Factors affecting the yield of parallel seam welding

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Factors affecting the yield of parallel seam welding [Copy link]

Factors affecting the yield of parallel seam welding

【Source: SMT Information Network】【Author: toptouch】【Time: 2004-12-30 14:31:47】【Click: 4490】

Abstract: For some optoelectronic devices used in special environments, sealing is required to prevent the circuit modules in the device from failing due to moisture, ions in the atmosphere, corrosive atmosphere, etc., and the device can be isolated, humidity reduced, and filled with protective gas to extend the service life of the device. This paper conducted experiments on the SSEC (Solid State Equipment Company) M-2300 parallel seam welding machine and found that the design of the fixture, the position of the electrode, the matching of the cover and the socket, and the packaging working parameters directly affect the yield of parallel seam welding. Keywords: packaging; parallel seam welding; yield rate Chinese Library Classification Number: 305.94 Document Identification Code A 1 Introduction The packaging of optoelectronic devices is to seal the assembled and electrically interconnected optoelectronic device chips and related functional devices and circuits into a special tube shell, and realize optical connection with the outside through the optical system inside the tube shell. Among the devices of our institute, many are finally packaged by parallel seam welding, such as optical fiber couplers, photodetector components, laser components, etc. Parallel seam welding is the sealing welding between the tube seat and the cover plate. Its purpose is to ensure the airtightness of the device, ensure the isolation of the tube core and circuit from the external environment, avoid the invasion of harmful atmosphere from the outside, limit the content of water vapor in the packaging cavity and control free particles, etc. This paper will mainly analyze the factors that affect the device packaging yield during the parallel seam welding process. 2 Working principle of parallel seam welding It is a kind of resistance welding. Two cylindrical roller electrodes are used to contact the metal cover to form a closed loop. The welding power is divided into two currents in the form of current from one end of the transformer secondary coil through one of the electrodes. One current flows through the cover, and the other flows through the tube shell and returns to the other end of the transformer secondary coil through the other electrode. The high resistance point of the whole circuit is at the contact point between the electrode and the cover. The current generates a lot of heat at the contact point, making it molten. After solidification, it forms a series of welds. Because the welding uses pulse current, the welds can overlap each other, forming an airtight filling weld. The packaging methods that can be used are: rectangular sealing, circular sealing, elliptical sealing, and array sealing. The packaging parameters are: power P (seal empirical power, watts), pulse PW (pulse width, ms), period PRT (pulse repetition rate, ms), speed S (seal speed, mm/s), pressure F (force, g), pulse interval PS (pulse spacing, mm). Total energy = P × PW × L / PRT × SL - socket package length (1) E = I2R 3 Influencing factors 3.1 The design of the fixture should first consider the clamping method of the fixture, so that the center of the fixture is basically consistent with the center of the turntable, and the tube holder should be clamped as firmly as possible; secondly, the heat dissipation of the tube holder should also be considered, especially for ceramic tube holders. 3.2 Matching of the tube seat and the cover plate Quality issues of the cover plate. ① The package edge of the cover plate is preferably 0.0889-0.127mm thick, with an edge of 90° (as shown in Figure 3), so that it can be in close contact with the seam welding surface of the tube seat; ② The upper edge of the cover plate is rounded to reduce the contact resistance between the cover plate and the electrode, and it is also convenient to reduce heat (as shown in Figure 4); ③ The lower edge of the cover plate is rounded to form an insulating gap, causing heat to flow on the sealing surface and affecting the rapid dissipation of heat (as shown in Figure 5); ④ The thinned edge reduces the contact resistance and the flow of heat on the sealing surface (as shown in Figure 6); ⑤ The convex edge that appears during processing will cause sparking. The corners of the cover plate and the tube seat should be rounded (as shown in Figure 7), otherwise it will cause sparking on the corner. The arc should generally be less than 76.2 μm. The arc is also to reduce heat. If a rectangular seal is used, the electrode contacts the corner twice, and the corner generates heat twice. The arc can reduce the probability of leakage on the corner. The size of the cover plate should be the same as the size of the tube socket to be packaged (as shown in Figure 8). It can also be slightly larger or smaller, but it cannot be larger than the package size by more than 25.4 μm or smaller than 76.2 μm (as shown in Figures 9 and 10). Otherwise, sparks may occur at any time during the packaging process, affecting the airtightness of the package. 3.3 Position of the electric board First of all, it should be noted that the position of the left and right electrodes should be as symmetrical as possible (as shown in Figure 1), so as to ensure the consistency of contact resistance and the consistency of weld width. Secondly, pay attention to the size of the delay distance (as shown in Figure 11). If the spark phenomenon occurs at the beginning of Pass 1 or Pass 2, the delay distance is too short. The delay distance can generally be set to 1.14mm or 0.045× 0.0254mm, or it can be set to about 1mm. If the spark phenomenon occurs at the end of Pass 1 or Pass 2, the welding distance (weld distance) is too long. The welding distance should be the sum of the package length of the sealed device and twice the delay distance. If the spark phenomenon occurs during the welding process, the automatic height should be adjusted. 3.4 Adjustment of working parameters The working parameters include "Power (W)", which ranges from 1 to 5000; "Pulse Width (ms)", which ranges from 1 to 100; REPTime (ms) (pulse period); which ranges from 1 to 5000; "DetectLevel'' (detection level), which ranges from 1 to 12000; "Delay Distance (mm)", which ranges from 0.00 to 200.00; "Weld Distance (mm or °)" (sealing distance or sealing angle), the rectangular sealing range is 0.00 to 200.00 mm, the circular sealing and elliptical sealing range is -725.00° to 725.00°; "Weld speed (mm/s)" (sealing speed), the rectangular sealing range is 0.02 ~36.00; the range of the circular elliptical seal is 0.00~4.52; "Force (g)" (pressure), its range is 1~1500. The adjustment of working parameters can only find the most optimized parameters, there is no absolute parameter. In this process, do as many experiments as possible. The following experiments were conducted on the 16A and 8A black ceramic tube sockets (detailed inspection ≤l0-3pa.cm3/S): From the following experimental results, it can be seen that: ① The change in pressure has little effect on the entire package yield rate. The change in pressure will change the contact resistance, but the change is very small. According to the energy formula, the contact resistance changes little, the change in the entire energy is also small, and thus the change in the thermal shock of the tube socket is also small; ② With the increase of power, the yield rate of the entire package is greatly affected. This is because the power increases, the energy increases, and the thermal shock of the tube socket increases. Some tube sockets cannot withstand the thermal shock, which causes damage to the tube socket itself and reduces the yield rate. Different tube sockets have different abilities to withstand thermal shock, which is also related to the structure of the tube socket. If the power is too large, the cover will be burned. 4 Conclusion In parallel seam welding, the fixture design should be reasonable, the cover plate and the tube socket should match well, the electrode position should be moderate, and the working parameters should be optimized, so that the yield rate can be greatly improved. Of course, there are other factors that affect the packaging results in the packaging process. In order to achieve a good result, there must be certain requirements for the performance of the tube socket (such as: the material of the tube socket, the strength of the tube socket and the structural design of the tube socket, etc.). Only through the efforts of many parties can the packaging results be broken through.