| Summary: | 碩士 === 明新科技大學 === 電子工程研究所 === 97 === In present, the manufacturing technology and equipment development in semiconductor fields are very advanced due to the market competition. However, the investment of the package technology, in contrast, is less that that of the previous. Therefore, in the package technology, some issues are still observed, such as the adhesion force of wire between chip and lead-frame in the integrated circuit (IC), the choice of lead-frame material and the contamination in mixing molding compound. All of these deteriorated factors are able to degrade the electrical characteristics and operational performance of ICs.
If there seriously exists on some contaminated metal particles in the mixing process of molding compound, the phenomenon of short or leakage current in packaged ICs will possibly be generated in operation. However, in the infant mortality (IM) experiment and the final test (FT) of IC reliability, the screening capability for the contaminated metal particles is generally over than the size, W x L ~ 120 x 120 um2. For the smaller size of these metal particles in ICs, the IM test is inferior. In this work, we propose an efficient test metrology combining the IM test and the soak test to stress the 1000ea of sampled SRAM ICs. To obtain the contrast groups, the identical samples were separately stressed by the IM test after 8 and 16 hours or the soak test with 40 and 80 hours were chosen. After the test, the failure rate of these two contrast groups was zero. Using the first test with soak test and the second test with the IM test, some tested SRAM ICs failed.
In failure analysis, the smaller contaminated metal size with scanning electron microscope was measured, about WxL = 15 x 120 um2. The composition of metal particle with energy-dispersive X-ray (EDX) exhibited two main peaks attributed to manganese (Mn) and ferrum (Fe). In speculation, the humidity effect after the soak test provided the electro-chemical reaction environment between two neighboring IC pins, spacing 160 um, in the fine pitch package. The IM test accelerated this electro-chemical reaction. Therefore, even though the smaller contaminated metal particles exist, they with the double combination test still can be screened out. Due to this effort, the risk selling ICs to customers is tremendously reduced. The assembly houses after information feedback are able to trace the root causes in production line and improve the package yield.
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