Is there Metal on the cantilever?  The metal in PolyMUMPs is 0.5um Au
with a thin adhesion layer.  When this gold is heated above ~100C, a
tensile stress will be induced when the die is cooled.  At 150C, this
stress can be as high as 200MPa.  The stress will relax some over time
(several days), but will not return to its original as deposited stress.
I am not aware of any methods to prevent this on PolyMUMPs other than
reducing the temperature of packaging or eliminating the Metal layer on
sensitive devices.

Stafford Johnson
Development Engineer
MEMSCAP, Inc.

-----Original Message-----
From: weiwei2 [mailto:weiwei2@pd.jaring.my]
Sent: Monday, May 05, 2003 12:25 PM
To: General MEMS discussion
Subject: [mems-talk] thermal effect on MUMPS


i did die attach of MUMPS die onto PCB using thermal cure epoxy at 150C.
it cause extra curling of MUMPS cantilever. how to solve this? is there
any literature on this?

LEOW
Universiti Teknologi Malaysia


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