Hi Bev - yea, we did that work many moons ago. The paper is in the 2004 IPC
APEX Conference Proceedings, Paper S32-1. The primary issue with stacking
capacitors or resistors is that the ceramic material is sensitive to
thermal shock so if the manual soldering is not done correctly or if the
solder iron tip touches the component body, you are pretty much assured
that you will have caused a crack. John Maxwell has an excellent paper on
the cracking of capacitors which lists the primary root causes. Stacking
capacitors or resistors is not for the faint of heart.

Dave


On Thu, Jul 24, 2014 at 7:46 PM, Bev Christian <[log in to unmask]>
wrote:

> Also take a look at the neat paper that Dave Hillman gave at IPC APEX, I
> think about 4-6 years ago.  The people at Rockwell stacked AND did the rel
> testing.
>
> Regards,
> Bev
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
> Sent: Thursday, July 24, 2014 9:44 AM
> To: [log in to unmask]
> Subject: Re: [TN] Hand Soldering Stacked SMT Components
>
> 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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