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Electrical test structures probed before release test

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Unformatted text preview: testers determine which ICs are good – Don’t want to package bad chips ($$$) – Label package properly (chip speed = $$$) • Testing MEMS functionality requires released MEMS – Current testers not compatible with MEMS • What could replace wafer test for MEMS? – Electrical test structures probed before release? – Test individually (manually) after release? – Test only after packaging? • MUST design with testing in mind! Microsystems Packaging: An Introduction Page 48 © 2003 Sandia National Laboratories Advanced Design Issues: Wafer Test • Design for Test – Is testing even possible? – Internal probe pads for test provided? – Self-test of device once it is packaged? • ADXL150 – Electrical self-test possible – Evidence of probing on “unused” pads, as well as “real” pads Microsystems Packaging: An Introduction Page 49 © 2003 Sandia National Laboratories Packaging Processes • • • • Wafer bonding Dicing/Singulation Pick and Place Mechanical Connection to Package/Circuit Board – Die attach • Electrical Connections/Interface – Wirebonding – Flip chip bonding • Sensing Connections/Interface – Connectors – Material types • Environmental Protection – Sealing – Overcoat deposition Microsystems Packaging: An Introduction Page 50 © 2003 Sandia National Laboratories Dicing: Separate Wafer into Die • Wafer sawing standard today – Diamond saw with coolant – Only used on unreleased wafers • Wafer-to-wafer bonding allows traditional sawing – Bonded glass, Si cover wafer on released MEMs wafer • Some alternate methods: – TI patent: partial saw, back grind – Saw wafers, protect MEMS with deposited films – Scribe and cleave – Other proprietary methods Microsystems Packaging: An Introduction Page 51 © 2003 Sandia National Laboratories Die Separation: ADXL150 • Rough, chipped edges indicate wafer saw • Believed to be post-release, using temporary protection for the MEMS devices • Note that you cannot use edges for precision alignment (spec is ±1° die to package) Microsystems Packaging: An Introduction Page 52 © 2003 Sandia National Laboratories Handling Individual Die Post-release • Free micromachines – Sensitive to particles – Damag...
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