Novel rework techniques for electronic assemblies

Soft soldering is the primary joining technology used in electronics assembly and is expected to remain so for the foreseeable future. Component removal for rework and repair is traditionally achieved by remelting of the solder, but the exposure of the assembly or its component parts to repeated soldering/desoldering cycles may cause both immediate damage and create a significant long term reliability hazard. Rework is also currently labour intensive and requires skilled operators. Area array components, such as ball grid arrays (BGAs), further increase rework process complexity due to the number and inaccessibility of the solder joints and, for some devices, the necessity to remove and replace the solder balls before component replacement. There is also a growing requirement to recycle/reclaim electronic waste, creating the need for an effective process for dismantling of printed circuit board assemblies (PCBAs). This paper presents a brief review of alternative nonthermal techniques for rework or dismantling of conventional soldered assemblies, including both chemical etchants and mechanical techniques. Results are then presented on trials of chemical etchants, where solder removal rates consistent with realistic times for component removal have been readily achieved using commercially available tin-lead strippers. Electrochemical techniques are also shown to be usable in specific applications, i.e. where electrical contact can be readily made to the solder joints to be removed and have the advantage of reclaiming the removed solder directly from the electrolyte.