Pete,
Actually there are different schools of thought on this subject.
So, I'll try to give at least a couple of reasons in each direction prior to my opinion.

1. removal of inner layer pads will help improve yields at fabrication due to reduction of failure opportunities (both drill and layer to layer).
2. non-removal of inner layer pads will improve reliability due to inner layer anchoring for through holes and reduced copper stress during high CTE excursions.

Now, here is what I think.
Depending on layer count, material properties and use environments there are times when you can remove unused inner layer pads and not reduce the overall product.
As a rule of thumb I try to maintain inner layer pads on all designs that are:

1. more than 6 layers
2. greater than .062" thick
3. use mismatched materials
4. have large range environment end use

There are other criteria to consider, but you should get the idea.
Most importantly is what is your use.
Are you designing for commodity or for space travel?
Are you comfortable with the stresses within your design?

Most PCB fabs would probably appreciate if not recommend removal of unused pads, while most reliability types would caution against.
Important is communicate, talk to the guys that are responsible for your product's reliability and get their opinions.
They might tell you they don't care or they might get real excited.
Remember that it is product requirements that should drive this issue not cost or ease.
Hope it helps,
FNK

Frank N Kimmey CID+
Principal PCB Designer
Powerwave Technologies Inc
Office 916-941-3159
Fax 916-941-3195
Cellular 916-804-2491
   
-----Original Message-----
From: Pete menuez [mailto:[log in to unmask]]
Sent: Wednesday, February 09, 2005 6:03 AM
To: [log in to unmask]
Subject: [TN] Removal of Non-functional pads


Can someone explain the advantage of removing non-functional pads on
innerlayers? We are contemplating adding non-functional pads to our designs
but want to understand the impact if we do.

Thanks

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