Thad, Circuits Assembly magazine featured this technique in its Sept. 1996 edition, in an article called "Advanced Surface-Mount Manufacturing Methods". The article included a table of formulas for pad size and paste volume. I know there are resources on the net as well; Amp has a discussion of this technique at www.amp.com/product/articles/dd66.html. When I worked with Motorola on 2 way radio products, we used this technique on every product. The joint does differ greatly from wavesolder joints, but it is still a robust joint and we did not see any significant ALT or field issue if the design work was done right and the process is controlled. Another thing: there are a lot of solder preforms that will aid this technique (preforms are put on the part before insert; this provides more stable solder volumes compared to screening into the hole). Chris Messner United Technologies Electronic Controls [log in to unmask] 219-358-3429 ______________________________ Reply Separator _________________________________ Subject: ASSY: IR Reflow of Thru-Hole Components Author: [log in to unmask] at internet Date: 1/10/97 12:46 AM Some questions for the Technet, One of our PCA Assembly subcontractors uses IR Reflow to reflow through hole parts instead of the traditional Wave. They typically use this technique for high density double side SMT/Through hole assemblies where there is no room for the keepouts necessary to mask the SMT parts during the wave process. The technique involves a double Paste screening operation to squeegee paste into the through holes. The board is run through IR to reflow both the SMT and the Thru Hole parts. The solder joints look completely different than a typical wave reflowed thru-hole part. In fact I think they would be considered rejectable per IPC-A-610B. The solder joints look as follows (forgive the art, I hope this tranlates well): | | ___________ | | __________ | | | | |* | | *| |** | | **| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |****| |** | | **| |* | | *| ________| | | |___________ | | | | |______| Where "*" is solder. --------------------------------------- I have several questions for the forum and would greatly appreciate feedback: 1. Is there an industry term for this type of reflow. I've heard it referred to as "intrusive reflow". Since I love catchy names, I'm soliciting one. 2. Is the technique in widespread practice in the industry or is it new? 3. Any comments on the reliability of such a solder joint. 4. Do standards (IPC or otherwise) exist that describe a "good" joint and a "bad" joint. I'm interested in IPC Class II product. 5. Are there any tricks of the trade in designing boards for this type of assembly. For example do I need to use modified (i.e. smaller) thermals on my through holes to insure good reflow. 6. Are there special processing techniques in assembly that will produce good joints. Example - screening paste on both sides or using special pastes. 7. How can these joints be non-destructively evaluated since they can't be seen other than microsection. Do periodic destructive tests need to be done per an AQL. 8. I'm aware that any through hole components that use this technique must be made of high temperature material to withstand IR, but are there any other restrictions regarding what type of components this assembly technique can be used for. I would appreciate any feedback or comments you might have on this. Thanks, [log in to unmask] *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** * If you are having a problem with the IPC TechNet forum please contact * * Dmitriy Sklyar at 847-509-9700 ext. 311 or email at [log in to unmask] * ***************************************************************************