Mask and mask-less injection molded solder (IMS) technology for fine pitch substrate bumping

摘要

We report the results of a new pre-solder bumping technology of injection molded solder (IMS) for fine pitch organic substrates. Pure molten solder is injected through a reusable film mask (mask IMS) or directly injected without a mask (mask-less IMS) on the pads of an organic substrate to overcome the limitation of current pre-solder bumping technologies such as solder paste stencil printing and micro-ball mounting. In the case of mask IMS, targeted solder height over the solder resist (SR) is designed into the mask which has desirable thickness and hole sizes. Three different solder bump heights such as 30, 50, and 70 microns over SR were demonstrated for commercial organic substrates which have a pitch of 150μm for 5,000 area array pads. To show the extendibility of the mask IMS bumping method to very fine pitch applications, 100μm pitch bumping of 10,000 pads and 80μm pitch bumping of 15,000 pads were demonstrated.