Process for depositing silver epoxy delivers higher throughput

DEK International announced that it has successfully developed processes for depositing silver epoxy and B-stage adhesives for die attach applications, promising higher throughput and repeatability as well as enhanced control over deposit characteristics, including total thickness variation (TTV) compared to existing solutions.

According to the press release, DEK's process for B-stage epoxy deposition allows application of die attach adhesive at the wafer level, at high rates of throughput. This streamlines package assembly and allows OEMs to outsource this process to a wafer specialist, if required, said the company. DEK's B-stage epoxy deposition process is capable of depositing a part-cured adhesive layer of nominal thickness 50?m, with TTV less than ±5?m, across the entire back-side of the wafer. DEK added that traditional wafer coating methods cannot match this combination of uniformity, repeatability and high throughput.

For attaching singulated die to a lead-frame or bond pad, DEK's new mass imaging process replaces dispensing as the means of depositing silver-loaded wet epoxy ahead of die attach. The company explained that many hundreds of deposits can be made simultaneously, which for the first time enables epoxy deposition to match the speed of die placement. Die placement rates are now moving beyond 40,000 units per hour, leveraging SMT pick and place technology.

In addition, DEK's mass imaging process for wet epoxy also provides greater control over the volume and shape of the deposit, by optimizing the stencil aperture. During the development of the process, DEK engineers identified a star-shaped epoxy deposit as the optimum shape for effective die attach without producing an excessive fillet, which may contaminate the die surface. Large numbers of star-shaped deposits can be created simultaneously using screen printing. And using a dispenser, a sequence of several dispense operations would be necessary to create each deposit, which is slower and less repeatable, said DEK.

"Mass imaging delivers the throughput, uniformity and repeatability that commercial producers of advanced semiconductor packages need in order to economically meet market demands for quality and price," said Clive Ashmore, global applied process engineer at DEK. "For die attach using B-stage or wet epoxy adhesives, our mass imaging processes outgun legacy techniques in every respect, to deliver a more highly optimized, faster, more repeatable and more cost-effective solution."