高密度印制电路板用铜箔的新型处理技术

New copper surface treatment technology for high density printed wiring board

在新一代电子产品中应用的系统封装(SIP),是将几片大规模集成电路芯片安装在一块高密度布线的印制电路板上,这种印制电路板的线条在20μm以下。作为这种印制电路板基材的关键技术有这样几个方面:为适应高速信号的传输所用低介电常数绝缘层的开发;确保绝缘层与导线的良好粘接以及导线表面粗糙度的降低等。该公司在印制电路用铜箔处理技术方面有一定的优势,例如能处理数十nm水平的粗糙度均匀的铜箔表面;在此基础上开发成功了与低介电常数树脂基材有着良好粘接性的新型铜箔表面处理技术。这种方法主要是在原来的氧化还原处理之前进行一次贵金属处理。表面的粗糙度可达到原来处理的1/10以下,而抗剥强度仍保持在0.6kN/m以上;而且,此项技术也适用于10μm以下线条的印制电路板。得出的板材在85℃,85%相对湿度,DC5V的条件下,1000小时后绝缘性能无异常变化,绝缘可靠性能优异。此项技术今后有望成为高密度印制电路板制造的重要技术保证。

System in packages, which consist of several LSI chips mounted on a printed wiring board（PWB） that uses wiring of a pitch less than 20 μm, are now being proposed for the next generation electronic equipment. Such PWB will be constructed using low permittivity insulator and flat-surface copper wiring, because the copper wiring transfers high frequency signals. One of the challenges for elemental technologies in making such PWB is to ensure the adhesion between the copper surface and low permittivity resin. We have developed a new copper surface treatment method that changes the flat surface into a uniformly rough surface having a level profile of a few dozen nm.to enhance the adhesion at the interface. This method involves processing noble metal prior to the oxidation and reduction processes used in the conventional copper surface treatment. This method will reduce the surface roughness to less than 1/10 that of the conventional method, the peel strength will be more than 0.6kN/m. Moreover, PWBs made by this method with 10 μm pitch wiring showed satisfactory insulation reliability with adequately high humidity test （no failure after 85 ℃,85%,5 dcv,1000h）. We hope that this method will become a elemental technology for making high density PWBs in future.