Post by thread:[EE]: Double sided SMT Soldering

I am to produce a run of double sided SMT PCB's boards shortly. I have assembled similar boards before, however I only had to deal with smaller components such as 0805's, 1206's and SOT-23's on the underside, with all the larger SMD on the top, on the second pass. My concern is for larger components on the underside falling off during the second pass through the oven. Do I go for this specialist adhesive glue and glue-dot the larger ones on? Is there a rule of thumb as to which require adhesives and which don't? I would welcome any comments and suggestions. Regards John Maud Forth Electronics Pietermatitzburg, South Africa -- http://www.piclist.com hint: To leave the PICList spam_OUTpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

Hi, John > My concern is for larger components on the underside falling off during the second pass through the oven. Do I go for this specialist adhesive glue and glue-dot the larger > ones on? Is there a rule of thumb as to which require adhesives and which don't? I would welcome any comments and suggestions. I use double sided boards with 0805 and SOT23 components on both sides and no glue at all. I use a small oven without a conveyor and with "burners" on both sides. Anything with a little more mass than 0805 resistors and capacitors requires glue ! Even 0805 varistors that are heavier than the capacitors fall off once in a while. With a conveyor oven the problem may get worse because of the vibration. SOIC components will surely require glue. Best regards, Alexandre Guimaraes -- http://www.piclist.com hint: To leave the PICList .....piclist-unsubscribe-requestKILLspam@spam@mitvma.mit.edu

Use solder paste with different melting points for the two sides (low melting on top). Peter -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics