Investigating thiol-epoxy composites for semiconductor die attach adhesives
- PDF / 291,461 Bytes
- 5 Pages / 432 x 648 pts Page_size
- 60 Downloads / 211 Views
Investigating thiol-epoxy composites for semiconductor die attach adhesives Andrew Wei,1 Radu Reit,2 and Walter Voit3 1 Department of Electrical Engineering, University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX 75080, U.S.A. 2 Department of Bioengineering, University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX 75080, U.S.A. 3 Department of Materials Science and Engineering, University of Texas at Dallas, 800 W. Campbell Rd., Richardson, TX 75080, U.S.A. ABSTRACT In this study, thiol-epoxy polymer composites are explored as candidates for hightemperature die attach applications. We present a polymer composite processing technique for die attach adhesives with low cure-stress. Lap shear samples of both a polymer adhesive and current industry adhesives were subjected to tensile testing and die shear strength was compared. At 260 °C, the candidate polymer adhesive exhibited a die shear strength of 0.500 MPa in comparison with 1.35 MPa and 0.258 MPa for two control adhesives. While samples showed less variation in properties in die shear strength between room temperature and 260 °C, the absolute die shear strength values were inferior to commercial adhesives at both room and elevated temperatures. We hypothesize that low cure stress networks, such as the thiol-epoxies presented, provide a compelling choice to engineer new die attach adhesives, but realize that further network refining is needed including the addition of adhesion promoters and other additives, a task better suited to industrial research with a focus in properties optimization. INTRODUCTION A critical processing step in modern integrated circuit packaging is the adhesion of semiconductor dies onto supporting metal leadframes prior to encapsulation. However, in hightemperature thermal cycling environments, a coefficient of thermal expansion mismatch between the die, leadframe, and adhesive can lead to device failure through delamination of the adhesive at the interface [1]. Thiol-epoxy polymer systems, which can be engineered to experience a significant drop in elastic modulus when subjected to temperatures above their glass transition temperatures (Tg), would help accommodate these thermal stresses. In addition, the strong affinity between the thiol functional groups and a surface gold coating on the leadframes was hypothesized to increase the die shear strength of samples incorporating the polymer adhesive [2]. In this study, thiol-epoxy composite adhesives were synthesized and subjected to lap shear testing. The demonstrated die shear strength was used as a metric for adhesive reliability. Differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) were also used to characterize the thermomechanical properties of the adhesives, followed by morphological characterization of the bond line and wirebonded dies via scanning electron microscopy (SEM) and optical microscopy, respectively.
27
EXPERIMENTAL METHODS Samples of current industry adhesives and nickel–palladium–gold (NiPdAu) leadframes were procured from Te
Data Loading...
