JPH03229486A - Printed wiring board - Google Patents

Abstract

PURPOSE:To prevent occurrence of a short circuit part due to a molten solder by a method wherein the width of one end of a land part being in proximity to the main body of an electronic component is made smaller than that of the other end of the land part and a gap part between adjacent land paris is formed to be wide on one end side. CONSTITUTION:On the occasion when a land part 2 for connection of a lead terminal of an electronic component is provided on the upper surface of an insulated base 1, the width of one end 4 is made smaller than that of the other end 3. When a gap part on the ends 3 and 3a sides between land parts 2 and 2a being adjacent to each other is denoted by (a) and a gap part on the ends 4 and 4a sides between them by (b), (b) is greater than (a). By making small the width of the end part of a bending part of the lead terminal of the electronic component wherein a molten solder is concentrated more often than in an end part corresponding to the fore end side of the lead terminal, in this way, a gap between the adjacent land parts is widened and a structure not causing occurrence of a short circuit part even when the molten solder is concentrated is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to printed wiring boards used in various electronic devices. As a result, the pattern density of conductive foils that form circuits has become higher, and the gaps between conductive foils have become smaller, resulting in the mounting density of various electronic components increasing by many times.

A conventional printed wiring board will be described below with reference to the drawings.

FIG. 3 shows the structure of a conventional printed wiring board, and FIG. 4 shows a cross section taken along the Moum' line of FIG.

In the figure, numeral 31 is a printed wiring board, on which a conductive foil 33 is disposed on the surface of an insulating substrate 32, on which electronic components such as ICs are attached and which form land portions 34 for soldering. An etching resistive film 36 having openings 36 is applied.

5 and 6 show a state in which electronic components 37 such as RC are mounted and soldered on the printed wiring board 31,
A lead terminal 38 of an electronic component 37 is placed on the land portion 34 and electrically connected with a solder 39. This is a solder short circuit that occurred during soldering.

In the above configuration, in the step of mounting the electronic component 37 on the printed wiring board 31, cream solder 39 is applied to the land portion 34 of the printed wiring board 31 using a screen printer or the like, and the leads of the electronic component 37 are applied using an electronic component mounting machine or the like. The terminal 38 is attached at a position that coincides with the land portion 34. Next, it is transferred to a furnace using an infrared heater or the like as a heat source, and is heated to melt the cream solder 39, and the land portion 34 and the lead terminal 38 are soldered.

Problems to be Solved by the Invention However, in the above conventional printed wiring board, the land portion 34
Since the adjacent gap 41 is small, molten solder flows into the gap 41, forming a solder short-circuit portion 4Q, and the land portion 34 may be short-circuited with the adjacent land portion.

In particular, this solder short circuit portion 40 tends to occur mainly at the bent portion 42 of the lead terminal 38 of the electronic component 37, as shown in FIG.

This is because the molten solder 39 tends to wick up and concentrate on the bent portion 42 of the IJ+ upper terminal 38.

The present invention solves these conventional problems,
It is an object of the present invention to provide an excellent printed wiring board that can prevent solder short circuits occurring in gaps between adjacent lands. In the shape of the land portion of the printed wiring board, the width of the land portion at one end close to the electronic component body is made smaller than the width of the land portion at the other end, thereby forming a gap portion adjacent to one end of the land portion to be wide. Therefore, according to the present invention, it is possible to widen the gap between the lands at the bent portion of the lead terminal where molten solder tends to concentrate, thereby preventing the occurrence of short circuits due to molten solder. An embodiment of the present invention will be described below with reference to the drawings. Figure 1 shows the configuration of an embodiment of the present invention, and the second casing shows the structure of an embodiment of the present invention. Figure 1 shows the state in which electronic components such as RE are mounted on the printed wiring board shown in Figure 1. 2. As shown in Figure 1, lead terminals (not shown) of electronic components are connected to the top surface of the insulating substrate 1. A land portion 2 is provided, and this land portion 2 has a width smaller at the other end 4 than at one end 3 thereof. Therefore, the distance between the land portions 2 and land portions 2a which are adjacent to each other is 3°31 at one end of the land portions 2, 2 &
A gap part a is formed on the L side, and the other end 4 of the land parts 2, 21L
, a gap is formed on the 4a side, and b) a is formed. FIG. 2 shows a state in which electronic components 6 such as ICs are mounted on a printed wiring board 5. As is clear from the diagram, lead terminals 7, 7 of electronic components 6 are shown.
The gap between the adjacent land portions 2, 2a corresponding to the bent portions 8, 8a of a is widened.

The width of the adjacent lands is made smaller at the end of the bent part of the lead terminal, where melted solder tends to concentrate, compared to the end corresponding to the tip side of the lead terminal of the electronic component. By doing so, the gap between adjacent land portions is widened, and the structure is such that short circuits do not occur even if the solder melted in the bath is concentrated.

Effects of the Invention As is clear from the above embodiments, the present invention has a shape of a land portion for connecting electronic components provided on the top surface of a printed wiring board.
The land width at one end close to the electronic component body is smaller than the other end, thereby increasing the gap between each land at the bent part of the lead terminal where melted solder tends to concentrate when connecting electronic components. Therefore, it has the effect that solder short circuits are less likely to occur between adjacent lands.

[Brief explanation of drawings]

Fig. 1 is a partial plan view showing the configuration of a printed wiring board according to an embodiment of the present invention, Fig. 2 is a partial plan view showing a state in which electronic components are mounted on the printed wiring board, and Fig. 3 is a partial plan view showing the configuration of a printed wiring board according to an embodiment of the present invention. FIG. 4 is a partial sectional view showing the configuration of the wiring board; FIG. 6 is a partial plan view showing a conventional printed wiring board with electronic components mounted and soldered; FIG. Figure 6 is a partial cross-sectional view taken along line 4B-B'.・・・・・・
・Other end of land portion, 6...Printed wiring board, 6...
...Electronic parts, a. b...Gap area.

Claims (1)

[Claims] In a printed wiring board in which two or more land portions made of conductive foil for connecting electronic components are provided adjacently on the upper surface of an insulating substrate,
A printed wiring board, wherein the width of one end of a land portion adjacent to an electronic component main body is smaller than the width of the other end of the land portion, and the gap portions adjacent to each one end of the two or more land portions are formed wide.