Frank Djennas

Investigation of plasma effects on plastic packages delamination and cracking

This paper investigates the use of a non-reactive plasma formed in a radio frequency discharge as a treatment to various substrates to reduce or eliminate the organic and inorganic contamination which prevents intimate interfacial contact. Argon was investigated as the plasma gas. The effect of time, chamber pressure, and power were studied. A goniometer was utilized to measure wetting contact angles as a quantitative measure of the cleaning effectiveness of the surface treatment. ESCA (electron spectroscopy for chemical analysis) data are correlated to substrate hydrophilicity, delamination and package cracking. The results show the argon plasma treatment to be an effective mean of reducing interfacial organic and inorganic contamination and improving the polyimide to mold compound adhesion. The improvement in package cracking performance brought about the argon plasma treatment is significant. >

Thin QFP design and development

The challenges presented by the low profile thin quad flat packages (TQFPs) are the design of the mold, control of the assembly operations of wire bonding and molding, moisture performance characteristics, and thermal and mechanical performance. The authors describe the design, modeling for manufacturability, and characterization of a TQFP. The design issues of the TQFP include package symmetry, die thickness, and wire bond loop height. Thermal, mechanical, and electrical modeling results are presented. The assembly process characterization and material selection are discussed. The package performance testing includes moisture weight gain studies, moist package cracking (popcorn) and delamination evaluation, temperature cycle, thermal shock, and autoclave. It is apparent from the moisture preconditioning data that care must be taken to keep the packages in a humidity-controlled environment. A preconditioning bake of 125 degrees C for 8 h hours should be mandatory if packages are exposed to a high humidity environment for a long time period. However, it is clear that when preconditioned appropriately, the TQFP package should have a reliability performance comparable to that of a standard QFP package.<<ETX>>

A novel, lower cost, thermally enhanced exposed silicon plastic package (ESPP)

The plastic Quad Flat Package has evolved into a large, high pin count package, however higher reliability and thermal dissipation requirements constitute the boundary conditions it must overcome to evolve as a viable high density package. The present mold compounds used as encapsulants have poor thermal conductivities and represent a large portion of the thermal resistance in the plastic package. Existing thermally enhanced plastic packages are prone to delamination, and higher costs. A new plastic package is proposed herein that achieves a new level of reliability and performance, all at a cost lower than the standard plastic package. The ESPP package integrity is analyzed and compared to other thermally enhanced packages. Thermal performance is measured and compared to other packages.<<ETX>>