JPS5814621Y2 - printed wiring board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printed wiring board in which a conductive pattern is printed on an insulating substrate, and more particularly to an improvement in a printed wiring board in which the entire surface is soldered almost simultaneously using a solder dip method or the like.

1 and 2 show an example of a conventional printed wiring board 1. FIG.

1 and 2, a printed wiring board 1 has a through hole (so-called through hole) 3 in an insulating substrate 2 made of Bakelite, glass epoxy, etc., through which terminals of electronic components such as resistors and transistors are inserted. At the same time, a conductive thin film 4 is deposited to form a predetermined wiring pattern for electrically connecting the terminals inserted through the through holes 3.

This thin conductive film 4 is formed on the soldered surface of the printed wiring board 1 (the surface of the paper in FIG. 1), and is used as a land for electrically connecting the terminal and the thin conductive film 4 by adhering solder. It has part 5.

Furthermore, in printed wiring boards that are soldered using a solder dip method, etc., in order to prevent solder from adhering to parts other than the land portions 5, a resist film 6 made of a material with poor wettability and adhesion with molten solder is required. is formed by adhesion.

That is, the resist film 6 is formed on the soldered surface of the printed wiring board 1, covering almost the entire surface of the printed wiring board 1 except for the land portions 5.

Further, on the surface of this resist film 6, an ink film 8 is formed to form a symbol mark 7 for displaying the relationship between terminals of an electronic component such as a resistor, a part number, etc.

Among these symbol marks 7, for example, in order to collectively represent the three terminals of a transistor, such as the base, emitter, and collector, a symbol mark 7 is designed to surround three land portions 5' that are electrically connected to these three terminals. symbol mark 7
' is provided.

A mark 7' surrounding such a land 5' is
In the case of electronic components such as transistors and ICs that have many terminals, clusters of terminals can be clearly identified even after soldering, making it easy to check for poor solder connections and replace parts during after-sales service. This is highly necessary because it is easy to do.

However, since the peripheral part of the land 5' to be soldered has a two-layer structure of the resist film 6 and the ink film 8, the thickness t of the end part becomes thicker and other marks are formed. It is difficult for solder to adhere smoothly, and the thicker the thickness t, the more air bubbles and the like are more likely to be included.

For this reason, there are disadvantages in that electrical contact failure during soldering increases and the strength of soldering tends to weaken.

Furthermore, due to the problem of relative placement accuracy between the resist film 6 and the ink film 8, if the positions are shifted by a distance d as shown in FIG. 3, the area of the window formed in the land portion 5' Since the area to which the solder adheres becomes narrower, problems such as a decrease in strength and poor electrical contact are likely to occur in soldering in this case as well.

The present invention was developed in order to eliminate these conventional drawbacks, and is designed to prevent the soldering strength and contact properties from decreasing when an ink film mark surrounding the land is formed. The purpose is to provide printed wiring boards.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

FIG. 4 is a sectional view showing the main parts of the printed wiring board 11 of the embodiment, and FIG. 5 is a partially cutaway plan view of the embodiment.

4 and 5, an insulating substrate 12 made of an insulating material such as Bakelite or epoxy resin is provided with through holes 13 for inserting terminals of electronic components, and at least the soldering surface (the fourth A good conductor thin film 14 is deposited on the upper surface (in the figure).

This good conductor thin film 14 is made of copper foil or the like on an insulating substrate 12.
After the soldering is applied to the surface, a predetermined wiring pattern connecting the through holes 13 is formed by etching or the like. It has a land portion 15 for attaching solder to electrically connect the terminal to the good conductor thin film 14.

Further, a resist film 16 is formed to cover the portion other than the land portion 15.

This resist film 16 is made of a material with poor wettability and adhesion with molten solder, and is formed using a solder dip method (also referred to as a solder dip method).

) etc., solder does not adhere to the surface of these resist films 16, but selectively adheres only to the exposed surface of the land portion 15.

Next, the mark 17 for indicating the three terminals of the transistor as described above was conventionally formed by depositing an ink film 18 on the surface of the resist film 16, but in the present invention, the mark 17 for indicating the three terminals of the transistor is 16 and land portion 15
The mark 17 is formed by depositing an ink film 18 over the periphery of the mark 17 .

That is, the dimension of the window for exposing the land portion of the ink film 18, for example, the diameter a, is set to be shorter than the diameter of the window portion of the resist film 16, and around the land portion 15, the ink film 18 is replaced with the resist film 16.

At this time, the area of the exposed portion of the land portion 15 is
This is the area of the window of the ink film 18 for displaying 7, and by setting this with high precision, the area for soldering can also be set with high precision.

Similar to the resist film 16, the ink film 18 has poor wettability or adhesion with solder, and solder does not adhere during processing when soldering is performed using a solder dip method or the like.

This ink film 18 is also a resist film having a different color from the actual resist film 16.

As is clear from the above description, near the periphery of the land portion 15, the periphery of the window of the ink film 18 is arranged inside the periphery of the window of the resist film 16, that is, on the side of the through hole 13, and these peripheries Since the ink film 18 is arranged in place of the resist film 16 in the area between the two, the window part of the land part 15 to which the solder is attached is covered with the ink film 1.
8 windows.

Therefore, the ink film 18 is formed around the window of the land portion 15.
The thickness is t for one layer, and the solder penetrates smoothly using the solder dipping method, etc., and there are no air bubbles, and the solder adheres reliably, so there is no electrical contact failure, and the soldering is strong. becomes large.

Furthermore, since the dimensions and shape of the window of the land portion 15 are determined by the dimensions and shape of the symbol mark 17 formed by the ink film 18, the decrease in the window area due to printing misalignment, etc., which is conventional, is prevented. This eliminates poor contact and strength loss when soldering.

It should be noted that the present invention is not limited to the above-mentioned embodiments; for example, a symbol mark in the shape surrounding a land portion can be provided not only on transistors but also on ICs, etc., as necessary. A similar configuration can be applied to the symbol mark.

[Brief Description of the Drawings] Fig. 1 is a plan view showing an example of the soldering surface of a printed wiring board, and Figs. 2 and 3 show conventional examples of different forms near the mark 7' in Fig. 1. FIG. 4 is a sectional view showing a main part of an embodiment of the present invention, and FIG. 5 is a partially cutaway plan view showing a main part of the embodiment. 11...Printed wiring board, 14...
Conductor thin film, 15... Land portion, 16...
・Resist film, 17...Symbol mark, 18
...Ink film.

Claims (1)

[Scope of utility model registration request] Soldering of a printed wiring board involves forming a conductive thin film on the surface according to the wiring pattern and forming a soldering portion on the land portion, and the soldering layer is formed on the surface so as to cover the outside of this land portion. and an ink film which becomes a symbol mark surrounding the land portion and most of which is disposed on the resist film, and the ink film is located inside the periphery of the opening window of the resist film in the land portion. 1. A printed wiring board characterized in that the ink film is arranged around the periphery of the opening window and extends around the exposed portion of the conductive thin film of the land portion.