JP2811199B2 - Method for filling foaming liquid material into recesses or through holes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for filling a concave portion or a through hole with a foamable liquid substance.

[Conventional technology]

In recent years, in printed wiring boards, etc., in order to protect recesses or through holes (through holes) during etching, filling holes, insulating materials in the through holes,
Demand for filling a conductive material for conductive processing of a through hole or the like has been rapidly increasing.

As a conventional method of filling these recesses or through holes, as shown in FIG. 4, a required amount of a material liquid is poured onto a surface of an object to be coated (Ob) having recesses and / or through holes. Is squeezed by a roller (11) or a squeezer, a brush, or the like, and the material liquid is pushed (L ₃ ) into the concave portion or the through hole of the object to be filled to fill or fill the hole.

[Problem to be solved]

The above-mentioned conventional filling method has several problems as follows. That is, first, originally, a solution is often used as a liquid used for filling the concave portion or the through hole, and these are diluted and blended to an appropriate viscosity with a solvent or the like so as to be optimal for filling. Things. Needless to say, these blending are performed by a separate blending and mixing apparatus, and are temporarily stored in a tank. Take it out according to its use, pour it into a certain amount on the surface of the object to be coated (Ob) having the above-mentioned concave portion and / or through-hole, squeeze it with a roller (11) or the like, and put it into the concave portion or through-hole. It was pushed. However, the amount other than that pushed, the roller (11) scraper is moved to notwithstanding et open-loop and article to be coated (Ob) Menjo due (L _4), wait until the next squeezing operation, moreover, these Is repeated many times. The solution thus formulated is exposed to the atmosphere for a few minutes to tens of minutes. Therefore, the solvent in the solution volatilizes with time, and the concentration, that is, the viscosity of the solution gradually increases. This results in an unsuitable viscosity for filling, as described above. That is, the viscosity gradually increases, and it becomes more difficult to push,
In some cases, the performance of the solution is also reduced.

Second, a certain force is required to sufficiently push the solution into the recess or through-hole, and the squeeze force is not sufficient, and may not sufficiently cover every corner or even the minute hole in the recess. . That is, in the squeeze, the embedding becomes more difficult as the diameter of the concave portion or the through hole becomes smaller and deeper, or as the viscosity of the solution becomes higher. In particular, in embedding the through-hole, there is a case where it is necessary to perform the indentation from the back side, that is, to perform the filling operation from both sides, because the indentation force is insufficient and the through-hole is insufficiently filled.

Third, in embedding work by squeeze, it is a precondition that the solution is liquid at room temperature. Therefore, it was impossible to handle a melt that was melted by heating.

Fourth, conventionally, as a material for filling the recess or through hole,
Non-effervescent liquid materials have been used. However, immediately after the filling, if the upper surface of the recess or the through hole is scraped, the fifth
As shown in the figure, a concave surface (Cf) occurred.

[Means for solving the problem]

In the conventional method of filling the recesses or through holes by squeezing, it is determined that the above problems are difficult to solve,
Another method not based on squeeze, that is, filling with a nozzle was performed, and at the same time, attention was paid to using a foaming material as a charging material.

There are various foamable liquid substances used in the present invention,
Let's take foaming hot melt adhesive for the moment.

The foamable hot-melt adhesive uses a foaming agent, but in the present invention, the most effective gas mixing method which is particularly used recently will be described. It is a gas (inert gas) in hot melt adhesive melted by heating
And mechanically stir and pressurize them. The gas (inert gas) then molecularly disperses or dissolves in the hot melt adhesive. That is, it becomes translucent syrup-like, and the presence of air bubbles is not visually recognized. When this is discharged into the atmosphere from a nozzle or the like, the pressure is released, the gas molecules collectively expand, the bubbles become larger and become visible, and a so-called whipped cream-like foamed hot melt adhesive is formed. You get it.
The generation device was invented by Nordson Corporation, our parent company, and was patented (Japanese Patent No. 1,380,
No. 841) is registered. The patent name is said to be an apparatus for producing a hot melt thermoplastic adhesive foam. The present inventor has performed stencil coating and roll coating with a foamable hot melt adhesive by the same apparatus and has obtained good results, and further applied it to conductive materials and resist agents, and at room temperature. The same good result was obtained also in the discharge in the above, so that the present application was submitted.

Therefore, first, the outline of the apparatus for manufacturing a hot melt thermoplastic adhesive foam, which is a patent apparatus of the Nordson Corporation, will be described. See FIG. The solid hot melt adhesive (HM) is supplied into the heating and melting tank (22) of the present apparatus (21), and is heated and melted by the electric heater (24). The molten hot melt adhesive (HM) is supplied into the mixer (26) from the bottom of the bath. The mixer consists of a pair of gears (27 and 28) meshing and rotating with each other. At the same time, gas is also supplied to the inlet of the gear. By the meshing rotation of the gear, the molten hot melt adhesive is mixed and stirred with the gas. At the outlet of the mixer, pressure is applied (approximately 40 kg / cm ² if the gas is air), and the melt of the hot melt adhesive and the gas are molecularly mixed, that is, the gas is melted of the hot melt adhesive. Dissolved in
Accordingly, there is no bubble (B) visually, and the same molten hot melt adhesive as before the gas mixing, that is, a syrup-like translucent adhesive can be obtained. In this way, under a certain pressure, it reaches the gun through the tube and is discharged from the nozzle into the atmosphere, the pressure is released, and the above-mentioned molecularly dispersed gas molecules also gather, Then, the foam expands sequentially, and visible bubbles are generated, that is, a discharged foamable hot melt adhesive in the form of a pop cream is obtained.

The foam of the hot-melt adhesive thus generated is a foamable hot-melt adhesive that provides more effects than the solid hot-melt adhesive as described above.

As described above, in the case of a foamable hot melt adhesive,
Liquid pressure foaming apparatus for the adhesive has been carried out by introducing a hot melt adhesive into an apparatus called a so-called foaming hot melt applicator. And a resist agent, and gas is fed under pressure without heating, and dispersed and compressed as bubbles in these liquids. These bubbles are so fine that they cannot be seen under pressure, but when released into the atmosphere, they gradually expand to become visible bubbles.

In the case of filling the concave portion or the through hole, the foamable material is filled into the concave portion or the inside of the through hole. Material penetrates to the part, and the surface of the concave part and both ends of the through hole, that is, the open part rises due to expansion (FLc)
Therefore, the surface of the opening does not remain concave due to scraping as in the case of a liquid, but rises immediately after the concave. That is, the edge (E) portion of the concave portion or the through hole can also be covered finely. (See FIG. 3). As described above, since the volume has increased several times due to foaming, the required amount is only a fraction, and the adhesive strength to the other party can be increased. It is done.

The gist of the present invention is that the end face of the tip of the nozzle is pressed against the surface of the substrate having the concave portion and / or the through-hole, and any one of them is fixed or moved while the foaming foam is pressed from the nozzle. This is a method of discharging the liquefied liquid substance to fill the concave portion or the through hole.

Next, the method of the present invention will be described with reference to the drawings. Please refer to FIG. The gun (2) is supplied with a pressurized foamable liquid substance (FL). However with these foaming gases inert gas, as described above, molecularly dispersed i.e. melted into the liquid below the gas (inert gas) is required pressure (40 kg / cm ² before and after at least 5 kg / cm ² or higher) Is what is being done. The end face (1F) of the tip of the nozzle (1) attached to the gun (2) has a flat shape, and the object (O)
Pressed on the surface of a). Therefore, the foamable liquid material does not leak from between them, and the material to be coated (Oa)
Into the recess or through-hole. Since the nozzle (1) or the object to be coated (Oa) moves in _one direction (R or R ₁ ), the foamable liquid substance discharged from the nozzle (1) is in or through each concave portion on the same surface. The pores will be filled. It is desirable that a radius be provided at both corners of the nozzle tip surface.

The liquid before the gas of the effervescent liquid substance (FL) is mixed with the gas is generally a solution, which is often a mixture of a plurality of liquids or a fixing agent dissolved in a solvent. After they are mixed by the mixing device, they are fed to a liquid pressurized foam generator, where the required pressure is applied and they enter the gun (2) through a tube. By opening the valve (3) in the gun,
The foaming liquid substance, ie, the foaming liquid (FL),
H), but since the tip of the nozzle (1) is in pressure contact with the surface of the object (Oa), there is no gap between them, and therefore there is no leakage to the outside, Things (O
It enters directly into the concave part (C) or the through hole (H) of a).
Further, (see FIG. 2) When the recess, if the size of the recess (the length in the running direction of S ₁ or nozzles) is a distance S ie from the nozzle holes of the flat surface of the nozzle (1F) (IH) If it is larger than the size, the gap (S ₁ −S = S
The solution is leaked from c), since the discharge pressure is lowered, it is desirable that the S> S _1. In this way, since the foaming solution (FL) has a certain pressure, it penetrates into every corner of the fine concave portion and is sufficiently filled. Further, the through holes are similarly filled.
In the case of a slot nozzle, the nozzle moves in a direction perpendicular to the direction of the nozzle to fill the concave portion or the through hole of the object with the foaming solution (FL ₁ ).

The features of the above-described method are listed as follows.

1) Foaming solution (FL ₁ ) discharged from nozzle ( ₁ )
Has a certain required pressure (at least 5 kg / cm ² or more), and is pushed while moving sequentially into various large or small concaves or through-holes of the object to be coated (Oa). The air in the through holes is purged while the bubbles expand under atmospheric pressure. Therefore, the foaming solution enters into the concave portion or the fine corners in the through-hole, finely fills the same portion, and at the same time, after the surfaces are scraped, the bubbles continue to expand. Alternatively, the edge portion of the through hole can be covered neatly.

2) A solution generally used for filling is diluted with a solvent or the like. Pressurized gas (inert gas)
Is discharged through the gas (2), the nozzle (1), and the like, and is pushed into the concave portion or the through hole of the object to be coated (Oa). Only after the nozzle (1) has moved away has the foaming solution in the recess or through hole been exposed to the atmosphere. Therefore, the solvent in the foaming solution is not volatilized at all until the foaming solution is filled in the concave portion or the through-hole, that is, it can be filled with the most appropriate viscosity at the beginning of compounding. is there.

3) As described above, in the conventional coating method using squeeze or the like, a pressurized solid type (non-foaming)
In the same way that the liquid material was not taken up, the foaming liquid material was not taken up, and in the method of the present invention, these were taken up and many advantages could be obtained. is there.

Experimental Example In this example, a foamable etching resist agent is filled in a through hole of a double-sided copper plated through-hole wiring board. The purpose of filling is to prevent the foil plated with copper on the inner wall of the through hole from being etched.

Coating object Double-sided copper plated through-hole wiring board (glass epoxy) Size 50 × 80mm Thickness 1.6mm Through hole (through hole) Hole diameter 0.3-1.0mmφ Total number 200 places Solution UV curable etching resist agent (foaming) Viscosity (before foaming) 15,000 cps (20 ° C) Foaming ratio 3 times Discharge pressure 5 kg / cm ² Nozzle moving speed 50 mm / sec Under the above conditions, foamable resist is discharged from the nozzle, and the nozzle is moved to move the substrate. Was filled with a foamable resist agent. As a result, all the large and small through holes were completely filled with the UV-curable etching resist agent (foamable). The edge of the concave portion or the through hole could be covered finely by the expansion of the resist agent. Then, after etching is performed by screen-printing (pattern printing) the etching resist agent on both sides of the substrate, no damage is observed on the copper plating foil on the inner wall surface of the through-hole, and the substrate is completely protected. It was confirmed.

The results of the above experimental examples are obtained by confirming the state of filling in the cross section of the through-hole portion of each test piece with a microscope.

In addition, on the surface of the substrate to be filled with the recesses or through holes by the method of the present invention, various coating means (spray method,
A solid or foamed coating film can be formed by a roll coating method, a curtain coating method, a screen method, etc., and various functions can be imparted.

〔effect〕

According to the method of the present invention, in the filling work of the foamable liquid substance into the concave portions or through holes, the foamable liquid material can be reliably and sufficiently filled into the small concave portions or through holes having a small hole diameter. In addition, it is possible to cover those edges neatly, and furthermore, does not volatilize even the solvent contained in the foaming solution during the work, that is, the filling work while maintaining the optimum viscosity at the time of compounding. Can be performed. Further, it has many advantages such as the ability to handle foamable melts and the like.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating the method of the present invention. FIG. 2 is a diagram showing the relationship between the size of the flat surface at the tip of the nozzle and the recess. FIG. FIG. 4 shows a conventional method of filling a concave portion or a through hole. FIG. 5 shows a state of a concave surface generated when a conventional non-foamable material is filled and scraped. FIG. 6 is an explanatory side sectional view of a known foamable hot melt generating apparatus. FIG. 7 is an "E"-"E" sectional view on the same figure. Explanation of main symbols: 1... Nozzle, 1F. End face of part, 2 ... Gun, 3 ... Valve, Oa, Ob ... Coating object, Cf ... Concave surface, FL,
FL ₁ ... foaming solution

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) B05D 1/00-7/26 H05K 3/06

Claims (4)

(57) [Claims] 1. A mixture obtained by mixing and mixing an inert gas into a liquid or a melt, and pressurizing the mixture to at least 5 kg / cm ² or more to form a foamable liquid substance. A foamable liquid material, characterized in that the foamable liquid material is filled with the foamable liquid material while being pressed or pressed on the surface of the object to be coated (Oa) having concave portions and / or through holes, and fixing or moving one of them. A method for filling a recess or a through hole. 2. The method according to claim 1, wherein the nozzle is a slot nozzle. 3. A mixture obtained by mixing and mixing an inert gas into a liquid or a melt, and pressurizing the mixture to at least 5 kg / cm ² or more to form a foamable liquid substance. , Pressed against the surface of the object to be coated (Oa) having concave portions and / or through-holes, filling the foamable liquid substance while fixing or moving one of them, and foaming on the surface of the object to be coated. Characterized by coating with a liquid material,
A method for filling a concave portion or a through hole with a foamable liquid substance. 4. A liquid or melt mixed with and mixed with an inert gas to form a mixture, and the mixture is pressurized to at least 5 kg / cm ² or more to form a foamable liquid substance. , Pressed against the surface of the object to be coated (Oa) having concave portions and / or through-holes, filling the foamable liquid material while fixing or moving one of them, and A method for filling a concave portion or a through hole with a foamable liquid material, comprising coating a liquid or a melt of the same type as the foamable liquid material.