Adhesion evaluation of adhesiveless metal/polyimide substrate for MCM and high density packaging
Directly metallized polyimide films are being widely used as advanced high-density packaging substrates. Adhesion of metal to polyimide is a key performance requirement of the film. Excellent initial adhesion and good retention after severe process steps and reliability stresses are required. In this paper, the adhesion performances of films with different types of polyimide and tie layer from multiple vendors have been evaluated. The interface failure mechanisms are also examined via SEM micrographs and XPS survey scans. Peel strength and its retention behaviour are characterized in term of tie layer materials, environmental stresses and surface analysis results. The object of this work is to select the proper base material for high-density flexible multilayer substrates, a technology which is under development by FCPT.
Moisture‐induced interfacial oxidation of chromium on polyimide
Interfacial strength of Cr/polyimide thin film structures and its durability to thermal exposure as a function of process variables was determined by 90° peel testing. Results were correlated with surface and interfacial characterization of thin film structures and peel failure surfaces using Auger, x‐ray photoelectron spectroscopy, and secondary ion mass spectroscopy techniques. Initial adhesion in as‐deposited Cr/polyimide structures exhibits a mild dependence on radio‐frequency Ar plasma surface modifications and deposition process conditions. However, the durability of these structures under thermal process cycles depends strongly on these process parameters, greater doses of energetic ion bombardment were seen to yield greater durability. Characterization of peel failure surfaces revealed that fracture in the as‐deposited and peeled samples occurs cohesively in the near surface region within the polyimide. Cohesive fracture was also seen in some samples after thermal process exposures, with peel stre...
Failure analysis for poor solderability of Au surface of PCB
Nonwetting is one of the common problems and is always rejected in electronic assemblies. ENIG pads of a PCBA exhibited nonwetting after lead-free reflow soldering. With the aid of stereomicroscope, SEM&EDS and XRF, a series of analysis was performed. And after visual inspection, surface and cross section analysis, thickness measurement and solderability test, it can be inferred that oxidation of plating surface was the main reason for nonwetting, and corrosion in Ni plating caused an adverse impact on solderalibity.