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DEK has developed a next-generation equipment and tooling package that enables the coating of wafers with ultra-thin die attach materials down to 25 microns in thickness. The solution, called DirEKt Coat™, consists of a Micron-class Galaxy mass imaging system, a DEK engineered ultra-flat pallet, a die attach stencil or screen and a specially designed squeegee.
Traditional dispensing methods and paste die attach processes have manufacturing challenges such as the inability to achieve emerging UPH (units per hour) requirements, limitations on chip footprint (due to chip fillet formation and resin bleed) and inherent quality and reliability issues that result from insufficient or uneven adhesive coverage. DEK’s DirEKt Coat™ effectively eliminates these issues, allowing the high-speed, high-accuracy uniform deposition of die attach materials as thin as 25 microns with tolerances of +/- 7 microns using a printing process.
The backside wafer coating process developed by DEK enables ultra-thin, precise deposits of die attach adhesive at high speed with a highly-accurate and flexible screen printing platform. With this method, bondline thickness can be controlled to customer specifications, fillet control is consistent with that of traditional film products without the 20-30% higher cost, UPH is exponentially higher than that of dispensing and additionally, the coated wafer can be pre-manufactured and stored until required. The key enablers that allow the deposition of an ultra-thin, 25 micron coating are the ultra-flat pallet that provides the stability and uniformity required to process wafers as thin as
100 microns and up to 300mm in diameter, and the specially engineered squeegee that delicately applies the adhesive paste to the backside of the wafer.
Other significant advantages to the DirEKt Coat™ process include the elimination of the fillet and subsequent reduction of paste adhesive volume (potentially by a factor of ten on die less than 0.5 x 0.5 mm), improved inventory control by concentrating the application of wet adhesive in the facility’s dedicated print area and streamlining the supply chain by requiring only one paste formulation for various process needs as opposed to the multiple thicknesses and widths necessary with films. Not only is DEK’s DirEKt Coat™ delivering advances in die attach material applications, but can be used for all wafer-level coating processes including epoxy and wafer-level protective backside coatings as well.
Additionally, because the process is run on a flexible mass imaging platform, the system can be easily re-deployed for other packaging applications such as wafer bumping, DirEKt Ball Placement™, thermal interface material (TIM) processing and encapsulation.
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