You are correct, Timothy, on both points.

BTW, some shops are doing up to 14:1 (depending on board thickness) and
aiming for 18:1 PTHs.

Ray


-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Timothy Reeves
Sent: Tuesday, April 03, 2001 10:50 AM
To: [log in to unmask]
Subject: Re: [TN] Low Aspect Via definition

I believe that refers to plated through holes, not blind- or micro-vias.
Aren't typical aspect ratios for microvias something like 0.5:1-1:1?

Timothy Reeves
ECD Circuit Board Division
13626 S. Freeman Road
Mulino, OR 97042
(800) 228-8198    Fax (503) 829-5482


|-----Original Message-----
|From: Guy Ramsey [mailto:[log in to unmask]]
|Sent: Tuesday, April 03, 2001 7:21 AM
|Subject: Re: Low Aspect Via definition
|
|
|How about IPC-2222 (for rigid boards)
|
|Table 9-4 Aspect Ratios
|
|less than or equal to 5:1 Level A General Design Complexity - Preferred
|Producibility
|
|6:1 to 8:1 Level B Moderate Design Complexity - Standard Producibility
|
|equal to or greater than 9:1 Level C High Design Complexity - Reduced
|Producibility
|
|
|
|
| Guy Ramsey
|American Competitiveness Institute
|Senior Lab Technician / Instructor
|610 362-1200 ext 107
|
|
|-----Original Message-----
|From: TechNet [mailto:[log in to unmask]]On Behalf Of Michael Simms
|Sent: Tuesday, April 03, 2001 9:34 AM
|To: [log in to unmask]
|Subject: [TN] Low Aspect Via definition
|
|
|Hello T'Netters,
|I've not received a single reply from the last posting
|of this question, so I'd like to repeat:
|What document defines a low aspect via?
|Is there a numerical cut-off between a low aspect via
|and other vias?  Certainly, in the 6012A document, acceptable
|minimum average copper thickness and absolute minimum
|copper thickness are defined for typical vias and
|low aspect vias. Is 3:1 a low aspect via? How about 4:1?
|Or 5:1?
|Any help out there?
|Mike Simms
|Trace Laboratories - Central

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