7. Reflow Removal Procedure.

This procedure follows all of the steps detailed in the Eutectic Procedure above with the exception of contacting the Vacuum Pick Up Assembly before eutectic condition so as to remove the component automatically when all leads reach the condition, In the Reflow Removal Procedure the vacuum is turned on, but the Vacuum Pick Up Assembly is not connected until the component is completely re-flowed.

It is critical in this procedure to use the no-clean paste flux and ensure all the leads contain flux before proceeding to remove the component as described previously.

The reflow time can either be calculated by close observation of the component during reflow, so that when the front, (easily visible), leads can be seen to be re-flowing, a time of twenty seconds (20) is added by noting the timer and waiting until the extra 20 seconds is completed, at which time the entire component is at reflow condition and the Vacuum Pick Up Assembly can be lowered Or as can be seen by the foregoing Eutectic Procedure, from learning the time from performing a single Eutectic Removal and the Reflow Time entered into a written procedure for future repair operations on the same type of component on the same circuit board.

Once Reflow has been reached, depress the Vacuum Pick Up Assembly lightly and gently down by hand, do not be heavy handed, a light and slow moving pressure should be applied with the forefinger, (avoid pressing the component into the reflowed solder on the contact pads, which could cause bridging), observe under the nozzle as the vacuum cup almost reaches the component body, the body will lift to the cup and you may slowly draw the component up into the nozzle, don’t release, but control the Vacuum Pick Up Assembly all the way back to the rest position. Release the Foot Pedal and the Reflow Time will be recorded.

It is not necessary to hot air level the contact pads as the contact pads are coplanar and free of spikes or bridging, next clean as previously described and apply new no-clean paste flux.

7.6 Placement of the component is as previously detailed in the Eutectic Removal Procedure with the exception that it is not necessary to add time to replace, when the timer reaches zero, the reflow cycle is complete.

 

Note:

The Chipmaster, (Illustration # 8) is a Low Temperature operation machine and will not damage board, components or degrade solder, providing Low Temperatures are used, this is recommended to be less than 450F (232C). Effectively this increases the "Window of opportunity" to rework a component and if for any reason you don’t succeed first time you may retry with confidence that you will not cause damage. As with any skill related activity, experience breeds success and practice will make the user highly skilled and the Chipmaster will respect the skills you have learned.

.

(Illustration # 8)

Previous Page