(August 2, 2010) — Henkel has extended its Wafer Backside Coating (WBC) portfolio to also include a solution for stacked-die packages. Ablestik WBC-8901UV has been designed to address the demanding requirements of multiple die stack applications for the memory market segment, including packages such as TSOPs, MCPs and flash memory cards (FMCs).

The formulation of Ablestik WBC-8901UV offers a robust and cost-effective alternative to current film-based solutions for die stacking processes, reducing the total cost of ownership as compared to film by as much as 30% to 50%, according to Henkel. Process flexibility is also enhanced with Ablestik WBC-8901UV, as packaging specialists can now adjust die attach thickness based on specific manufacturing requirements and can also select their dicing tape of choice. Film die attach materials are generally supplied in pre-determined thicknesses as a bundled product that incorporates the dicing tape.

Applied via a spray coating method following the wafer thinning process, Ablestik WBC-8901UV is precisely deposited across the back of the silicon wafer, following which the material is B-staged using a UV irradiation process. After this step, dicing tape is laminated to the wafer, backgrinding tape is removed and the wafer is diced in preparation for die pick-up and placement. Henkel is currently partnering with spray technology and backgrinding equipment manufacturers to deliver an integrated, in-line process solution for this unique WBC advance. 

Traditional deposition methods have challenged WBC for applications that dictate ultra-thin wafers (less than 75µm) and coating thicknesses of 10µm or less. Screen and stencil printing, while viable on thicker wafers, may not be able to accommodate today’s ultra thin wafers and material uniformity may be impacted by screen mesh marks or the “scooping” effect that comes from squeegee traverse. Historically, spin coating resulted in material waste of 70% or greater, which negated the material cost savings. Ablestik WBC-8901UV and new spray coating technology have resolved these issues, delivering a precise wafer coating as thin as 10µm with a total thickness variation across the wafer of ±10% and remarkably low material waste of less than 20%. Wafers as thin as 50µm have been successfully processed using this method.

In 2011, Henkel expects to be able to achieve 5µm coating thicknesses or better with further development of Ablestik WBC-8901UV.

For more information, log onto www.henkel.com/electronics