JPS6010692A - Printed circuit board - 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 wiring boards, particularly when attaching electrical components having lead terminals to printed wiring boards. l! The electrical parts of this printed wiring board are soldered on the opposite side by passing through the through holes of the printed wiring board.A Franks wetting prevention film is provided on the printed wiring board to prevent flux from getting wet in unnecessary areas. The present invention relates to a printed wiring board.

Printed wiring boards are made by etching copper foil pasted onto the surface of a finely layered board to form a circuit pattern according to an electrical circuit, and to which electrical components such as resistors and capacitors can be attached. To attach these electrical components, their lead terminals are soldered to the lands of the circuit pattern.

In this case, soldering has a land on the side where the electrical components are attached to the printed wiring board, and unlike this, there is a circuit pattern formed on the opposite side of the printed wiring board where the electrical components are attached and there is a soldering land. There is.

The latter printed wiring board has a through hole formed therein, and the lead terminal of the electrical component is inserted into this through hole, so that the electrical component can be attached with a band on the opposite side. There is.

By the way, when soldering, first apply flux to the surface of the printed wiring board on the side that has the soldering land, and then form a film of this flux on the soldering land to prevent its oxidation. Soldering is supplied to the land.

In this case, since the flux consists of a reducing agent such as rosin, alcohol, and amine hydrochloride, when this flux is applied to a printed wiring board, it wets not only the lands but also other parts during soldering. If this extends to the through ball, it may rise along the wall of the through hole and the electrical component mounting may flow out to the side.

In particular, if the wall surface of the through-hole is covered with copper foil or if lead terminals of electrical components are inserted into the through-hole, the flux will wet these easily, making it even more likely that flux will leak out as described above. . In this way, if the flux flows out to the side when installing electrical parts, it will wet the electrical parts, and the operation of electrical parts that require precise movement such as switching parts, contacts, potentiometers, variable resistors, IC sockets, etc. May cause defects. In addition, if the flux that flows out spreads further and wets the surrounding area, dust will adhere to it, and if the solvent in the flux evaporates and forms a film, this dust will remain and short circuit the circuit. Sometimes.

Conventionally, before applying flux, a piece of tape is placed over the opening of the through hole on the side where the electrical component is installed, and after applying the flux, the lead terminal of the electrical component is inserted into the through hole while tearing the tape. After automatic soldering of electrical components other than through the through-holes, soldering through the through-holes is performed manually. However, doing so requires a lot of man-hours, and the soldering process makes it difficult to fully automate the process.

As described above, the present invention has been developed to prevent the flux from rising up the through ball during flux application and wetting the side of the electrical component mounting process, and there has been no good method for automating the entire process of soldering electrical components. In order to improve this point, we installed a flux wetting prevention film on the parts that would be problematic if they got wet with flux.This makes it possible to solder without spreading flux to unnecessary parts, thereby increasing the reliability of the operation of electrical parts. This enables fully automated soldering of electrical components without sacrificing performance.

To this end, the printed wiring board of the present invention has a circuit pattern on one side of the board and has a through hole passing through the board connected to this circuit pattern, and leads electrical components from the other side of the board. In the wiring board on which the terminal is inserted through the through-hole and soldered to the circuit pattern, repel flux on the surface of the board on which the electrical component is attached and at least on the surface of the board on which the electrical component is attached, even if it is not inside the through-hole. It is characterized by providing a flux wetting prevention film containing a surfactant. In particular, the above object can be better achieved by using a silicone-based or fluorine-based surfactant.

The flux wetting prevention film in the present invention consists of a coating of a composition containing a surfactant, and this composition includes:
Examples of silicone-based and fluorinated materials include silicone oil, silicone polymer, fluorinated silicone oil, fluorinated silicone resin, and fluorinated hydrocarbon-containing polymer.

Silicon-based Po1on L, Po1on T, KF96. KS-
700, MS-701, MS-707, MS-705F
, MS-706, MS-709, KS-709S,
KS-711゜KSX-712, MS-62F, KS
-62M, KS-64,5ilicolube G-
430, 5ilicolube G-540+ 5il
icolube G-541 or higher Shin-Etsu Chemical Co., Ltd. Sl+-200, S■-210,5l (-1109,5
H-3109,5H-3107,5t(-8011,F
S-1265,5yli-off23. DCpan G
laze 620 or more Toray Silicon ■ Fluorine-based Gui 71J -MS-443, MS-543, MS-7
43, MS-043, ME-413, ME-810 or higher Daikin Industries Florado FC-93, FC-95
, FC-98, FC-129, FC-134.

FC-430, FC-431, FC-721 and above Sumitomo 3
M side association Sumiflunon pp-8], FP-81R,
pp~82. FP-84C, FP-8dR, FP-8
6 or more Sumitomo Chemical (Tarusha Surflon SI?-100,5
R-100X or above, these surfactant compositions manufactured by Seibi Kagaku ■ have a surface tension of, for example, 6 to 20 dyn.
/ cm (based on the Defou X-I method described later).

Other surfactants having such surface tension or compositions of mixtures of the above-mentioned surfactants and other surfactants can also be used. These surfactants are mixtures of polymers, but mixtures of the surfactants of these compositions and/or other surfactants in a solvent may also be used. Diluted versions of the compositions may also be used. As a solvent for this purpose, a solvent that dissolves or disperses the surface active agent and imparts coating properties is used. This solvent is preferable because it evaporates after coating and eliminates the stickiness of the film left behind. As for other properties of the solvent, it is preferable that the above composition be able to wet the surface of the printed wiring board well when it is applied. Such things include: 1. Halogen-containing hydrocarbons such as Ll-lichloroethane are preferred.

The concentration of the surfactant in the surfactant composition is preferably 0.1 to 5% by weight for silicone-based surfactants and 0.01 to 2% by weight for fluorine-based surfactants.

In addition to the above-mentioned surfactant and solvent, a composition containing a surfactant mentioned above may contain a resin, a lubricant that becomes slicker after film formation, and other additives.

Among these, those containing resin are also useful in reducing the stickiness of low-molecular surfactants.

The composition used in the present invention is applied to the side of the printed wiring board where electrical components are attached. This application method is as follows:
In addition to spraying and brushing, there are methods in which the coating material is jetted and the printed wiring board is brought into contact with it, methods in which the coating material adhering to the roll is scraped off with a doctor knife and applied to the wiring board, and the coating solution is foamed. There is a method in which a printed wiring board is brought into contact with the bubbles. This applied material is dried by appropriate means. This forms a film. This film is applied to electrical parts of printed wiring boards in advance.
Form on the side. In this case, a coating film of the composition of the present invention may be formed before the through balls are formed on the printed wiring board, and then the through holes may be formed. A coating film formed from the above-mentioned composition of the invention may also be used. In the latter case, the flux wetting prevention film is also formed in the through hole, which is more preferable. The dry coating film of the flux wetting prevention film is preferably in the range of several mg/% to 5 g/%.

To solder electrical components to a printed wiring board on which a flux wetting prevention film has been formed as described above, transport the printed wiring board with the side to be soldered facing down (1+J) and solder the printed wiring board. Apply flux to the exposed side and insert the lead terminal of the electrical component, or insert the lead terminal of the electrical component into the through ball from above and then apply flux.At this time, apply flux to the printed wiring board. Since the electrical parts are mounted on the side and the off-lux wetting prevention film is formed, the flux is repelled by this and does not flow out to the side where the wetting prevention film is located.

Particularly when the flux prevention film is formed on the through-pole, the flux does not rise up the through-hole, so that the above-mentioned electrical component mounting can more reliably prevent the flux from flowing out to the side. In this way, even if the wall of the through hole is made of copper foil, or even if the lead terminal of an electrical component is inserted into the through hole, the flux will be repelled by the through hole wall, so the flux will flow through the through hole. It doesn't rise. In addition, the soldering side of the printed wiring board other than the land may be a marking ink layer, a solder resist layer, or the fabric of the printed wiring board.
The surface to be coated with the flux wetting prevention film mentioned above may be any surface such as a marking ink layer, other coating layer, fabric of a printed wiring board, etc.

The print I/wiring board coated with flux as described above is brought into contact with, for example, jet solder in a conventional manner, and the solder spots are soldered. At this time, the flux coating film becomes liquid or gas due to the heat of the molten solder and tries to ascend the through hole, but if the through pole has a flux wetting prevention film, the liquid is repelled by this. The problem is that there is no flux wetting prevention film on the through pole, and even if the flux flows out to the side where the electrical parts are installed, if there is a flux wetting prevention film here, the liquid will not easily wet the flux wetting prevention film. However, it does not try to diffuse and is forced back into the through hole.

Next, a third embodiment of the present invention will be described based on FIGS. 1 and 2.
This will be explained with reference to the figures.

Example 1 A copper-clad laminate 1 was printed with Sis I- for etching, dried, etched to form a pattern 2 made of copper foil, washed with water and dried, and then etched with oxides, etc. of a circuit pattern 2-t. Surface treatment to remove solder resist 3
After applying and hardening, marking ink 4 for clearly indicating the position of the circuit, etc. is applied and hardened. At this time, marking ink is applied to the laminate 1 on the opposite side and hardened. Thereafter, the outer shape is determined by pressing, and through balls 5.5 are formed at predetermined positions. Here, perform the surface treatment in the same manner as above to prevent oxidation of circuit pattern 2! Apply preflux 6 for L and dry. Next, 1-96 (silicone oil 100% by weight) illustrated in -F was added to 1. Ll
) Spray onto the surface of the (5 layers) and through-hole walls to a concentration of 5% by weight with 80 to 10
The flux wetting prevention film 7 is formed by heating and drying at 0° C. for 11 to 3 minutes. The surface tension of this KF-96 was determined by the Dunouy method ((■-■Using a Dunouy surface tension meter manufactured by Futajima Manufacturing Co., Ltd., the measurement temperature was 20℃, and the standard solution was distilled water at 20℃ (72,7
20 dy when measured with 5 dyn 7 cm)
n/cm. In this way, the pudding 1 to the wiring board of this example are produced.

Transfer this printed wiring board to the automatic soldering machine with its circuit pattern side facing down, and apply electrical component glue - F l'1.
The jif element 8 is inserted into the through hole of this wiring board.

The flux film 9 is then applied by bringing a flux wiring board into contact with this circuit pattern side to form a flux film 9.

At this time, no flux was seen rising up from the through-hole, and no flux was observed flowing out from there. Next, solder the molten G:1 solder by contacting the solder jet solder above with the circuit pattern, and solder the solder inlet part 10.
form. At this time, most of the flux skin melted and became liquid or gaseous, but no flow of this liquid liquid from the through holes 5.I was observed. This is clear from the fact that no flux film is seen around the openings of the through balls 5, 5, . . . with a diameter of 1 +*m, as shown in FIG. For comparison, the above KF-
In the case where 96 was not applied but treated in the same manner as above, flux was observed to flow out from the through hole. As shown in Fig. 3, this is a through hole 5,5.
The flux film 9 is seen around the periphery with a spread of about 2 to 5 mm, and these adjacent ones are interconnected and traces of flux flow are seen, so it is clear that each Pt has τ0.Example 2 The same process as in Example 1 was carried out except that the flux wetting prevention film was not formed in the through holes 5, 5, . . . . As a result, although some flux was observed to have flowed out, the flowed flux film 8 as shown in Figure 3 was not observed.

Example 3 The stock solution of Daifree 743 exemplified above was applied in the same manner as in Example 1, and soldering was performed in the same manner as in Example 1. As in Example 1, no leaked flux film was observed as shown in Figure 2. Ta.

Although the above was an example of a general printed wiring board, the Fura Nox wet prevention pattern 1 of the present invention can also be formed on other industrial printed wiring boards that are processed using conventional processing steps. Similar effects can be obtained.

As explained above, according to the present invention, since the flux wetting prevention film is provided on the printed wiring board,
When applying flux at step 1, even if there is a through hole in the printed wiring board and an electrical component glue terminal is inserted through it, if a film to prevent flux from getting wet is formed in this through hole, the flux will be applied to the through hole. In addition, there is no flux wetting prevention film on the through ball, and when installing electrical components, if there is a flux wetting prevention film on the surface of the wiring board in Example 1, the flux will not spread on this surface. The same holds true even when the applied flux is heated by contact with molten solder. In this way, the flux will not flow out onto the surface where the electrical parts are taken, causing malfunction of the electrical parts.
Inconveniences such as short circuits caused by dust can be avoided, and the conventional method of using tape, which is time-consuming, can be avoided, reducing the number of man-hours and improving work efficiency.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional perspective view of a part of a printed wiring board according to an embodiment of the present invention, and FIG. 2 is a cross-sectional perspective view after the board is removed.
FIG. 3 is a diagram corresponding to FIG. 2 using the conventional printer 1 to wiring board. In the figure, 1 indicates a laminate as a substrate, 2 indicates a circuit pattern, and 5
．． 5... is a through hole, 7 is a flux wetting prevention film,
8 is a lead terminal. June 30, 1980 Patent applicant Ginya Ishii Figure 1 Figure 2 Figure 3

Claims (2)

[Claims] (1) The board has a circuit pattern on one side and a through hole that passes through the board to be connected to the circuit pattern, and the lead terminal of the electrical component is inserted into the through hole from the other side of the board. - In a wiring board to be soldered to a circuit pattern, the surface of the board on which the electrical components are attached and at least the surface of the through-hole on the side of the board where the electrical components are attached contain a surfactant that impairs flux wetting. A printed wiring board characterized by being provided with a Franks wet prevention film. (2) The printed wiring board according to claim 1, wherein the surfactant is silicon-based and/or fluorine-based.