JPS6112385B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a semiconductor device, and particularly to a method of surface treatment of external leads of a semiconductor device.

Conventionally, the surface treatment of external leads of semiconductor devices was
Various methods have been used depending on the purpose and use of the semiconductor device. Conventional techniques can be broadly classified into the following three methods. The first method is often used for resin-sealed semiconductor devices and glass-sealed semiconductor devices, and involves performing electrolytic plating after sealing the semiconductor element and before cutting the external leads.
Next, the second method is to perform electrolytic plating on the external leads when manufacturing the container or lead frame, as seen in semiconductor devices using multilayer ceramic containers and some resin-sealed semiconductor devices. After the semiconductor elements are assembled, no surface treatment is performed, and the products are manufactured in the plated state. Furthermore, the third method, which is applied depending on the case, involves immersing the external lead in a solder bath to adhere the solder.

However, such conventional methods have the following drawbacks in terms of product cost. In other words, in the first method, an electrolytic plating production line must be built to perform electrolytic plating after encapsulating the semiconductor element, but this production line requires investment in wastewater treatment equipment and restrictions on location due to recent strict environmental regulations. In reality, this is becoming impossible. Moreover, even if it were possible, the cost of the product would increase accordingly. In addition, in the second method, since the semiconductor device assembly process is performed after plating, materials such as Sn (tin), which easily oxidizes at high temperatures, cannot be used, and Au
However, expensive metals such as (gold) had to be used, and product costs could not be lowered. Furthermore, although the third method definitely reduces material costs, it is difficult to mass-produce semiconductor devices because they are made individually, and the quality of the solder in the solder bath changes from moment to moment as impurities melt into it. To maintain this, the solder in the solder tank must be replaced each time, making it difficult to reduce costs.

It is an object of the present invention to eliminate such drawbacks and provide a semiconductor device that is inexpensive and of stable quality.

The present invention is characterized in that a solder paste is applied to the external leads of a semiconductor device and then baked.

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

1A, B, and C are perspective views of a semiconductor device whose surface is treated using a conventional solder bath. For example, a semiconductor element is connected by a known method to a lead frame 1 in which a long thin metal plate such as Kovar is pressed to form a continuous pattern for each semiconductor device, and thin metal wires are wired at predetermined locations to form an assembly. A semiconductor device semi-finished product 3 sealed with an epoxy resin 2 is formed (FIG. 1A), and each semiconductor device semi-finished product 3 is
are individually separated using a press, and further, the external leads 4 are formed into a predetermined DIP shape using a press. Thereafter, a mark is applied to the resin surface of each semiconductor device semi-finished product 3 and dried (FIG. 1B). With the external lead 4 thus formed into almost the final shape, a suitable flux is applied to the external lead 4, and the lead is immersed in a solder bath containing, for example, Pb--Sn eutectic solder. Finally, the structure in which the external lead 4 is provided with the solder bath 5 (FIG. 1C) is shipped.

By the way, with such conventional methods, semiconductor devices cannot be dipped into solder unless they are separated individually, making it difficult to mass-produce, and also requiring man-hours and costs to manage the amount of impurities in the solder bath and replace solder. This resulted in an increase in product costs.

2A, B, and C are perspective views of a semiconductor device according to the present invention. For example, for a semi-conductor semi-finished product 3 comprising a lead frame 1 made of conventionally known Kovar or the like and an epoxy resin 2 sealed with a semiconductor element etc. by a known method (FIG. 2A), the Kovar surface is first cleaned. Therefore, perform solvent cleaning such as Triclean or alkaline cleaning such as Nonipol, and then add acid cleaning such as HCl. Thereafter, solder paste 6 is formed on the external leads 4 by screen printing (FIG. 2B). This solder paste 6 is made of fine particles of Pb-Sn of about 350 mesh, for example.
(38%) It is commercially available with approximately 70% solder and other resins, ammonium chloride, soft petroleum, wax, etc.

Now, after applying the solder paste, it is baked at around 170℃ to ensure complete adhesion. This firing can be performed in a regular thermostatic oven, electric furnace, or belt (continuous) furnace. Furthermore, a mark is applied to the resin surface of the semiconductor device semi-finished products 3 and dried, each semiconductor semi-finished product 3 is separated from the lead frame, and external leads are formed (FIG. 2C).

In this way, the method for manufacturing a semiconductor device of the present invention involves applying a solder paste and baking it, so that it can be mass-produced and manufactured at a lower cost than in the past.

Further, for example, the stamping process may be performed before applying the solder paste and the baking after application may also serve as the sealing drying, so there is no stipulation.

[Brief explanation of the drawing]

FIGS. 1A to 1C are perspective views showing a conventional method for manufacturing a semiconductor device in the order of steps. FIGS. 2A to 2C are perspective views showing an embodiment of the present invention in the order of steps. In the figure, 1...lead frame, 2...
...Resin, 3...Semiconductor device semi-finished product, 4...External lead, 5...Solder layer, 6...Solder paste.

Claims (1)

[Claims] 1. A method for manufacturing a semiconductor device, comprising at least the steps of forming a solder paste layer on at least a portion of an external lead of the semiconductor device, and firing the solder paste layer.