JPH0832211A - Production of printed wiring board - Google Patents

Abstract

PURPOSE:To prevent a solder from flowing into a through hole by filling the through hole with a UV ray curing resin while bulging from the surface of a board and abrading the bulged part after curing of resin thereby filling the through hole with the UV ray curing resin over the entire depth. CONSTITUTION:When a printed wiring board 100 having a through hole 20 is produced, the through hole 20 is filled with a UV ray curing resin 50 while bulging from the surface of a board 10. The board 10 is then sandwiched by a translucent mold releasing film and the resin 50 is cured by irradiating b with UV-rays. The UV-curing resin 50 bulged onto the surface of the board 10 is then abraded and removed. This method provides a through hole into which the solder does not flow at the time of mounting an electronic device on the pads, or a through hole in which the solder resist is not ruptured through expansion of the air in the through hole at the time of drying or hardening of solder resist.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board and a method of manufacturing the same, and more particularly, to a through hole having at least one end exposed on the surface of a substrate and mounting an electronic component extending at the one end of the through hole. And a solder resist that covers the one end of the through hole.

[0002]

2. Description of the Related Art Conventionally, various types of printed wiring boards have been devised. Among them, as shown in FIG. Various through holes such as so-called blind via holes exposed on the surface of the substrate and the other end embedded inside the substrate, and through holes so-called interstitial via holes embedded at both ends inside the substrate. There is something. Then, among such through holes, through holes having at least one end exposed on the surface of the substrate, such as through through holes and blind via holes, the printed wiring can be made more dense or a printed wiring board can be provided. A structure in which a pad for mounting electronic components is extended at one end exposed on the surface for the purpose of suction fixing during a continuity test, that is, a structure having a through hole in the mounting effective area of the pad for mounting electronic components. Alternatively, one end exposed on the surface may be covered and sealed by the solder resist.

[0003]

However, in the conventional printed wiring board, there is no problem in the through hole in which both ends of the interstitial via hole and the like are arranged inside the base material. A through hole (hereinafter simply referred to as a through hole) having at least one end exposed on the surface of the substrate, such as a through hole or a blind via hole, has the following problems.

First, when the pad is provided at one end of the through hole exposed on the surface of the substrate, the electronic component is generally mounted on the pad by soldering. At this time, the solder flows into the through hole. The desired amount of solder cannot be obtained on the pad surface, which lowers the reliability of electrical connection between the electronic component and the pad, and in some cases causes a so-called Manhattan phenomenon that the electronic component starts up, resulting in poor connection of the electronic component. was there.

It should be noted that a pad is not provided directly at one end of the through hole to connect the through hole and the pad directly, but a connection pattern or the like is provided between the through hole and the pad, and a through hole is formed by this connection pattern. If the pad is connected, the above-mentioned problem does not occur, but in order to meet the recent demand for downsizing and high density of printed wiring boards and fine mounting of electronic components, the connection pattern is omitted. The surface of the substrate must be effectively utilized, and it has been necessary to extend the pad at one end of the through hole, in other words, to form the through hole in the pad.

Next, when one end of the through hole exposed on the surface of the substrate is covered with the solder resist, this solder resist is applied to the surface of the substrate. It will not be covered. That is, the solder resist coating is in a state of being peeled off from the surface of the substrate and floating. For this reason, the solder resist in a portion that is not adhered to anything may fall off due to direct or indirect stress from the outside, and the fragments may become dust.

Further, for example, when both ends of the through-hole are covered with solder resist, or when one end of the blind via hole exposed on the surface of the substrate is covered with solder resist, the solder resist In some cases, the solder resist ruptured due to the expansion of air in the through holes due to the heat treatment during drying and curing, and dust was generated. When the dust of the solder resist is generated in this way, the environment of the manufacturing process of the printed wiring board is significantly polluted, or the dust adheres to the surface of the printed wiring board to cause a connection failure when mounting an electronic component. It may cause trouble. For this reason, it is necessary to reliably prevent the generation of dust in the solder resist.

It should be noted that if the surface of the substrate is coated with a solder resist while avoiding the through holes, the above-mentioned problems will not occur. Many small-diameter through holes are densely arranged on the surface, and it is very difficult to avoid this and coat the solder resist on the desired part of the printed wiring board. It was obliged to coat the surface with a solder resist.

The present invention has been made in order to solve such a problem, and an object thereof is to provide an electronic component even if it has a through hole in the electronic component mounting effective area of the pad. Can be implemented reliably,
In addition, a method of manufacturing a printed wiring board capable of reliably preventing generation of dust due to breakage of a solder resist coating even if a structure in which one end of a through hole having a cavity inside is covered / sealed with a solder resist is provided. Is to provide.

[0010]

Means for solving the above problems will be described with reference to the reference numerals used in the drawings. "A printed wiring board 100 having through holes 20 will be manufactured. (1) Step of filling the through hole 20 with the photo-curable resin 50 so as to bulge from the surface of the substrate 10; (2) Both sides of the substrate 10 are sandwiched by a translucent release film 64. A step of irradiating the photo-curable resin 50 with light to cure the photo-curable resin; (3) the photo-curable resin 50 flowing out to the surface of the substrate 10.
And a step of polishing / removing. Also,
Preferably, a through hole is formed in the target printed wiring board, the inner wall of the through hole is plated for conduction, and then the steps (1) to (3) are performed, and then, The circuit is formed on the surface of the target printed wiring board.

[0011]

As described above, according to the method for manufacturing a printed wiring board of the present invention, after the photocurable resin 50 is filled in the through holes 20 so as to bulge from the surface of the substrate 10 and cured,
Since the bulging portion is polished, it has the following effects. (1) When the electronic component is mounted on the pad 30 having the through hole in the electronic component mounting effective area, the photocurable resin 50 can be reliably filled over the entire depth of the through hole 20. Therefore, it is possible to more reliably prevent the solder from flowing into the through hole 20. Therefore, it is possible to mount in a state where the amount of solder is properly secured, and the physical and electrical connection reliability is also excellent.

(2) Even when a desired portion of the surface of the substrate 10 is covered with the solder resist 40, the through hole 20 filled with the photocurable resin 50 is formed in another solder resist 40.
The solder resist 40 can be continuously coated in the same manner as the surface of the substrate 10 to be coated with the solder resist 4
Therefore, it is possible to satisfactorily cover the surface with no unevenness. As a result, it is possible to reduce the number of cleaning steps because the processing solution is well drained in various steps and is not brought into the next step. The presence of the through hole 20 is hardly noticeable on the outer surface of the substrate 10, and the image recognition of the pad 30 during inspection and automatic mounting of electronic components is facilitated and the appearance is excellent.

(3) By using the backing plate 64 when the photo-curable resin 50 is printed and filled, the photo-curable resin 50 can be filled in the swelling state from the through-hole 20, so that the through-hole 20 can be filled. The air inside can be removed reliably, the rupture of the solder resist 40 and the photocurable resin 50 due to the expansion of the air can be prevented more reliably, and the generation of dust can be prevented. (4) The surface of the substrate 10, that is, the smoothness of the pad 30 and the through hole 20 existing therein can be sufficiently ensured, and when the electronic component is mounted on the pad 30, a photocurable resin is used. 50 does not interfere with the electronic component, and when printing the solder paste on the pad 30 for mounting the electronic component, the adhesion between the mask for printing the solder paste and the substrate 10. Since the property is improved, it is possible to prevent the variation in the printing of the cream solder, and to suppress the bleeding of the cream solder on the back surface of the printing mask (metal mask), which can prolong the plate cleaning cycle. (5) When the entire printed wiring board 100 is subjected to acid cleaning as a pretreatment for various steps, particularly in the small-sized through hole 20, the acid cleaning liquid remains in the through hole 20 and the conductor inside the substrate 10 is removed. Although the circuit may be corroded and broken, by filling the through hole 20 with the photocurable resin 50, the acid cleaning liquid does not remain in the through hole 20, and the acid of the conductor circuit inside the substrate 10 is prevented. Corrosion disconnection due to residual cleaning liquid can be reliably prevented. (6) Through-holes (including simple through-holes without through-hole plating) can be completely sealed if necessary, which significantly increases the area where display processing such as mark printing can be performed. It is also possible to easily form a unique identification display.

On the other hand, the printed wiring board 100 manufactured according to the present invention has a "through hole 20 of which at least one end is exposed on the surface of the substrate 10 and an electronic component mounting extending at the one end of the through hole 20". In a printed wiring board 100 having a pad 30 or a solder resist 40 covering the one end of the through hole 20,
The through hole 20 is filled with the photocurable resin 50. "

That is, the printed wiring board 1 as described above is used.
Reference numeral 00 denotes a pad 30 for mounting an electronic component formed on the surface of the substrate 10, having a through hole 20 in the component mounting effective area, or a solder coated on a desired portion of the surface of the substrate 10. The resist 40 may be any one having one of the through holes 20 in the covered area. In other words, the through hole 20 filled with the photo-curable resin 50 may be at least one of the through hole 20 having the pad 30 extended at one end or the through hole 20 having one end covered with the solder resist 40. Of. That is, in the printed wiring board 100 in which the inflow of solder into the through hole 20 is a problem when mounting the electronic component, the through hole 20 having the pad 30 extended at one end (the component mounting of the pad 30 is effective). A through hole 20) existing in the area is filled with a photo-curable resin 50. Alternatively, in the printed wiring board 100 in which dust generation due to breakage of the solder resist 40 is a problem, one end of the solder resist 40
The photo-curable resin 50 in the through hole 20 covered by
It is filled with.

Therefore, in the case of the through hole 20 in which the pad 30 is extended (the through hole 20 existing in the component mounting effective area of the pad 30), when the electronic component is mounted on the pad 30, the conventional structure is used. The solder is through hole 2
It does not flow into 0, and the desired amount of solder is surely secured. Therefore, the electronic component is reliably mounted on the pad 30, and the electrical reliability between the electronic component and the pad 30 can be sufficiently ensured.

On the other hand, in the case of the through hole 20 existing in the area covered by the solder resist 40,
Solder resist 40 in the through hole 20 part
However, without leaving bubbles inside, the through hole 20
It will be adhered to the photo-curable resin 50 filled in, and will be firmly adhered to this part as well as other parts. Therefore, it is possible to reliably prevent the solder resist in the portion of the through hole 20 from falling off.

The photo-curable resin 50 may be cured by being irradiated with light after being filled in the through hole 20.
The through hole 20 can be easily and surely filled without damaging the substrate 10 or the through hole 20 itself, and since the photo-curable resin 50 is cured by light, it is uniform over the entire depth of the through hole 20. It will be hardened and the quality will be sufficiently secured.

[0019]

Embodiments of the manufacturing method of the present invention will now be described in detail with reference to the drawings. First, a pilot hole 21 to be a through hole 20 is formed in a substrate 10 made of a so-called copper clad laminate having a copper foil (not shown) on the surface layer (a) and (b), and the substrate 10 is subjected to panel plating, A plating layer 31 and a through hole 20 electrically connected to the plating layer 31 are formed on the surface of the substrate 10 (c). Here, the base material 10 is
It may be a multi-layer substrate having one or more conductor circuit layers inside, and in this case, the through hole 20 is not necessarily a through hole and may be a blind via hole. Further, it may be a simple glass / epoxy base material having no copper foil on the surface layer. When using a simple glass / epoxy base material, a treatment for improving the adhesion to the panel plating or electroless plating on the surface (for example, physically polishing the surface to roughen it, or an adhesive for electroless plating). It is necessary to apply).

Next, a desired through hole 20 is filled with a photocurable resin 50 by a screen printing method so as to bulge from the surface of the substrate 10, and light is irradiated through a translucent release film 64. And cured (d). Here, the pad 30 is not extended to one end (a through hole other than the through hole 20 existing in the component mounting effective area of the pad 30), and one end is not necessarily covered with the solder resist 40. It is not necessary to fill the curable resin 50. According to the screen printing, a mask 60 for screen printing is formed on the surface of the substrate 10.
The photo-curable resin 50 is filled in the through holes 20 with the squeegee 61. When the photo-curable resin 50 is filled in the through-holes, the back surface of the substrate 10 is filled with the photo-curable resin 50. Through hole 20
A backing plate 62 having an opening 63 (larger than the through-hole 20 in diameter by 1.5 mm or more) corresponding to a portion (in this embodiment, has a stack of two 1.6 mm thick glass epoxy substrates). The photocurable resin 50 may be filled in such a manner that the photocurable resin 50 swells from the back surface of the substrate 10 so that the smoothness of the front and back surfaces of the substrate can be obtained.

Further, particularly when the blind via hole is filled with the photo-curable resin 50, the photo-curable resin 50 is used.
If the substrate 10 is degassed in a vacuum after the application, the air does not remain in the blind via holes and the photocurable resin 50 can be filled well. Further, in a so-called exposure step of irradiating light such as ultraviolet rays to cure the photocurable resin 50, the photocurable resin 50 printed and applied as needed is temporarily dried by touch (a thin skin is formed on the surface layer). Then, both surfaces of the substrate 10 are sandwiched by a translucent release film 64 in which a release layer (manufactured by Kimoto: Kimotect # 2X-TA8X) is adhered to a polyester base film (175 μm thick) to form the substrate 10. The transparent release film 64 and the transparent release film 64 are exposed in a vacuum state (d-4 in FIG. 3). As a result, residual air bubbles inside the through hole 20 are discharged, and the exposure device is not contaminated by the uncured photocurable resin 50.
The surface of the substrate 10 and the exposed surface of the photocurable resin 50 are substantially parallel to each other, which is very convenient because it is not necessary to polish and remove a large amount of the photocurable resin 50 in the subsequent polishing step.

Further, when sandwiching the substrate 10 on which the photo-curable resin 50 is applied by printing with the translucent release film 64, first, the backing plate 62 surface side of the substrate 10 is used as the translucent release film 64. By laminating (d-2 in FIG. 3), the photocurable resin 50 is formed on the surface that was the squeegee surface side during printing.
Of the squeegee surface at the time of printing, and the translucent release film 64 is laminated on the surface which was the squeegee surface side at the time of printing (FIG. 3).
D-3) is preferable. This can prevent bubbles from entering the through holes 20 when the translucent release film 64 is laminated. Further, when an acrylic resin such as epoxy acrylate is used as the main component as the photo-curable resin 50, the photo-curable resin 50 is uniformly cured over the entire depth of the through hole 20 because of its excellent light transmittance. It is convenient to do so.

Next, the translucent release film 64 is released,
A portion of the cured photocurable resin 50 that bulges from the substrate 10 is polished and removed by using a surface polishing machine such as a buffing machine, a belt sander or an oscillation sander to ensure the smoothness of the surface of the substrate 10 ( e). Next, substrate 1
An etching resist 32 is formed on the surface of the plated layer 31 of 0 (f), unnecessary portions of the plated layer 31 are removed by etching (g), and a conductor circuit having a desired pattern is formed on the surface of the substrate 10 (h). . Here, on the surface of the substrate 10, a pad 30 for mounting an electronic component, which is extended to one end of a desired through hole 20, is formed.

Finally, a desired portion of the surface of the substrate 10 is covered with a solder resist 40 to obtain a printed wiring board 100 (i). Here, the through hole 20 covered with the solder resist 40 is filled with a photocurable resin 50. The technique described above is not limited to this embodiment, and the photo-curable resin 50 is filled even in the through hole 20d in which the pad 30 is not extended or the solder resist 40 is not covered. May be. In this case, the substrate 1 due to the acid or the like remaining in the through holes 20 as described above due to the chemical treatment in the manufacturing process.
It is possible to reliably prevent corrosion breakage of the conductor circuit inside 0, corrosion of the through hole 20 itself, and the like.

Needless to say, it can be applied to a printed wiring board for forming a surface layer circuit by electroless plating such as an additive method or a built-up method. Further, in the present embodiment, only the through-holes subjected to the conductive plating (through-hole plating) have been described, but the conductive plating (through-hole) formed for the purpose of cutting the plating lead wire of the inner layer or the outer layer of the substrate. The same can be applied to so-called through holes that have not been subjected to hole plating).

Next, the printed wiring board 100 manufactured by the manufacturing method of the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of a printed wiring board 100 manufactured by the manufacturing method of the present invention. In this printed wiring board 100, the substrate 10 is a multilayer substrate having a conductor circuit inside, and the through-hole 2
0a, the blind via hole 20b, the interstitial via hole 20c, and the like, electrically connect the conductor circuit formed on the surface of the substrate 10 and the conductor circuit inside the substrate 10 by various through holes 20. There is. The through hole 20 having one end exposed on the surface of the substrate 10 has a pad 30 for mounting an electronic component extended on one end thereof, or a solder resist 40 having one end covered on a desired portion of the surface of the substrate 10. Is covered by.

The through holes 20 are filled with a photocurable resin 50. The printed wiring board 100 manufactured by the manufacturing method of the present invention is
Not only the through hole 20 exposed on the surface of the substrate 10 is filled with the photo-curable resin 50, but at least the through hole 20 in which the pad 30 is extended or the through hole 20 in which the solder resist 40 is covered is photo-cured. Any resin may be used as long as the resin 50 is filled therein.

[0028]

As described in detail above, according to the method for manufacturing a printed wiring board of the present invention, the through hole or the solder resist which does not have a possibility of inflow of solder when mounting an electronic component on a pad is dried. Thus, the printed wiring board has a through hole in which air inside the through hole expands during curing and the solder resist is ruptured, so that dust is not generated. Therefore, according to each of the present inventions, it is possible to provide a printed wiring board by which electronic components can be surely mounted on a pad and dust of a solder resist can be reliably prevented by a simple method. it can.

[Brief description of drawings]

FIG. 1 is a partial sectional front view showing an embodiment of a printed wiring board obtained according to the present invention.

FIG. 2 is a process drawing showing the method for manufacturing a printed wiring board according to the present invention.

FIG. 3 is a process drawing showing the method for manufacturing a printed wiring board according to the present invention.

FIG. 4 is a partial sectional front view showing a conventional printed wiring board.

[Explanation of symbols]

10-Substrate 20-Through hole 20a-Through through-hole 20b-Blind via hole 20c-Interstitial via hole 20d-Through hole 21-Through hole lower hole 30-Pad 31-・ Plating layer 32 ・ ・ Etching resist 40 ・ ・ Solder resist 50 ・ ・ Photo-curing resin 60 ・ ・ Mask 61 ・ ・ Squeegee 62 ・ ・ Attach plate 63 ・ ・ Aperture 64 ・ ・ Transparent release film 100 ・ ・Printed wiring board

Claims (1)

[Claims] 1. In manufacturing a printed wiring board having a through hole, (1) a step of filling the through hole with a photocurable resin so as to swell from the surface of the substrate; (2) both surfaces of the substrate. Sandwiching a light-transmitting release film to irradiate the photo-curable resin with light to cure it; (3) polishing the photo-curable resin flowing out to the surface of the substrate;
A step of removing; a method of manufacturing a printed wiring board, comprising: