Gem Services, Inc.

Mohammad Eslamy

Anthony C Tsui

Ming Zhou

Anthony Chia

Hongbo Yang

Jian Xu

Embodiments in accordance with the present invention relate to techniques which avoid the problems of deformation in the shape of a solder connection in a flip chip package, resulting from solder reflow. In one embodiment, a solder-repellent surface is created adjacent to the solder to constrain the reflow and thereby maintain the vertical profile of the solder. Examples of such a solder-repellent surface include an oxide (such as Brown Oxide) of the lead frame, or a tape (such as Kapton) which is used as a dam bar to control/constrain the solder flow on the leads prior to the encapsulation step. In another embodiment, the solder connection may be formed from at least two components. The first component may reflow at high temperatures to provide the necessary adhesion between solder ball and the die, with the second component reflowing at a lower temperature to provide the necessary adhesion between the solder ball and the leads. An example of such multi-component connections include a first high temperature reflow solder ball paired with a second low temperature reflow solder. Another example includes a solder ball with a hard core (such as Cu, stainless steel, or a plastic material stable at high temperatures) coated with a lower temperature reflow material.

Interconnection of lead frame to die utilizing flip chip process

Embodiments of the present invention relate to the use of stamping to form features on a lead frame of a semiconductor device package. In one embodiment, portions of the lead frame such as pins are moved out of the horizontal plane of a diepad by stamping. In certain embodiments, indentations or a complex cross-sectional profile, such as chamfered, may be imparted to portions of the pins and/or diepad by stamping. The complexity offered by such a stamped cross-sectional profile serves to enhance mechanical interlocking of the lead frame within the plastic molding of the package body. Other techniques such as selective electroplating and/or formation of a brown oxide guard band to limit spreading of adhesive material during die attach, may be employed alone or in combination to facilitate fabrication of a package having such stamped features.

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Palo Alto, CA, United States of America

Mohammad Eslamy