HIGH TEMPERATURE DISCRETE POWER SEMICONDUCTOR PACKAGE WITH MOISTURE RESISTANCE FOR UNLIMITED FLOOR LIFE
Publication Date: 2016-Nov-17
The IP.com Prior Art Database
A technique to improve adhesion property of an adhesive used in a molding material to connect with a metal substrate within a power semiconductor die package is disclosed. During molding operation, material flows over a substrate, a power semiconductor die, and bond wires within the power semiconductor component. The substrate is usually composed of elements, such as, Cu, Ni, or Ag, among others. The bond wires are made up of Al or Au. Adhesion of a mold compound is directly related to package reliability, specifically in use-conditions or accelerated testing, where environment is one of a high temperature and/or high moisture. As a result, Moisture Sensitivity Level (MSL) rating of the package is improved, thereby, allowing package to sustain high temperature reflow process for solder attachment of a semiconductor component during circuit board assembly.
The present invention relates generally to a power semiconductor die assembly, and more particularly to a technique for improving adhesion property of an adhesive used in a molding material to connect with a metal substrate within a power semiconductor die package.
Generally, a molding compound has a tendency to separate from a power semiconductor die, lead frame, and wire-bonds. The separation can occur during assembly of the power semiconductor component during soldering into a system such as a printed circuit assembly. Meanwhile, the molding compound gains moisture from proximal environment. During high temperature assembly (such as soldering), the moisture is rapidly heated, thereby, increasing internal pressure in the power semiconductor die component. If the adhesion between the molding compound and bonded surfaces is less than the pressure build-up, a separation may occur.
A separation in power electronics may not cause immediate failure of a semiconductor component. However, the separation weakens reliability of the semiconductor component. One reliability issue is an air gap over a terminal of semiconductor die. For example, one property of the molding compound is to provide sufficient dielectric properties across terminations of the power semiconductor die to reduce occurrence of arcing. When an air gap is present, instead of molding material, the arc occurs at higher voltages, thereby, resulting in failure of the power semiconductor die. Another reliability issue occurs if moisture or other compounds of high ionic content accumulate in the air gap. In such condition, a path is provided for ionic movement across the terminals of the power semiconductor die. However, ionic movement across terminals of the power semiconductor die enables higher occurrence of arcing and subsequently failure of the power semiconductor die. Another reliability issue is the loss of electrical connection due to mold compound separation causing subsequent wire-bond separation from either the leadframe and/or die resulting in higher on resistance or lack of gate connection.
A conventional technique includes electrochemical process for depositing an adhesion promoter layer on an electrically conductive body. The electrically conductive body includes a metal and/or an alloy and/or a semiconductor and an adhesion promoter layer provided on at least one surface of the electrically conductive body. The adhesion promoter layer includes a metal, in particular zinc, and a porous, in particular plate-like and/or needle-shaped and/or sponge-like, surface structure. The adhesion promoter layer is deposited on at least one surface of the electrically conductive body. The adhesion promoter layer including the same substance as an anode, and the adhesion promoter layer is deposited by cathodic reduction of metal ions of the anode and/or cathodic reduction of...