Fitting the tiny parts

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Viv Roney
Posts: 9
Joined: Sat Apr 28, 2018 6:49 pm

Fitting the tiny parts

Post by Viv Roney » Mon Aug 13, 2012 6:51 am

Hi Guys

I really struggled with the SC70 parts on the PDM board.

My old method used to be to hold the part in place with some transparent tape, align the legs, solder one leg, remove tape, realign legs and solder the rest of them.

This doesn't work with the SC70 package (or the smaller SSOP) even using the finest bit on a quality solder station, the package is just too small to secure whilst soldering.

A different technique which worked very well for me was to put a tiny dab of stationary gel-adhesive where the body of the package goes, and then place the part, the adhesive holds it enough to adjust for perfect alignment. Leave to set for a while (but not hard), then solder a leg on one side, then readjust if necessary, and solder all the legs on the other side, and then finish the first side. Inevitably all the legs get soldered together, but that's ok, the excess can be removed easily provided that the alignment was perfect - I use firstly a reflow bit (the one with a well in the tip), and then if necessary pre-fluxed solderwick.

Note to Matthew: on the PDM board, there are no traces and pads for C24 and C25: C24 is no problem, but C25 was very challenging there being no exposed trace a jumper wire to a tiny pin is required. If anyone is interested, I can explain how I managed it.

Cheers to all



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