プリント基板の微細穴加工技術に関する研究: 樹脂付きエントリーシートによる穴位置精度と穴壁面粗さの改善

摘要

近年，スマートフォンやタブレット端末等の情報通信機器の普及にともない，電化製品の多機能化•小型化が進んでいる.これら電化製品に搭載されるプリント基板（PCB）には，平面配線と立体配線が形成されるが，後者は一般的に導通穴（スルーホール）が用いられている.プリント基板の高密度化，微細化を実現するために，導通穴加工の品質向上が不可欠である.生産性向上を目的にプリント基板を複数枚重ねて同時に加工する導通穴は，直径0.1mm～0.3mmでL/D=10～20と極小径深穴である.また，プリント基板の材料はガラスクロス，シリカ，樹脂，銅箔等を含んだ複合材料である.これらのさまざまな要因により，切りくず排出不良，ドリルの曲がり，切削温度上昇等が生じることでドリル折損や穴位置精度•穴壁面粗さの悪化につながる.%The smaller through holes of printed circuit boards (PCBs) are required for the multifunctional information communication devices. This paper describes some experiments on the effect of entry sheet (E/S) on the micro drilling quality of PCB. Especially the effect of the resin painted on E/S on the micro drilling quality was investigated. The effect was examined by performing the micro drilling tests of PCB using the aluminum E/S and the resin painted aluminum E/S. Resin films used were the polyethylene-glycol (PEG) based film and the wax-based film. The effect of the E/S on the position error of hole center was determined by measuring the centripetal action with the non-contact displacement sensor. The effect of the E/S on the hole wall roughness was also determined by examining the relationship between the drill temperature decrease during drilling due to the use of E/S and the adhesion of resin film to the drill. From these experiments, the followings were obtained:(1)On the position error of hole center, the wax-based film is better than the PEG-based film. (2) On the hole wall roughness, the PEG-based film is better than the wax-based film.