CTE values from:
Improvements of Thermal Resistance and Thermal Stress in
Quasi-Monolithic Integration Technology (QMIT) with a New
Fabrication Process
M. Joodaki, A. Tarraf*, M. Salih, D. Albert**, H. Schröter-Hohmann*, W.
Scholz**,
G. Kompa, H. Hillmer* and R. Kassing**
Dept. of High Frequency Engineering, Kassel University, Wilhelmshöher Allee
73, 34121 Kassel, Germany
* Dept. of Technological Electronics, Kassel University, Heinrich-Plett Str.
40 (IMA), 34132 Kassel, Germany
** Dept. of Technological Physics, Kassel University, Heinrich-Plett Str. 40
(IMA), 34132 Kassel, Germany
http://amsacta.cib.unibo.it/archive/00000143/01/GaAs_6_Joodaki.pdf
GaAs CTE (ppm/K) Temp ( K )
5.6 200
5.7 300
5.9 400
6.0 500
6.2 600
6.3 700
The CTE of BeO ceramics is approximately 9.0 from room temp to the same max
temp.
Aluminum Nitride ceramics (typically about 98% AlN) have about 2/3 the
thermal conductivity of BeO (typ. commercial grades of BeO may have therm
cond of about 275 W/mC) and have a CTE of about 4.5 - 5 in this same temp
range.
If you can tolerate an electrically conductive substrate for the die attach,
a Cu/Mo/Cu sandwich material can match GaAs almost perfectly and provide
very good thermal conductivity (244 W/mC for 20/60/20 Cu/Mo/Cu, with a CTE
of 6.3 from RT to 400C...data taken from ELCON).
Due to the large GaAs dimension and the fragility of GaAs this could be a
challenge. Having said that, we do GaAs die attach directly to Cu (CTE
about 16 - 17.8 for a -40/125C temp range)using Ag-epoxy all the time, but
the max GaAs dimension is generally 1 - 5 mm, but the thickness is often 100
um. Make sure dicing quality is very good, with very little chip outs, and
very small chip out dimensions, especially on the die surface edges that are
in tension, which will depend on your substrate of choice.
Have fun.
Best regards,
Leo
Director of Applications Engineering
ASAT, Inc.
3755 Capital of Texas Highway, Suite 100
Austin, Texas 78704
ph 512-383-4593
fx 512-383-1590
[log in to unmask]
www.asat.com
The information contained in this electronic message is CUSTOMER/SUPPLIER
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-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Sundog
Sent: Monday, August 29, 2005 12:34 PM
To: [log in to unmask]
Subject: [TN] GaAs and BeO Coefficient of Therma Expansion curve
Dear all,
Does anyone has a GaAs CTE curve (vs. temperature). I am trying to solder a
10mmx1mmx0.14mm GaAs die to a BeO substrate with AuSn solder. I am not
quite sure if there CTE is matched well enough.
Thanks
Sundog
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