Amada UNIFLOW 4 REMOTE, Operation Manual, Page: 173 / 176

APPENDIX E: GUIDELINES FOR REFLOW SOLDERING
UNIFLOW
®
4 PULSED HEAT CONTROL
990-908 E-11
11
Force Control And Simple System Examples
Most reflow joints of this nature require fewer than
20lbs. (9 Kg.) pressure. A range of force control
modules is available to suit all applications up to
150lbs. (68Kg.). Force must be precisely controlled.
Force can be calibrated and set to the correct level to
achieve the right thermal transfer of heat to the solder
joint. It is desirable to have co-planarity adjustment in
the thermode mounting or the head itself, for ease of set
up. Modern designs have either air or motorized
actuation and built in valves for thermode cooling.
Many heads are modular in construction and therefore
versatile for integration into tooled or semi automatic
fixtures. Linear slides allow loading and unloading of
the parts away from the bonding area.
Rotary table systems are preferred for high volume production. The operator can be loading one set of
parts concurrent with another set of parts being soldered. This doubles the output from one operator,
thus reducing the labor cost.
Quality Control And Inspection
Pressure is maintained as the joint is cooled. Therefore there is little chance of a dry joint occurring.
The imprint of the thermode should be seen on the solder joint and be even in width and length. There
should be visual evidence that reflow has occurred and when the parts are peeled apart the resulting joint
will have a granular appearance over the soldered area. There should be no evidence of burning or
delamination of the pads to board or flex. Where a single sided flex is used, there maybe marking or
discoloration on the top of the polyimide but no burning or separation should be seen. Any flux residues
can be cleaned after the reflow process. No clean, low residue fluxes do not require post cleaning.
Temperature and time process data can be collected from the control and displayed in graphical format
to illustrate process stability.
Process Maintenance
Maintenance of the cleanliness of part fixtures is required to ensure that the parts continue to sit flush to
the base. Periodic maintenance of the thermode is also needed to prevent the build up of baked on flux.
Using a flux solvent, or cleaning the thermode with a very fine emery or grit paper mounted to a flat
rigid surface will maintain good thermal transfer to the parts. Care must be taken so as not to round the
edges of the thermode or spoil the flatness. There is a distinct difference between the pollution of the
thermode for soldering processes where the thermode is positioned directly on the leads in contact with
the solder and those where the thermode is in contact with a
Kapton surface. In the first case the
pollution and thermode wear is much higher, and cleaning must be done on a more regular basis. The
thermocouple joint connection must be kept clean and in good order to ensure repeatable temperature
control. Thermocouple types K and E are not eroded by flux but type J can be attacked and eroded.