Soldering to Gold A Practical Guide Solder （黄金一个实用指南的焊料焊接）.pdfVIP

Soldering to Gold- A Practical Guide by Ronald A. Bulwith Background/History Gold has always seemed to find a place in electronic applications because of the very versatile characteristics it possesses. Historically, it has been used as an etch resist, contact surface finish, protective coating, wire bondable surface finish, die attach surface, and solderable coating. It has been in the role of a solderable coating where some confusion and misconception has always existed. The misunderstandings have been with respect to the impact of Au on the soldering processes, along with the resultant effects on the properties of the solder connections created. In the past, the average thicknesses of applied Au deposits were much greater than those currently being applied. In most cases, this was specifically related to the particular application and plating solution. Some applications required harder, fine grained deposits where the use of codeposited hardening elements, grain refining additives, and brighteners were necessary. In these applications, smooth, shiny, thinner coatings were generally applied ( £30m -inches). These types of coatings were generally applied to contact surfaces and to areas requiring overall environmental protection. In other applications, Au deposits with either no additives, or low levels of additives, were required in order to attain the required properties for the specific application. The rougher, duller, matte finish of such Au deposits was found to be an advantage in direct die attach and wire bonding to devices utilizing leadframes in their construction. In situations such as these, the Au thicknesses were sometimes fairly substantial (30m - inches). In most of the aforementioned applications, very little consideration was given to the subsequent soldering operations to which these components would be subjected. As a consequence, these rel