Recent improvements of the Kloften & Kloften
June 17, 1996
1. Two Step Overlap Splicing of Leadframes for Microchips
The "Two Step Splicer" described in Issue No.8 has been modified for the splicing of leadframes for microchips 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 operations.
The procedure is now as follows:
1.1 Solder feed controlled as in the present model (Stepping solenoids driven by pulser controlled by timers):
o When the power is turned on, the holder goes to the rear position.
o After placing the first strips on the locator pins in the right hand lower jaw, cutting the strip and pulling it back to the soldering position, the the jaw is closed and the assembly raised to the top position.
o The left strip is placed, cut, pulled back and the upper jaw lowered. This last action will start the solder feed.
o When the right jaw assembly is lowered, a micro switch closes to start the following sequence:
(1) After 0.25 seconds an air valve is energized to operate a cylinder which pushes the top electrode down onto the rear carrier strip.
(2) 0.3 seconds later an 814 timer is energized to start the heating current. At the same time (or a fraction of a second later) a contact is operated to discharge a condenser through the second stepping solenoid to reverse the shaft one step.
(3) 0.5 seconds after the 814 timer has timed out, the top electrode lifts, and the step motor moves the holder towards the front, until it is stopped by a Non Contact Sensor as the latter reaches past the outer edge of the second carrier strip.
(4) The electrode is again lowered and the procedure under (2) is repeated, only now a second 814 timer controls the length of the heating cycle.
o When the two jaw sets are opened (to remove the spliced lead frame), the top electrode holder will go the the rear position, ready for the next splicing operation.
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1.2 Solder feed using a step motor, if possible driven from the same "driver" as the one used for the "Screw Type" motor.
o When the upper left jaw is lowered the step motor starts feeding solder, the length fed determined by a timer, either of the "814" type or one controlled by means of a pot meter.
o (1) through (4) as above except that under (2) the step motor is reversed for a pre-determined (fixt) number of steps.