattern mask, developed using a special developer and rinse solution, and postbaked. A resist was formed on parts other than the circuit part.

Next, using a biroline plating solution manufactured by Burnyou Murayama Co., Ltd. and using a thin aluminum plate as a cathode, the initial current density θ, j
After plating with an average film thickness of 2 μm μm using A/dFFI'', the current density was increased to ♂ly'dnl, and the total thickness was
. . OAm thick copper was formed in the circuit portion. After that, 1. Polyimide film made by DuPont Co., Ltd., film thickness 2J
The film thickness after drying of Bostik's phenolic resin-nitrile rubber adhesive [XA364-4J] was 5 μm).
On both sides of the insulating substrate coated to a thickness of μm, the electrolytically plated material was attached with the aluminum thin plate on the outside by thermocompression bonding for 3θ minutes at J-θ°C, and then the null-hole forming area was A hole of θ and 7θmB was made with a drill. Thereafter, activation treatment was performed using activating liquid activator (Neogan) 834, reducing liquid reducer (Neogan) WA, manufactured by Nippon Kanigen Co., Ltd. (pH 111), and electroless nickel plating (Schumer S, manufactured by Nippon Kanigen Co., Ltd.). −
680) was carried out. After that, 336 aluminum thin plates were added.
It was removed by etching with a solution prepared by diluting deuterium ts hydrochloric acid with water at a ratio of 2:3. Next, using a birophosphate copper plating solution manufactured by Bershoku Murayama Co., Ltd., a film thickness of 10θμ was obtained at a current density of l'A/d/.
m (wiring density 5 lines/s++) copper plating was performed. After the plating was completed, the electrical resistance between the front and back patterns was measured through the through holes and found to be 5 mΩ or less for all through holes. In addition, no depression was observed on the inner wall of the through hole (No. 2).

Example 3 A negative resist [Microresist 747-110c manufactured by Eastmango Duck Co., Ltd.] was applied on a zinc thin plate with a film thickness of 50 μm.
After drying, the film was coated to a thickness of 2 μm, pre-baked, exposed to light using a high-pressure mercury lamp through a circuit pattern mask, and treated with special current 1fII and S-Vs solutions, and then post-coated. Baking was performed to form a resist on portions other than the circuit portion.

Next, a copper birophosphate plating solution manufactured by Hahnyoku Murata Co., Ltd. was used as a layer, and a thin zinc plate was used as a cathode, and the initial current density / A / dm' was applied.
The average film thickness! After μm copper plating, the current density r A/
dm", and a total of jθμm thick copper was formed on the circuit part. After that, the conductive pattern surface was overcoated with an insulating film (WI-640 manufactured by Hitachi Chemical Co., Ltd.), and 5G copper manufactured by Cemedine Co., Ltd.
-Using EPOEF-008 engineered poxy resin adhesive,
Attach the two sheets with the other ship's thin plates on the outside.

Next, drill the through-hole forming part to θ, 70wall.

I made a hole in it. After that, the activation liquid activator Neogant 834 manufactured by Schuling Co., Ltd., which had already been pH adjusted,
Activation treatment was performed using a reducing solution (Reduci Neogan) WA, and then the zinc thin plate was removed by etching with a 5-layer sodium hydroxide solution. After that, electroless copper plating (-430 manufactured by Muromachi Chemical Co., Ltd.) was performed, and then No.9-
Using a pyrotetraphosphate steel plating solution manufactured by Murata Co., Ltd., a film thickness of jθμm (wiring density of 1 line/,
) Copper plating was performed. After the plating was completed, the electrical resistance between the front and back patterns was measured through the through holes and found to be less than 1 mΩ for all through holes. In addition, no depression was observed on the inner wall of the through hole (No. 2).

Example: A negative resist "Microresist 747-110c" manufactured by Eastmango Duck Co., Ltd. was applied on a thin tin plate with a film thickness of 20 μm.
After drying st J, apply it to a film thickness of s 11m.
After prebaking, it was exposed to light using a high pressure mercury lamp through a circuit pattern mask, developed using a special developer and rinse solution, and postbaked to form a 7-gist in areas other than the circuit area.

Next, using a birophosphate copper plating solution manufactured by Hahnyoku Murata Co., Ltd., and using a thin tin plate as a cathode, steel was plated with an average film thickness of O, S μm at a current density of O6/Vd-, and then the current density was changed to jA.
Increased to 7dm'! Copper with a thickness of θ μm was formed in the circuit portion. After that, the conductive pattern surface was overcoated with an insulating face (WI-640 manufactured by Hitachi Chemical Co., Ltd.), and
Using G-BPOHP-008 poxy resin adhesive, stick the two sheets together with the thin tin plate facing outside. Next, a hole of 0.7θ1θ was drilled in the through hole forming portion. After that, the activation liquid activator Neogant 834 manufactured by V Nealing, which had already been pH adjusted. Activation treatment was performed using a reducing solution reducer (Neogan) WA, and then the thin tin plate was removed by etching with an aqueous sodium hydroxide solution having a weight ratio of J. After that, electroless steel plating (MK manufactured by Muromachi Chemical Co., Ltd.)
-430), and then copper plating with a film thickness of jθμm (wiring density) was performed using a Viroline plating solution manufactured by Barshaw Materials Co., Ltd. at a current density of A/dm'. After the plating was completed, the magnetic resistance between the front and back patterns was measured through the through holes, and it was found to be less than jmQ in all through holes.

Furthermore, no depression was observed in the through-hole formation area.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] A resist was provided on a thin metal plate in areas other than the circuit area, electrolytic plating was performed to form a conductor in the circuit area, and then the thin metal plate was attached to both sides of the resulting conductive insulation layer with the metal thin plate facing outward. , perform the drilling for the through-hole, then perform the activation treatment for electroless plating, and then remove the metal sheet after electroless plating has been completed, or alternatively, remove the metal sheet. 1. A method for forming a through-thread diode, characterized by performing electroless plating from the beginning and then performing electrolytic plating.