JPS62261195A - Formation of conductive circuit by lithography - 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 a method of forming a conductive circuit on an insulating substrate by a drawing method.
``A latent image of a circuit pattern is created by drawing on an insulating substrate using a drawing ink containing an organic compound complex of platinum and/or palladium, and after drying the ink, the insulating substrate is coated with metal ions (e.g. Fine metal particles of gold, silver, platinum and/or palladium produced by immersion in an electroless plating bath containing copper ions) and a reducing agent (e.g. formalin), and the reducing agent in the bath reduces the organometallic complex compound. is used as a catalyst nucleus to advance electroless plating to develop a circuit pattern by depositing metal (e.g., copper) on the substrate, and then to deposit metal (e.g., copper) on the substrate by electroless plating or electroplating. The present invention relates to the formation of a conductive circuit by a drawing method, which involves forming a conductive circuit on the substrate by thickening the substrate.

Conventionally, as the name of printed wiring boards suggests, printing or similar methods have been the mainstream for creating conductive circuits for electrical machines and electronic devices. For example, in the substrative method, a resist pattern of a circuit pattern is formed on a copper-clad laminate by printing or photolithography,
After that, the exposed portion of the copper foil was etched away by dipping it in a copper etching solution to form a circuit, which was a basic method.

There are various additive methods, but the basic method here is to first create a circuit pattern plate, and then transfer the circuit pattern from this plate onto an insulating substrate to form a conductive circuit. (For example, JP-A-59
-88891 and JP-A-59-136988).

In any case, the conventional method of making printed wiring plates is suitable for mass production, and is not suitable for making a small number of printed wiring plates. For example, even if a single printed wiring board is to be prototyped, the circuit pattern board must first be made up.

When developing electronic devices and electrical machines, the circuit design and prototype production of printed wiring boards to be incorporated into the equipment must be repeated many times, and each time a prototype circuit pattern needs to be created. However, it had the disadvantage that it took too much time.

The purpose of this invention is to use a pen block to output a circuit pattern designed using a CAD (computer-aided design) system or the like using a drawing ink containing an electroless plating catalyst. This is an attempt to form a conductive circuit by directly drawing a circuit pattern on an insulating substrate.

The direct writing method of the present invention has the advantage that the time required for prototyping a conductive circuit can be significantly shortened compared to conventional printing methods.

Next, an embodiment of the invention will be described in detail, using a pen plotter as a drawing means, as an example.

In this invention, a conductive circuit is formed on an insulating substrate in the following three steps.

(a) A circuit pattern is drawn on an insulating substrate using a plotter ink containing an organic compound complex of gold, silver, platinum, and/or palladium.

(Here, only the latent image of the circuit pattern is obtained.) (b) Next, the substrate is immersed in an electroless plating bath.

The organometallic complex drawn on the substrate (circuit pattern) is immediately reductively decomposed by the reducing agent of the electroless plating solution, producing fine particles of elemental metals of the component elements, and producing nuclei with catalytic action. This nucleus acts as a ζ rigger and electroless plating progresses. The circuit pattern is developed and subsequent plating is applied to form a conductive circuit.

(c) The substrate is taken out of the electroless plating bath, washed with water, and dried.

Electroless plating, also known as chemical plating, is a method in which a reducing agent is added to an aqueous solution of metal salts such as copper, nickel, and cobalt to reduce and precipitate metal ions. It is said that fine metal particles whose surfaces are chemically active, which serve as the so-called catalytic core, are required. The surface of the newly generated metal fine particles is chemically active and induces the subsequent reduction and precipitation of metal ions, resulting in continuous reduction and precipitation of metal.

Conventional electroless plating methods utilize colloidal palladium produced from palladium chloride and stannous salts as catalyst nuclei. However, since this combination is applied in an aqueous system, the catalyst nuclei (colloidal palladium) attached to the surface of the plated body are likely to separate back into the bath during the subsequent aqueous electroless plating, and the weak adhesion force It was a drawback.

Catalytic nuclei that fall off from the surface of the plated object cause so-called aging of the plating solution, and also cause short circuits in the formation of conductive circuits using the fully additive method. Falling off of catalyst nuclei is a phenomenon that must be absolutely avoided. In this respect, the prior art catalyst core (colloidal palladium) has major drawbacks and cannot be used in the method of the present invention.

As is well known in the art, in addition to the colloidal palladium mentioned above, various metals produce fine metal particles having a catalytic action (surface active) in electroless plating. For example, gold, silver, platinum, copper, nickel, etc. are known to have catalytic activity by appropriate chemical activation.

Furthermore, according to recent technical knowledge, in addition to the above-mentioned palladium chloride, various palladium compounds can be used to generate palladium fine particles that have a catalytic effect. For example, many child metal complex compounds are unstable, and Ll is sensitive to heat and water, and is sensitive to oxygen in the air, so it can be decomposed into component elements by a relatively mild activation method.
That is, there are some that liberate simple metals. Such simple metals are fine metal particles whose surfaces are chemically active, and are extremely effective as catalyst nuclei for electroless plating. Furthermore, organometallic complex compounds are generally insoluble or poorly soluble in water, which is advantageous for forming a conductive circuit by a fully additive method.

Many compounds are known today regarding so-called organic compound complexes of transition metals such as gold, silver, platinum, palladium, etc., and their synthesis methods have been reported in various publications (
For example, edited by the Chemical Society of Japan, New Experimental Chemistry Course, Volume 12, Organometallic Chemistry (1972), J, Am, Chem, Soc.
, 60 882 (+938), Inorz, 5yn
Th.

+3 52 (+972) and J, Chem, S. . ,
, 1976 A, 423).

However, even though organic compound complexes of transition metals are generally unstable, the degree of instability varies depending on each complex compound. For example, complexes vary, such as those that are particularly sensitive to heat and easily decompose, those that react with water and are easily hydrolyzed, and those that are particularly sensitive to oxygen in the air. For example, JP-A-59-8
In the organometallic complex compound (bisbenzonitrile balano-14 dichloride) disclosed in No. 8891, in order to generate palladium fine particles having catalytic action,
It is explained that after heating to 0°C, it is necessary to activate with hydrazine sulfate and an aqueous sodium hydroxide solution, and then further immerse in an isopropyl alcohol-potassium hydroxide solution for complete activation.

The present inventor has discovered a group of organometallic complex compounds that are decomposed by reducing agents used in electroless plating, particularly formalin in copper plating baths, to liberate fine metal particles, and has also shown that they have a plating catalytic effect. confirmed. When these organometallic complex compounds are used, there is no need for a special activation method as claimed in JP-A-59-88891, and the generation of plating catalyst nuclei and the progress of copper plating can be simultaneously performed in a copper plating bath. It can be carried out. Taking advantage of this feature, we have devised the formation of a conductive circuit by the drawing method of the present invention. Examples of organometallic complex compounds that can be used in the present invention include the following. That is, butadiene palladium dichloride, 1
．． These include 5-cyclooctadiene palladium dichloride, diacetonitrile palladium dichloride, di-μm chloro-bis(η-allyl)nipalladium (■), diacetonitrile platinium dichloride, dicyclopentadiene gold(1) chloride, and the like.

The above organometallic complex compound is used under the conditions of electroless copper plating (for example, 0.1-0.5 mol/1 formalin (37%)).
, ptl 12.0-12. 5. Temperature 23-70
C), it rapidly decomposes and liberates surface-active metal particles, making it extremely effective as a catalyst for electroless copper plating.

When these organometallic complex compounds are used, JP-A-59-8
There is no need for a special activation process as claimed in 8891, and the board on which the circuit pattern has been drawn has the advantage that after the solvent has been volatilized, it can be immediately placed in an electroless plating bath and plating can be started.

A drawing ink is prepared by dissolving the above organometallic complex compound in an organic solvent in a range of 0.5-5% by weight. Of course, the content of the organometallic complex compound may be more or less than this, but generally, if it is less than 0.5% by weight, electroless plating will not occur sufficiently, and if it is more than 5% by weight, Depending on the type of solvent, the solubility may be exceeded, and higher concentrations are unnecessary as a catalyst for electroless plating.

Organic solvents suitable for this purpose include methylene dichloride, 1.
Examples include 1.1-trichloroethane, methyl ethyl ketone, acetone, benzene, toluene, xylene, tetrahydrofuran, and dioxane.

Since the higher the vapor pressure at room temperature, the higher the evaporation rate, it is preferable to mix two or more types of solvents in order to improve the quick drying properties of the ink. In this way, blurring of the circuit line width during drawing can be minimized.

Further, the solvent used in the present invention must be completely dehydrated. Otherwise, the organometallic complex will hydrolyze and form a precipitate, which will shorten the life of the drawing ink. Generally, dehydration of the solvent can be accomplished to some extent by simply adding anhydrous calcium chloride, allowing it to stand, and then filtering it. However, anhydrous calcium sulfate is preferred for dehydrating acetone.

The insulating substrate to be drawn is a normal paper phenolic substrate (
If the heat resistance of the board is not a concern, you can use an ABS resin board. However, an insulating substrate that already contains palladium particles is not suitable as a substrate for the fully additive method. An ABS resin plate surface-etched with a dichromic acid-sulfuric acid mixture exhibits excellent circuit peel strength.

Before drawing, the substrate must be cleaned, but this can be done in the same way as the degreasing process of conventional electroless plating, i.e., thoroughly cleaned by immersing it in an acidic aqueous solution containing a surfactant, then rinsing with water, and drying. do.

With the method of the present invention, through-hole plating can also be obtained simultaneously with the formation of conductive circuits. That is, after drilling a hole with a router, it is sufficient to apply 0.05 to 0.2 milliliters of drawing ink to the inner wall of the through hole using a microsyringe.

The composition of the drawing ink is summarized as follows.

Organic solvent: 99.5-15% by weight Organometallic complex compound: 0.5-5% by weight Oil-soluble colored dye
Since the bleeding of the circuit line width is greatly influenced by the surface condition of the substrate (state of surface roughening), a small amount of resin compound or rosin derivative may be added when there is a large amount of bleeding. However, in this case, care must be taken as plotter points are likely to become clogged.

The oil-soluble colored dye is used here to make the latent image of the drawn circuit pattern easier to identify with the naked eye, and is not necessarily necessary.

Fill the plotter point with the drawing ink of the above composition,
A circuit pattern is drawn on the insulating substrate using a pen plotter. To dry the ink, just leave it at room temperature.
10 minutes), and then the substrate is directly immersed in the electroless plating bath. When the humidity in the air is high, it is thought that the organometallic complex absorbs moisture and is hydrolyzed, but this does not affect the subsequent electroless plating. For example, if a printed board is left in the air for a week and then placed in an electroless plating bath, circuit plating will be formed in the same way.

The composition of the electroless plating bath may be the same as that used in conventional fully additive methods. For example, the following composition can be used.

Copper sulfate (CuSO4・51-1tO) 0,
04 mol/l Formalin (37%) 0.3 mol/I Sodium hydroxide (Na01-1) pl-1
= 12.2EDTA-4NaO, 1 mol/1 nonionic surfactant 250 mg/
lα,α“-Dipyridyl 20 rng/l After developing the circuit pattern latent image on the board by electroless plating, it is better to continue electroless plating to thicken the copper, and also to reduce costs. Electroplating may also be used.

In this case, it is necessary to attach a bus bar to the circuit pattern.

The conductive circuit thus formed will not have very strong peel strength if the anchoring effect on the substrate surface is not sufficient. However, as a prototype circuit, this is sufficient.

The above has described the formation of a conductive circuit by a drawing method using a pen plotter. However, other drawing means can also be used. For example, when drawing a circuit pattern latent image using an inkjet printer, the above drawing ink can be used as is.

Next, examples of the present invention will be shown.

Palladium chloride, P d Cl 2 (purity 99.75
%.

4.0 g of Nippon Steel (Nippon Chemical) and benzonitrile (reagent-grade distilled with PtOs, boiling point 190°C) approx. 2
00 ml was placed in a 500 ml flask, heated to 100°C on an oil bath, and stirred. After stirring for about 30 minutes, it was filtered hot and a yellow precipitate formed when the filtrate was cooled.

This was filtered using a Buchner funnel, and when the filtrate was further diluted with petroleum ether, a precipitate was formed again. These two precipitates were combined and washed with petroleum ether to give bisbenzonitrile palladium dichloride (PhCN).
Obtained 8.04 g of PdcIz complex (yield 92.8%)
.

8.0 g of bisbenzonitrile palladium dichloride obtained above was dissolved in about 500 ml of dry benzene (reagent-grade distilled with P, 0., boiling point 80 ° C.),
Butadiene gas is introduced into the solution at 5-8° C. under a nitrogen stream, and then the temperature is raised to room temperature, and when butadiene gas is introduced for about 30 minutes, a clean pale yellow precipitate is deposited. Stop introducing butadiene gas when the precipitation no longer increases,
It was immediately filtered with suction. The residue was washed with petroleum ether and dried (yield: 1.8 g). The petroleum ether was concentrated to obtain an additional 2.5 g of residue. A total of 4.3 g of butadiene palladium dichloride complex was thus obtained (90% yield). This complex was stored in a desiccator in a cool, dark place and used for preparing a drawing ink.

Butadiene palladium dichloride 1 synthesized with D-yu drawing ink glue, 1
．． OK was dissolved in 60 ml of an equal Ji1 mixture of methyl ethyl ketone and acetone at room temperature. Methyl edyl ketone is made by adding anhydrous sodium sulfate and anhydrous potassium carbonate to reagent grade, left overnight to dehydrate it, and acetone is made by adding anhydrous calcium sulfate to reagent grade, left overnight to dehydrate it. Each was used. Add benzene to this butadiene palladium dichloride solution and make the whole solution 100%
It was prepared in m1. The dry benzene used in the above synthesis was used as benzene.

C1 Drawing of circuit pattern The plotter point was filled with the drawing ink prepared above, and a circuit pattern was drawn on a paper phenol substrate (not coated with copper) using a pen plotter. A plotter point with a line width of 0.2 mm was used. This drawing ink is quick drying and dries very quickly.

Development of a conductive circuit by electroless plating The substrate on which the circuit pattern latent image was drawn as described above was immersed in a copper plating bath having the following composition.

Copper sulfate (CuSO-・5HtO) I 2 g/
l Formalin (37% concentration) 6 m I
/ Sodium monohydroxide 12g/I
EDTA-2Na, 30 g/
l Polyethylene glycol derivative 250 mg /
1α, α°-dipyridyl 20 mg
/1 temperature for about 30 minutes, during which time the substrate was gently rocked in the bath. After a few minutes, hydrogen gas is generated and the progress of electroless plating can be observed. Thereafter, the substrate was taken out from the plating bath, washed with water, and then copper was deposited thickly on the circuit by electroplating to obtain a conductive circuit on the substrate. Generally, the composition of an electroless plating bath requires delicate R adjustment, and if the plating is completed too quickly, voids may occur in the plating film and a good conductive circuit may not be obtained. be. In such a case,
It is convenient to use a commercially available electroless plating solution for through-hole plating prepared by a specialist.

Claims (1)

[Claims] A latent image of a circuit pattern is drawn on an insulating substrate using a drawing ink containing an organic compound complex of gold, silver, platinum, and/or palladium, and after drying the ink, the insulating substrate is placed in an electroless plating bath. Developing the circuit pattern by immersing it in water to develop a conductive circuit.
Formation of conductive circuits by drawing method.