APPENDIX E: GUIDELINES FOR REFLOW SOLDERING
UNIFLOW
®
4 PULSED HEAT CONTROL
990-908 E-7
7
Flex Pad Width
Note that the flex pad finishes short of the PCB pad. This is to allow easy inspection of the joint.
PCB Pad Width
Extra width allows for excess solder and ease of inspection. PCB pad is approximately three times the
width of thermode.
SUGGESTED THERMODE WIDTH / PAD
LENGTH AND PITCH
PCB
Pad Pitch
Thermode
Width
mm / inches mm/ inches
0.8 / 0.031 1.5 / 0.059
1.2 / 0.047 1.5 / 0.059
1.4 / 0.055 2.0 / 0.079
1.5 / 0.059 2.5 / 0.098
1.6 / 0.063 2.5 / 0.098
1.8 / 0.071 2.5 / 0.098
2.0 / 0.079 3.0 / 0.118
3.0 / 0.119 3.0 / 0.118
The dimensions above are guidelines only. Some experimentation may be required, due to different
solder volumes.
Thermode Positioning
When positioning a thermode on an exposed or windowed flex, it is important that the thermode is not
positioned too close to the edge of the main body of the flex. Some flex circuits have thinner and
thicker coatings on either side of the traces running through them. If this is the case position the thinner
side next to the PCB. This will reduce the chance of the thermode damaging the trace as it pushes it
down to the surface of the trace on the PCB.
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