(More wood to the bonfire...)
In addition to the other comments, to expand on what Moonmeister said,
possible that your vendor is using foil construction now versus core
construction. For 4-layer boards, foil construction starts with a core
board already processed and adds laminate/prepreg to the outside with copper
foil added last, then processed. Core construction uses 2 cores (Layers 1 &
2, then Layers 3 & 4) with laminate/prepreg in between.
Does the master (or drill) drawing define board construction, or is it left
to the vendor's discretion?
Roger M. Stoops, CID [log in to unmask]
TRIMBLE NAVIGATION LLC
-----Original Message-----
From: Genny Gibbard [mailto:[log in to unmask]]
Sent: Tuesday, February 26, 2002 11:36 AM
To: [log in to unmask]
Subject: Re: [TN] The board looks funny...
That is kind of what I was wondering, Moonman.
Does it appear that our board manufacturers usually etch the copper on the
back of the top sheet of FR4, and instead this manufacturer etched it on the
top of the inner sheet of FR4, so we are seeing the other side of the
copper? As far as I figure, the layer spacing would be effectively the
same, so can anyone see any problems with one type of construction over the
other?
The deeper layer is dark like the close layer usually appears, so to me it
looks like the same processes were used but both inner layers were etched on
the inner sheet of FR4, versus etching them on the inside of the outer two
sheets.
Or, considering the other answer I received regarding no oxide coating, or
double treatment: are these bad things?
Thanks.
-----Original Message-----
From: Earl Moon [mailto:[log in to unmask]]
Sent: February 26, 2002 10:14 AM
To: [log in to unmask]; [log in to unmask]
Subject: Re: The board looks funny...
Just depends on which layer you look at - one on the back of the top layer
or one more down
MoonMan
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