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Subject:
From:
Steve Gregory <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Steve Gregory <[log in to unmask]>
Date:
Tue, 22 Mar 2011 20:19:43 -0400
Content-Type:
text/plain
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text/plain (242 lines)
WOW! 21,000 apertures!

For solder paste? If it was solder paste, what size mesh type was printed? 
What size were the apertures? Were they round or square? How thick was the 
stencil?

Sorry for all the questions, but I just had to ask...

Steve

-----Original Message----- 
From: Ahne Oosterhof
Sent: Tuesday, March 22, 2011 7:23 PM
To: [log in to unmask]
Subject: Re: [TN] AW: [TN] Large Board Printers

Especially in the newer stencil lasers it is very easy to cut a stencil
after the proper size metal is already glued to the mesh. When cutting the
bare metal sheet before it is mounted in the frame it is exposed to a
different tension than after it is glued to the mesh. The affect of that
tension difference can be noticed especially in stencils for large boards or
panels. (The error due to tension difference can be as much as 65um for a
125um thick stencil.)

Ahne.

PS: my test vehicle was for a board of about 500x350mm with 21,000
apertures.
PPS: Electroformed stencils during manufacture see no stress in the metal!



-----Original Message-----
From: Steve Gregory [mailto:[log in to unmask]]
Sent: Tuesday, March 22, 2011 14:18
To: [log in to unmask]; [log in to unmask]
Subject: Re: [TN] AW: [TN] Large Board Printers

Hi Ahne,

When you say "Stencils cut in a frame" what does that mean?

Aren't most all stencils cut in stainless foil outside of a frame, and then
the foil bonded to the frame around the periphery with a polyester mesh?

Steve

-----Original Message----- 
From: Ahne Oosterhof
Sent: Tuesday, March 22, 2011 12:45 PM
To: [log in to unmask]
Subject: Re: [TN] AW: [TN] Large Board Printers

I have been looking for pad-to-pad location accuracy on circuit boards, but
have been unable so far to get clear answers.
I did a study for large board (or panel) aperture-to-aperture location
accuracy for stencils made with different processes and on different laser
systems. The results were quite surprising and have been presented at the
most recent Pan-Pacific conference and are available in the proceedings.
REPORTED CONCLUSION:
For a stencil with optimum aperture positioning accuracy we can conclude
that it is critical to choose the best manufacturing method based on three
main factors: 1. Laser cutting shows better results than photo based
processes, 2. Stencils cut in a frame show very little distortion and 3.
Stencils cut on modern lasers showed significantly better positioning
accuracy.

Would you believe error ranges of more than 175um (7mil)!! And board
pad-to-pad errors only make things worse.

Ahne Oosterhof.


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Neifer, Gebhard
Sent: Tuesday, March 22, 2011 08:13
To: [log in to unmask]
Subject: [TN] AW: [TN] Large Board Printers

Good question Steve and I do not have a good answer for you but an
additional question for the forum that relates to the same subject:
Is there an IPC specification that specifies the pad to pad dimension
tolerance. My first guess was that I may find something in IPC-A 600, but no
cigar. Does anybody have an idea whether there is a spec regarding the
location tolerances smt pad to smt pad?

Thanks, cheers,
Gebhard




-----Ursprüngliche Nachricht-----
Von: TechNet [mailto:[log in to unmask]] Im Auftrag von Steve Gregory
Gesendet: Dienstag, 22. März 2011 12:14
An: [log in to unmask]
Betreff: [TN] Large Board Printers

Morning all,



I'm wondering if any of you have had any experience with large board ( 22 X
24" and greater) printers? In particular the Surface Mount Techniques
AUL-2220. How well does it do with small apertures (0201 apertures) and fine
pitch?



Any comments good or bad are welcome. If you would prefer to reply offline,
reply to me directly.



Are there any other players out there that do large board printers?



Thanks!



Steve Gregory









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