Dai-ichi Kogyo Seiyaku Co., Ltd.

Takuji Nakano

Takeshi Fujita

Akira Taniuchi

Chuzo Isoda

Setsuo Nishibori

Katsuaki Matsuo

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.

Method for drilling thru-holes on a lamination substrate and a sheet

Hexabromocyclododecane may be synthesized at a high yield in pure form by brominating 1,5,9-cyclododecatriene with bromine in a C.sub.4 -C.sub.8 saturated aliphatic alcohol in the presence of a boron trifluoride complex, neutralizing the reaction mixture with a non-aqueous base, and recovering the resulting crystals of hexabromocyclododecane.

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Kusatsu, Japan

Takuji Nakano