I am tring to solder an IC, UCC2844C onto a PCB using solder paste and T962A Infrared IC Heater but I end up soldering IC pads between themselves.

Anyone has any idea how to avoid this? Am I maybe putting too much paste on the PCB?

  • \$\begingroup\$ Probably too much paste. How are you applying it? \$\endgroup\$ – brhans Jan 12 '17 at 16:47
  • \$\begingroup\$ I'm using a solder paste syringe. \$\endgroup\$ – MarkoP Jan 12 '17 at 16:56
  • \$\begingroup\$ What type of package are you trying to solder? \$\endgroup\$ – 12Lappie Jan 12 '17 at 16:59
  • \$\begingroup\$ @12Lapointep It's either a 8-TSSOP or 8-MSOP. I'm not sure, I'm new to this stuff. \$\endgroup\$ – MarkoP Jan 12 '17 at 17:04
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    \$\begingroup\$ If you look at the thickness of a 'typical' solder paste stencil, you'll probably find its about 6mil (0.006") and the aperture in the stencil is often smaller than the size of the pad. Now compare that with the thickness & size of the blob of paste you're dispensing from your syringe... You probably only need to 'kiss' the surface of your pad with the end of the syringe to have enough paste. \$\endgroup\$ – brhans Jan 12 '17 at 17:10

Yes there is probably too much solder paste on the PCB. That is one thing that could be an issue. Have you tried removing some of the solder paste with solder wick? This way you will probably remove most of the solder paste of in between IC pins. If one of the IC pin comes out to be open and not connected to the pad, you will need to solder it back again.

For this reason, I like to use a method called "drag soldering" to solder my ICs to a printed circuit board. I make sure I put plenty of flux on the PCB and by using a small amount of solder, I can simply drag it along to form the solder joints.

This is only applicable if you have TQFP type of packages since the pins are accessible. QFN packages will make it impossible to re-solder if there is a mistake. So consider the amount of solder paste you are using initially as a big indicator of whether or not you will create shorts between pins.

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    \$\begingroup\$ Resoldering QFN packages is by no mean "impossible". If there is little exposed metal it may be hard to add solder or create a connection where there wasn't one previously, but excess solder can be removed - if it's not lifting the IC above the board, it will be bulging out to the side where you can get at it. When designing a board, if you have space to extend the pads outside the IC outline and not cover that area with solder mask, hand detail soldering will be much easier. And of course with a hot air tool you can remove the chip entirely, cleanup and start over, or simply adjust it. \$\endgroup\$ – Chris Stratton Apr 26 '17 at 14:55

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