Soldering ICs

s2 · Post by s2 » Mon 05/14/07 1:36 pm

Here's a question for all you soldering gurus out there. I need to solder a 28 SOIC to a project board. I went out and bought an itty bitty tip for my soldering station...

My question is what is the right temperature at which to solder one of these little guys? Are there any other special precautions or tricks of the trade I should know before risking my $15 IC?

Thanks!

floridajack · Post by **floridajack** » Mon 05/14/07 1:40 pm

s2,

haven't done any ss soldering an a while, but i used to use a heat adsorbing paste to prevent creep up the leads. also seems to me that the trick was to hit 'em fast and hot. somebody can probably recommend a temp - i'll have to look it up. if no one else replies, i can tonight.

fj

brownnote · Post by **brownnote** » Mon 05/14/07 1:41 pm

I use DIP sockets whenever possible...don't worry about the heat and pop in the fresh IC.

floridajack · Post by **floridajack** » Mon 05/14/07 1:47 pm

+1 on the sockets - if you have room.

also remember you now have a mechanical joint that is subject to corrosion issues. there is some stuff called stabilo that will cut down on corrosion. big problem with memory chips (back in the 8086 days) i prefer solder if the chip is never coming out.

fj

s2 · Post by s2 » Mon 05/14/07 2:00 pm

It is a surface mount digital IC, so it has to be soldered. Even if I use a socket, I have to solder it to the socket adapter. I don't think I have any choice but to solder it unless someone knows something I don't.

jckid66 · Post by **jckid66** » Mon 05/14/07 3:35 pm

if its SMT the you will need solder paste as for temp we used to get the iron up to 735 hot and fast.... contact me I have a lot of web sites bookmarked for smt soldering...

Bill

hucky · Post by **hucky** » Mon 05/14/07 9:13 pm

1. prepare the pcb with the solder wire
2. position the smd circuit to the pcb
3. put a desolder wick on top of the smd legs like you want to desolder the part
end of soldering smd circuit on pcb

the desolder wick is protecting the smd part from overheating and you get no short circuits between the legs.

this is my "handmade" working procedure to remove and install smd parts on circuit boards.

davent · Post by **davent** » Mon 05/14/07 9:30 pm

s2 wrote:Here's a question for all you soldering gurus out there. I need to solder a 28 SOIC to a project board. I went out and bought an itty bitty tip for my soldering station...

My question is what is the right temperature at which to solder one of these little guys? Are there any other special precautions or tricks of the trade I should know before risking my $15 IC?

Thanks!

S2,

Here's a video tutorial for soldering surface mounts. Hope you find it useful.

http://tangentsoft.net/elec/movies/tt03.html

dave

csbradley · Post by **csbradley** » Mon 05/14/07 9:33 pm

I think the easest method is to use a wide blade talon iron that can span all the pins at once. Ok, I use a nice Metcal MX iron, expensive yes, but one of the best investments you can get if you do lots of soldering.

Otherwise, I would just tin the board with solder. Position the IC (glue if needed, you don't want the IC to move), and then heat and melt the solder one side at a time. You may want to individually solder the pins on the four corners to make sure it is positioned perfectly. Take solder wick and wipe the top of the pins clean of excess solder. The soldering is pretty easy. You can solder all the pins on one side at once, then wipe off all the excess solder, and check the circuit to make sure you don't have any shorted pins.

Now desoldering that guy will be a pain without hot air or a talon iron, so you really only get one chance. Maybe practice on a cheap quad op-amp or something. With hot air, I would start with around 400 - 450C. It's easy to get impatient and turn it too hot and burn the board.

CSB

jckid66 · Post by **jckid66** » Tue 05/15/07 12:13 am

S2,
Here are a few links that I have found in my travels

http://www.geocities.com/vk3em/smtguide/websmt.html

http://www.engineeringlab.com/smtsolder.html

davent,
As a former tech with Honeywell I feel the guy in the video is inducing too much heat IMHO into the chip with his technique. This might be ok for an opamp but would never fly with some thing like a processor also the tip is too big for the job. For SMT you want a SMALL tip. Also myself I prefer paste when soldering SMT components
But again it’s all a matter of taste (what works for you) I hope this helps you??

S2 if you have any other questions contact me

Bill
M.A., E.E.T

paulster · Post by **paulster** » Tue 05/15/07 5:09 am

s2 wrote:My question is what is the right temperature at which to solder one of these little guys? Are there any other special precautions or tricks of the trade I should know before risking my $15 IC?

If you're using a tiny bit then you'll get very little temperature drop when it comes into contact with the device legs, unlike when you're trying to solder to a turret for example.

You can use a much lower temperature (320C / 610F), still be able to melt the solder, and dump a lot less heat into the device.

As has already been said, tin the pads on the board, stick it down or tack two opposing corners. Then do each leg, one at a time and rapidly, allowing cooling time between. If you have any trouble with one then don't keep at it, go back to it later.

If you can get a pair of tweezers or something to act as a heatsink when soldering then that'll help too.

sjfirebird · Post by **sjfirebird** » Tue 05/15/07 6:01 am

Don't forget the ESD strap.

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