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MEMS PACKAGING & ASSEMBLY ISSUES
SMTAi 2000 Chicago Ken Gilleo, PhD ET-Trends Intellisense © ET-Trends LLC
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OUTLINE MEMS Introduction & Survey Packaging challenges
Assembly issues MOEMS; let there be light* (optics) Conclusions * control © ET-Trends LLC
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Nano World Where all technology converges Optics Electronics Mechanics
The convergence point of electronics, mechanics, physics, chemistry and biology, etc. Electronics Mechanics MEMS MOEMS OE OM Optics Where all technology converges © ET-Trends LLC
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Micro-Electro-Mechanical System
MEMS Micro-Electro-Mechanical System Semiconductor processing used Merges mechanical motion & electronics VERSATILE sensing computing motion control U of W Marauder MEMS Monster? © ET-Trends LLC
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MEMS Processing Electronics fab: standard methods Silicon Machining:
Define mechanical parts by lithography Form sacrificial SiO2 in “removal” areas Etch away SiO2 to free mechanical parts Many other micro-machining processes are available © ET-Trends LLC
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MEMS Motion Deformable; cantilevers, beams, membranes Sliding, linear
Rotating; partial, full, multi-plane Rotating Inter-contact; gears, wheels Hinges Combinations Sandia, UW, AD © ET-Trends LLC
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MEMS “Engines” Electrostatic; very efficient* Thermal Electromagnetic
Pneumatic Hydraulic Photoelectric *Surface area is relatively high, mass is very low; surface effects are important © ET-Trends LLC
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MEMS Products © ET-Trends LLC
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MEMS Structures IBM MEMS DNA Detector © ET-Trends LLC
Electrostatic Relay - UW
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More MEMS Are the Microbots” coming? Guess? © ET-Trends LLC Tweezers
UW-Madison
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The real problem may be Lack of KNOWLEDGE,
Packaging The real problem may be Lack of KNOWLEDGE, not Lack of TECHNOLOGY © ET-Trends LLC
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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 © ET-Trends LLC
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MEMS Packaging Types Traditional hermetic; metal or ceramic
Cap-on-Chip wafer-level device-level Silicon Sandwich Near- and non-hermetic Selective/partial packaging © ET-Trends LLC
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Packaging No Standards DPL Modules, TI (HERMETIC) (HERMETIC)
Accelerometer (CAP) Ink Jet MEMS in TAB Package (SELECTIVE) © ET-Trends LLC (HERMETIC) MicroRelay - Cronos (HERMETIC) (HERMETIC)
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Selective Encapsulation
MEMS Ink Jet “Gun” I-TAB package This type of machine can be used to selectively encapsulate MEMS- one like this is used on ink jet cartridges. Courtesy of Speedline MEMS bare die © ET-Trends LLC
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Cap-on-Carrier Silicon or Metal Cap Molded or Liquid Encapsulant
MEMS IC Solder, weld, or polymer This packaging method is suitable for accelerometers, gyroscopes and other motion detectors that can be sealed. © ET-Trends LLC
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Cap-on-Chip (level-0) CAP Vacuum MEMS Chip
Seal Vacuum MEMS Chip Can now be handled like an ordinary die - almost! © ET-Trends LLC
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Cap-on-Chip Variants Etched Silicon, ceramic, glass
Indent Reflow Sealing (IMEC) Wafer-Level Protected (AMKOR) Silicon Sandwich; GIT Metal, low CTE? Plastic? © ET-Trends LLC
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Cap-on-Chip Overmolding
1. Apply cap to device or wafer; solder, weld, bond. MEMS IC May require gel coat to protect thin cap 2. Attach & bond device 3. Conventional overmolding followed by solder ball attach. © ET-Trends LLC
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MOEMS Projection Mirrors Photonics Switches Gratings Fiber Aligners
Micro-opto-electro-mechanical systems Projection Mirrors Photonics Switches Gratings Fiber Aligners Modulators, Shutters Movable Lenses A Market powered by the Internet! A Technology that will power the Internet! © ET-Trends LLC
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Cronos (JDS-Uniphase)
Optical MEMS or MOEMS Fiber Alignor Cronos (JDS-Uniphase) Micro-Mirror Lenses Array Rotating Mirror-UCLA Pop-Up Lens Micro-Mirror Array - TI © ET-Trends LLC Shutter - Sandia Cross-switch mirror
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Micro-Mirror Close-up by TI
on off World’s most complex machine? Ref. “Digital Light Processing TM for High-Brightness, High-Resolution Applications” Larry J. Hornbeck, © ET-Trends LLC
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MOEMS Micro-Mirror WINDOW HEAT SINK HERMETIC Getter Weld or seal
Ceramic HEAT SINK HERMETIC 250,000 mirrors MEMS Digital Mirrors one section © ET-Trends LLC
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Flip Chip for MOEMS? Light Pipe Encapsulant MEMS FLIP CHIP Underfill
© ET-Trends LLC
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MOEMS Flip Chip BGA Package
Seal or dam MEMS IC Light Pipe © ET-Trends LLC
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GETTERS Agents that counteract harmful contaminants within a sealed package; this includes solids, liquids, gases and combinations. Will guard and control package environment over an extended time. © ET-Trends LLC
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Types of Getters Particle: attracts and holds. Moisture: desiccant.
Gas: adsorbs/chemically converts to liquid or solid. Combinations. Others are possible. © ET-Trends LLC
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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 © ET-Trends LLC
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Available Getters Moisture Particle Hydrogen Combinations
© ET-Trends LLC
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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 © ET-Trends LLC
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Accelerometer Example
For air bags INOPERABLE Analog Devices Chip Sensing Mechanism (AD) High surface area = high attraction = “STICTION” Result of rough handling = “dead” component © ET-Trends LLC
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Stiction Solutions Liquid lubricants Gases, vapors
Polymer films; Fluorinated Parylene Treatments Design; “no contact” © ET-Trends LLC
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Assembly Factors Component skew Component non-coplanarity
All change accelerometer behavior Component skew Component non-coplanarity Solder joint mass and shape Flux residue Board thickness Board warpage © ET-Trends LLC
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Conclusions MEMS: a key 21st century technology
The packaging is more difficult Expect new & unusual packages Assembly has new constraints New guidelines are needed © ET-Trends LLC Let’s take the bite out of MEMS
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