Two polymeric coatings, a silicone gel (Dow Corning 6646) and an epoxy resin (Dexter FP 4402), were glob-top coated onto representative microelectronic circuits, AT&T Triple Track Testers (TTTs), and subjected to the Pressure Cooker Test (PCT). Coupling monolayers were self-assembled on the TTTs prior to encapsulation to improve the moisture protection capabilities of the coatings. Leakage current measurements were made to evaluate the effect of applied monolayers on the moisture protection capability. The moisture protection capability was assessed in short-term and long-term leakage current measurements. MHDA (16-mercaptohexadecanoic acid) and APS (gamma-aminopropyltriethoxysilane) monolayers, in combination with silicone gel and epoxy resin respectively, exhibited very good moisture protection performance.
The goal of the Reliability without Hermeticity (RwoH) Project is to find non-hermetic coatings for use on MCMs. As a means of down-selecting coating materials, Sandia ATCOI test chips in 40 pin DIPS were coated with non-hermetic, polymer materials, including silicone gel, filled epoxy, and polyimide. After preconditioning through temperature cycling and salt atmosphere, the parts were subjected to one of three different temperature, humidity, and bias conditions: HAST (140"C, 85% RH, +40V), 85/85 (85'C, 85% RH, +40V), or PCT (121"C, 99.6% RH). No universal relationship between lifetime in HAST and 85/85 testing was observed-the effects appear to be material dependent. Electrical test data suggest that failures on coated parts (with standard SiN chip passivation) do not occur on die circuitry (triple tracks) and instead occur on bond-wires and bond-pads.
This paper focuses on mechanical testing designed to determine the static failure envelope for a conductive adhesive. Samples were made by bonding copper pegs together with the conductive adhesive. The samples were then tested at various loading conditions including tension, tension shear, and compression shear. Results were analyzed in order to check for correlations between the data and the testing procedures. The statistical distribution of the data was also analyzed. Furthermore, a finite element model of the test sample was constructed and used to verify the assumptions made with respect to the interpretation of the data. The data from various loading conditions was then used to construct the static failure envelope of the material. A modified Coulomb–Mohr failure criterion was used to model the failure envelope of the conductive adhesive. This criterion contains four material constants to be determined experimentally. Once these parameters are determined, a failure envelope can be easily constructed. The envelope can then be used to predict failure at any combination of shear and normal stresses. The test results showed that the empirical data are well characterized by the modified Coulomb–Mohr failure envelope.
A set of processes has been developed and demonstrated to interconnect flip chips with an electrically conductive adhesive material to laminates. Paste deposition uses a photolithography process to define room temperature stable thermoplastic, conductive adhesive bumps that are 0.2 mm in dameter and 0.
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