Paul:
In spite of Kathy's euphoria, there is at least three caveats:
1) Screen the paste rather than dispensing it, if possible.
In addition to oblong pads, the screening process will create
"stalagmites" on the bottom side of the board. Since paste is 50%
metal by volume and 50% flux, more paste is required to fill the
hole with solder and create adequate filleting on both sides.
Dispensing alone may not provide the additional volume required to
fill the hole.
2) Lead protrusion of the through-hole components should be less
than the thickness of the board.
Longer lead length tends to distribute paste along the entire lead
protrusion and may rob solder from the barrel. The shorter the
protrusion, the better, as long as it meets IPC-A-610B conditions.
3) Don't let the paste dry out while on the stencil.
If items 2 and 3 happen simultaneously, the entire column of paste
could be pushed out of the barrel by the blunt lead of the T/H
component and can reflow as a "ball on the end of a stick". This
could, in turn, create an electrical disconnect that you would have
to inspect for. The desirable action is for the paste that is
pushed out of the hole during T/H component insertion to wick back
into the barrel and help create the bottomside fillet.
If your processes are under control and you deal with these potential
"gotchas", you should have good success.
Good Luck!
Bill Fabry
Plantronics, Inc.
[log in to unmask]
______________________________ Reply Separator _________________________________
Subject: Re: [TN] paste-in-hole components
Author: "TechNet E-Mail Forum." <[log in to unmask]> at INTERNET
Date: 4/9/98 4:43 PM
I have printed solder paste on through hole pads and it worked really well!!
The apertures were made an oblong shape to allow enough solder to be printed
over the hole. The connector was installed into the wet solder paste and
ran through the oven. We had excellent wetting on both sides.
Hope this helps a little.
Thanks,
Kathy Palumbo
> ----------
> From: Paul Stolar[SMTP:[log in to unmask]]
> Sent: Thursday, April 09, 1998 3:27 PM
> To: [log in to unmask]
> Subject: Re: [TN] paste-in-hole components
>
> Content-Transfer-Encoding: 7bit
>
>
>
> I am also in the beginning throes of paste in hole. But I will be
> trying to dispense the paste. Are you planning on screening or
> dispensing?
>
>
> ______________________________ Reply Separator
> _________________________________
> Subject: [TN] paste-in-hole components
> Author: [log in to unmask]> Jeff Hempton
> <[log in to unmask] at internet
> Date: 4/9/98 4:18 PM
>
>
> Greetings fellow Technetters,
> I am in the beginning throes of implementing serious paste-in-hole
> (PIH) here at UT. I have some limited experience/success in this
> area,
> but would like to tap into some of you PIH users that have been
> involved longer, and are Grand Wizards of the PIH process:
> 1) Could you please forward any info you can share on component
> suppliers that are manufacturing/willing-to-manufacture leaded
> components (connectors,etc.) for this process?
> 2) Same question for feeder manufacturers, taping houses, etc.
>
> If you are a vendor, please respond to me directly instead of
> replying to Technet. ANY info shared would be DEEPLY appreciated.
> Thanx in advance!
>
> United Technology Electronic Controls
> Jeff L. Hempton, Sr. SMD Engineer
> 3650 West 200 North
> Huntington, In
> 46750-9002
> Phone: 219-359-3514
> Fax: 219-358-0695
> E-mail: [log in to unmask]
>
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