Armstrong, Westerman, Hattori, McLeland & Naughton
Method for drilling thru-holes on a lamination substrate and a sheet used therein
 First of all, a high molecular sheet comprising a composite whose principal component is a special water soluble high molecular compound, or a multilayer sheet wherein a water soluble high molecular layer is piled on sheet material is prepared. Then, said sheet is layered on the entry side of a lamination substrate comprising insulating material and metallic foil. In this state, thru-holes are formed in the lamination substrate through said sheet. When forming thru-holes, said water soluble high molecular compound serves as a lubricant so as to extend drill life. In addition, it is possible to drill a lot of substrates, which are layered, at one time, resulting in the improvement of production efficiency. 
Dai-Ichi Kogyo Seiyaku Co., Ltd.
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Katsuaki Chuzo Takeshi Takuji
Matsuo Isoda Fujita Nakano