Prediction of multilayer printed wiring board temperatures during lamination

Measurements of temperature histories of epoxy/glass prepreg layers during multilayer printed wiring board lamination have been recently obtained. In the present paper, it is shown that the temperature histories may be predicted by an analysis of the transient heat flow process within the MLB. The analysis requires a knowledge of the press platen temperature history during laminations and the thermal resistance of the padding material. Theoretically predicted results show close agreement with the experimental data for both 5 layer and 15 layer MLB's using the "hot press" as well as the "cold press" cycles. The present method may be used in the design of MLB lay-ups, in particular the determination of the necessary padding thickness to achieve heating rates which give adequate timing "windows" for cure pressure applications. The present theory has been applied to study the effect of kraft paper padding on the prepreg temperatures. Results are shown for both 15 and 5 layer laminations employing the hot press as well as cold press cycles. The number of kraft paper sheets used is shown to have a significant bearing on the temperatures.