| | Dear Freinds, | | DOES ANY ONE OF YOU WILL BE KIND ENOUGH TO GIVE SOME INPUT ON DOUBLE SIDE REFLOW OF COMPONENTS WHAT ABOUT BOTTOM SIDE COMPONENT HOLDING DURING 2ND SIDE REFLOW? ANY IDEA OTHER THAN USING SLDERPASTE WITH OFFSET MELTING POINT, EPOXY DISPENSING FOR BOTTOM SIDE COMPONENT HOLD AND KEEPING BOTTOM 2ND SIDE COOL (BOTTOM) USING FANS WHILE REFLOWING UPPER SIDE. | | RIZVI | Do you have specific cases of parts falling off, or are you looking for general info? Mr. Rizvi, I'm going to ask you to do something odd. Dip your finger in a glass of water. Now, point that finger at the ground. They water will hang on your finger tip. That property of a liquid is known as surface tension. That same property applies to molten solder. It will hang onto your board and any component in contact with it. The surface tenison of solder is even higher than that of water. I run a double sided reflow process all the time without the need for any adhesives or a special profile. Surface tension keeps my components on board. Let me put it this way. I have a board with multiple QFP240s that I hang upsidedown during my second pass through the reflow oven. They are made by Analog Devices and have a heat sink built in so they have a considerable mass. I believe you will find the equation somewhere in this forum. If not, look at www.ITM-SMT.com and you will find your answer. Don't get fancy. Keep it simple. It works. Regards, Justin Medernach
reply »