Reflow 2 4 min 280c 350c peak reflow profile critical

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Unformatted text preview: itch 3. Bondpad spacing should be uniform 4. Pads should be labeled or numbered Microsystems Packaging: An Introduction Page 65 © 2003 Sandia National Laboratories Hermetic Seals for Packages • Welding: Seam, e-beam, laser – High local heating (1000-1500°C), little die heating – Most popular hi rel sealing (~80% military) (TO Can) • Glass: Lead–Zinc–Borate soft glasses – Inert, insulator, impermeable to moisture... – Low strength, brittle, physi- and chemisorbed H2O – Pre-glazed lids and package in ~420°C belt furnace • Brazing: Au–Sn (80:20) fluxless eutectic – Preform tacked to Au plated Kovar lid or package – Typ. reflow: 2-4 min. >280°C (350°C peak) – Reflow profile critical: 3-5% more Au can raise liquidus 280°C to 450°C, can be caused by dissolution of plated Au in package Microsystems Packaging: An Introduction Page 66 © 2003 Sandia National Laboratories Advanced Design Issues: Sealing • Does your device have to be hermetically sealed? – Reliability, lifetime, design environment – Very hard to qualify packages for 20 year lifetime – May need a getter material in package to maintain vacuum or humidity requirements over lifetime • Cost tradeoffs in sealing – Fiber connections: hermetic (solder) seal requires a metallized fiber end ($$$) Microsystems Packaging: An Introduction Page 67 © 2003 Sandia National Laboratories Vacuum Sensor (Pirani Gauge) • Poor design because all the bondpads are on one side Microsystems Packaging: An Introduction Page 68 © 2003 Sandia National Laboratories Please Don’t Ask Us to Wire Bond This Microsystems Packaging: An Introduction http://www-bsac.eecs.berkeley.edu/~warneke/SmartDust/index.html Page 69 © 2003 Sandia National Laboratories Uncooled Infrared Detector • This commercial product also uses epoxy die attach • Eutectic and glass die attaches require higher temperatures and put more stress on die but they don’t outgas Microsystems Packaging: An Introduction Page 70 © 2003 Sandia National Laboratories Package Depends on the Application (Neural Stimulator) Microsystems Packaging: An Introduction Page 71 © 2003 Sandia National Laboratories J....
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This note was uploaded on 09/02/2010 for the course MEEN 5050 taught by Professor Himanshuj.sant during the Spring '10 term at University of Utah.

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