DocumentCode :
984175
Title :
On short-time-scale stress wave phenomena and initiation of mechanical faults in flip-chip configurations
Author :
Nagaraj, Mahavir ; Suh, C. Steve
Author_Institution :
Dept. of Mech. Eng., Texas A&M Univ., College Station, TX, USA
Volume :
5
Issue :
2
fYear :
2005
fDate :
6/1/2005 12:00:00 AM
Firstpage :
224
Lastpage :
230
Abstract :
Small scale mechanical faults including microcracks and interfacial delaminations that compromise the integrity of solder balls and bimaterial adhesion are crucial issues impacting the reliability of flip-chip devices of small feature sizes. A small rise in junction temperature in a gigahertz flip-chip ball grid array (BGA) is found to initiate broadband, dispersive stress waves having a main frequency in the 200-800 MHz range. Numerical investigations incorporating a generalized thermoelasticity formulated to account for short-time-scale thermal-mechanical phenomena show that these waves, although fast-attenuating with the short presence of a few microseconds upon power-on, propagate in the bulk and along bonding interfaces with extreme time rate of change of stresses as high as 1011 Pascal/s (or 1011Watt/m3 in equivalent units). The high frequency and high power density associated with the propagating stress waves provide potent mechanisms for the formation of geometric singularities such as microcracks, small scale delaminations, and debond at short time scales (several microseconds). These singularities would eventually lead to mechanical detachment and ultimate electrical failure subject to the coefficient of thermal expansion (CTE) mismatch-induced stress state at operating temperature on a longer time scale (several minutes).
Keywords :
ball grid arrays; failure analysis; flip-chip devices; microcracks; reliability; 200 to 800 MHz; ball grid array; bimaterial adhesion; coefficient of thermal expansion; electrical failure; flip-chip; interfacial delaminations; mechanical faults; microcracks; reliability; stress wave phenomena; thermoelasticity; Adhesives; Bonding; Delamination; Dispersion; Electronics packaging; Frequency; Lead; Temperature distribution; Thermal stresses; Thermoelasticity; Device reliability; flip chip; short-time-scale effects; wave propagation;
fLanguage :
English
Journal_Title :
Device and Materials Reliability, IEEE Transactions on
Publisher :
ieee
ISSN :
1530-4388
Type :
jour
DOI :
10.1109/TDMR.2005.846828
Filename :
1458738
Link To Document :
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