How to Assemble Flexible Printed Circuits with Lead Free Solder Alloy

Step-by-Step Guide

1. 1

   Step 1: Assemble the components temporarily.

   To assemble flexible PCBs with wave or reflow soldering, you need to arrange the electronic components and keep them in their place temporarily with the help of adhesives. , Use fixed as well as sprung pallets locations pins to provide flexibility.
   
   The pins should have protrusion of approximately
   0.010″ above the flex circuit., These thermal relief areas help in improving the delta T at the time of reflow of lead-free solder alloy.
   
   In case you plan to using vapor phase for the reflow, you should consider the drain holes under the flex., Allow the protrusion of pallet clips by recessing a
   0.006″ (150um) stencil on the base of the foil.
   
   You should recess the stencil by
   0.003″.
   
   Use 2 varying sizes of apertures on 3 different footprints of electronic components for solder paste printing.
   
   For efficient SMT PCB assembly soldering, you need to place the recesses around pin protrusions from the pallet., To fix the lead-free soldered parts in place, the PCB assembly should be heated either by passing through a preheated and controlled oven, by using a hot air pencil, or with the help of an infrared lamp.
2. 2

   Step 2: Locate pins for flexibility.

3. 3

   Step 3: Set the base of pallet: The base of the pallet used in SMT PCB assembly needs to have thermal relief areas.

4. 4

   Step 4: Print the lead-free solder paste.

5. 5

   Step 5: Heat the assembly.

Detailed Guide

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