What Green means: Challenges for failure analysis

Electronics industries have changed over to lead-free solders and green mold compounds that have no bromine, or antimony-based flame retardants. This change has caused lots of stress for the failure analysts as well as the device itself, specially, the chips. Adhesion promoters are sometimes added to the green flame retardants to improve the adhesion to the device lead frames and substrates to prevent delaminations, which can lead to sticking in the molds. Green compounds also are more sensitive to moisture, absorbing it more, and leading to higher package stresses. Lead-free solders are much less mechanically compliant than lead-based solders, so they will transmit printed wiring boards (PWB) stresses to the device more easily. A failure analyst must take care when removing devices from their boards to minimize thermal shock and package stresses. Device cross sectioning must be approached carefully, especially in the case of flip-chips on organic substrates.