JPH07273267A - Method of bonding lead - Google Patents

Abstract

PURPOSE:To simplify a laser irradiation apparatus and to shorten a laser bonding process by a method wherein, when a lead for a lead frame on which a semiconductor-integrated-circuit element is mounted is bonded to a terminal for connection, a part to be bonded is irradiated with a laser beam from vertically. CONSTITUTION:In a lead frame which is formed of a 42 alloy, the tip part of an inner lead 10 is made thin by a half etching operation. On the other hand, at a terminal, for connection, for a printed-wiring board 11 on which a chip is mounted, an Au plating operation is conducted to the surface of a Cu pattern via an Ni-plated layer. Then, at a part in which the tip part of the lead as a vertically above part to be connected is overlapped with the terminal for connection is irradiated with a laser beam from, so that the part is welded and bonded. Thereby, the driving mechanism of a laser light source is not required, and a laser bonding apparatus is simplified. In addition, the time required for a bonding operation is shortened, and a bad effect due to heating to the printed-wiring board due to an increase in the time required can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a lead frame for mounting a semiconductor integrated circuit element (hereinafter referred to as a chip) and connecting it to an external circuit, and more particularly to a method for joining a lead and a connecting terminal.

[0002]

2. Description of the Related Art A method for joining a lead of a lead frame and a connecting terminal by welding by laser irradiation is well known, and generally, a laser beam is applied obliquely from above to a joining portion.

The places where the welding is required are terminals for connecting the outer lead tips to external circuits such as a printed wiring board. A terminal for connecting a printed wiring board that mounts the tip of the inner lead and the chip. There is.

For example, in the case of connecting a quad flat package (a semiconductor package using a lead frame having a structure in which leads project in four directions), the laser irradiation direction is changed each time the joint (side) is changed. Since it is necessary to change the (optical axis), the laser irradiation device becomes a large-scale device requiring its driving mechanism.

[0005]

In recent years, the number of leads in a lead frame has tended to increase (hereinafter referred to as "multi-pinning") due to the demand for higher integration and higher functionality of semiconductor devices. However, there is also an adverse effect that the printed wiring board having the connecting terminals is damaged by the temperature rise.

It is an object of the present invention to provide a lead joining method capable of simplifying a laser irradiation device and shortening a laser joining process.

[0007]

In order to achieve the above object, according to the present invention, a laser beam is applied vertically upward to a joining portion (a portion where a lead tip portion and a connecting terminal overlap).

Preferably, laser bonding is performed by using a lead frame having a structure in which the tip of the lead is thinner than other portions.

[0009]

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

(1) Lead frame 0.15 mm thick 42 alloy (Ni 42% by weight, balance ...
Fe) is molded by a known method, and the lead frame 10
Got At this time, the tip portion of the inner lead was made to have a thickness of 0.09 mm by known half etching.

(2) Chip-Mounted Printed Wiring Board On the other hand, the connection terminals of the printed wiring board 11 on which the chip is mounted are plated with Au to a thickness of 1 to 2 μm on the surface of the Cu pattern via the Ni plating layer. It is a configuration.

(3) Laser Bonding The above (1) and (2) are laser bonded using an apparatus schematically shown in FIG. <Joining conditions> Laser light source: YAG laser Laser beam diameter: 20 μm Laser output: 1 W Irradiation time: 0.2 seconds / read Under the above conditions, the laser bonding process was repeated for the number of leads while moving the XY stage. .

[0013]

[Effects of the Invention] The laser bonding apparatus is simplified without the need for a drive mechanism of the laser light source. By reducing the lead thickness of the welded part, the joining time is shortened, it is easy to handle lead frames with multiple pins, and the adverse effects of heating the printed wiring board due to the increase in the required time are reduced. It was

[0014]

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a joining method of the present invention.

[Explanation of symbols]

 10 ... Lead frame 11 ... Printed wiring board

Claims (2)

[Claims] 1. A method of joining a lead of a lead frame on which a semiconductor integrated circuit element is mounted and a connecting terminal by welding by laser irradiation, wherein laser light is vertically irradiated from above the bonding portion. Lead joining method. 2. The lead joining method according to claim 1, wherein a lead frame whose lead end portion, which is a joining portion, is processed thinner than other portions is used as the lead frame.