A new evalaution method of adhesion between glass/epoxy composite substrate and copper foil for multilayer ircuit board applications

摘要

There have been several researches for characterization of the adhesion problems from the viewpoint of fracture mechanic,s such as underfill adhesion performance of area-array packages and rehabilitation of infrastructure with the use of FRP sheets (1-2). Adhesion stability of multilayer circuit boards has come an important issue in the electronic package industry. A typical multilayer construction consists of several layers of woven glass/epoxy composite substrate and copper foil. Pos-manufacturing processes with thermal shock such as solder masking, solder reflow and wave soldering cause several types of damage, which significantly affect on the performance of the package. One is macroscopic delamination at interfaces between the composite substrate and the coppr foil or at interlayer in the substrate. Another oen is microscopic fracture in the substrates such as measling and crazing (3-4). It is necessary for a new test method to enable to evalaute the macroscopic and microscopic damages at the same time. Conventional peeling test is suitable to measure the adhesion strength. However, is is impossible that the macroscopic and microscopic damages and/or the adhesion at substrate/copper interface in core-layer are estiamted. In this study, we propose Mode I interlaminar fracture toughness test as a new technique that is able to quantitatively measure the interfacial fracture energies of multilayer circuit board systems usign a fracture-mechanics approach. In order to relate a geometry of the copper foils to the fracture energies, effect of the copper foil style was characterized at first.