How to Press Compliant Pins into Printed Circuit Boards
To successfully assemble connectors to a printed circuit board (PCB), a variety of processes are used with the two most common techniques being either a soldered connection or a pressed in compliant pin. To assemble connectors using compliant pins, several requirements need to be defined and satisfied in order to minimize defects.
Press Type
To press fit a compliant pin, normally either a direct acting air press or servo press is used. Press selection depends on the user’s need for force, level of control, type of inspection and degree of monitoring. Typically, the force required to press a pin ranges from 1 to 44 pounds with a tolerance allowance of up to 20%.
Process Monitoring
A common misconception is that by using force and distance you can ensure that all pins are present and pressed completely into the board. In reality, this type of process monitoring ensures only that there is adequate interference between a group of pins and the board, and the pins are properly aligned and correctly seated. Unfortunately, unless the assembly has very few pins, force and distance is not a reliable way to monitor the presence of all pins and proper press fit.
This force/distance graph shows a 3-pin application and the ability to detect:
1) Misaligned board
2) Missing pin
3) Bent pin
4) Missing board
5) Seating of board
Inspection and Measurement
Even though each application has its own specific requirements, the following inspection criteria should be considered:
- Presence of every single pin prior to the press cycle
- Presence of every single pin after completion of the press cycle
- Height between the top of the PCB and the pressed in compliant pin after press cycle
- Height of all pins relative to each other
- Levelness of the PCB
- Elevation of PCB relative to the housing
- Consistency of multiple assembly modules within one station
Methods of Inspection
- Physical/mechanical dimensional inspection using precise low force probes in combination with laser sensors
- Measurements using multiple laser sensors
- Continuity check for compliant pins
- Visual inspection
- Levelness inspection of PCB via sensors at three or four locations.
SCHMIDT Technology has designed and built assembly cells for a wide variety of compliant pin applications. To see examples of these assembly cells, please visit our Press Selection Assistant or call us at 1-800-959-1218 to discuss your specific requirements. |
