This study presents the development of a die separation system with an in-situ w-EDD (Electro discharge dressing) technology and the study of die separation on silicon wafer substrate. Traditional electroformed diamond wheel tool has a low content of diamond abrasives and low rigidity of the substrate, which must be directly discarded after clogging leading to a high cost of tool. In this study, a BD-PCD (Boron-doped Polycrystalline Composite Diamond) in which possesses a content of diamond abrasive more than 95% and high rigidity is employed to instead of the traditional electroformed diamond wheel tool to improve the tool lifetime. To avoid clogging happened during working, an in-situ discharge dressing technology by which combines the designed "in-situ dressing mechanism" with the "PWM (Pulse-Width Modulation) power source" is developed. The diamond tool can be in-situ dressed in a short time without unloading. The PWM power source readily generates a current train with high-frequency, high-peak and shot-pulse time, which facilitates quickly form a high density spark erosion crater (chip-pocket) on the surface of the diamond wheel and expose the sharp cutting edge. In addition, a thin diamond wheel tool with lower graphitization layer can also be readily obtained. Experimental results show that the developed in-situ discharge dressing technology can quickly finish a diamond wheel tool with a thickness of 30 μm, a length of 400 μm and an aspect ratio of 13: 1. The diamond cutting edges and chip pockets with high density and uniform distribution has been revealed on the wheel surface. To compare the kerf quality, A KCR (Kerf Chipping Ratio) is proposed to perform a die separation at a faster feed-rate and brittle-like grinding depth under a brittle-like regime grinding, which meets the allowable chipping of commercial scribe line and reduces processing time. Experimental results confirm that the chipping, wavy cutting and slant cutting of the traditional electroformed diamond wheel can be improved by using the dressed BD-PCD wheel tool. By applying the mechanism of intellectualized grinding force feedback, a die separation with an array of 10×10 on silicon wafer substrate is verified, it was found that the KCR on the front and back of the wafer reached 3.26 and 1.87, respectively, which were better than the commercial KCR (the larger the KCR, the smaller the chipping at groove edge). Moreover, a scribe line with high-straightness and -wall verticality can be achieved, which is helpful in the semiconductor industry and great commercial value.
|Effective start/end date||2019/08/01 → 2021/07/31|
- In-situ w-EDD
- Brittle-like regime grinding
- die separation
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