New plastic materials have been developed over the past few years to specifically address the needs of surface mount reflow processing conditions. Liquid Crystal Polymers (LCP), Polyphenylene Sulfides (PPS) and Polycyclohexylene Terephthalates (PCT) have excellent high temperature properties due to their high Heat Deflection Temperature (HDT) and excellent moisture resistance. Additionally, they have excellent dimensional stability, low warpage and can be molded in thin sections to reduce the amount of mass to be heated.

Typical plastic materials used in connectors are shown in the accompanying chart. Insulator materials such as glass filled polyesters, which are well established for wave soldered through-hole connectors, are generally not desirable for reflow soldering due to their low heat deflection temperature. Additionally, other high HDT plastics have proven unsuccessful in many surface mount applications. Heat deflection temperature can help predict the short term effect of high temperatures, but does not necessarily indicate when permanent distortion or thermal relaxation of molded in stresses might occur in an actual connector. Because of subtle differences in design or molding processes, two connectors molded with the same material could perform differently in the same application. Likewise, with two identical connectors except for the plastic, it is possible for the one with the lower HDT to outperform the one with the higher HDT in a particular application.

When specifying surface mount connectors, it is important that the actual processing times and temperatures be noted. Quoting heat deflection temperatures is not sufficient.