JPS63278263A - Semiconductor device - Google Patents

Abstract

PURPOSE:To enhance the soldering performance of a semiconductor device by a method wherein a solder film applied to the neighborhood of each curved end part of a lead is flattened at the curved end part. CONSTITUTION:Each of two or more leads 5 which have been formed by protruding from four side faces of a package 2 is curved to be J-shaped toward a direction of the rear of the package 2. Solder films 1 are applied to the neighborhood of curved end parts. Flat faces 1a are formed on the solder films 1 in such a way that, when this package 2 is placed on a board 8, the individual leads 5 come into contact with the surface of the board 8 uniformly at these curved end parts. In order to form the flat faces 1a at the solder films 1, the package 2 is placed, e.g., on a grindstone whose surface is flat and is ground. By this setup, the soldering performance of a semiconductor device is enhanced when the device is mounted on the board.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a technique that is effective when applied to a semiconductor device in which external leads are curved in a three-shape shape toward the back surface of a package.

[Conventional technology]

A semiconductor device in which external leads (hereinafter simply referred to as leads) are curved in a three-shape toward the back surface of the package, so-called P L CC (Plastic Leaded Ch)
Regarding semiconductor devices of the ip carrier type, for example, Nikkei McGraw-Hill, published June 11, 1984,
“Nikkei Electronics Special Issue/Micro Devices J,
There is a description in (P148 to P153).

By the way, with the increasing integration of semiconductor devices, the above-mentioned PLCC or SOJ (Soma
ll 0utline J-Lead Package
)-type semiconductor devices have come into widespread use.

To mount this PLCC type or SOJ type semiconductor device on a board, solder cream or solder paste is applied to predetermined locations on the wiring patterned on the surface of the board, and a package is placed on top of it. , a common method is soldering by solder reflow.

Therefore, during solder reflow, the reliability of soldering, so-called solderability, is determined by ensuring that the multiple leads curved in a 3-shape toward the back of the package are in uniform contact with the solder paste. This is important for improving.

[Problem that the invention seeks to solve]

However, the inventors of the present invention have found that the above-mentioned PLCC type or SOJ type package structure has the following problems.

In other words, in these package structures, it is difficult to curve the multiple leads protruding from the side of the package into a three-shape shape with uniform precision, resulting in variations in the height of the curved end of each lead. Therefore, when the package is placed on top of the solder paste, some of the leads may not come into contact with the solder paste, which causes problems such as poor continuity between the lead and the wiring, and insufficient bonding strength. It has become.

Furthermore, the surface of the lead is plated with tin (Sn), for example, but when the lead is curved into a three-shape shape, excessive distortion tends to occur particularly at the curved end. Therefore, the corrosion resistance of the curved end portion decreases, causing corrosion of the lead.

An object of the present invention is to provide a technique for improving soldering properties when mounting a semiconductor device on a substrate.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Means for solving problems]

A brief overview of typical inventions disclosed in this application is as follows.

That is, a solder film is formed near each curved end of a plurality of leads protruding from the side surface of the package, and
A semiconductor device is provided in which the solder coating on each curved end is flattened so that each lead uniformly contacts the substrate surface.

[Effect]

According to the above-mentioned means, when the package is placed on the substrate, the plurality of leads are brought into uniform contact with the substrate surface, and the solder wettability of the leads is improved by the solder coating near each curved end. Therefore, this eliminates problems such as poor conduction between the leads and wiring and insufficient bonding strength between the package and the board after soldering.

〔Example〕

FIG. 1 is a sectional view showing a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a side view of essential parts of this semiconductor device placed on a substrate.

The semiconductor device of this embodiment is a semiconductor device having a PLCC type package structure, and as shown in FIG. 1, a package 2 molded with epoxy resin or the like,
It is composed of a plurality of leads 1 made of copper (Cu) or the like whose surface is plated with tin (STI) or the like.

At approximately the center of the inside of the package 2, a semiconductor pellet 3 on which a predetermined integrated circuit is formed is attached onto a tab 4 via a bonding material (not shown) made of silver (Ag> paste or the like). Further, around this tab 4, a plurality of internal leads 5 integrally formed with the lead 1 are formed radially in a non-contact state with the tab 4, and are made of gold (Au).
), etc., and is electrically connected to the semiconductor pellet 3 via a conductive wire 7 .

On the other hand, each of the plurality of leads 5 protruding from the west side of the package 2 is curved in a 3-shape toward the back surface (lower side of the figure) of the package 2, and is located near the curved end. The solder film 1 is deposited and the leads 5 are arranged so that when the package 2 is placed on the board, the curved ends of the leads 5 are uniformly brought into contact with the surface of the board.
A flat surface 1a is formed on the solder coating 1.

To form this solder film 1, for example, the package 2 may be dipped in a solder pool, whereby solder is applied to the vicinity of each curved end of the plurality of leads 5 at the same time. Further, in order to form the flat surface 1a on the solder coating 1, the package 2 may be placed on a grindstone with a smooth surface and ground. The solder film 1 is uniformly planarized.

In order to solder the semiconductor device having the above structure to a substrate such as a printed wiring board, solder cream 10 is applied to predetermined locations of wiring 9 patterned on the surface of the substrate 8, as shown in FIG. and place package 2 on top of it. At this time, the flat surfaces 1a of all the leads 1 are brought into uniform contact with the solder cream 10. Next, this substrate 8 is carried into a reflow oven (not shown) and solder reflow is performed, thereby completing the soldering of this semiconductor device to the substrate 8.

As described above, according to this embodiment, the following effects can be obtained.

(1) By forming a solder film 1 near each curved end of a plurality of leads 5 protruding from the side surface of the package 2, and flattening the solder film 1 at the curved end, these leads Even if the heights of the curved ends of the leads 5 vary when the leads 5 are curved into a tri-shape, all the leads 5 are uniformly brought into contact with the surface of the substrate 8. Therefore, problems such as poor conductivity and insufficient bonding strength between the leads 5 and the wiring 9, which will occur later in soldering, are eliminated.

(2), ! Since the solder film 1 was formed near the curved end of the J-board 5, the lead 50 was easily removed during reflow.
Improves solder wettability.

(3), ') - Since the solder coating 1 is formed near the curved end of the lead 5, corrosion of the lead 5 at the curved end can be prevented.

(4) Due to the above (1) to (3), the soldering properties of the semiconductor device when mounted on a board are improved.

Although the invention made by the present inventor has been specifically explained above based on Examples, it goes without saying that the present invention is not limited to the Examples and can be modified in various ways without departing from the gist thereof. Nor. For example, the materials of the package and leads may be changed as desired.

Further, in the above explanation, the invention made by the present inventor is mainly applied to a semiconductor device having a so-called PLCC type package structure, which is the field of application thereof, but the present invention is not limited to this. For example, the present invention can also be applied to an SOJ type semiconductor device.

〔Effect of the invention〕

A brief explanation of the effects obtained by typical inventions disclosed in this application is as follows.

That is, a solder film is formed near each curved end of a plurality of leads protruding from the side surface of the package, and
By flattening this solder coating at the curved end, the plurality of leads can uniformly contact the substrate surface when the package is placed on the substrate. Therefore, in soldering, problems such as poor conduction between leads and wiring and insufficient bonding strength between the package and the substrate are eliminated, and the soldering properties of semiconductor devices are improved.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a semiconductor device according to an embodiment of the present invention, and FIG. 2 is a side view of a main part of this semiconductor device mounted on a substrate. DESCRIPTION OF SYMBOLS 1...Solder film, 1a...Flat surface, 2...Package, 3...Semiconductor pellet, 4...Tab, 5...
・External lead, 6...Internal lead, 7...Wire,
8... Board, 9... Wiring, 10... Solder cream. /-Gakutafu 4, /a-3 Komian θ-Shotfu ρ

Claims (1)

[Claims] 1. A semiconductor device in which a plurality of external leads protruding from the side surface of a package are curved toward the back surface of the package, and the curved ends are brought into contact with the surface of a substrate and soldered to the substrate. By forming a solder film near each curved end of the plurality of external leads and flattening the solder film at each curved end, each external lead uniformly contacts the substrate surface. A semiconductor device characterized by: 2. The semiconductor device according to claim 1, wherein the solder coating is flattened by grinding the solder-adhering surface of each external lead with a smooth grinding means.