Our customers sometimes require a membrane keypad with a connection that calls for flex circuits directly connected to rigid boards versus using connectors. Connecting a flexible circuit directly to a printed circuit board requires a manufacturing procedure called hot bar solder or heat seal lamination. There are many benefits for using a direct flex-to-board connection. 

The Main Benefits of Hot Bar Solder Lamination:

1. Saves vertical height in the design

2. Fast temperature ramp-up and cool-down 

3. Closed loop temperature control

4. Can be more reliable than fine pitch connectors

5. Accurate positioning of the parts

6. Multiple connections can be made simultaneously

7. Cost effective due to elimination of third component such as connector