Pin Through-Paste with Lead-Free

We no advice to give you on the topic, but maybe while you're waiting for others to reply, reading a trade journal article on the topic might help. Below is a link to "Pin-in-hole reflow (PIHR) and lead-free solder joints" by David Bernard, Bob Willis. It is from Issue 7.10 - October 2007 of "Global SMT & Packaging" magazine. http://www.globalsmt.net/documents/Technical_Articles/7.10-bernard.pdf

Pin In Hole/Intrusive Reflow Check List ["Pin-in-hole reflow (PIHR) and lead-free solder joints" D Bernard, B Willis, "Global SMT & Packaging" Issue 7.10, October 2007] * Are your through-hole components compatible with reflow soldering temperatures? Do they meet the minimum requirement of the IPC/IEC component compatibility standards of 250*C for lead-free? * Can you obtain the throughhole components in packaging suitable for automatic assembly? Manual assembly is always possible but automation will improve consistency. * Have you calculated your throughhole and lead-to-hole ratio for automatic and manual insertion? You may have to do this if you normally group holes to reduce the number of drill sizes in printed board manufacture. Lead size plus 0.010" is normal. * What standoff height do you have on the components, where are the component standoff feet located and will they contact your paste deposit? A minimum standoff height should be 0.010". * Have you tested your solder resist with your solder paste during reflow? Does it cause solder balling? It is often necessary to print paste on to the resist to obtain the correct volume of solder to fill the hole after reflow. * Have you calculated the stencil thickness required to fill your plated through-holes with solder after reflow? The following calculation is one of the basic references available: Volume of Paste = (Volume of PTH - Volume of pin) x 2 * Have you told your stencil manufacturer that through-hole apertures are required on your new stencil? Normally we tell the stencil supplier to take them out, don't we? Also have you shown your supplier a connector, he may have a lot of experience with PIHR? * Have you discussed changes to your soldering standards for pinin-hole reflow assembly with your quality department and your customer? You can achieve 100% fill but positive fillets are more difficult. The joints will also look different but it is easy to meet the requirements of IPC-A-610D! * Have you specified your component lead lengths and can you control them? Lead length control is crucial and should ideally give a protrusion of 1-1.5mm below the board. * Do you know how strong solder wave and hand soldered joints are? In fact, they are no different than through-hole reflowed joints but remember, someone will ask you !

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We've done some tests on this and got good results. Of course it can be dependant on the paste properties (thinking of slump in particular), and you need to get the heat under the connector which can be more critcal than in a leaded evironement, but in general, with our paste we got the same results leaded as leadfree.

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