六层刚挠结合板通孔等离子清洗研究

Plasma Desmear Research of through Hole in Six-layer Rigid-flex Printed Circuit Board

六层刚挠结合板由于其通孔线路层数多,深径比大,在等离子清洗时总是出现层间清洗不均匀,孔壁过于粗糙,玻璃布处清洗过量等问题。本文通过研究等离子在孔内的渗透能力与不同气体含量之间的关系确定等离子清洗的总体含量,并研究不同的CF_4:O_2比例对等离子层间均匀性,玻璃布处清洗程度影响,最终确定六层刚挠结合板的等离子清洗的参数。清洗后的通孔经孔金属化后,可靠性高,经过两次热冲击(280℃,10秒)后孔壁依然良好。

In six-layer rigid-flex board,there are high conductive layers and through holes with high ratio of depth to diameter.In plasma desmear process,hole wall problems such as nonuniform desmear in different layers,excessive roughness and excessive desmear in glass cloth part are usually appeared.In this paper,the relation between penetration and various total plasma gas amounts was obtained to determine desmear gas amount.The ratio influences of CF_4:O_2 to the uniformity of different layers and excessive desmear in glass cloth part were also researched.With the results above,plasma parameters for six-layer through hole were determined.After plated,the through hole expressed high reliability,even after two thermal shock tests(280℃,10secs) with that plasma parameters.