JPS5969952A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent moisture intruding from the interface of an external lead and a resin in the vicinity of the external lead by attaching a metal, which is the same as a wiring metal for a pellet or an ionization tendency thereof is larger than the wiring metal, to the external lead and at least a part of a section enclosed with the resin of a hanging pin for holding of a pellet mounting section. CONSTITUTION:Thin-film layers 11 made of the same material as a wiring on a chip or a material, the ionization tendency thereof is larger than the wiring metal material, are formed. The metal layers may be formed in the vicinity of pads for bonding wires, and moisture reaches pad sections 3 when it intrudes from the interface of the leads 1 and the resin 8, but the pad sections 3 have large resistance against moisture and do not react with moisture because they are formed by Au or Ag, and moisture reaches the surface of the pellet along the bonding wires and corrodes wiring Al. However, moisture intruding along lead wires is in contact with aluminum layers formed near the bonding pads 3, reacts with aluminum and corrodes aluminum. The moisture consumes after it corrodes aluminum, and does not intrude in the direction of the pellet.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a semiconductor device, and particularly to a resin-sealed semiconductor device with improved moisture resistance.

Resin-sealed semiconductor devices can be manufactured at low cost, and due to improved reliability due to improvements in resin properties and molding technology, resin packages are currently the mainstream of IC packages.

FIG. 1 is a sectional view of a conventionally commonly used resin-sealed IC. 1 and 2 are lead frames mainly made of copper alloy or iron alloy, 1 is an external lead, and 2 is a bullet mount part. Thin films 3 and 4 of gold or silver are formed on the surface of the bullet mount portion 2 and on the bonding pad portion of the bonding wire of the external lead 1. A silicon chip 5 having aluminum wiring on its surface is connected to the bullet mount part 2 by a brazing material 6.

Further, the silicon chip 5 and the bonding portion 3 of the external lead are connected by a gold bonding wire 7. Aluminum wire is sometimes used as the bonding wire 7, but gold wire is almost always used in molded ICs from the viewpoint of production technology. In addition, 8 is made of molded resin and the dust pellet mounting part, a part of the outer board, and the bonding wire are inserted.

Although the reliability of resin-sealed semiconductor devices formed in this manner has been improved, the reliability is lower than that of metal or ceramic packages, and moisture resistance is particularly problematic. As mentioned above, aluminum is used for the internal wiring of the IC, but corrosion of the aluminum occurs due to the intrusion of water. Therefore, in order to solve this problem, it is necessary to prevent moisture from entering the aluminum wiring portion.

On the other hand, the routes for moisture to enter a resin-sealed semiconductor device are thought to be through the interface between the lead frame and the resin and the bulk itself. However, water rarely reaches the pellet surface directly through the resin, and most of the water enters through the interface between the lead and resin, and then reaches the pellet along the bonding line and the pellet mount. It is known to reach the °C pellet section through a holding hanging bottle. If there is a defect such as a crack in the molding resin, it can be removed by visual inspection, so it can be seen that the interface between the lead and the resin should be given the most attention to prevent moisture from entering.

On the other hand, in mold ICs, as the density increases, the internal wiring of aluminum on the pellet becomes finer,
The size of the net is increasing.

However, due to the demand for miniaturization, the distance between the pellet and the package surface has become shorter, and the number of leads has increased due to higher integration, making the conditions increasingly poor in terms of preventing moisture intrusion. In particular, miniaturization and an increase in the number of leads directly affect the heat of the pellet and create gaps between the leads and the resin since the heat capacity is small when soldering the IC.

To address these problems, nine methods have been taken to make it difficult for gaps to form between the lead and the molding resin, such as selecting the coefficient of thermal expansion of the resin and the lead, and improving ease of compatibility, but it is difficult to solve the problem satisfactorily. It is.

It is also possible to use gold, which does not easily react with moisture, for the wiring on the pellets, but since it is rarely used for inexpensive ICs such as molded products, aluminum is used exclusively.
I'm here.

Even though some of the moisture may enter the mold resin, it does not mean that it is so large that it becomes waterlogged.
It is clear that the longer the moisture that enters the lead is retained at the leads, the slower the moisture will enter the pellet surface and the life of the IC will be extended.

Therefore, the present invention has been made to address the above-mentioned problems, and it is an object of the present invention to provide a highly reliable resin-sealed semiconductor device that prevents moisture from entering from the interface between the lead and the resin near the external lead. be.

The gist of the present invention is that, in a resin-sealed semiconductor device, at least a part of the external lead and the portion sealed in the resin of the holding dose bottle of the pellet mount part is ionized to be the same as the wiring metal of the pellet or more ionized than the wiring metal. A semiconductor device is characterized in that a metal with a large tendency is layered.

The present invention will be described in detail below based on Examples.

FIG. 2 is a sectional view of a semiconductor device according to an embodiment of the present invention. In the figure, numerals 1 to 10 indicate the same parts as in the conventional figure 1. The difference from the conventional example is that at least a part of the external lead sealed in the molding resin is made of a material that has the same monthly rate as the wiring on the chip (aluminum in this example) or has a higher ionization tendency than the wiring metal material. Forming a thin film layer 11'C
The point is that there is. This metal layer may be formed in the vicinity of the bonding line pad, and an aluminum thin film may be formed over a relatively wide area to also serve as a conventional pad.

When such a structure is used, moisture is absorbed from the interface between the lead 1 and the resin 8, and when it reaches "C", the conventional Au.

Or, it reaches the pad part 3 of Ag, but the pad part 3 is A
Since it is made of aluminum or Ag, it has poor resistance to moisture, and moisture reaches the surface of the pellet along the bonding line and corrodes the wiring A7 without reacting. However, as described above, the moisture that has entered along the lead wire comes into contact with the aluminum layer provided near the bonding pad 3, reacts with the aluminum, and erodes the aluminum. As mentioned above, this invading moisture is not so large as to cause water immersion, so when this moisture corrodes the aluminum, it is consumed and no longer intrudes in the direction of the pellet.

In other words, this method takes advantage of the fact that the aluminum layer exists and the moisture that has entered the pellet does not reach the aluminum wiring portion of the pellet while it is reacting with the aluminum. Incidentally, since the cut portion of the repin held in the pellet mount portion is also exposed to the outside, the moisture resistance of the semiconductor device can be improved by the same treatment.

Next, the semiconductor device with the structure shown in FIG. 2 in which the present invention was implemented and the conventional semiconductor device with the structure shown in FIG.
The relationship between time and failure rate was determined. This relationship is shown in Figure 3. In Figure 3, AI/
i is the conventional product, and B is the result of an embodiment of the present invention. As is clear from this figure, with the conventional product A, the defective rate was quite large after 100 hours, and after that, the defective rate suddenly increased. This shows that lifespan is significantly extended.

As explained above, according to the present invention, it is possible to improve the moisture resistance of a resin-sealed semiconductor device, which has not been sufficiently effective only by improving the moisture resistance of the mold resin, and to significantly improve the reliability. .

In the above embodiment, C is the metal formed near the bonding pad of the external lead, and C mainly refers to aluminum, but it is not limited to aluminum.
Metals with a greater tendency to ionize than aluminum, such as Ca
, Mg, Ce, etc.

[Brief explanation of drawings]

Fig. 1 is a cross-sectional view of a conventional resin-sealed semiconductor device, Fig. 2 is a cross-sectional view of a resin-sealed semiconductor device according to the present invention, and Fig. 3 is the result of an accelerated humidity test of the conventional product and an embodiment of the present invention. FIG. DESCRIPTION OF SYMBOLS 1... External lead, 2... Pellet mount part, 3... External lead bonding pad, 4... Pellet mount part conductive layer, 5...
...Pellet, 6...Rowing material, 7...
...Bonding wire (Au wire), 8...Mold resin, 9...External lead exterior plating, lO.
°°・°°Aluminum internal wiring, 11... Waterproof metal layer, A... Conventional product moisture resistance characteristic curve, B...
Old...Moisture resistance characteristic curve of one embodiment of the present invention. 221- 躬/圀8Z图'θθ Time 3rd figure

Claims (2)

[Claims] (1) In a resin-sealed semiconductor device, at least a portion of the external lead and the part encapsulated in the resin of the holding dose bottle of the bullet mount part has a tendency to ionize the same as or has a greater tendency to ionize than the wiring metal of the bullet. A semiconductor device characterized by having metal attached thereto. (2) The metal attached to the wiring metal of the bullet, the external lead, and at least a part of the resin-sealed portion of the holding hanging pin of the bullet mount are both aluminum. The semiconductor device according to item (1).