The single pin insertion SPI pressfit technology is a through hole assembling technology, where pins are pressed into the plated through hole PTH of printed wiring board PWB. During the pin insertion, a gas tight, solderless joint is created between pin and PTH. The reliability of the SPI boundig technology can be examined through different factors. My ask was to examine the effect of the different SPI process parameters on the reliability of SPI joints.
Through industrial experience and my own measurements the following assumptions have been made on the effect of the following factors on the reliability of SPI joints.
With non linear increase of the number of press fit zones, the forces required to push-out the pins clearly increase.
The different tool geometries used to manufacture the press fit zones of similar pins and the press-side geometry of pins has no significant effect on the reliability.
The pressing speed has no significant effect on the reliability in the examined interval.
A general assumption can be made, the aging of PWB during reflow cycles has an effect on the push out. By increasing the number of reflow cycles the push out force values decrease.
As a result of the TC process, the push out force values decrease in a non significant way, meaning that the TC process has a reliability decreasing effect.
The inadaquate positioning offset of pin and hole has an effect on reliability and push out. Until a certain offset is reached the push out forces increase, after that they tend to decrease.
During my research I have managed to get a glimpse of the SPI technology and where it might be applicable.
By the study of different technical literature, industrial experiences and my own measurement can I say, that the SPI through hole assembling technology with the SPI joints is a reliable technology, if we go through quality requirements.