JPH0423388A - Printed 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 Field of the Invention The present invention relates to a printed circuit board that constitutes the circuits of word processors, personal computers, CAD terminals, etc., and particularly relates to a printed circuit board on which terminals for various elements are arranged at high density. It is something.

Conventional technology Although the integration of semiconductor integrated devices is progressing, it is rare that a circuit can be constructed only with semiconductor integrated devices, and individual semiconductor devices (diodes, power transistors, etc.) and passive elements (resistors, capacitors, etc.) placed on the printed circuit board,
Generally, it is wired to form a circuit. Furthermore, a plurality of semiconductor integrated circuits are often combined at the same time. Wiring width inside one semiconductor integrated device (1 to 5 μm
), the wiring on the printed circuit board is 1ran~5+
The wiring is as thick as n+n, and its efficiency is not very good in terms of the degree of integration of the wiring itself. Therefore, double-sided wiring or a laminated wiring structure of three to five layers may be employed.

Figure 5 shows a state in which the terminals of an element (semiconductor elements as active elements and chips as a general term for various passive elements) are mounted on a printed circuit board. This is an example in which connection terminals are arranged in two directions of various elements. Each connection terminal 1 is electrically connected at a predetermined fixed position by solder 4 in correspondence with a printed wiring 3 on a printed circuit board 2. .The unconnected parts 5 of the printed wiring are coated with an insulating film 6 on the surface, so the solder 4 is not applied.In the example shown in this figure, the element is fixed to the printed circuit board with adhesive in advance, and then soldered. Electrically fixed and connected.

Problem to be Solved by the Invention Since the degree of integration on a printed circuit board is not very high compared to the degree of integration inside the device, devices with a large number of bins and a fine pitch between them (semiconductor integrated circuit devices, etc.) There is a high possibility that problems will occur with terminal connections when integrated onto printed circuit boards.As semiconductor devices become more multifunctional and sophisticated, the number of terminals on semiconductor devices tends to gradually increase. For example, DSP
(Digital Signal Processor) and MPU (Micro Processing Unit) A multi-pin package with more than 200 bins is used, and 256-bin PGA (Pin Grid Array) and QFP (Quadro Flat Package) are in practical use. . Furthermore, as the amount of data to be handled increases and processing speed increases, the width of the data bus and command bus has become 32 bits or 64 bits, and connectors and connection terminals with a large number of terminals have become necessary.

On the other hand, since the size of the device is required to be small,
High density is essential for semiconductor device packages and connectors. Currently, on printed circuit boards,
It has been put into practical use with a pinch size of about 0.5 mm, but there is a need for an even smaller pinch size. However, narrowing the wiring pitch on a printed circuit board dramatically increases the risk of short circuits with adjacent wiring. Connection terminal provided on the chip (
Leads also become smaller in accordance with the wiring pitch, so they are easily deformed and connected to adjacent wiring when mounted on a printed circuit board. In order to solve these problems, attempts have been made to leave the terminals (leads) uncut until just before the printed circuit board mounting rate, but this has not been a sufficient solution.

FIG. 6 shows how the terminals of an element are connected on a printed circuit board and short-circuited due to deformation. The connection terminal 1 is easily deformed by mechanical force when the lead (connection terminal) is separated or during subsequent transportation. In particular, when the pitch becomes smaller, the mechanical strength of the connecting terminal 1 decreases, making it easier to deform, and at the same time,
A small amount of deformation will cause contact with the adjacent terminal and cause a failure. In FIG. 6, the connecting terminal 1 is fixed with solder 4 diagonally away from the original connecting part of the printed circuit board 3, so that the solder 4 is electrically connected to the adjacent connecting terminal. .

FIG. 7 shows a situation in which the terminals of the element are connected on the printed circuit board due to too much solder, resulting in a short circuit. After the leads (connecting terminals) are separated, the connecting terminals 1 are coated with solder to facilitate caulking and soldering. When mounting on a printed circuit board, the solder on the leads flows and comes into contact with the adjacent terminals, causing defects.

Means for solving ma It is unavoidable that the connecting terminal becomes thinner as the wiring pitch increases, and it is also unavoidable that the mechanical strength decreases as the connecting terminal becomes thinner. Therefore, it is necessary to take measures to prevent the connection terminal from becoming defective even if the connection terminal is slightly deformed. The same applies even if a defect occurs due to an inappropriate amount of solder.

In the prior art, the printed circuit board is generally flat, and a conductive layer is formed thereon and etched according to a predetermined pattern, so that the conductive layer is at a higher level than other printed circuit board surfaces. If this positional relationship is reversed and a conductive layer is buried in the groove, even if the connection terminal is slightly deformed,
Positioning of these terminals becomes easier, and even if there is excess solder, the possibility of solder bridging between adjacent terminals is reduced, making it possible to provide a structure that is less prone to defects.

That is, in a substrate that holds various elements fixedly and constitutes a circuit, the surface of the substrate corresponding to the connection terminals of the various elements is larger than the surface of the substrate corresponding to the connection terminals of the various elements.
By forming a low concave portion inside, the occurrence of defects at the connection portion is reduced.

Since the connection part is inside the working recess, even if the lead is deformed,
The wall prevents you from getting too close to the adjacent reed. Furthermore, since the recess can store a larger amount of solder, the solder that flows out will not come into contact between the terminals.

Example Embodiments of the present invention will be described below with reference to the drawings.

Figure 1 shows a state where an element (semiconductor element as an active element and a chip is a general term for various passive elements) is mounted on a terminal or a printed circuit board as explained in the conventional example. . In FIG. 1, there is an example in which connection terminals are arranged in two directions of various elements. Each connection terminal 1 is electrically connected to a printed wiring 3 on a printed circuit board 2 at a predetermined fixed position by solder 4. The surface of the unconnected portion 5 of the printed wiring is covered with an insulating film 6, so that the solder 4 does not stick to it. In the example shown in this figure, the elements are first fixed to the printed circuit board with adhesive and then electrically fixed and connected with solder.

FIG. 2 shows a case where the terminals of an element are deformed and connected and shorted on a conventional printed circuit board. The connection terminal 1 is easily deformed by mechanical force when the lead (connection terminal) is separated or during subsequent transportation.

In particular, when the pitch becomes small, the mechanical strength of the connecting terminal 1 decreases, making it easy to deform, and at the same time, even a small amount of deformation causes contact with an adjacent terminal, resulting in a defect. In Fig. 2, the connection terminal 1 is diagonally removed from the original connection part of the printed circuit board 3, but because the wall of the recess prevents it from coming close enough to the adjacent terminal to cause a problem, There is no solder 4 or electrical connection between them.

FIG. 3 shows a conventional case in which the amount of solder is too large and the terminals of an element are connected on a printed circuit board, resulting in a short circuit. After the leads (connecting terminals) are separated, the connecting terminals 1 are coated with solder to facilitate caulking and soldering.

When mounting on a printed circuit board, the solder on the leads may flow and come into contact with the adjacent terminals, causing defects.
In this embodiment, since the recess stores more solder, it is not connected to an adjacent terminal.

As explained above, the optimal value for the size of the recess changes depending on the thickness and width of the connection terminal, but making it too deep will make the process difficult and reduce the yield, while a recess that is too shallow will not provide sufficient effect. Therefore, the depth is approximately 1 to 3 times the thickness of the connecting terminal (lead) (approximately 0.5 to 3 m1.I), and the width of the recess is 0.05 to 0.0 m.
A width of about 5 mm is suitable.

FIG. 4 illustrates a method for forming a recess according to the present invention. In FIG. 4 (al), a predetermined pattern of resist 42 is formed on a printed circuit board 41 on which no wiring pattern is formed on the surface, in order to roughly form recesses. Using the resist 42 as a mask, a predetermined amount (0,5
mm to 3 mm) is shown in the etched state. FIG. 4 (In C1, metal thin film 43 (from 0.1m+a to 0.5-) that will become printed wiring after removing resist 42
A state in which a pattern of a resist 44 for connection terminals has been formed is shown. FIG. 4fd) shows the state in which the metal thin film 43 is etched using the connection terminal resist 44 as a mask, and the semiconductor integrated element is then mounted on a printed circuit board using a normal method.

The material of the printed circuit board is not particularly limited, and Evokin resin, glass fiber laminate, etc. can be used.

As described in detail, in the present invention, the leads (connection terminals) of semiconductor integrated circuit elements with a pinch size of IM to 0.5 mm or less,
When mounting on a printed circuit board, the connection between the staking connection terminal and the printed circuit board wiring section is made lower than the other printed circuit board surface and a recess is formed to prevent connection failures due to short circuits between adjacent connection terminals. It can be prevented.

[Brief explanation of the drawing]

FIGS. 1, 2, and 3 are diagrams explaining the present invention in detail, and in each figure (al is a plan view, (bl and (C1 are sectional views). are diagrams for explaining the manufacturing method of the present invention, and Figures 5, 6, and 7 are diagrams for explaining the conventional example, and in each figure (al is a plan view, (bl and (
C1 is a cross-sectional view. 1... Connection terminal, 2... Printed circuit board, 3... Printed wiring, 4... Solder. Name of agent Patent attorney Shigetaka Awano 1 person Figure (oL) L-+B' (b) / ,・Connection 5...Principal color self-dismissal cough non-i 9 people p6...East Iromi 1 Kushiryo PI Mo (C) (b) Shi6' (C)

Claims (1)

[Claims] 1. A printed circuit board comprising a substrate, an element fixedly held on the substrate, and a recess formed in a predetermined position of the substrate, the element fixed and held within the recess.