Variable Frequency Microwave Processing of Underfill Encapsulants for Flip-Chip Applications

2003 ◽  
Vol 125 (2) ◽  
pp. 302-307 ◽  
Author(s):  
Patricia F. Mead ◽  
Aravind Ramamoorthy ◽  
Shapna Pal ◽  
Z. Fathi ◽  
I. Ahmad
Keyword(s):  
Flip Chip ◽  
Microwave Processing ◽  
Variable Frequency ◽  
Particle Settling ◽  
Convection Oven ◽  
Innovative Technique ◽  
Cure Time ◽  
Underfill Encapsulant ◽  
Rapid Cure

This paper discusses an innovative technique for rapid cure of polymeric encapsulants such as underfills used in direct chip attach devices using variable frequency microwaves (VFM). VFM processing reduces the cure time for underfill encapsulants to 10 min or less, as compared to 30 or more minutes when using convection oven methods. We report here the results of our investigations measuring key material attributes of VFM and conventionally cured underfill encapsulant samples, and we also have characterized voiding and delamination characteristics of flip-chip with underfill test structures. Finally, particle settling in the flip-chip with underfill test structures has been characterized. Our results show that the VFM technique produces underfill attributes that are comparable to conventionally cured samples.

Investigation of Variable Frequency Microwave Processing for Electronic Packaging Applications

2003 ◽  
Vol 125 (2) ◽  
pp. 294-301 ◽  
Author(s):  
Patricia F. Mead ◽  
Aravind Ramamoorthy ◽  
Shapna Pal
Keyword(s):  
Electronic Packaging ◽  
Flip Chip ◽  
Failure Modes ◽  
Electronic Devices ◽  
Electrical Performance ◽  
Variable Frequency ◽  
Operating Parameters ◽  
Radiation Stress ◽  
Convection Oven ◽  
Electrical Degradation

This paper summarizes the effects of the variable frequency microwave (VFM) technique for rapid cure of polymeric encapsulants (such as flip-chip underfills) on the performance and reliability of electronic devices. Initial electrical performance of selected commercial IC packages following the application of VFM radiation stress has been recorded, and the performance has been compared to packages that were treated with comparable temperature cycles as applied in a convection oven. Failure analysis was performed on packages that showed electrical degradation to identify likely degradation and failure modes of the packaged ICs. Overall, our results show that VFM technology can safely be applied as an electronic packaging technology. However, proper control of VFM operating parameters is needed to ensure favorable performance of electronic devices.

scholarly journals Adhesive Bonding Via Exposure to Variable Frequency Microwave Radiation

1996 ◽  
Vol 430 ◽  
Author(s):  
Felix L. Paulauskas ◽  
April D. McMillan ◽  
C. David Warren
Keyword(s):  
Microwave Radiation ◽  
Adhesive Bonding ◽  
Microwave Processing ◽  
Input Power ◽  
Epoxy Adhesive ◽  
Single Frequency ◽  
Homogeneous Distribution ◽  
Variable Frequency ◽  
Slight Reduction ◽  
Cure Time

AbstractAdhesive bonding through the application of variable frequency microwave (VFM) radiation has been evaluated as an alternative curing method for joining composite materials. The studies showed that the required cure time of a thermosetting epoxy adhesive is substantially reduced by the use of VFM when compared to conventional (thermal) curing methods. Variable frequency microwave processing appeared to yield a slight reduction in the required adhesive cure time when compared to processing by the application of single frequency microwave radiation. In contrast to the single frequency processing, the variable frequency methodology does not readily produce localized overheating (burnt or brown spots) in the adhesive or the composite. This makes handling and location of the sample in the microwave oven less critical for producing high quality bonds and allows for a more homogeneous distribution of the cure energy. Variable frequency microwave processing is a valuable alternative method for rapidly curing thermoset adhesives at low input power levels.

Interactions between Variable Frequency Microwave Underfill Processing and High Performance Packaging Materials

2013 ◽  
Vol 2013 (1) ◽  
pp. 000461-000466 ◽  
Author(s):  
Mamadou Diobet Diop ◽  
Marie-Claude Paquet ◽  
Dominique Drouin ◽  
David Danovitch
Keyword(s):  
High Performance ◽  
Flip Chip ◽  
Coefficient Of Thermal Expansion ◽  
Curing Temperature ◽  
Variable Frequency ◽  
Asymmetric Distribution ◽  
Unexpected Result ◽  
Scanning Calorimetry ◽  
Negative Effect ◽  
Curing Methods

Variable frequency microwave (VFM) has been recently proposed as an alternative underfill curing method that provides flip chip package warpage improvement as well as potential underfill cure time reductions. The current paper outlines how such advantages in VFM processing of underfill can be compromised when applied to high performance organic packages. VFM recipes for three underfill materials were developed by performing several VFM curing runs followed by curing rate measurements using the differential scanning calorimetry method. The VFM curing rate was seen to strongly dependent upon the underfill chemistry. By testing flip chip parts that comprised large and high-end substrates, we showed that the underfill material has negligible impact on VFM warpage with the major cause attributed to the coefficient of thermal expansion mismatch between the die and the substrate. Comparison between the convection and the VFM methods indicated two warpage tendencies that depended upon the VFM curing temperature. First, when both curing methods used comparably high temperatures, warpage increases up to about + 20% were found with VFM. This unexpected result was explained by the high-density Cu loading of the substrate which systematically carried heat generated by VFM energy from the die/underfill system to the substrate. Since this high-end substrate consists of sequential dielectric/Cu layers with asymmetric distribution of Cu, additional stresses due to local CTE mismatches between the Cu and the dielectric layers were induced within the substrate processed with VFM. Second, warpage reductions down to about − 22% were obtained at the VFM curing temperature of 110°C with a curing time similar to that of convection cure. This suggests that the negative effect of the local CTE mismatches were no longer at play at the lower VFM temperatures and that the significantly lower final cure temperatures produced lower total shrinkage of the die and the substrate. Finally, due to lower elastic moduli, the cured VFM parts showed better mechanical reliability with no fails up to 1500 cycles.

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