DEK fine pitch autoflex pin breakage| 19 March, 1999
I think we are getting closer to being very happy with DEK stencil printers of the 265 GSX variety. However, problems continue arising concering fine pitch autoflex tooling pin breakage.
We are told by the British engineering establishment, they are seeing very little breakage but ours. All be it, we do run 6 SMT lines front ended with these nearly great machines (maybe not MPM calibre), and we see about 5 pins break per week at the "glans" interface where the pin is screwed and loctited into the retainer cup (DEK says something else). We run many different board configurations with about 12 million placements per month with a great majority being fine pitch requiring corresponding pins.
The break is as if some torsional or side loading force was excercized. Upon further examination, while understanding the acceleration and air pressure force (10 Bar or about 140 psi? accelerating the pins from 0 to 60 in about a nanosecond) we see evidence of complete separation of the pin from its retainer. The metal seems fatigued with a small tip left remaining as if it had been subjected to tensile and elongation testing and failed the pull at about 10K psi.
The pins probably are machined on swiss screw equipment. They are necked down just before the threads meet the main shaft body. This is wherein lies the probable cause. It is possible the pins are fatiguing because of acceleration and some side loading after acceleration and upon making board contact when the table rises.
The question is: Do any other DEK users have similar problems? If so, how often?