JPS5831111B2 - Powder coating that can be chemically plated and its manufacturing method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a powder coating material that can be chemically plated and that is suitably used in the production of printed wiring boards with a metal core, and a method for producing the same.

In recent years, with the miniaturization and higher performance of electronic devices, performance requirements for printed wiring boards have become more sophisticated, and at the same time, economic efficiency has also been required.

For example, it must have a high degree of dimensional stability without warping or twisting, it must have the rigidity to withstand the mounting of a large number of heavy parts, it must have a high degree of thermal conductivity to quickly remove the heat generated from the mounted parts, and scales that can be supplied at low cost.

Conventional synthetic resin laminates cannot fully meet these demands, so iron, stainless steel, aluminum,
The trend is toward printed wiring boards with metal cores such as copper.

In printed wiring boards with metal cores, it is essential to insulate the metal core, and for this purpose, a wide range of resins are available that have the required properties such as heat resistance and the ability to easily form an insulating resin layer of uniform thickness. Powder coating methods are attracting attention because of their advantages such as being solvent-free, saving resources, and generating little pollution.

The powder coating method generally involves blending thermosetting resins such as epoxy resins, phenolic resins, acrylic resins, and polyester resins with hardener fillers, catalysts, pigments, spreading agents, etc. as appropriate.
Powder coatings are made by melting and kneading at a low temperature where almost no crosslinking reaction occurs, and after cooling, are crushed to adjust the particle size to about 300μ or less. Method of immersing and attaching, ■Electrostatic method in which one end of the object to be coated is grounded, a high voltage is applied to the tip of the spray nozzle, and powder and air are sent at the same time, causing the charged powder to fly and adhere. Spraying method: ■ Place the object to be coated with one end grounded on top of a powder paint tank with a perforated plate at the bottom, and send ionized air from below the perforated plate using a high voltage power supply to produce charged floating powder. Electrostatic dynamic immersion method, in which the object to be coated is placed in the cloud and the powder is attached to it, or ■ Contact charging of the powder between a DC negative electrode and an AC electrode to generate a cloud and grounding. The powder is attached to the object to be coated using a method such as the electrostatic vibration method, which is used to electrostatically attach it to the object to be coated. A film is obtained.

Conventionally, when forming printed circuits by chemical plating in the production of printed wiring boards, chemical plating directly on the thermosetting powder coating did not provide sufficient adhesion, so Furthermore, a step of providing a rubber composition (adhesive) layer to improve adhesion, that is, a step of applying an adhesive varnish, is essential, which avoids complicating the process and reducing economic efficiency. There was no negative feeling.

In addition, even when chemical plating is performed directly on a thermosetting powder coating, the coating surface obtained by thermosetting is chemically roughened to form a roughened surface shape, and then sensitizing and activating are performed. Baiting treatment is performed to adsorb noble metal ions that have chemical plating catalytic ability, such as Sn and Pd, and metal deposition is performed by chemical plating, but in this case, the state in which the noble metal ions are adsorbed In other words, it is extremely difficult to print a negative pattern of metallurgical resist while maintaining the catalytic activation state before chemical plating.
Therefore, chemical plating requires deposition (panel plating) over the entire area of the catalyst adsorption surface.After this, the necessary circuits are formed, which is a complicated process that always involves etching the panel plating in areas other than the circuits. It is what you need.

The present invention has been made in view of these points, and the chemical plating powder coating of the present invention contains 0.0 parts by weight of a chemical plating catalyst per 100 parts by weight (hereinafter simply referred to as "parts") of a thermosetting resin.
06 to 1.2 parts, and 1 to 30 parts of a rubber having a conjugated double bond and a polar group in the molecule, and has a viscosity of 105 centipoise or less during at least one period of the heat curing step, and the present invention The method for producing powder coatings consists of 50% by weight of the chemical plating catalyst contained in the final powder coating.
(hereinafter simply abbreviated as %) The above includes 3 to 50% thermosetting resin with a melting point of 150'C or less, 5 to 60% inorganic filler, and 80% or less rubber having a conjugated double bond and a polar group in the molecule. and the melting point is 150°C during at least one period of the kneading process.
The composition is characterized in that it is kneaded in advance at a temperature equal to or higher than the melting point of the following thermosetting resin, and this kneaded composition is further kneaded together with the thermosetting resin and pulverized.

The thermosetting resin used in the present invention is one used in powder coating of epoxy resin, phenol resin, acrylic resin, and polyester resin pipes in general.

As the rubber having a conjugated double bond and a polar group in the molecule, one type or a mixture thereof of acrylonitrile butadiene polymer, styrene butadiene polymer, acrylonitrile phtadiene styrene resin, and polybutadiene resin can be used. 2) IJ groups, hydroxyl groups, carboxyl groups, acid amide groups, etc.

The rubber having conjugated double bonds is preferably one having 30% or more double bonds per monomer unit constituting it, from the viewpoint of improving circuit adhesion after roughening.

Since the rubber used in the present invention has a polar group in its molecule, it can be uniformly mixed with the thermosetting resin.

Uniform mixing is extremely important in order to obtain homogeneous powder, uniform charging, and therefore uniform adhesion.

In order to achieve uniform mixing with the thermosetting resin, the Mooney viscosity (according to ASTM D1646-63) is 90ML1.
-) 4 (100°C) or less rubber is preferably used.

A rubber with a Mooney viscosity of 90 or lower can be selected as appropriate, but even rubbers with a Mooney viscosity of 91 or higher can be easily lowered to 90 or lower by using a roll wire, liquid, or dissolving in a solvent.

1 to 30 parts of rubber are mixed with 100 parts of thermosetting resin.

This is because if it is less than 1 part, a roughened surface with good adhesion of the circuit by chemical plating cannot be obtained, and if it is more than 30 parts,
This is because it is difficult to form into a powder coating, and the smoothness of the baked-cured coating film is extremely poor, and various properties such as heat resistance and insulation properties necessary for coating films on printed circuit boards are deteriorated.

When powder coatings require a high degree of heat resistance or when normally liquid rubber is used, sulfur, sulfur compounds, vulcanizing agents such as oil-modified phenols, and vulcanization aids are used as auxiliary materials for the rubber. You can also use

As the chemical plating catalyst, metals belonging to Group Ⅰ and Group 1B of the Periodic Table of Elements, such as nickel, gold, silver, platinum, palladium, rhodium, copper, iridium, etc., or their oxides, chlorides, bromides, These include fluoride, ethyl acetate, fluoroporate, nitrate, sulfate, acetate, etc.

Particularly useful are palladium, gold, platinum, copper, palladium chloride, gold chloride, platinum chloride, copper oxide or their combinations with stannous chloride.

In the present invention, the amount of catalyst required to deposit chemical plating reliably and stably is 0.00 parts per 100 parts of thermosetting resin.
A good range is 0.006 to 1.2 parts, preferably 0.02 to 0.06 parts.

If it is less than 0.006 part, the reliability of plating precipitation decreases,
This is because if the amount exceeds 1.2 parts, the economic burden on the final product cannot be ignored.

Forming a smooth coating film on the surface of a metal plate by powder coating is extremely important in order to improve various properties required for a printed wiring board.

For this purpose, the viscosity of the powder must be 105 centipoise or less, preferably 103 centipoise or less, during at least one period of the heating step in which the thermosetting powder coating applied to the surface of the metal plate is heated to form a cured coating film. It is necessary that the following is true.

The viscosity in this heat curing step can be adjusted to a required value depending on the molecular weight of the powder and the curing speed.

Measurement of melt viscosity is carried out using HAAKE's POTOVISKO1.
This is carried out by using an RV-2 device, setting the temperature increasing rate at 4.5° C./min to the rotor PK-n, and measuring the flow torque in the rotational speed range of 0.1 to 10 rpm.

As fillers, zirconium silicate, calcium carbonate, silicon oxide, zinc white, magnesium oxide, titanium oxide, etc. can be used, and it is also effective to use two or more types with different solubility in acids and alkalis. It is.

These are important in providing an auxiliary effect to create a roughened shape in the chemical roughening process, and 20%
It can be used in an amount of 0 parts or less, preferably 100 parts or less.

The feature of the method for producing a chemically plateable powder coating according to the present invention is that a chemical plating catalyst such as a noble metal having plating catalytic ability is combined with a part of the thermosetting resin which is the main component in the final powder coating; A relatively large amount of high molecular weight rubber and an inorganic filler are included in the forced kneading process, and at least part of the kneading process heats the entire system above the melting point of the thermosetting resin to melt and liquefy them. By doing so, it is possible to obtain a dispersion in which the high molecular weight rubber and the chemical plating catalyst are simultaneously present at high concentrations.

Due to the uniform presence of this dispersion in the final powder coating, the insulating coating film is formed during the plating pre-treatment step, so that the rubber having conjugated double bonds and polar groups in the molecules present in the coating film is Based on its unsaturation, it is susceptible to proton-donating reactions and is attacked by oxidizing acids, promoting roughening and elution.
As a result of easy chemical roughening and good surface exposure of the catalyst present at the same time, the plating precipitation effect is extremely remarkable, and the adhesion with the deposited metal is fully exerted due to the polarity effect of the high molecular weight rubber. It is something that

In this case, the ratio between the high molecular weight rubber and the chemical plating catalyst contained in the final powder coating does not necessarily have to be constant, and the ratio between the two can be adjusted during the coating process. , at least 50% of the catalyst contained in the final powder coating
The above amount is necessary for effective plating precipitation to be a composition in which the thermosetting resin, inorganic filler, and relatively large amount of high molecular weight rubber are kneaded in advance.

In addition, in order to sufficiently disperse and mix the chemical plating catalyst with the high molecular weight rubber or inorganic filler in a short period of time, the chemical plating catalyst is first dispersed in an organic solvent solution of the thermosetting resin, or It is effective to disperse the plating catalyst and carrier (alumina, silica, clay, etc.) in an aqueous hydrochloric acid solution.

In this case, in order to perform sufficient pre-dispersion, it is desirable that the viscosity of the thermosetting resin solution system be 10'' poise or less.

Further, after the pre-dispersion has been sufficiently performed, the solvent or aqueous solution is removed as necessary before being tested.

A method for producing a powder coating of the present invention, which comprises forcibly kneading a plating catalyst and a high molecular weight rubber with a thermosetting resin and an inorganic filler in advance at a higher concentration than in the final powder coating. , the thermosetting resin content is 50% of the system.
If the amount is more than 3%, the high molecular weight rubber will easily flow in the molten resin phase and will not be subjected to shearing force, resulting in a reduced dispersion effect, while if it is less than 3%, the lubricating effect will not be sufficient.

If the melting point of the thermosetting resin is 150°C or higher, thermal deterioration of the rubber will occur when the wires are mixed, various difficulties will arise in the kneading operation, and the viscosity of the resulting powder coating will increase. A resin having a melting point of 150° C. or lower is used because it does not exhibit a viscosity of 105 centipoise or lower during at least one stage of curing.

Similarly, if the filler content is 60% or more, the lubricating action and solvent action of the thermosetting resin will be inhibited, and if it is less than 5%, the shear force action with the rubber will be insufficient.

Further, the reason why the rubber content is limited to 80% or less is that the filler and thermosetting resin contents are relatively reduced, which reduces the above-mentioned dispersion effect.

On the other hand, if it is less than twice the amount in the final powder coating, the efficiency of rubber dispersion is not good, which is not preferable.

As the inorganic filler, zirconium silicate, calcium carbonate, silicon oxide, zinc white, magnesium oxide, titanium oxide, aluminum silicate I, etc. can be used.

These are important in providing an auxiliary effect to create a roughened shape in the chemical roughening process, and in the kneading process, they apply shearing force to the high molecular weight rubber and molten thermosetting resin to disperse the components. This contributes to

This is also the reason why 5 to 60% of inorganic fillers are mixed.
% or less, the roughening effect is insufficient and the shearing force application effect is insufficient.

On the other hand, if it exceeds 60%, dispersion and kneading becomes difficult and the amounts of other components are relatively reduced, making it impossible to obtain sufficient coating performance.

These chemical plating catalyst, rubber, thermosetting resin, and inorganic filler are kneaded using a kneader, a pressure kneader, a mixing roll, an extrusion kneader, or the like to form a highly concentrated dispersion of the plating catalyst and rubber.

The high-concentration dispersion of plating catalyst and rubber thus obtained is kneaded again with other ingredients required for the final powder coating, and then coarsely milled using a pulverizer such as an Asago-type pulverizer or a micro pantum mill for shoes. Grind, pulverize.

It is preferable that the pulverization be carried out by a conventional method to the extent that substantially all particles of 300 μm or less are obtained.

Formation of a printed circuit by chemical plating is carried out by applying a metal coating to areas other than the circuit portion, and then chemically roughening the area and immersing it in a chemical plating bath.

For chemical roughening, ordinary roughening solutions such as chromium mixed acid can be used. Examples of chemical plating solutions include CUST201 (manufactured by Hitachi Chemical Co., Ltd., electroless plating solution), CC-4 plating solution (
Ordinary products such as Hitachi Chemical's electroless plating solution can be used.

In addition, prior to chemical roughening, pre-soaking in an organic solvent is performed,
When the coating surface is swollen, the unsaturated polymer surrounded by the crosslinked resin can be easily roughened.

Examples of these organic solvents include mixed solvents of alcohols and methyl ethyl ketone, pyridine, dimethylformamide, trichloroethylene, and the like.

As explained above, in the present invention, a hardened coating film that is easily chemically roughened and made hydrophilic and has improved circuit adhesion of printed circuits by chemical plating is applied to the surface of a metal plate using the powder coating method. Because the chemical plating catalyst is uniformly dispersed in the cured coating, it can be formed with excellent smoothness.
Deposition of chemical plating is stabilized and reliability of circuit formation is improved.

Example 1 1 part of palladium chloride, 250 parts of acrylonitrile butadiene rubber (Nipole 1032 manufactured by Nippon Zeon Co., Ltd.), 150 parts of epoxy resin (Epico-11004 manufactured by Shell Chemical Co., Ltd.), and 80 parts of calcium carbonate and 20 parts of zirconium silicate as fillers. and kneaded for 20 minutes.

The kneaded composition taken out is a dispersion containing 50% rubber and 0.2% palladium chloride.

22 parts of the high concentration dispersion of palladium chloride and rubber;
14 parts of calcium carbonate and 130 parts of epoxy resin (Epicor 1004 manufactured by Shell) were kneaded with a mixing roll, cooled and solidified, and then coarsely pulverized to 166 parts of the mixture, 6.6 parts of dicyandiamide, 1 part of finely powdered silica, One part of a flow control agent (Modaflow, manufactured by Monsanto) was added, and this composition was dry mixed using a Henschel mixer, and then melt-kneaded using a Co-kneader PR-46 manufactured by Buss.

After cooling and solidifying, crush into 60 mesh 8 (mesh opening 250)
A powder was created through the process.

Next, the powder coating was applied to a 1.2 mm thick iron plate using an electrostatic dynamic coating device with a lid (080 V, 10 seconds), and baked at 180°C for 60 minutes to harden it to a thickness of 150 μm. A substrate with an insulating coating was created.

The portions of this substrate other than the circuit pattern portion were screen-printed using a mesh resist to cover the substrate, and the surface was roughened by immersing it in a roughening solution.

The immersion conditions were as follows: 40 parts were soaked at 1° C. for 15 minutes, and then taken out, neutralized, and washed with water twice.

Next, it was directly immersed in CC-4 plating solution (electroless copper plating solution manufactured by Hitachi Chemical Co., Ltd.) as a chemical plating bath for 35 minutes.
Copper plating was performed to μ skin thickness.

Note that the plating circuit area was approximately 30% of the entire board area.

The plating was deposited uniformly, and when the state of the plating was observed using a microscope with a magnification of 60 times, no unplated portion was observed in the circuit portion.

Further, when this sample was subjected to post-cure drying at 160° C. for 60 minutes, the peel strength of the circuit portion was measured and found to have a value of 1.65 to 1.85 kg/cm.

Example 2 A plating catalyst prepared by uniformly dispersing and adsorbing 0.3 parts of palladium chloride and 2.7 parts of stannous chloride on 100 parts of aluminum silicate in an aqueous solution of hydrochloric acid was applied to an acrylonitrile phytadiene column (Nipole DN-401 manufactured by Nippon Zeon Co., Ltd.). 100
180 parts of styrene-butadiene polymer (Turprene 406 manufactured by Philips) 5 parts of calcium carbonate as a filler
0 parts, 15 parts of aluminum silicate, and 100 parts of epoxy resin (Epicoat 1004 manufactured by Shell) at 90°C.
A high-concentration dispersion of catalyst and rubber was prepared by kneading in a pressurized kneader heated to .

Next, 10 parts of calcium carbonate and 12 parts of epoxy resin (Epicoat 1004 manufactured by Shell) were added to 54.5 parts of the dispersion.
0 parts, 6.3 parts of dicyandiamide, 1 part of finely powdered silica,
1 part of the flow control agent Modaflow and 5 parts of the above-mentioned noble metal-containing filler were added, and the other steps were the same as described in Example 1 to prepare a powder coating and perform plating for forming a circuit, and observe the precipitation state of the plating. It was confirmed that the plating was deposited uniformly, and the peel strength of the circuit part of this product was 1.60.
It had a value of ~1.85 kg/Cm.

Comparative Example l The composition of the final powder coating is exactly the same as that described in Example 1, but in the case of a substrate made by adding a catalyst at the stage of preparing the powder coating, the plating precipitation was not sufficient and it was not necessary. There were undeposited parts in some parts of the circuit.

In addition, the peel strength of the precipitated part is 1.2 to 1.5 kg.
/crn.

Claims (1)

[Claims] 1. Contains 0.006 to 1.2 parts by weight of a chemical plating catalyst and 1 to 30 parts by weight of a rubber having a conjugated double bond and a polar group in the molecule, based on 100 parts by weight of a thermosetting resin. A chemically plateable powder coating having a viscosity of 105 centipoise or less during at least part of the heat curing step. 2 For 100 parts by weight of thermosetting resin including the following steps,
Contains 0.006 to 1.2 parts by weight of a chemical plating catalyst, 1 to 30 parts by weight of a rubber having a conjugated double bond and a polar group in the molecule, and 105
A method for producing a powder coating that can be chemically plated and has a viscosity below centipoise. A, 50% of the chemical plating catalyst contained in the final powder coating
At least 3% by weight of thermosetting resin with a melting point of 150°C or less
50% by weight, 5 to 60% by weight of inorganic filler, 80% by weight or less of rubber having a conjugated double bond and a polar group in the molecule,
In addition, at least one period of the kneading process, the composition is pre-kneaded at a temperature equal to or higher than the melting point of the thermosetting resin having a melting point of 150° C. or lower, with a composition containing twice as much as the final powder coating. B. This kneaded composition is further kneaded with a thermosetting resin and pulverized.