JPH0356936A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent faulty soldering by containing a dummy pattern which is interrupted halfway in any of pads for soldered joint arranged in a line on a printed wiring board and forming a wiring pattern which extends in both directions. CONSTITUTION:In order to unify the heat capacity of the pads for joint 2 arranged in a line, the comparatively short dummy pattern 3, which is the shortest one allowed by heat conductivity and a soldering working time on the wiring pattern 1 so as to fit the purpose of unifying the heat capacity, is added even to the pad where the wiring pattern 1 extending in both directions from the pad for joint 2 need not be formed as the wiring of a circuit to form the wiring pattern. Therefore, all the pads for joint arranged in a line on the printed wiring board necessarily have the wiring patterns 1 and 3 extending both directions. Thus, the soldering working is mass-produced with high yield and reliable products are obtained.

Description

[Detailed Description of the Invention] [Industrial Field of Application] This paper describes how to solder connect external connection lines or conductive patterns when mass producing liquid crystal display devices in which adjustment circuits are mounted on printed wiring boards. This invention relates to a liquid crystal display with an improved yield in the process of soldering to pads.

[Liquid product labeling for mass production using conventional technology]! Even in A position, it is common.
t has a control circuit mounted on a printed wiring board.

In the case of a liquid crystal display device, solder connection pads formed on a printed wiring board and used for connection with the outside are often arranged in a straight line (Japanese Patent Laid-Open No. 114226/1983).

Conventionally, a wiring pattern was formed in only one direction from the four solder pins used for connection with the outside.

However, in recent years, there has been a strong demand for miniaturization, etc.
There is a strong need to improve the distribution density of circuits on printed wiring boards.
Printed 1'512 wire boards, which have wiring patterns extending directly in two directions from the pads themselves, are now being used for some of the necessary interconnection pads arranged in a straight line. Ta.

[Problems to be Solved by the Invention] However, in a liquid crystal display device using a high-density printed wiring board as described above, a problem has arisen in that the incidence of soldering defects at connection pads is higher than in the past.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device that prevents the occurrence of soldering defects as described above.

[Means for Solving the Problems] In order to achieve the above object, in the present invention, each of the solder connection pads arranged in a straight line on the printed wiring board must include a dummy pattern that is interrupted in the middle. We decided to form a wiring pattern that extends in both directions.

[Function] As a result of conducting an A-inspection of a large number of defective soldering products, the present inventors found that
It was determined that the cause of this was that during the process of connecting external connection lines or conductive patterns, the temperature of the connection pads arranged in a straight line on the printed wiring board was not constant.

FIG. 2 is a diagram showing the vicinity of connection pads arranged in a straight line on the conventional high-wiring density printed circuit board for a liquid crystal display device. In the figure, 1 is a wiring pattern and 2 is a connection pad.

The present inventors further discovered that the main cause of temperature differences between seemingly similar pads arranged in a straight line is that, in order to improve wiring density, wiring patterns extending in both directions from a certain pad are shaped or However, on other pads, it is distributed only in one direction from the pad. It was also discovered that the pattern was merely shaped.

Therefore, in order to unify the heat capacity of the connection pads arranged in a straight line, the heat capacity is unified even for pads that do not need to form wiring patterns extending in both directions from the connection pads. A relatively short dummy pattern, which is the shortest that is allowed by heat conduction on the wiring pattern and soldering time, is added and shaped to meet the purpose, and arranged in a straight line on a printing wire cutting machine. All of the connecting pads were made to have wiring patterns extending in both directions.

[Embodiment] The upper figure is a diagram showing the vicinity of connection pads arranged in a straight line in a printed wiring board according to an embodiment of the present invention. In the figure,
1 is a wiring pattern, 2 is a connection panode, and 3 is a dummy pattern for unifying heat capacity.

In the case of this example, as a result of experiments, the length of the dummy pattern was determined to be at least 0.5 times the length of the solder connection pad. In the actual soldering operation, first, solder paste is applied in a straight line, including all the connecting pads arranged in a straight line and their intermediate parts, usually by a printing method. Thereafter, the connection lines or connection patterns to be soldered, which are also arranged in a straight line, are placed on top of the corresponding connection patterns, and a heating tool extending in the straight line direction is pressed from the outside thereof. In the embodiment of the present invention, even if the temperature of the heating tool is constant (the temperature is the same for any part corresponding to any connection pattern), the connection pads have almost the same heat capacity, so all the connection pads have the same temperature. As the temperature rises and there is no temperature unevenness between the pads, if the temperature setting of the heating tool is appropriate, all the connection pads will reach solder paste 1.
The pads are similarly covered with melted solder of approximately the same temperature, and all soldering is successful on all pads. Note that the surface of the intermediate part between the connection pads on the printed wiring board is not coated with metal, so molten solder will not adhere to it. It will fall off.

[Effects of the Invention] As explained above, according to the present invention, the soldering work between the connecting pads arranged in a straight line on the printed circuit board equipped with the percussion circuit and the external connecting wires or patterns can be done at a high cost. It is mass-produced with high yield and produces highly reliable products.

[Brief explanation of drawings]

FIG. 1 shows a printing layout of one embodiment of the present invention! A diagram showing the vicinity of the connection pads arranged in a straight line on the board, Figure 2 is a conventional LCD display! FIG. 3 is a diagram showing the vicinity of connection pads arranged in a straight line in a high-wiring density printed wiring board for A-type.

Claims (1)

[Claims] 1. In a liquid crystal display device in which a drive circuit is mounted on a printed wiring board, any of the solder connection pads arranged in a straight line on the printed wiring board must have wiring that extends in both directions, including dummy patterns that are interrupted in the middle. A liquid crystal display device characterized by forming a pattern.