JPS582063Y2 - High density wiring board - Google Patents

Description

[Detailed Description of the Invention] The present invention aims to improve the wiring efficiency of wiring boards such as printed wiring boards and ceramic wiring boards.

Figure 1 shows the through hole in a conventional printed board.
...and through-hole land 11 on both upper and lower surfaces...
It is a cross-sectional view showing the wiring state between .

As is clear from the diagram, the through hole is also connected to the wiring pattern 21.
．． 22 also has the same structure on both the upper and lower surfaces, and in order to improve the wiring patterning rate in such printed boards, the pitch of the regular grid must be adjusted to the standard grid size (2, 5
4 mm) or deformed lands where the width of the land located at the intersection of the regular grid is small, so that many patterns can be arranged between the lands.

However, there is a limit to increasing the pattern density by simply reducing the dimensions in this way, and it may be difficult to do so.

The present invention provides a wiring board that can improve wiring efficiency without having such disadvantages.According to the present invention, the land diameter can be reduced to widen the space between lands, and the pattern accommodation rate can be increased. However, the through-hole openings on the side facing the land are also made smaller, whereas the through-hole openings on the other side are made larger.

FIG. 2 is a sectional view showing an embodiment of the wiring board according to the present invention.

In the illustrated example, the through holes 3 are tapered, and while the upper openings of the through holes are approximately the same size as conventional ones, the lower openings are smaller.

Then, adjust the land 31 according to the size of the through-hole opening.
.......

32... is also increased to ensure a sufficient width d of the land.

According to this configuration, since the land configuration on the upper surface side of the insulating plate 4 is the same as the conventional one, the pattern arrangement between the lands 31 and 31 is also the same as the conventional one, and only one land can be arranged as shown by 51.

However, on the lower surface side, the outer diameter of the lands 32... is smaller and the space between both lands 32.32 is wider than on the upper surface side, so two patterns can be accommodated between them like 52.53. .

Therefore, the wiring efficiency is doubled, although only on one side.

Moreover, since the lands 32 are small not only in their outer diameters but also in their inner diameters, the width d of the lands 32 can be kept as sufficient as the normal large-diameter lands 31, and the functionality of the lands will not deteriorate. .

However, although the through-hole opening is smaller on the small-diameter land side, there is no particular problem because the other (upper) side is the normal size.

In other words, if you make the through hole small in diameter over its entire length,
Due to the throwing power of the plating solution, there are problems such as making it difficult to plate the area, but if one side is made as large as before, as in the present invention, the plating solution can easily penetrate, so it is difficult to plate the area. There is no risk that hole plating will be lower than before.

On one wiring board, there is no need to standardize all large-diameter lands on one side and small-diameter lands on the other. It goes without saying that through-holes with upside-down sizes can be used together.

When inserting a component lead into a through hole, 3...
It is easier to insert component leads when the opening on the top surface, which is the component mounting side, is larger, as shown in the figure.

On the other hand, there is a concern about solder rising during dip soldering, but soldering can be done even if the through-hole opening on the surface side is small.
Since the solder pressure is greatest at the lower end of the through hole, solder buoyancy is relatively easy.

If the opening on the component mounting side is small, as in 3', it is difficult to insert the component lead, but the solder is sure to swell.

In any case, component leads for high-density wiring are usually relatively thin, so there is no problem.

In the unlikely event that there is a problem with inserting component leads, it is effective to use the through-hole shape of this invention exclusively for via holes. There is also a dedicated board, so
It is ideal for such substrates.

In the case of Fig. 2, the through hole has a tapered shape and the diameter changes continuously, but it is also possible to create a through hole 3'' in which the diameter changes stepwise as shown in Fig. 3. be.

In this case, if the substrate 4' is a multilayer substrate, it is preferable that the hole diameter changes depending on the position of the inner layer pattern 33.

Furthermore, when holes are made by laser processing, etc., the laser beam incident side tends to become large in diameter due to sag, etc., as shown in Figure 4. , the disadvantages of laser processing quality can be turned into advantages.

As described above, according to the present invention, since one opening of the through hole is smaller than the other opening, the outer diameter of the land facing the smaller opening can be reduced without narrowing the land width. Therefore, more wiring patterns can be accommodated than on the other side, and the wiring efficiency of the entire wiring board is improved.

Therefore, the need for discrete wiring to compensate for the shortage of wiring patterns can be reduced or eliminated.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a through-hole portion in a conventional printed board, FIG. 2 is a cross-sectional view of a through-hole portion in a printed board according to the present invention, and FIG. 3 is a cross-sectional view of a through-hole portion showing another embodiment of the present invention. FIG. 4 is a sectional view of a pre-hole of a via hole when the present invention is applied to a ceramic substrate. In the figure, 3.3/, 3// are through holes, 31.
32 is a land, 4.4' is an insulating substrate, 51, 52.53
is the wiring pattern.

Claims (1)

[Scope of utility model registration request] The diameter of the lower opening of the through hole and its land are of the normal standard size, while the diameter of the other opening of the through hole and its land are the same as the standard size of the through hole opening and the diameter of its land. The wiring pattern on the small-diameter land side is formed to be smaller than the diameter of the through-hole land, and is arranged so that the wiring density on the small-diameter land side is higher than the wiring density on the standard land side. High-density wiring board.