Recent improvements of the Kloften & Kloften
June 1, 1996
1. Two Step Splicing.
The "Two Step Splicer" described in Issue No.8 has been modified for the splicing of leadframes for micro chips by replacing the air cylinder for the movement of the upper electrode holder with the type of step motor which is used in the "Wide Strip" splicer. This has made it possible to automate more of the splicing operation.
The procedure is now as follows:
o When the power is turned on, the holder goes to the rear position.
o After completion of the first splice (rear carrier), the top electrode will automatically lift to clear the carrier and move to the front soldering position where it again will be lowered to complete the second splice.
o When the two jaw sets are opened (to remove the spliced lead frame), the top electrode holder will automatically go the the rear position, ready for the next splicing operation.
Note that a non-contact sensor is used to locate the correct position for the second (front) splice, which means that there is no need for any adjustment when changing from one leadframe width to another as long as the lead and the pilot hole diameters are the same.
If the lead or the pilot hole diameter is different for the new leadframe, a locator bar in each of the two lower jaws must be changed. This just means pulling the two old bars out of their grooves and pushing in the new set, an operation which takes but a few seconds. The lead adjustment is incorporated in the locator bars, assuring correct lead without the need for further adjustment.
2 Overlap-splicing across the width of a leadframe.
Some leadframe manufacturers prefer overlap-splicing over butt-splicing, since the butt-splices may be difficult to detect.
Our "Wide Strip" splicer may be used to overlap-splice across the whole width of a leadframe strip.
The operation is much like the one described above, only now the top electrode stays down until the whole strip width has been spliced. (The curved upper electrode receives heat pulses continually as it is "rolls" across the strip).
This method is particularly well suited when the splice cannot be place between leadframes, but must cross one leadframe. Splicing only the two carrier strips might, in this case, cause loose pieces to catch on wipers in the plating line.