What about overprinting the solder and placing them tight against each other? 
Depending on pad size, you might even make it within standard Class 2 specs. 
The trend over the years has been to deliberately reduce the size of solder 
fillets because that actually increases reliability, so I'd think pad sharing 
would be fine from that perspective.

Wayne

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ron Feyereisen
Sent: Thursday, July 24, 2014 8:56 AM
To: [log in to unmask]
Subject: Re: [TN] Hand Soldering Stacked SMT Components

Hi Pat,

Thermal jet would be the better method but we're using hand soldering methods 
to minimize set-up time and to keep up with production.
We're hoping that this stacking requirement is temporary and that the customer 
will re-spin the PCB design to eliminate the stacking altogether. It's not a 
real estate issue, it appears to be an 'oops' and that this is the band aid.

I'm hoping that the placement pre-reflow method will work so we can perform 
the requirement in one fell swoop.

I'll also take a look at the IPC-7711/7721 manuals.

Thanks for the advice!

Ron


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Patrick Goodyear
Sent: Wednesday, July 23, 2014 5:36 PM
To: [log in to unmask]
Subject: Re: [TN] Hand Soldering Stacked SMT Components

Ron,

Are your techs attempting it with a soldering iron or a thermal jet?
Jetting is easist IMHO since you never touch the components with the hot jet 
and only heat what needs heating, if done correctly the part will
self align.    Make sure you can adjust airflow to minimize side force
on the components soft and hot is the way to do it.     I haven't tried
stacked components but it works great on hair thin leads and SMT
components.   We had Pace PRC-2000 repair stations where I worked and
they had thermal jet units as part of the features.     I have also done
it with stand alone units but it is a little harder, less control.

pat goodyear
PG&E control technician, retired.


On Wed, Jul 23, 2014 at 12:20 PM, Ron Feyereisen wrote:

> Hi Technetters,
>
> I'm looking for some sort of documented technique (if one exists) and
> advice on hand soldering stacked SMT components.
> We're currently working on a production job that requires hand
> soldering a 0603 resistor on top of an already reflowed capacitor of
> the same size and we're experiencing some fallout with one side not
> being completely connected at the top of the stack with a full fillet.
> Inspection is having to inspect at 10x mag and it's slowing down
> throughput.
>
> Any advice on improving our soldering techniques would be much
> appreciated!
>
> Thanks,
>
> Ron
>
> Ron Feyereisen
> Continuous Improvement Mgr., CIT
>
>
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