JPS58209194A - Method of connecting via solder leadless chip carrier to printed circuit 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 The present invention relates to a method for soldering a leadless chip carrier to a printed circuit board.

Conventionally, when connecting a leadless chip carrier made of ceramic to a printed circuit board made of glass, epoxy, or other materials with different coefficients of thermal expansion by soldering, it is necessary to reduce the large shear force generated at the solder joint due to the application of temperature cycles. In order to alleviate this problem, a method has been proposed in which the height of the solder swelling portion is increased. In this method, the solder is piled up high on the solder connection band, so if the amount of solder piled up is increased, accidents such as solder bridges occurring between adjacent solder connection bands and solder flowing down from the pads may occur. As a result, large shear stress occurs in the solder joint, which leads to fatigue of the solder and impairs the reliability of the joint.

The present invention provides a method for easily connecting a leadless chip carrier and a printed circuit board, which eliminates the above-mentioned drawbacks. This method is characterized in that solder is poured into the recesses of the photoresist layer formed in a raised manner and facing the pads, and the terminals of the leadless chip carrier are connected to the solder raised in the recesses.

Next, an embodiment of the present invention will be described with reference to the drawings.

FIG. 1(a) is a partial plan view of a printed circuit board including pads for soldering a general leadless chip carrier, where 10 is a printed circuit board made of glass, epoxy, etc., and 11 is a printed circuit board made of copper foil, etc. It is a solder connection pad consisting of.

) in FIG. 1 is the bridge/upper circuit W board 10 shown in FIG. 1(a).
12 is a leadless chip carrier made of ceramic, and 16 is a tres chip carrier.
Terminal 2 and 14 are solder made of 64Sn/36Pb or the like.

FIG. 2(a) shows the printed circuit board "'1" according to the present invention.
In the partial plan view of 0', a film-like photoresist layer 20 is formed on the printed circuits 1 &1o' in a raised manner except for the pad 110 area, and a recess 20a is formed in the photoresist layer 20 facing the pad 11. It is something.

FIG. 2(b) shows the printed circuit board 1 shown in FIG. 2(a).
The solder connection method of the present invention is as follows, showing a partial cross-section of a state in which a leadless chip carrier is soldered using 0'. That is, FIG. 2(a).

As shown in FIG. 2, solder 14 is poured into the recess 20a of the photoresist layer 20 and raised, and the solder 14 connects the terminal 13 of the leadless step carrier 12 and the pad 11 of the bullet circuit board 10'.

According to this embodiment, since the photoresist layer 20 is thicker than the solder connection pad 11, it is possible to ensure a high solder bulge height.

According to this embodiment, the thickness of the photoresist layer 20 can be up to about 100 .mu.m, so it is expected that the solder build-up height will be greater than that.

As explained above, in the present invention, solder is poured into the recesses of the photoresist layer formed on the printed circuit board to build up the solder. This has the effect of alleviating shear stress at the connection portion and increasing the reliability of the solder connection portion of the leadless chip carrier.

[Brief explanation of the drawing]

FIG. 1(a) is a partial top view of a printed circuit board including pads for soldering a typical leadless chip carrier, and FIG. 1(b) is a partial plan view of a typical leadless chip carrier and a printed circuit board. FIG. 2(a) is a partial plan view of the printed circuit board according to the present invention, and FIG. 2(b) is an embodiment of the present invention.
1 is a partial cross-sectional view of a solder connection of a leadless chip carrier using a printed circuit board with a film-like photoresist layer; FIG. 10'... Board, 11... Bat for solder connection, 12
...Leadless chip carrier, 13...A1 of leadless chip carrier, child, 14...Solder, 20
... Photoresist layer, 20a... Photoresist layer patent applicant NEC Corporation

Claims (1)

[Claims] (1) In a method of directly connecting a leadless chip carrier to a printed circuit board by soldering, solder is poured into a depression in a photoresist layer formed on the printed circuit board, and the solder raised in the depression is attached to the leadless chip. A method for soldering a leadless chip carrier and a printed circuit board, the method comprising connecting terminals of the carrier.