| 摘要 |
PROBLEM TO BE SOLVED: To provide a cover-lay film which prevents an electrical insulating film from shrinking when stripping a mold-release material from the electrical insulating film at mounting of a flexible printed wiring board and improves the mounting workability and therefore improves the productivity of a flexible printed wiring board. SOLUTION: A cover-lay film comprises a mold-release material/a heat- resistant adhesive/an electrical insulating film, wherein an electrical insulating film having an elastic modulus F [kgf/mm2] of 100<=F<=1,000 and a mold-release material having an elastic modulus R [kgf/mm2] of 50<=R<=500, are used. Here, the tension Tf [kgf/mm2] of the electrical insulating film when attaching the electrical insulating film having a heat-resistant adhesive to the mold-release material, and the tension Tr [kgf/mm2] of the mold-release material are 0.1<=Tf, Tr<=2.0, and the elastic moduli F, R and tensions Tf, Tr satisfy the formula: 0.5<=Tr.F/(Tf.R)<=3.0.
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