Matsushita Electric Industrial Co., Ltd. has discovered the mechanism how iodine contained in ultraviolet cured resin causes wire bonding area inside a CCD device to corrode. Tetsumasa Maruo, Chief Engineer, Production Engineering Center, Semiconductor Company of Matsushita revealed this fact at "Mate 2007 Symposium on Microjoining and Assembly Technology in Electronics" held at Pacifico Yokohama on February 1, 2007.
The problem that iodine contained in ultraviolet cured resin makes wire bonding area corrode is believed to be the cause of Sony Corp.'s CCD malfunction dispute, which became known in October 2005. In the controversial CCD, a glass substrate over the package was bonded using ultraviolet cured resin containing iodine in its photopolymerization initiator. This iodine is said to react to moisture in the air, corrode the bonding area, and cause wire bonding to age, degrade faster and come unstuck. As a countermeasure, Sony has stopped using ultraviolet cured resin containing iodine to bond CCD packages since the defect was discovered.
In tests reproducing the malfunction, Matsushita's engineers including Maruo noticed in some cases the corrosion did not occur even though using ultraviolet cured resin containing iodine. After investigating deeper, they found out corrosion was closely related not only to iodine but also fluorine, which becomes alienated from ultraviolet cured resin, and bonding condition of the wire-bonded area. The company explained ultraviolet cured resin containing iodine can possibly be used to bond CCD packages with its reliability undamaged, if a right kind of ultraviolet cured resin, from which fluorine hardly become estranged, is chosen and intensity of wire bonding is enhanced.