JPH02267993A - Manufacture of printed wiring board - Google Patents

Abstract

PURPOSE:To perform highly reliable plating by providing a hole with a stepped part forming a large diameter and a small one in a substrate material and after that, providing a through-hole with a stepped part. CONSTITUTION:A hole is made on the halfway of depth of a substrate 2 consisting of a laminated plate where copper is placed on both faces of its plate with a large-diameter drill and after that, the hole is made from the rear side of the plate with a small-diameter drill. Then the hole equipped with a stepped part is made. Then, if a circuit is formed by performing plating 3 at a thorough-hole, a through-hole substrate 2 equipped with the stepped part is manufactured. In this way, as a large-diameter hole 6 is made on the halfway and a small-diameter hole is made at a remainder of the board having a thin material, it is easy to make the small-diameter hole. Since the small- diameter hole has a small aspect ratio and the hole is opened, highly reliable plating is thus performed.

Description

DETAILED DESCRIPTION OF THE INVENTION An object of the present invention is to reduce the diameter of a hole that penetrates from the middle of a through hole into which a component is inserted to the back surface, thereby increasing the wiring and mounting density on the back surface.

Conventionally, mounting methods have generally shifted to some extent from insertion mounting to surface mounting in order to increase packaging density. Parts may be included. As shown in Figure 1, if the component holes are of the same diameter and pass through, and the feet of the component are exposed on the back side, surface mount components cannot be mounted on the back side near the hole. It is difficult to increase the density of mounting wiring because it has to avoid the land of the hole.

In addition to this, according to the present invention, the feet of the component do not protrude from the back surface, so surface mount components such as flat packages can be mounted above the hole on the back surface into which the component has been inserted, or near this hole.
It is possible to mount surface mount components and route wiring, increasing the mounting and wiring density to 11.

Next, the manufacturing method of the present invention will be explained with reference to the drawings.
If you drill a hole halfway through a double-sided copper-clad laminate as shown in Figure 2 using a large-diameter drill as shown in Figure 3, then use a small-diameter drill to drill the hole from the back side, it will form a stepped hole as shown in Figure 4. You can make a hole in it. Thereafter, by performing through-hole plating as shown in FIG. 5 and forming a circuit, a stepped through-hole board as shown in FIG. 6 can be manufactured. FIG. 7 shows this board with insert components and surface mount components mounted thereon.

To make a stepped hole, you can first drill a small diameter hole and then use a large diameter drill to drill the hole from the back side, or you can use a drill with a stepped blade to make the hole all at once. In addition, it goes without saying that care must be taken to remove the cutting powder from the drill by physical methods or treatment with chromium sulfuric acid or permanganic acid after drilling.

When the diameter of the through hole is made smaller to increase the density (so-called via hole), if the substrate material is thick, the diameter of the through hole becomes 0.
It is very difficult to drill small diameter holes such as 15 mm or 3.1 mm, and even if you do drill them, the cost is high and the holes are difficult to stop.In addition, through-hole holes with a high aspect ratio like this must be plated stably. is difficult. A via hole with a conductive hole halfway through does not penetrate through the hole, so
It is difficult to remove air bubbles during plating, and the flow of the plating solution is also poor, making it difficult to apply highly reliable plating.

On the other hand, in the present invention, a large diameter hole is drilled halfway and then a small diameter hole is drilled in the remaining extremely thin material, so the small diameter hole is easy to make, and the aspect ratio of the small diameter is small for plating.
Since the holes go through, you can attach highly reliable plating.

If you open the component insertion hole halfway, it will be difficult to remove the gas inside the hole when soldering the component, so not only will you not be able to apply enough solder inside the through hole.
A separate via pole must be provided for continuity to the back side.

According to the present invention, since the hole is penetrating, it can serve as a hole for degassing the solder and for conducting electricity to the back surface.

The pitch of inserted parts, which used to be 2.54 tnm for wiring between pins, can now be mounted and wired at a pitch as small as 1.27 mm, which has a significant effect.

By determining the length of the legs of the inserted component and the depth of the large diameter hole, there is an advantage that the height of the component from the board surface can be set accurately.

This method can be applied not only to double-sided boards, but also to multilayer boards, metal core boards, additive boards, etc.
The scope of its application is thought to be very wide.

[Brief explanation of drawings]

Figure 1: A cross-sectional view of a normal through-hole for inserting components and soldering after inserting a component Figure 2: A cross-sectional view of a double-sided copper-clad laminate Figure 3: A cross-sectional view of a hole drilled halfway with a large-diameter drill Figure 4: From the back side Figure 5 Cross-sectional view of holes drilled with a small diameter drill Figure 6 Cross-sectional view of through-hole plating Figure 7 Cross-sectional view of circuit formed Figure 7 Cross-sectional view of parts mounted Code (1) Surface copper foil (2) Base material (3) Through Hole plating layer (4) Solder (5) Component foot (6) Large diameter hole
(7) Small diameter hole (8) Through hole (9) Circuit (1
0) Surface mount components (11) Flat package Figure 1 Figure 2

Claims (1)

[Claims] Use a large diameter and a small diameter drill or a drill with a stepped blade to drill large and small diameter stepped holes in the board material, then plate the through holes to form the stepped through holes. How to manufacture printed circuit boards with holes