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#37- Wire Bond Comparison of Different Aluminum Alloys and Thicknesses


Abstract: As manufacturing of electronic components for the automotive industry becomes increasingly global, variations in material selection on different continents raise questions regarding compatibility to meet performance requirements.

Wire Bond Comparison of Different Aluminum Alloys

This Materion Technical Materials paper compares wire bondability of two aluminum alloys commonly used in leadframe material systems for hybrid applications. The two aluminum alloys used are A91145 and AlSi1 which are the standard materials, used for years as the bonding pads for automotive leadframes, for the US and European markets, respectively. These two alloys are similar in chemistry containing 99.0% minimum aluminum, with the main difference being impurity levels which can affect hardness. These alloys will be studied using different inlay thicknesses and also different leadframe base metal variations. These alloys will then be wire bonded using standard machine settings and a range of typical wire diameters. Wire bonds will be subjected to standard pull testing, shear testing and visual inspection to determine if differences in aluminum alloy, hardness or thickness and leadframe base metal selection effect wire bond quality.

All the samples used in this study are from production products and are being used in a variety of sensors and power modules.The metal combinations being evaluated are aluminum alloy A91145 inlaid into C19400 (U.S. standard) and aluminum AlSi1 inlayed into C51900 (European standard). The material properties for these four alloys will be shown and discussed in detail.

Elements Evaluated in the Study

AlSi1 thickness to be evaluated is 10 – 30um (0.0004” - .0012”). A91145 aluminum will be evaluated in three thicknesses, 0.0004 – 0.0012”, 0.002” and 0.005” minimum. The wire used in all the tests will be grade 99.99% aluminum supplied by SPM. The three wire diameters used for bonding will be .006”, .010” and .015” and wire bonding will be done using an Orthodyne Electronics Model 3600Plus Wire Bonder utilizing standard default settings. Orthodyne Electronics will do the pull and shear testing and characterize the initial bond nugget quality and grade the bonds. Materion Technical Materials will do the metallurgical examinations of the wire bonds to better understand any differences that may exist within the tested material systems.