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I have a MSOP10 package with an exposed pad. How do I solder this, if at all possible, with just my temperature controlled iron?

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Have not tried myself but here is video of soldering QFN (I believe exposed pad technique should be identical with MSOP): http://www.youtube.com/watch?v=d-f-SBC0GrU

For general SMD soldering I found this helpful: http://www.youtube.com/watch?v=3NN7UGWYmBY

BTW: Kudos for makers of this two videos.

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Ideally you put a via in the center of the pad, so you can do it from the back. If one isn't there and you can drill a hole, that may work as well, possibly using some wire to couple the heat to the pad.

If the pad has a plane (or very large trace) leading outside of the package, you may be able to get heat into the joint via that (possibly after scraping off solder resist).

If you have a few parts to do like that, it may be worth it to do it on a hot plate. Tin the part and pad (preferably use paste), then heat it up to 240-250°C for a brief time (non-contact IR thermometers are handy for this).

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  • \$\begingroup\$ Yeah, I am going to be doing assembly with hot plates or toaster ovens, but I'd like to do the first few prototypes with an iron. \$\endgroup\$ – Thomas O Nov 12 '10 at 19:49
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    \$\begingroup\$ @Thomas - The easy option is to not do it at all. If the pad is electrically connected to one of the pins, you could get away with it for prototyping, where you'll be running it in a very controlled environment (25°C mostly) for not very long. \$\endgroup\$ – Nick T Nov 12 '10 at 19:53
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An MSOP10 package doesn't have an exposed pad according to any datasheet I can find. Here's a link[PDF] to Fairchild's description - It's just a smaller SOIC. What are you working on?

In general, though, if you've got a package with an exposed pad, the general method for soldering pads underneath a package is one two large vias (large enough to push a soldering iron tip and solder through), which should allow you to heat up that ground pad and the solder will wick around to the whole thing.

You may be able to expose some of the pad on the circuit board and heat that up (use a big chisel tip!). However, be aware that this is difficult to do right sometimes. Especially if you can't see the wicking action, it's really hard to get the bottom of the package to heat up enough to get solder to pull up to it. Often, all you get is a dome of solder on the pad and a cold joint at best to the underside of the chip.

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  • \$\begingroup\$ There are variants with MSOP10 EP, e.g. LT3757. \$\endgroup\$ – Thomas O Nov 12 '10 at 19:57
  • \$\begingroup\$ It's quite common on power devices to see both MSOP and SOIC variants with an exposed pad in the center for heatsinking. \$\endgroup\$ – Peter Green Mar 30 '17 at 12:56
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Put several small vias underneath ( better than fewer lare ones for themal conduction, leave a hole in the bottom solder resist, or scrape of resist. Apply some paste to the pad,place the part, and apply heat & a little solder for thermal contact to the underside and wait til the paste reflows.

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Perhaps attaching a small flat piece of aluminum to a conventional solder iron tip would work. Solder will not "wet" or flow onto aluminum. But the aluminum would get as hot as the tip.

First get solder onto each pad, using an iron or solder paste. Position the chip on top. Press the flat edge of the hot aluminum against all the chip leads along one side of the chip at once. The heat will reflow the solder already there.

I haven't tried this yet.

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  • \$\begingroup\$ I think you've missed the point of the question. The OP has an exposed pad on the bottom of the package (that's what the EP stands for) which is not accessible to the iron. Soldering the side pads is quite easy. \$\endgroup\$ – Dmitry Grigoryev Mar 30 '17 at 13:13

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