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ET-Trends LLC 1 MEMS PACKAGING & ASSEMBLY ISSUES Ken Gilleo, PhD ET-Trends gilleo@ieee.org SMTAi 2000 Chicago SMTAi 2000 Chicago Intellisense Slide 2 ET-Trends LLC 2 OUTLINE MEMS Introduction & Survey Packaging challenges Assembly issues MOEMS; let there be light* (optics) Conclusions * control Slide 3 ET-Trends LLC 3 Nano World Where all technology converges The convergence point of electronics, mechanics, physics, chemistry and biology, etc. Electronics Mechanics Optics MEMS OEOM MOEMS Slide 4 ET-Trends LLC 4 MEMS Semiconductor processing used Merges mechanical motion & electronics VERSATILE sensing computing motion control Marauder MEMS Monster? Micro-Electro-Mechanical System U of W Slide 5 ET-Trends LLC 5 MEMS Processing Electronics fab: standard methods Silicon Machining: Define mechanical parts by lithography Form sacrificial SiO 2 in removal areas Etch away SiO 2 to free mechanical parts Many other micro-machining processes are available Slide 6 ET-Trends LLC 6 MEMS Motion Deformable; cantilevers, beams, membranes Sliding, linear Rotating; partial, full, multi-plane Rotating Inter-contact; gears, wheels Hinges Combinations Sandia, UW, AD Slide 7 ET-Trends LLC 7 MEMS Engines Electrostatic; very efficient* Thermal Electromagnetic Pneumatic Hydraulic Photoelectric *Surface area is relatively high, mass is very low; surface effects are important Slide 8 ET-Trends LLC 8 MEMS Products Slide 9 ET-Trends LLC 9 MEMS Structures IBM MEMS DNA Detector Electrostatic Relay - UW Slide 10 ET-Trends LLC 10 More MEMS Tweezers UW-Madison Are the Microbots coming? Guess? Slide 11 ET-Trends LLC 11 The real problem may be Lack of KNOWLEDGE, not Lack of TECHNOLOGY The real problem may be Lack of KNOWLEDGE, not Lack of TECHNOLOGY Slide 12 ET-Trends LLC 12 Packaging Challenges MEMS devices can be very fragile pre-package handling concerns more protection by package Most require hermetic package ($$$) MOEMS (later) requires a window & controlled atmosphere. Biggest challenge: cost-effective, high volume packaging Slide 13 ET-Trends LLC 13 MEMS Packaging Types Traditional hermetic; metal or ceramic Cap-on-Chip wafer-level device-level Silicon Sandwich Near- and non-hermetic Selective/partial packaging Slide 14 ET-Trends LLC 14 Packaging MicroRelay - Cronos (HERMETIC) Accelerometer (CAP) Ink Jet MEMS in TAB Package (SELECTIVE) DPL Modules, TI (HERMETIC) No Standards (HERMETIC) Slide 15 ET-Trends LLC 15 This type of machine can be used to selectively encapsulate MEMS- one like this is used on ink jet cartridges. Courtesy of Speedline Selective Encapsulation Ink Jet Gun I-TAB package Ink Jet Gun I-TAB package MEMS bare die MEMS Slide 16 ET-Trends LLC 16 Cap-on-Carrier MEMS IC This packaging method is suitable for accelerometers, gyroscopes and other motion detectors that can be sealed. Silicon or Metal Cap Molded or Liquid Encapsulant Solder, weld, or polymer Slide 17 ET-Trends LLC 17 Cap-on-Chip (level-0) MEMS Chip CAP Vacuum Seal Can now be handled like an ordinary die - almost! Slide 18 ET-Trends LLC 18 Cap-on-Chip Variants Etched Silicon, ceramic, glass Indent Reflow Sealing (IMEC) Wafer-Level Protected (AMKOR) Silicon Sandwich; GIT Metal, low CTE? Plastic? Slide 19 ET-Trends LLC 19 Cap-on-Chip Overmolding MEMS IC 2. Attach & bond device May require gel coat to protect thin cap 1. Apply cap to device or wafer; solder, weld, bond. 3. Conventional overmolding followed by solder ball attach. Slide 20 ET-Trends LLC 20 MOEMS Projection Mirrors Photonics Switches Gratings Fiber Aligners Modulators, Shutters Movable Lenses Micro-opto-electro-mechanical systems A Market powered by the Internet! A Technology that will power the Internet! Slide 21 ET-Trends LLC 21 Optical MEMS or Cronos (JDS-Uniphase) Micro-Mirror Lenses Array Micro-Mirror Array - TI Pop-Up Lens Rotating Mirror-UCLA Cross-switch mirrorShutter - Sandia Fiber Alignor Slide 22 ET-Trends LLC 22 Micro-Mirror Close-up by TI on off Ref. Digital Light Processing TM for High-Brightness, High-Resolution Applications Larry J. Hornbeck, hbek@dlep1.itg.ti.com Worlds most complex machine? Slide 23 ET-Trends LLC 23 MOEMS Micro-Mirror WINDOW HEAT SINK Ceramic Weld or seal MEMS Digital Mirrors one section HERMETIC Getter 250,000 mirrors Slide 24 ET-Trends LLC 24 Encapsulant Flip Chip for MOEMS? MEMS FLIP CHIP Light Pipe Underfill Slide 25 ET-Trends LLC 25 MOEMS Flip Chip BGA Package MEMS IC Seal or dam Light Pipe Slide 26 ET-Trends LLC 26 Agents that counteract harmful contaminants within a sealed package; this includes solids, liquids, gases and combinations. GETTERS Will guard and control package environment over an extended time. Slide 27 ET-Trends LLC 27 Particle: attracts and holds. Moisture: desiccant. Gas: adsorbs/chemically converts to liquid or solid. Combinations. Others are possible. Types of Getters Slide 28 ET-Trends LLC 28 Why Use Getters? Remove harmful agents from the device environment. Control atmosphere for many years. Provide the maximum security and reliability; highest life expectance. Protect optics; mirrors, lenses Reduce wear Slide 29 ET-Trends LLC 29 Moisture Particle Hydrogen Combinations Available Getters Slide 30 ET-Trends LLC 30 Assembly Issues Safe handling; some are shock sensitive Orientation; can be critical PWB & joint; change affects MEMS sensitivity Testing; not well established for some devices Free path; light, sound, molecules Slide 31 ET-Trends LLC 31 Accelerometer Example Analog Devices Chip Sensing Mechanism (AD) Result of rough handling = dead component Result of rough handling = dead component High surface area = high attraction = STICTION High surface area = high attraction = STICTION For air bags INOPERABLE Slide 32 ET-Trends LLC 32 Stiction Solutions Liquid lubricants Gases, vapors Polymer films; Fluorinated Parylene Treatments Design; no contact Slide 33 ET-Trends LLC 33 Assembly Factors Component skew Component non-coplanarity Solder joint mass and shape Flux residue Board thickness Board warpage All change accelerometer behavior Slide 34 ET-Trends LLC 34 Conclusions MEMS: a key 21st century technology The packaging is more difficult Expect new & unusual packages Assembly has new constraints New guidelines are needed Lets take the bite out of MEMS