JPS6088496A - Method of forming through hole connector of board for electronic 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 Field of Industrial Application The present invention relates to a method for forming a small through-hole connection portion that electrically connects the front and back sides of an electronic circuit board through a through hole provided therein. It's from Jrumu.

Prior Art In printed wiring boards, etc., which have a predetermined pattern of conductive parts made of copper foil, conductive paint, etc. on both the front and back sides, through-hole connections are formed in through-holes that are made by penetrating the board at predetermined locations. However, a structure is adopted in which the conductive parts on both the front and back sides of the board are electrically connected by the through-ball connection part. A method for forming a through-hole connection is to apply an undercoat containing a material with plating receptivity or plating f'' characteristics to the inner surface of the through-hole and the area surrounding the front end of the through-hole, and then apply a layer of the undercoat to the area surrounding the front end of the through-hole. Two known methods are known: a plating method in which a conductive plating layer is formed by applying chemical plating on the through hole, and a painting method in which a conductive paint such as silver paint is applied to the inner surface of the through hole and the area surrounding the open end of the through hole. In these methods, when applying paint to the inner surface of the through hole and the area surrounding the open end of the through hole, for example, a thin rod coated with paint is inserted into the through hole of the substrate. A method of reciprocating is used.

By the way, when electrically connecting the front and back sides of the board using the through lJ' Also, in order to facilitate the mounting of electronic components on the electronic circuit board, [well, a through hole with approximately equal diameter should be formed inside each through-hole connection portion into which the lead wire of the electronic component can be inserted. is desirable. Therefore, in each through-hole connection part, the paint is uniformly applied to the inner surface of the through-hole (=J I
However, it is desirable that the structure has a through hole with the same diameter on the inside. However, in general, when applying paint to the inner surface of the through-hole of a beam plate, there is a tendency for excessive paint to adhere to the inside of the through-hole, so a through-hole as described above is formed at each through-hole connection. Otherwise, a special process is required to form the through-hole, making the formation of the through-hole connection considerably troublesome.

As a method of forming a small through-hole connection part with a through-hole inside (14 times, apply paint and insert a thin rod into the through-hole of the board to connect the inner surface J3 of the through-hole and the open end of the through-hole. After applying paint to the surrounding area, there is a method of inserting a thin rod that does not contain paint into the through hole and moving it back and forth to remove excess paint, and a method similar to the above. A method has been proposed in which the excess paint is removed by blowing compressed air into each through-hole to which the paint has been applied, or by vacuum suction. There is.

However, in the former method, since the paint is deposited on the thin stick for removing excess paint, the thin stick for removing paint must be cleaned after removing the excess paint. This has the disadvantage of complicating the process. Furthermore, this method has the disadvantage that it is difficult to make the inner diameter of the through hole uniform, and that the amount of paint deposited on the inner surface of the through hole also varies considerably. In addition, in the latter method, compressed air is blown uniformly into each through-hole where paint is applied. In order to prevent air from leaking, it was necessary to install a jig to hold the board against the air outlet (or air inlet). In this method, in order to prevent the paint blown out (or sucked in) from each through-hole from scattering to areas other than the area around the front end of the through-hole, paint is not applied. This has the disadvantage that it is necessary to cover the parts that should not be covered with a mask, making processing of the board complicated.

OBJECTS OF THE INVENTION The purpose of the present invention is to propose a method for forming a through-ball connection part for an electronic circuit board, which makes it possible to easily form a through-hole connection part having a through hole with a substantially uniform inner diameter. be.

Structure of the Invention A first invention of the present application provides an electronic circuit board; After applying a conductive paint to the inner surface and the area surrounding the open end of the through hole, the conductive paint is centrifuged from one open end side of the through hole to the other open end side with the fluidity of the conductive paint changing to the right. This method is characterized by applying force to remove excess conductive paint.

Further, a second invention of the present application provides a method for forming a through-hole connection portion that electrically connects the front and back sides of the substrate through a through-hole provided in the substrate for electronic circuits. After applying an undercoat paint that has fluidity and plating receptivity or plating ability to a region surrounding the open end of the through hole, one open end of the through hole is coated with the undercoat paint having flowability. A centrifugal force is applied from one side toward the other frontage end to remove excess undercoat paint, and then conductive plating is not applied on the welding undercoat paint that has avoided drying of the undercoat paint. It is something.

2, when centrifugal force is applied to the board while the paint has fluidity, each through-hole connection part has an approximately average diameter of about 0.03 to 0.05 utm smaller than the inner diameter of the through-hole of the board. It has become clear that it is possible to uniformly form through holes having a certain inner diameter. In addition, when centrifugal force is avoided, the paint flows on the inner surface of the through hole and adheres uniformly to the inner surface, so the paint can be evenly applied to the inner surface of each through hole using the minimum amount of paint. It has become clear that through-hole connections with uniform thickness can be formed without leaving unpainted areas. Furthermore, excess paint removed by centrifugal force can be collected and reused, so paint t1
It is economical and does not go to waste. In addition, centrifugal force can be applied by attaching a 1% temporary to a rotating body such as a rotating drum, and it can be easily applied regardless of the necking or shape of the through hole.
Since it can be carried out using a single jig and equipment, automation is easy and mass production is easy. Furthermore, according to the above method, a through hole is reliably formed at each through hole connection part, so there is no need to inspect whether or not a through hole is formed, which simplifies the process and improves C. Manufacturing efficiency can be greatly improved.

In this specification, "undercoat paints that have good plating receptivity or plating properties" are used to apply chemical coatings to substrates that cannot be self-applied with chemical plating (electroless plating). Refers to a paint that is pre-applied to a portion of the plate to enable it to be plated. For example, silver paint, copper, etc.
Paints that can be chemically plated by containing metals in the resin, such as paints containing lumber, epoxy-modified phenol paints, and ABS resin paints, can themselves be plated. = Resin paint with the right properties,
Alternatively, a liquid coating 1 or the like may be used in which a metal such as palladium, tin, or nickel is dissolved in a solvent.

Shomoto River 1! In lil, the term "paint" is interpreted in a broad sense, and is not limited to paints containing resin, but also includes IC solutions made by dissolving substances in a solvent that have high properties or plating receptivity. Zuru.

In addition, in this specification, the edict "electronic circuit board" refers to
It shall be interpreted in the broadest sense, with conductive parts (regardless of whether they are good conductors or resistors, as long as they have good conductivity) on both the front and back sides. It is intended to include any substrates that are electrically connected to each other by conductive through-hole connections. Therefore, not only the circuit board on which electronic components are mounted, but also the substrates constituting the electronic components mounted on the five circuit boards are included in the electronic circuit board to which the present invention is applied.

EXAMPLE In this example, a phenolic resin laminated substrate 1 having a thickness of 1#++++ and having a cross-sectional shape as shown in FIG. 1 was used as an electronic circuit board. A conductive part 3 made of copper foil is on the surface of base &1.
A through hole 2 is formed through the substrate and each part of the conductive part 3 connected to the back side of the substrate. In the urine invention, the shape of each through hole is arbitrary, but in this embodiment, a hole is formed near one open end of each through hole 2 and gradually becomes smaller toward the one open end side or the other front end side. By forming the tapered portion 2a in the following direction, each through hole 2
was formed into a trumpet shape. J3 This tapered shape is the shape seen when through-hole formation processing is performed using a punching press or the like.

In this embodiment, a silver paint having a viscosity of 14-16 voices is used as an undercoat paint, and as shown in FIG. It was 11 times. The method for applying this paint is to use a known method of simultaneously inserting thin rods into each through-hole and applying the paint to the inner surface and both sides of each through-hole.
After coating the paint 4 around the edges, the substrate 1 is placed on the inner periphery of a rotating drum that has numerous through holes formed in the peripheral wall, and while the paint 4 has fluidity, the substrate 1 is rotated. The drum was rotated and a centrifugal force F of 40 to 50 G was applied for 5 seconds from one front end of each through hole 2 to the other open end as indicated by the arrow IC in FIG. In this case, the substrate 1 is pushed onto the inner periphery of the rotating drum by the centrifugal horn and fixed, so no special positioning means is required.

As described above, centrifugal force is applied to the substrate with paint applied to each through hole, and as a result, excess paint in the through holes is removed.
As shown in FIG. 3, it was confirmed that through holes 5 having a substantially uniform inner diameter were formed in all parts of the pipe to which the paint 4 was applied. Next, after drying the paint n4, chemical copper plating (the plating layer is not shown) was applied on the layer of the paint n4 to complete the through-hole connection part 6. After forming the through-hole connections in this manner, a conductive layer 7 connected to each through-hole connection 6 was formed using silver paint on the back mi side of the substrate as shown in FIG. The inner diameter of each completed through ball connection part 6 is 0.03 to 0.
．． The lead wire is inserted into the through hole 5 and soldered.
However, it was confirmed that soldering could be done with sufficient bullet holes.

When we repeated the experiment using the same procedure as above while varying the viscosity of the paint in the range of 0.01 to 1000 voices, we found that
It has become clear that by adjusting the centrifugal force and the application time of A depending on the viscosity of the paint, it is possible to form a through-hole connection portion having a through hole of approximately uniform diameter. For example, even when using a liquid paint with a very low viscosity similar to water,
Good results can be obtained by setting the centrifugal force to about 1.5G, and when using high viscosity paint, the b centrifugal force can be reduced to 130G.
By setting the applied force to about 140 G and extending the opening/opening period, it was possible to form a through-hole connection portion having a through hole with a uniform inner diameter. From these results, the viscosity of the paint can be determined as <L, in which case the centrifugal force should be increased.
It has also been found that when the viscosity of the paint is the same, the greater the centrifugal force, the shorter the application time.

Also, the shape of each through hole of Ic is made into a trumpet shape as shown in the figure.
It has been found that when centrifugal force is applied from the side opposite to the tapered portion 2a as indicated by the arrow in FIG. 2, good results can be obtained even if the centrifugal force is reduced. Note that even when a through hole without a taper is provided, such as a through hole formed by a drill, the same good results can be obtained by applying a stronger centrifugal force than when a through hole with a taper is provided. This has been confirmed.

As in the above embodiment, if the structure is constructed using silver paint and no copper plating on top of it, soldering properties can be imparted, but the present invention does not apply plating in this way. The case is not limited to this, and the through-hole connection portion may be formed using only the conductive paint 5. In this case, the through-hole connection portion can be formed by simply applying a paint as shown in FIG. 2, then applying centrifugal force to form a through hole as shown in FIG. 3, and then drying it.

In addition, when plating is performed by applying a Metsuki 4 imparting coating such as a palladium-containing solution, cracks tend to occur in the plating due to the expansion and contraction of the substrate. If plating is applied through a layer of strong silver paint or the like, cracks can be prevented from occurring in the plating.

If the excess paint is removed by centrifugal force as in the present invention, the excess paint can be recovered and the recovered paint can be reused.

In the above embodiment, the conductive part 3 is formed in copper foil on the surface of the board 1 in advance, and after the through-hole connection part 6 is formed, the conductive part 7 is formed with silver paint on the back surface of the board. However, it goes without saying that the present invention can be similarly applied to a platform for forming through-hole connection parts on a board on which conductive parts are previously formed using copper foil or the like on both sides of the board.

Although the substrates 1 and 1 are made of phenolic resin laminated substrates in the above embodiments, the present invention can be applied regardless of the material of the substrates.

Effects of the Invention As described above, according to the present invention, centrifugal force is applied to the substrate while the paint has fluidity, so that through-holes having approximately uniform inner diameters are uniformly formed in each through-hole connection portion. Can be formed. In addition, when centrifugal force is applied, the paint flows on the inner surface of the through hole and is applied uniformly to the inner surface, so the paint can be applied uniformly to the inner surface of each through hole using the minimum amount of paint. Through-ball connections with uniform thickness can be formed without leaving unpainted areas. Furthermore, centrifugal force can be applied by mounting the substrate on a rotating body such as a rotating drum, and can be applied using simple jigs and equipment regardless of the arrangement or shape of the through holes, making it easy to automate. Therefore, mass production can be easily carried out. Furthermore, according to the method of the present invention, since a through hole is reliably formed at each through hole connection part, there is no need to inspect whether or not a through hole is formed, which simplifies the process. The manufacturing efficiency can be greatly improved, and the cost of electronic circuit boards can be reduced.

[Brief explanation of the drawing]

1 to 4 are cross-sectional views sequentially showing the steps of an embodiment of the present invention. 1... Electronic circuit board, 2... Through hole, 2a...
Tapered part, 3... Conductive part, 4... Paint, 5... Through hole, 6... Through-hole connection part, 7... Electrically conductive part. ” - continuation even 1) tT2! ': jji (spontaneous) October 311, 1972] Commissioner of the Patent Office Manabu Shiga IF Ji 1, Indication of Case Patent Application Ill Eye 8-195279
”;”. 2. Name of the invention: Formation of a through-hole contact part on an electronic circuit board/J'd, 3
, Relationship with the person making the amendment $171 1'T n'1 Applicant Hokuriku Electric II I
I-Gyo Co., Ltd. 4, Agent: Shinbashi, Minato-ku, Tokyo / 1-31-6 Bun Ill Building, 6th Floor Details H
) Full text 6, ? As stated in the separate sheet of contents of lli-masa.

Claims (8)

[Claims] (1) In a method for forming a through-hole connection portion that electrically connects the front and back sides of an electronic circuit board through a 4J through-hole provided in the board, surrounding the inner surface of the through-hole of the board and the front end of the through-hole. After applying conductive paint to the area, remove excess conductive paint by applying centrifugal force from one front end side of the through hole toward the other front end side while the conductive paint has fluidity. A method for forming a through-hole connection part of an electronic circuit board, characterized by: (2) One end of the through hole (4) has a tapered shape in which the diameter gradually decreases from one front end side to the other front end side of the through hole. A method for forming a through-hole connection portion of an electronic circuit board according to claim 1, characterized in that the method comprises: (3) The method for forming through-hole connections in an electronic circuit board according to claim 1 or 2, wherein the conductive paint has a viscosity of 0.01 to 1000 poise. (4) In a3 of the method for forming a through-hole connection portion that electrically connects the front and back sides of an electronic circuit board through a through-hole provided in the board, the inner surface of the through-hole of the board and the open end of the through-hole are After applying an undercoat paint that has fluidity and plating receptivity or plating ability to the surrounding area, from one frontage end side of the through hole to the other frontage end side in a state where the undercoat paint has flowability. A substrate for electronic circuits, characterized in that excess undercoat paint is removed by applying centrifugal force toward , and then a conductive layer 4- is applied on top of the welded undercoat paint, which has been dried. How to form through-hole connections. (5) The vicinity of one U1 opening end of the through hole is tapered so that the diameter gradually decreases from one front end side to the other front end side of the through hole. 5. A method for forming a through-hole connection portion of an electronic circuit board according to claim 4. (6) The method for forming through-hole connections in an electronic circuit board according to claim 4 or 5, wherein the undercoat has a viscosity of 0.01 to 1000 voids. (7) The method for forming a through-hole connection portion of an electronic circuit board according to any one of claims 410-5 to 6, characterized in that the undercoat paint has a silver coating. . (8) The undercoating paint is a paint containing palladium, [Formation of through-hole connection portions of electronic circuit boards according to any one of claims 4 to 6] Method.