JPS59198735A - Seam welding process - Google Patents

Abstract

PURPOSE:To prevent an electrode from sparking in case of coming into contact with the edge of a cover and separating from the cover by a method wherein welding current or voltage value is reduced in case a welding electrode firstly comes into contact with the cover and separating from the same. CONSTITUTION:Welding current is reduced down to the value not sparking at the time point A when a welding electrode 7 firstly comes into contact with a cover 3 then the current is augmented up to the value required for welding operation while the current is reduced again down to the value O not sparking immediately before the time point B when the welding electrode 7 separates from the cover 3. The electrode 7 may be prevented from sparking in case of coming into contact with the cover 3 by means of supplying said electrode 7 with slope current such as rectangular wave and since wave etc. The slope current may be supplied e.g. by a power supply 14 receiving signals representing the results of an encoder 12 encoding the movements of a jig 9 detected by a photosenser 13.

Description

Detailed Description of the Invention (1.1 Technical Field of the Invention The present invention relates to a seam cold welding method, specifically a parallel displacement seam welding method.
The present invention relates to a method for preventing sparks from being generated when a welding electrode first contacts and leaves a lid on a pan cage base during seam welding using a welding machine.

(2) Background of the technology One method of attaching a lid to a semiconductor package is seam welding. Figure 1 is a cross-sectional view of a semiconductor package (hereinafter referred to as a car package). In the figure, 1 is a package base, 2 is a sealing frame brazed to the package base l, 3 is a lid, and 4 is a semiconductor chip. , 5 indicates a wire for connecting the semiconductor chip 4, and 6 indicates an outer lead connected to the wire 5 via a wiring layer within the package base 1, respectively.

The lid 3 is welded to the C seal frame 2 by a seam welding machine, and the seam welding method when a parallel movement seam welding machine is used as the seam welding machine is shown in a plan view in Fig. 2. The package fixed to a jig (not shown) is moved in the direction shown by arrow I in FIG. power is added.

The electrode 7 has a lid 3 made of Kovar or 4270I.
The lid 3 is melted and welded to the seal frame 2 made of Kovar or alloy 42 by the Joule heat generated at the contact area between the lid 3 and the seal seam 2.

When all of the long sides of the lid 3 are welded and the welding electrode 7 is removed from the lid 3 by 1 islt, turn the jig 90' as shown by the arrow 2 in FIG. 2 (bl) to change the orientation of the package.

Next, as shown in FIG. 2 (C1), the gap between the electrodes 7, 7 is widened, the package is moved in the direction of the arrow (■), and the short side of the lid 3 is welded to the seal frame 2.

Although the above process can be performed in air, it is performed in a sealed chamber called a dry box to prevent oxidation.

The welding method described above is schematically shown in the front view of Fig. 3, where the electrode 7 is initially placed at the position shown by the solid line.When the electrode 1.7 first comes into contact with the edge of the lid 3, the welding current is turned on. , the package is moved in the direction of arrow IV, and the position when electrode 7 comes to the opposite edge of lid 3 is shown by the dotted line in the figure, and when electrode 7 leaves 11 from this position, the welding current changes to leaf F. Become.

(3) Prior art and problems When the welding electrode first contacts the lid and when it separates from the lid, the electrode 7 is in contact with the edge of the lid 3,
The current path is restricted, and snow leaks occur. At that time, the edge portions of the seal frame 2 and lid 3 may be chipped along the line 8 due to the strong force shown in Fig. fiS4 and the sparks flying in the direction shown by the arrow. be. If this happens, even if the lid 3 is welded to the seal frame 2G by later welding, the sealing 1 at this chipped part will be incomplete and the sealed N2 gas will leak from that part, or moisture from outside will enter the pan cage. I decided to go in, 21'.

This adversely affects the manufacturing yield of conductor packages and product reliability.

(4) Zero aspect of the invention The present invention addresses the above-mentioned conventional problems and solves the above-mentioned problems in the prior art. - An object of the present invention is to provide a seam welding method that prevents generation of sparks when an electrode comes into contact with the edge of the lid and when it separates from the lid during seam welding using a welding machine.

(5) Accomplishment of the invention According to the invention, a metal lid is placed on a sealing frame attached to a semiconductor pancage base, and a pair of welding electrodes are brought into contact with two opposite sides of the lid. When performing seam welding by moving the welding electrode or the semiconductor pancage substrate in parallel, the welding current or voltage value is decreased when the welding electrode first contacts the lid and when it separates from the lid. The first aspect is achieved by providing a seam welding method characterized by controlling so that sparks are not generated between the welding electrode and the welding electrode.

(6) Embodiments of the Invention In order to solve the problems of the prior art described above, the inventor of the present application considered passing a slope current shown in a rectangular wave and a sine wave in (b) to the 51st g1fal. The horizontal axis shows time (
'F) and the vertical axis is the current (f).
Regarding the current waveform, a weak current that does not generate sparks is passed around point A when the welding electrode first contacts the lid, and then a current necessary for welding is passed. Further, if the time point at which the welding electrode separates from the lid is B, then just before approaching H, the °C current value is weakened to 0 so as not to cause sparks.

By passing such a slope current, around the time A when the welding electrode first contacts the lid and at the time B when the welding electrode comes off from the lid, the electrode 7
By suppressing the value of the current flowing through the electrode to a weak value that does not generate sparks, it is possible to prevent sparks from being generated when the electrode 7 contacts the edge of the lid 3.

The slope current as described above is not shown in Figure 6. Obtained by 'e. The jig 9 to which the package is fixed engages with the shaft 10 of a normal XY drive system, and the shaft 10 and the motor 11
It can be driven in the left and right direction (X direction) as seen in the figure. The shaft 10 is connected to an encoder 12 via a motor 11, and the movement of the shaft 10 in the X direction, and hence the movement of the jig 9 in the X direction, is transmitted to the encoder 12.
is detected by the photosensor 13, and the detection result is sent as a signal to the power source 14, which controls the current flowing through the pig iron 14 through the electrode 71. If you measure the length of the lid 3 in the X direction at the front, then the electrode will come in contact with the lid! 1S
The current value is automatically Hi-controlled until the condition II is removed. Regarding movement in the Y direction, since the direction of the package can be changed by 90 degrees, the current value can be controlled using the same principle as above, so the current value can be controlled by the same principle as shown in Fig. 2 (a) and (
Seam welding shown in ( ]).

When the electrode contacts the lid, it is possible to prevent sparks from occurring when the electrode comes into contact with the lid.

According to the method of the present invention, when the electrode comes into contact with the edge of the lid in seam welding for welding a lid to a semiconductor device using the parallel movement method, that is, This prevents the generation of sparks when the current is turned on and off, which is highly effective in improving the manufacturing yield and reliability of semiconductor packages.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a semiconductor pancase, Figure 2 is a plan view of a semiconductor package to explain seam welding using the parallel force method, and Figure 3 is the arrangement of electrodes and semiconductor packages in seam welding. ): A front view showing , Figure 4 is an enlarged view of the lid and seal frame of the semiconductor package in Figure 1,
FIG. 5 is a diagram of the slope current used in the method of the present invention, and FIG. 6 is a layout diagram of an apparatus for carrying out the method of the present invention. ■-Buff cage base, 2-Seal frame, 3-Lid,
4-semiconductor chip, 5' wire, 6-outer lead, 7-welding electrode, 8-missing wire, 9
- Jig, 10 - Axis, l 1 - Morph, 12 - Claw sensor, 13 - Encoder, 14 - Electrode Figure 1 Figure 3 Figure 4N @2 Figure

Claims (1)

[Claims] A metal lid is placed on the seal frame attached to the semiconductor package base, a pair of welding electrodes are brought into contact with two opposing sides of the lid, and the welding electrodes or the semiconductor package base are moved in parallel to perform seam welding. When the welding electrode first contacts the lid and when it separates from the lid, the welding current value or voltage (ii'i) is reduced to prevent sparks between the lid and the welding electrode. A seam welding method characterized by control.