JPH0439778B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Technical Field of the Invention The present invention relates to a seam welding method, and particularly to a method for welding a metal seal frame attached to a base of a semiconductor package and a metal lid placed thereon. Regarding.

(b) Technology Background Although many recent semiconductor devices are molded packages due to improvements in semiconductor chip packaging technology, devices that require high reliability or are used in special environments still rely on metal or other devices. Products that use a hermetically sealed package made from a combination of materials such as ceramics occupy an important position.

Seam welding according to the present invention is a method of attaching a lid to the package, and is already a well-known method, but it is desired that the seam welding be completely airtight after welding.

(c) Prior art and problems Figure 1 is a cross-sectional view of an embodiment of a semiconductor package, Figure 2 is a plan view a and b for explaining seam welding in the semiconductor package, and Figure 3 is a diagram of the seam welding. FIG. 4 is a front view showing the arrangement of the welding electrode and semiconductor package in an example of the conventional method, FIG. In this figure, 1 is a semiconductor chip, 2 is a semiconductor chip, and 2 is a semiconductor chip.
is a lead terminal, 3 is a package base, 4 is a seal frame, 5 is a lid, 6 is a welding electrode, 7 is a chip, 8
indicates the crack, and A and B indicate the direction, respectively.

The semiconductor package shown in FIG. 1 has a main body made of, for example, ceramic, a semiconductor chip 1 mounted therein, and a package base 3 that leads out the circuit of the semiconductor chip 1 to external lead terminals 2, and a square frame-shaped package made of, for example, Kovar. A sealing frame 4 is soldered to this, and a lid 5 made of, for example, a Kovar plate is attached to this.
are welded airtight using seam welding.

The seam welding method is as shown in Figure 2.
The lid 5 is placed on the seal frame 4 and the unwelded semiconductor package fixed to a jig (not shown) is moved in the direction of arrow A shown in FIG. By passing a current of, for example, about 150 amperes between the pair of welding electrodes 6 that are in contact with each other on the sides, the portion directly below the contact point between the seal frame 4 and the lid 5 is heated by Joule heat on the two sides. The long sides of the seal frame 4 and the lid 5 are welded by continuous melting along the sides. After welding all of the long sides, rotate the jig 90 degrees and attach the welding electrode 6.
Then, as shown in Figure b, move the semiconductor package in the direction of arrow B and weld the short sides in the same way.

In the above seam welding, the conventional method of supplying electricity between the welding electrodes 6 is as shown in FIG.
The semiconductor package on the right side of the figure is moved in the direction of arrow A while the welding electrode 6 is not in contact with the lid 5, and when the welding electrode 6 comes into contact with the lid 5, energization is started (ON), and the welding electrode 6 is brought into contact with the lid 5. It is turned off (OFF) just before you leave the machine.

In this seam welding method, since the contact between the welding electrode 6 and the lid 5 is point contact at the corner of the lid 5, especially when starting current flow between the welding electrodes 6, there is a gap between the welding electrode 6 and the lid 5. When sparks are generated, not only the lid 5 but also the corner portions of the seal frame 4 may be scattered, resulting in chipping 7, as shown in FIG. And since the welding condition of these 7 chipped parts is uncertain,
The hermeticity of the semiconductor package becomes incomplete.
Furthermore, the temperature of the package base 1 gradually rises due to heat conduction within the package base 1 of the Joule heat, and when the length of the long side is long, the temperature rise becomes large, and the package base 1 is heated as shown in FIG. Cracks 8 may occur in the base 1. The occurrence of such chips 7 and cracks 8 poses a problem that adversely affects the manufacturing yield and reliability of semiconductor devices.

(d) Object of the Invention In view of the above-mentioned conventional problems, the object of the present invention is to place a metal lid on a metal seal frame attached to a semiconductor package base, bring a welding electrode into contact with the side of the lid, When performing seam welding between the seal frame and the lid by energizing the welding electrode while relatively moving the welding electrode and the semiconductor package base in the direction of the side, sparks are generated when the energization starts. It is an object of the present invention to provide a seam welding method capable of suppressing the occurrence of cracks and also suppressing the occurrence of cracks in the package base.

(e) Structure of the Invention The above object is to place a metal lid on a metal seal frame attached to a semiconductor package base, bring a welding electrode into contact with the side of the lid, and connect the welding electrode to the semiconductor package base. and energizing the welding electrode while relatively moving the welding electrode in the direction of the side to perform seam welding between the seal frame and the lid, the step of starting the energization at the middle of the side. This is achieved by a seam welding method characterized by:

Since the contact between the welding electrode and the lid at the time of starting the current flow between the welding electrodes is in the middle on the side of the lid,
Unlike the conventional case of corners, it is stable, so it is possible to suppress the generation of sparks, and by the above operation, the side to be welded is divided into at least two parts, and the length of one weld is shortened. Because it will be shorter,
The rise in temperature of the semiconductor package base is reduced, making it possible to suppress the occurrence of cracks in the semiconductor package base. By combining a plurality of welding operations on the side to which the above operation has been performed, it is possible to weld the entire length, thereby making it possible to weld the desired complete airtightness.

(f) Embodiments of the invention Examples of the invention will be described below with reference to the drawings. The same reference numerals indicate the same objects throughout the figures.

FIG. 6 is a front view showing the arrangement of the welding electrode and the semiconductor package in an embodiment of the seam welding method according to the invention shown in FIG. 2, FIG. 7 is a diagram showing the welding order, and FIG. 8 is the same. FIG. 3 is a diagram showing the welding order of another example, where C indicates the direction and ~ indicates the order, respectively.

FIG. 6 is a diagram corresponding to FIG. 3 in the conventional method, and the method of supplying current between welding electrodes 6 according to the present invention is as follows:
As shown in the figure, welding of one set of sides is divided into two stages. That is, in the first step, the semiconductor package is moved in the direction of arrow A, and when the welding electrode 6 comes to approximately the center position of the side of the lid 5, energization is started (ON).
However, the welding process ends (OFF) immediately before the welding electrode 6 leaves the lid 5. In the second step, the semiconductor package is moved in the direction of arrow C, and when the welding electrode 6 is slightly in front of the previous energization start (ON) point, energization is started again (ON), and the lid is closed in the same manner as before. 5
It is turned off (OFF) just before you leave the machine. By doing this, at the energization start point (ON), the contact between the welding electrode 6 and the lid 5 is at the middle of the side of the lid 5, so unlike the case of the corner of the conventional example, the contact between the welding electrode 6 and the lid 5 is stable, so there is no spark. This makes it possible to suppress the occurrence of welding, and the energization areas at the energization start (ON) point overlap, so that the two divided welds are completely connected.

Furthermore, according to this method, the length of one welding is shortened, and the temperature of the package base 1 decreases between the end of energization in the first stage (OFF) and the start of energization in the second stage (ON). Therefore, the temperature rise in the package base 1 is smaller than in the conventional example, and it becomes possible to suppress the occurrence of cracks 8 in the package base 1 shown in FIG. 5.

Figure 7 shows the welding order when this seam welding method is applied to the long and short sides of the lid 5, and Figure 8 shows the welding order when applied only to the long sides. . In the method shown in Figure 8, the contact surface between the welding electrode 6 and the lid 5 becomes familiar when welding on the long side ends (OFF), so even if the welding starts (ON) on the short side, there is no spark. The method shown in FIG. 7 is preferable when the welding length is short on the short sides, and the welding length is short on the short sides.

The inventor of the present application has confirmed that not only the method shown in FIG. 7 but also the method shown in FIG. 8 can provide a practically sufficient effect in semiconductor devices.

Note that cracks in the package base 1 are suppressed by shortening the length of one weld as described above, so if it is too long even if it is divided into two parts as in the example above, it is sufficient to divide it into three or more parts. , the method thereof is also included in the present invention.

(g) Effects of the Invention As explained above, according to the configuration of the present invention, a metal lid is placed on a metal seal frame attached to a semiconductor package base, and a welding electrode is attached to the side of the lid. When performing seam welding between the seal frame and the lid by energizing the welding electrode while moving the welding electrode and the semiconductor package base relatively in the direction of the side, It is possible to provide a seam welding method that can suppress the generation of sparks during the welding process and suppress the generation of cracks in the package base, and has the effect of making it possible to improve the manufacturing yield and reliability of semiconductor devices. .

[Brief explanation of drawings]

Fig. 1 is a sectional view of an embodiment of a semiconductor package, Fig. 2 is a plan view a, b for explaining seam welding in the semiconductor package, and Fig. 3 is an example of a conventional seam welding method. Figure 4 is a front view showing the arrangement of the welding electrode and semiconductor package, Figure 4 is a diagram showing a chip in the seal frame and lid that occurs during welding, Figure 5 is a diagram showing a crack in the package base, and Figure 6 is a diagram showing a crack in the package base. FIG. 2 is a front view showing the arrangement of the welding electrode and the semiconductor package in one embodiment of the seam welding method according to the present invention, FIG. 7 is a diagram showing the welding order, and FIG. 8 is another embodiment of the method. It is a figure showing the welding order of. In the drawings, 1 is a semiconductor chip, 2 is a lead terminal, 3 is a package base, 4 is a seal frame, 5 is a lid, 6 is a welding electrode, 7 is a chip, 8 is a crack, A, B, C are directions, ~ The order is shown respectively.

Claims (1)

[Claims] 1. Place a metal lid on the metal seal frame attached to the semiconductor package base, bring a welding electrode into contact with the side of the lid, and align the welding electrode and the semiconductor package base relative to each other in the direction of the side. A seam welding method comprising the step of energizing the welding electrode while moving the welding electrode to perform seam welding between the seal frame and the lid, and starting the energization at the middle of the sides.