WAFER-BUMPING STENCILS MAINTAIN ACCURACY ON 300MM FORMAT

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WAFER-BUMPING STENCILS MAINTAIN ACCURACY ON 300MM FORMAT
06 June 2003 - Tecan

In addition to the supply of standard wafer-bumping stencils, proven specialist Tecan is now producing stencils in the next-generation large format, of 300mm x 300mm (12in x 12in), while maintaining close tolerance and high resolution across the whole image. The ultra-accurate stencils are produced by electroforming, resulting in mirror-finish aperture walls, which ensure optimum solder paste release characteristics when depositing solder paste directly onto silicon wafer die.

The wafer-bumping stencils, or masks, cater for the increasingly high component densities and finer pitches associated with components such as chip-scale packages, micro ball-grid arrays (uBGAs) and flip-chip designs. For example, a typical stencil for a multi-die 150mm (six-inch) wafer may require 300,000 apertures, or over 500,000 for a 200mm (eight-inch) wafer. The 300mm x 300mm images may typically have in excess of two million apertures and hole diameters of 60 to 125 microns, in a 50 micron thick stencil.

For present-day and next-generation applications, the high-tolerance stencils allow users to significantly reduce defects and re-work while maximising the available yield from a given wafer, providing optimum results.

The company produces highly accurate mirror finish stencils which have apertures with exceptionally smooth side walls and a trapezoidal cross-section. Apertures of the dimensions highlighted are optimised using a combination of shape, with radiussed squares offering the best ratio of aperture base to wall. Refinements such as these ensure optimum paste release characteristics, for the finer ball pastes used in wafer-bumping, significantly improving the consistency of solder paste volume and regularity.

Process control is a fundamental element in the success of CSP, BGA and similar packaging. The adoption of Tecan electroformed stencils provides the ability to tightly control each assembly process to ensure repeatable high yields. The technology represents a significant step forward in the reduction of production costs for such increasingly miniaturised silicon substrate electronics components.

The following CAD formats are accepted, Gerber (RS274X), GWK, DPF and HPGL. All parts are produced within the company's strict ISO9002 quality-control regime.

http://www.tecan.co.uk

About: Tecan
Tecan is a world-class, ISO 9001:2000 registered precision metal part and tool manufacturer, based in Weymouth, UK. Formed in 1970, Tecan offers the 'total' one-stop contract-manufacturing solution - from technology development through to rapid prototyping and volume production.

Tecan's team of experienced engineers work closely with the customer to develop manufacturing solutions to meet their exact cost and tolerance requirements. Years of process development have culminated in Tecan being able to cost-effectively manufacture metal parts with feature sizes down to 2-micron at sub-micron accuracy - and to put that into perspective, there are 1,000-microns to one millimetre.

Technological innovation and expertise form the basis of Tecan's success, and have provided the platform for the development of competences in several process technologies, including:

• Photo Chemical Machining (PCM)
• Photo ElectroForming (PEF)
• Precision photolithography
• Precision electroplating

Tecan works on a global basis with a diverse range of OEM customers, who are involved in a wide array of industries. The nature of Tecan's competences, combined with its commitment to R&D, allows it to stretch to meet the requirements of virtually any application.

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  • For June 2003
  • From Tecan
  • For Photochemical Machining (PCM)