Patent ID: 7147927

Claim:
A biaxially oriented polyester film produced from a polyester comprising: (1) diacid residues comprising at least 90 mole percent of terephthalic acid residues, naphthalenedicarboylic acid residues or combinations thereof; and (2) diol residues comprising at least 90 mole percent of 1,4-cyclohexanedimethanol residues, wherein the polyester film is stretched at a ratio of about 2.5× to 3× in the machine direction (MD) and about 2.5× to 3× in the transverse direction (TD) at stretching temperatures between 90 and 110° C., wherein the stretched film is subsequently heat-set at an actual film temperature of from 260° C. to Tm, wherein Tm is the melting point of the polyester as measured by differential scanning calorimetry (DSC), while maintaining the dimensions of the stretched film, and wherein the biaxially oriented and heat-set polyester film undergoes not more than 3% shrinkage when immersed for 10 seconds in a solder bath preheated to 260° C. and exhibits a coefficient of thermal expansion value of 10–85 ppm/° C. when measured between 120 and 150° C., and a coefficient of thermal expansion value of 10–42 ppm/° C. when measured between 25 and 90° C.