Gold Versus Tin Leads

PC Magazine published a recent article describing what our Technical Support staff has been describing for several years; the deleterious effects of using mismatched SIMM contact material. The conductive quality of the material has almost no influence.

The primary negative effects arise from the corrosive nature of 'dissimilar metals'. Corrosion can take place at any time, with any metal. But a corrosive environment is intensified at the junction of two different metals. In the process of corroding, a small amount of electrical current is produced. This corrosion induced current can interfere with the current meant to transmit or retain information in a DRAM chip. The point of corrosion also creates a point in an electrical circuit that has a capacitance value where there should be none. Electrical capacitance is a core property that makes the storage of memory in a DRAM chip possible. Any capacitance outside the designed value can be detrimental to the DRAM devices ability to store information. The corrosion side-effect that has the most serious influence is the physical break-down of the metal contacts. As the material breaks down, the contacts may separate and lose contact. Higher capacity modules are much more sensitive to the side-effects of corrosion than lower capacity modules. That's why it wasn't as much of an issue before 16MB SIMMs.

Corrosion can be prevented by some simple measures. First, keep the contacts clean and dry. Oils from hands can be the moisture needed to set the stage. Use of a good quality contact cleaner and clean towels can nearly eliminate the corrosive environment. Simply cleaning the contacts once a year with alcohol and Q-Tips can help any system, regardless of the contact material used. Another factor is moisture in the air. Maintaining a stable room temperature and stable humidity level is important for the longevity of any computer component.

MPM avoids introducing mismatched contact material whenever possible. In some cases it's unavoidable. If an MPM customer discovers that we sent a mismatched SIMM, it has been our policy to replace it immediately. We have this policy to reduce the number of technical support calls generated by a failing module.