JPS5838626Y2 - Printed board - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a printed circuit board with improved through holes.

FIG. 1 shows the structure of a conventional printed circuit board.

1 is a substrate, and 2 is a conductor printed on the substrate 1.

3 is an electroless plating layer formed on the conductor 2 and the through hole 6 formed in the substrate 1, and 4 is an electrolytic plating layer formed on the electroless plating layer 3.

The conductors 2 on both sides of the substrate 10 are electrically connected to each other by both plating layers 3 and 4.

Since sufficient strength and electrical connection cannot be ensured with the electroless plating layer 3 alone, the electrolytic plating layer 4 is formed on the electroless plating layer 3 to form a double layer structure.

A resist layer 5 is further formed on the component mounting surface (the upper surface in the figure) of the electrolytic plating layer 40 to prevent adhesion of dirt.

A hole 5a is formed in the resist layer 5 in correspondence with the through hole 6, and the diameter of the hole 5a is set to ensure secure adhesion with solder when a pin I of a component (not shown) is inserted. Therefore, the diameter of the through hole 6 is larger than that of the through hole 6.

In such a conventional printed circuit board, the diameter of the hole 5a of the resist layer 5 is larger than the diameter of the through hole 6, so when the pin 7 of the component is inserted into the through hole 6, the plated layer 3 , 4, resulting in insufficient electrical connection.

Also, when attaching the solder from the solder attachment surface (lower surface in the figure) of the board 1 and gluing the pin I into the through hole 6, the flux passes through the through hole 6 to the component mounting surface side. This caused flow and poor contact with the moving parts of the volume, IC sockets, etc.

Therefore, it was necessary to perform steam cleaning, etc.

An object of the present invention is to eliminate the above-mentioned drawbacks and provide a printed circuit board with no damage to through holes and no leakage of flux.

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

In these figures, parts corresponding to those in FIG. 1 are designated by the same reference numerals, and their explanations will be omitted.

The difference from FIG. 1 is that holes corresponding to the through holes 6 are not formed in the resist layer 5 (see FIG. 2).

While forming a hole 5a in the resist layer 5 with a diameter corresponding to the diameter of the pin γ of the component (smaller than the diameter of the through hole 6),
It will be inserted into the through hole 6 (see Figure 3).

Therefore, the resist layer 5 serves as a continuous protective film, and the possibility that the plating layers 3 and 4 in the through hole 6 will be damaged by the pin 7 is reduced.

The pin 7 of the component is inserted into the through hole 6 by an automatic insertion machine (not shown), but since the position of the through hole 6 on the substrate 1 is accurately numerically controlled by the automatic insertion machine, the resist layer 5 There is no problem in inserting the pin 7 even if the hole 5a is not formed in advance.

Also, when inserting pin 7 by manual operation,
Since the resist layer 5 is usually transparent, the position of the through hole 6 can be visually confirmed.

Furthermore, when attaching the pin 7 in the through hole 6, since only the hole 5a with the diameter corresponding to the pin 7 is used in the resist layer 5, the flannel and slag will leak onto the component side. There is little risk.

This can be further ensured by providing the resist layer 5 with appropriate viscosity.

Note that the resist layer 5 does not necessarily need to be in a state where the through hole 6 is completely closed before the pin 7 is inserted, but may be in a state where the hole is the same as or slightly smaller in diameter than the pin 7.
That is, it may be in a state where a part of the through hole 6 is covered.

As described above, in the present invention, there is less risk of through-holes being damaged by component pins, and leakage of slack during solder attachment can be reduced.

In addition, there is less possibility that the particles will rise excessively to the component mounting surface side than necessary.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a conventional printed circuit board, and FIGS. 2 and 3 are cross-sectional views of a printed circuit board according to the present invention. 1...Substrate, 2...Conductor, 3...
... Electroless plating layer, 4... Electrolytic plating layer.

Claims (1)

[Scope of utility model registration request] A printed circuit board comprising a substrate, a through hole formed in the substrate, a conductor formed on the substrate, and a resist layer covering at least a portion of the through hole.