Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


BOTTOM SIDE COMPONENT HOLDING DURING DOUBLE SIDE REFLOW

ZULFIQAR H. RIZVI

#15984

BOTTOM SIDE COMPONENT HOLDING DURING DOUBLE SIDE REFLOW | 6 May, 1998

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

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Chrys

#15988

Re: BOTTOM SIDE COMPONENT HOLDING DURING DOUBLE SIDE REFLOW | 6 May, 1998

| 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?

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ETS, LLC

#15987

Re: BOTTOM SIDE COMPONENT HOLDING DURING DOUBLE SIDE REFLOW | 6 May, 1998

ETS has a proprietary way of handling this problem. Please contact me offline to discuss. Sincerely, Brian Stumm ETS, LLC 3939 N. Freya St. Spokane, WA 99207 509-483-0900 (voice) 509-483-0331 (fax) ets@eznet.com (e-mail) | 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

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Justin Medernach

#15989

Re: BOTTOM SIDE COMPONENT HOLDING DURING DOUBLE SIDE REFLOW | 6 May, 1998

| | 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

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D.Lange

#15986

Re: BOTTOM SIDE COMPONENT HOLDING DURING DOUBLE SIDE REFLOW | 6 May, 1998

| 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 What Justin says holds true weird but so! I as well have been soldering doublesided SMT for a long time. There are certain packages that will not "hang on". If you are so lucky to have most of these parts on the same side of the board then run that side up second pass. The only parts I have had to leave off consist mainly of SMT connectors and crystal oscillators. The surface area of the wetted part of the device is insufficient to prevent the mass from hanging. You may want to dispense a spot of adhesive after printing to known problem parts so that during first pass it will cure the adhesive during paste reflow (not optimum adhesive profile but good fix). Note: surface tension will not align parts that are glued down. Run next side and your done.

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Bob Willis

#15985

Re: BOTTOM SIDE COMPONENT HOLDING DURING DOUBLE SIDE REFLOW | 9 May, 1998

How about checking out the Reports on Double Sided Reflow and Pin IN hole Reflow from the SMTA head office. They are both available now so give the SMTA a call !!!! | 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

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