How to Solder a Wire to Surface-Mount IC With Pins VERY Close Together?

We do embedded software, but the hardware is produced by our customer (we don't control it).

Sometimes we need to attach a wire (for monitoring a serial or I2C interface, or for timing instrumentation) to a surface-mount IC where the pins are VERY close together.  The pins are so close together that I can't solder a wire to it, even using high-power optics and the finest soldering iron tip available.

Are there any special tools, equipment, training, or techniques that might help with this?

Thanks!

On 06/26/2018 09:51 AM, dashley@gmail.com wrote:
> We do embedded software, but the hardware is produced by our customer (we don't control it).
> 
> Sometimes we need to attach a wire (for monitoring a serial or I2C interface, or for timing instrumentation) to a surface-mount IC where the pins are VERY close together.  The pins are so close together that I can't solder a wire to it, even using high-power optics and the finest soldering iron tip available.
> 
> Are there any special tools, equipment, training, or techniques that might help with this?
> 
> Thanks!
> 

Wide iron tip, not narrow.  You don't care if you reflow the adjacent 
pins, you only care about keeping the (already tinned) blue wire in the 
right place while the solder is wet.

And like riflery or photography, hold your breath out before the 
delicate bit, not in.

Alternatively, you may have better luck finding a via or trace that you 
can scrape the soldermask off with an Xacto knife than trying to hit the 
pins proper.

-- 
Rob Gaddi, Highland Technology -- www.highlandtechnology.com
Email address domain is currently out of order.  See above to fix.

On 06/26/18 17:51, dashley@gmail.com wrote:
> We do embedded software, but the hardware is produced by our customer (we don't control it).
>
> Sometimes we need to attach a wire (for monitoring a serial or I2C interface, or for timing instrumentation) to a surface-mount IC where the pins are VERY close together.  The pins are so close together that I can't solder a wire to it, even using high-power optics and the finest soldering iron tip available.
>
> Are there any special tools, equipment, training, or techniques that might help with this?
>
> Thanks!

Part of the hardware design is to put test points on the board where
they are needed and always build in enough diagnostic capability :-)...

Chris

> Sometimes we need to attach a wire (for monitoring a serial or I2C interface, or for timing instrumentation) to a surface-mount IC where the pins are VERY close together.  The pins are so close together that I can't solder a wire to it, even using high-power optics and the finest soldering iron tip available.
> 
> Are there any special tools, equipment, training, or techniques that might help with this?

You didn't state any specific dimensions so it's hard to answer with 
specifics.

Perhaps a hot air soldering station would be useful if you don't trust 
your narrow soldering tip.  Hot air will reflow the adjacent pins. 
Using hot air is tricky if you've never done it before.  It can be 
practiced.

I've found that the narrow Metcal tips just don't carry enough heat for 
good results for individual pin soldering.

JJS

On Tuesday, June 26, 2018 at 12:51:35 PM UTC-4, David T. Ashley wrote:
> We do embedded software, but the hardware is produced by our customer (we don't control it).
> 
> Sometimes we need to attach a wire (for monitoring a serial or I2C interface, or for timing instrumentation) to a surface-mount IC where the pins are VERY close together.  The pins are so close together that I can't solder a wire to it, even using high-power optics and the finest soldering iron tip available.
> 
> Are there any special tools, equipment, training, or techniques that might help with this?

You should be involved in the hardware specification development so that you can insert test points for the likely points you would like to access.  

Otherwise you might be able to attach your probes more easily to a trace connected to an IC than the IC itself.  You can scrape the solder mask off of a spot on a trace and solder to the trace with no risk of shorting to another point.  If vias are not covered you can use them as an attachment point for wires. 

Rick C.

On Tuesday, June 26, 2018 at 12:51:35 PM UTC-4, David T. Ashley wrote:
> We do embedded software, but the hardware is produced by our customer (we don't control it).
> 
> Sometimes we need to attach a wire  to a surface-mount IC 

> 
> Are there any special tools, equipment, training,
> or techniques that might help with this?
> 
> Thanks!

You probably already have the illuminated magnifying glass.

Based on the qualities of the tch here that can do it,
I'd say you need a surgeon's hands and lots of practice!

Good luck
Ed

dashley@gmail.com writes:

> We do embedded software, but the hardware is produced by our customer
> (we don't control it).
>
> Sometimes we need to attach a wire (for monitoring a serial or I2C
> interface, or for timing instrumentation) to a surface-mount IC where
> the pins are VERY close together.  The pins are so close together that
> I can't solder a wire to it, even using high-power optics and the
> finest soldering iron tip available.
>
> Are there any special tools, equipment, training, or techniques that
> might help with this?
>

I always manage to solder wires, e.g.

<https://ee.devereux.me.uk/ADS7947.jpg>

 :)

However if you are talking about actual pins like a QFP or MSOP then I
have found there are miniature test hooks that work pretty well, better
than I expected. They are usable with fairly small pitches. Certainly
fine with 0.5mm pitch QFPs for example.

There are many types but e.g.

<https://www.digikey.co.uk/product-detail/en/e-z-hook/X2015BLK/461-1000-ND/528221>


-- 

John Devereux

John Speth <johnspeth@yahoo.com> wrote:
> I've found that the narrow Metcal tips just don't carry enough heat for 
> good results for individual pin soldering.

I'd suggest that being generous with flux will help here - there are times
when there's enough heat in there, but not enough to break down the oxide. 
Flux can get the whole lot going.  Jelly flux can be useful in staying where
you want it until you get the iron in.

Theo

On Tuesday, June 26, 2018 at 3:40:48 PM UTC-6, Chris wrote:
> Part of the hardware design is to put test points on the board where
> they are needed and always build in enough diagnostic capability :-)...

Around here I get back boards with "sorry, no space for your test
points, ya know thats why we're using 0402 - but we'll solder on
some test fly-wires for ya"...

On 28.06.2018 4:31, Dave Nadler wrote:
> On Tuesday, June 26, 2018 at 3:40:48 PM UTC-6, Chris wrote:
>> Part of the hardware design is to put test points on the board where
>> they are needed and always build in enough diagnostic capability :-)...
>
> Around here I get back boards with "sorry, no space for your test
> points, ya know thats why we're using 0402 - but we'll solder on
> some test fly-wires for ya"...
>

Is that a metric or imperial package? Sounds a little bit ambiguous. ^_^

Gene.