----- Original Message -----

From: [log in to unmask]>Denis Lefebvre

To: [log in to unmask]>[log in to unmask]

Sent: Tuesday, November 13, 2001 5:53 AM

Subject: Re: [TN] Aspect Ratio

At 09:59 AM 11/13/2001 +0800, you wrote:

I have been leaving through IPC-2221 on aspect ratio but did not have
any value on this information. Can some kind soul provide the answers to
my questions :

1. what is the current achievable/acceptable aspect ratio for plated
through hole?

Most domestic shops can easily do a 6:1 aspect ratio.

2. Is there a different on the aspect ratio for PTH via? If yes, please
provide.

No. Any plated through hole regardless of function. It's a matter of the ratio of hole diameter vs laminate thickness. For example; a 12mil PTH in a 60mil laminate is a 5:1 aspect ration. (60/12) a 10 mil PTH in a 60mil laminate is a 6:1 aspect ratio and so on.

3. What is the aspect ratio for micro via of HDI Type 1 and Type II
board?

Depends on the hole diameter and the thickness of the laminate you're drilling.

4. How about the aspect ratio for blind via on normal PTH board?

See #3

A big THANK YOU to all who will be responding!
Regards - Wee Mei

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