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Ash Small

Fri Dec 22 2017, 01:40AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Seasonal greetings, everyone, I've not posted here for a while.

I've just been practicing my soldering techniques.....SOT-23-5 high speed op amp.....Fourth attempt.....It is possible

What's the kindest way to clean the flux off these little critters?

the_anomaly

Fri Dec 22 2017, 02:07AM

Registered Member #19 Joined: Thu Feb 02 2006, 03:19PM
Location: Jacksonville, FL
Posts: 168

Middle pin is the fun one right?

I usually use isopropyl alcohol followed by a gentle brush. It does ok. I'm interested to hear if anyone has a better solution.

Ash Small

Fri Dec 22 2017, 02:17AM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

Middle pin was the one that caused all the problems, but I sorted it.

First one lost a leg, second one made a bid for freedom before I'd soldered anything, I think it's probably reached the outer regions of the known universe by now. Third one lost a leg, fourth one submitted without a struggle

Perseverence

the_anomaly

Fri Dec 22 2017, 02:54AM

Registered Member #19 Joined: Thu Feb 02 2006, 03:19PM
Location: Jacksonville, FL
Posts: 168

I've become a fan of placing a small dab of hot glue then dropping the chip into it upside down. Tacking the chip to a hard immovable surface makes it a bit easier.

Dr. Slack

Fri Dec 22 2017, 08:49AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

I use 0.1" blob board, though you can make an equivalent footprint with a couple of cuts on 0.1" stripboard.

Take the middle pin of a SOT-23-5 (also works for every other pin of a SOT-8/14/16 0.05" pitch package) and bend it up. Now the remaining pins can be soldered down onto the 0.1" grid.

Put a blob of solder on one pad first, and then sweat one leg onto that pad first to immobilise the IC. Solder the other legs properly. That's not the way we were taught in soldering school, but I find I only have two hands, not three. Re-flux that first joint just to make sure.

Finally solder wires, I usually take a bit of 7/0.2 apart to provide them, to the 'up' pins, and tack them down elsewhere on the blob board.

Ash Small

Fri Dec 22 2017, 12:33PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

I ended up leaving the middle pin where it was (actually, bending it down further) then bending the other four. After trying various 'third hands', I ended up sticking it in a lump of blu-tac. Blu-tac can also be used to pin it down as you add the legs.

What's the best way to clean the flux off?

I plan to use it on 0.1" strip-board. I've already scraped it.

I did look at some of the adaptors available, but decided to try this first.

2Spoons

Fri Dec 22 2017, 08:51PM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

If I was trying to use this on strip board I'd glue it down 'dead-bug' style first and use either >0.2mm enamelled wire (the sort with meltable enamel' or 30g wire-wrap wire.

These things http://www.roadrunnerelectronics.com/Wiring-Pencils are great for this kind of work
https://www.electrolube.com/products/cleaning/flu/solvent/ is awesome for flux removal. And many other things that need dissolving /cleaning.

Ash Small

Fri Dec 22 2017, 10:46PM

Registered Member #3414 Joined: Sun Nov 14 2010, 05:05PM
Location: UK
Posts: 4245

While I feel I've achieved something, I do need to find a better way, this is a bit of a nightmare, it's my fourth attempt. It still might work, but I'll be surprised if it does, I'm just populating the rest of the board. It's a simple audio buffer/boost, just an exercise to see if I can get a high speed op amp to do anything other than oscillate, if anything at all

Conundrum

Sat Dec 23 2017, 02:13PM

Registered Member #96 Joined: Thu Feb 09 2006, 05:37PM
Location: CI, Earth
Posts: 4059

Blutak works well for LEDs if you need to solder wires to them.

Bending the leads is actually not optimal, I use a pre-tinned piece of wire then apply tiny drop of flux to that and solder.

2Spoons

Sun Dec 24 2017, 12:43AM

Registered Member #2939 Joined: Fri Jun 25 2010, 04:25AM
Location:
Posts: 615

if you have a laser printer then making little single sided prototype pcbs is pretty easy with the toner transfer method. I got it down to the point I could bang out a small proto board in half an hour. If you do everything in SMT then theres no drilling.
I recommend "Press'n'Peel Blue" for this process.

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