Hi Stacy,
I'm confused by the dimensions you list - 1.125 inches for the height of a
bare pcb? 125 mils (0.125 inches) is a thick board in my book. The old
standard was a 62 mil board and the new standard/typical board is 93 mils
thick for a 14/16 layer design. How many layers does a SIMM/DIMM have?
PCB height should be easy but Mr. Murphy likes to show up - on the off-shift
from my experience. Thickness tolerance requires balancing the customer's
need for a consistent product with enough leeway to account for process
variations. Also, I'm amazed when people forget a panel has natural
variations in thickness due to construction.
Typically, I've seen the overall thickness tolerance held at +/-10% with a
tighter tolerance for individual layer spacing to meet any impedance
requirements. More advanced designs might have a +/-5% tolerance.
Achieving uniform thickness across a panel or an entire press load requires
properly maintained lamination & measurement equipment - the presses,
heating and cooling systems, and the micrometer. Hitting the nominal
lamination thickness starts with proven (or best guess) numbers in the first
place.
Hans
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Hans M. Hinners
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Gunship Team
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-----Original Message-----
From: My Nguyen [mailto:[log in to unmask]]
Sent: Friday, December 21, 2001 5:48 PM
To: [log in to unmask]
Subject: Re: [TN] Panel Layout Standardization - PCB height increment
Hello Technetters,
Thank you so much! You guys are awesome!
Yes Steve, thanks for your input, you don't mind if I
quote it in my report "50,000/year just for waste
solder paste on X-out modules for 1 mil module/month"
(our volume is about not less).
The problem of X-Out, from my concern, is how to
provide good support in Solder Paste Printing process
as we do second side product. Width different
component height (D-Pac Stack, TSOP, SOJ, high/low
profile capacitors, different PCB thickness), it is
not easy to find flexible/cost effitive tool for the
support toolings. Even with one product but the X-Out
position shift from block to block.
THE SECOND QUESTION IS PCB HEIGHT. WE WANT THE LAYOUT
ENGINEER TO FOLLOW THE 0.125 INCREMENT. (I.e for DIMM,
the dimension will be 5.25x1.00/1.125/1.250/1.375...)
By doing we can standardize the panel size, the tools,
fixture, etc. However, I do not know is there any JDEC
spec or any other spec on PCB height or its increment.
Please advise,
Stacy
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