Polyimide substrate bonded to other substrate

US8107777B2 · kind B2 · utility

Inventor

• John Farah · Attleboro, US

Key dates

• Filing date: Apr 2, 2009
• Grant date: Jan 31, 2012
• Expiry date: Mar 21, 2030

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T428/265
• WIPO field: Optics
• WIPO sector: Instruments

Abstract

Polyimide substrates are bonded to germanium wafers having an epitaxially grown III-V layer and a metal layer. The polyimide substrate and the Ge, wafer are subsequently thinned by grinding and etching to reach a final thickness of 25 μms Ge on 25 μms adhesive layer on 50 μms polyimide substrate. The choice of adhesive is of paramount importance. There are several requirements for the adhesive layer to act as a permanent carrier of the thin fragile multi junction solar cell. The adhesive must remain flexible after curing and have a low CTE. The use of an adhesive that cures without the addition of heat, preferably at room temperature. Furthermore, the adhesive layer has a uniform thickness preferably less than 25 ums (1 mil) and be void-free. A clear adhesive which does not contain any particles in order to obtain a smooth uniform void-free bond line. However, clear adhesives have CTE's that are larger than 80 ppm/°C. and which can be as high as 200 ppm/°C. or more above the glass transition temperature.