Hi Victor-
No, I don't know of direct IPC standards on this. I'd think it would be in
the specification for your laminate (such as FR4). The laminates probably
list a maximum resin weight percentage. But that would be for the whole
shebang, obviously that falls apart when you get into a small enough area.
Just how small are you talking about?
Reasons for it happening:
-High flow pre-preg with very uneven metal loading from a vertical
perspective. (Unbalanced layer-to-layer unevenness results in warpage, but
if you had a whole lot of metal with edges all ending in the same spot on
each layer, then the resin would be displaced to the areas with less
copper.)
-Cutouts in pre-preg to accommodate cavities or other special structures.
-Poorly made laminate/prepreg. In that case, it should fail the spec on
resin weight percentage.
Wayne
From: [log in to unmask] [mailto:[log in to unmask]]
Sent: Friday, July 25, 2014 1:26 PM
To: [log in to unmask]; Wayne Thayer
Cc: [log in to unmask]
Subject: RE: PWB, rich epoxy area witin laminate
Wayne,
Are you aware of any IPC STDs which cover this anomaly or even bench
marking? I hope PWB/PCB gurus will chime in on this topic.
Victor,
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Thursday, July 24, 2014 3:44 PM
To: [log in to unmask]
Subject: Re: [TN] PWB, rich epoxy area
Resin rich will be weaker, lower dielectric constant, more subject to
cracking, higher coefficient of expansion. Actual effect on
reliability/product use depends on how close the design relies on "normal"
laminate specs.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Victor Hernandez
Sent: Thursday, July 24, 2014 3:37 PM
To: [log in to unmask]
Subject: [TN] PWB, rich epoxy area
Fellow TechNetters:
Can a rich epoxy area/site within a PWB laminate be harmful. What can
happen and what could be the reason for the rich epoxy area? Where can I
fins supporting literature in IPC STDs and or bench marking.
Victor,
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