Hi Phil,
You mean like Tantalum capacitors? I just went back and double checked the
gerbers for the board that I took a photo of earlier today, and the solder
paste apertures are 1-to-1 with the metal layer.
We also ran the other side of the board that I took the photo of and I
couldn't find any mid-chip solder balls anywhere.
Out of curiosity I called my stencil vendor and asked them if they did any
reduction to the apertures as standard to the gerbers I send, and they said
no. The only reductions that they do are the ones that I specify, and I do
occasionally, or I have some special footprint that I want to see, like for
Teledyne GRF relays for example. But as a rule I leave all the passive
apertures alone.
Like I said, in my case with a water soluble paste and a 4-mil thick stencil
and no homeplates, I very rarely see mid-chip solder balls.
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro
Sent: Tuesday, May 01, 2012 1:28 PM
To: [log in to unmask]
Subject: Re: [TN] Homeplates on 4 mil thick stencils?
Steve,
I would check your wrap around termination capacitors. There are many ways
to skin that cat and I suspect your paste aperture is already less than
1-to-1.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Tuesday, May 01, 2012 7:28 AM
To: [log in to unmask]
Subject: Re: [TN] Homeplates on 4 mil thick stencils?
Hi Richard,
I just looked closely at some product that we were running today that's
using a 4-mil stencil (with no homeplates), and I don't see any mid-chip
solder balls, and I looked at where they would most likely occur if there
were to be any:
http://stevezeva.homestead.com/4-mil_no_homeplate.JPG
I can't say that we NEVER have any, sometimes it happens, like when the
wrong sized part is used on a footprint designed for something else (oh
wait, that never happens!). But overall, usually don't see them when we use
a 4-mil thick stencil.
Steve
-----Original Message-----
From: Stadem, Richard D. [mailto:[log in to unmask]]
Sent: Monday, April 30, 2012 3:56 PM
To: TechNet E-Mail Forum; Steve Gregory
Subject: RE: [TN] Homeplates on 4 mil thick stencils?
Steve,
Somewhat related to the other discussion on cleaning of no-clean:
Do you wash the assemblies after reflow, and is that why you do not see any
mid-chip solder balls?
Do you wash any CCAs that have been processed with a no-clean solder paste
or no-clean wire solder?
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Monday, April 30, 2012 2:42 PM
To: [log in to unmask]
Subject: Re: [TN] Homeplates on 4 mil thick stencils?
BTW I forgot to add I don't homeplate anything...
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Monday, April 30, 2012 3:16 PM
To: [log in to unmask]
Subject: Re: [TN] Homeplates on 4 mil thick stencils?
Hi Ioan,
We use 4-mil thick stencils quite often and I don't see mid-chip balling...
Steve
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Ioan Tempea
Sent: Monday, April 30, 2012 2:54 PM
To: [log in to unmask]
Subject: [TN] Homeplates on 4 mil thick stencils?
Dear Technos,
It is my first 4 mil stencil and I was wondering if mid-chip balling is
still an issue at this thickness (no-clean process). Should I still
homeplate the apertures of passives, as I fear insufficient solder?
Thanks,
Ioan Tempea, ing.
Ingénieur Principal de Fabrication / Senior Manufacturing Engineer T |
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