These are old callouts that date back to pre-1977 changes to the MIL
spec 13949.
They refer to "hot-strength retention" epoxy glass laminates for
double-sided.  GB is non-FR.  GH is FR.  See slash sheets 3 and 5 (?)
for the old MIL-P-13949.

In IPC-4101A, the spec sheets that apply to these are GB => 4101/22 and
GH => 4101/23.
Today, most laminators will offer you their 170C FR4, which are covered
by 4101/24, but some laminators have dual qualification to the /23 also.

I don't think any non-FR epoxy resin is used today. People just
substitute the FR versions.

Jim Paulus

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Franklin D Asbell
Sent: Wednesday, September 15, 2004 11:21 AM
To: [log in to unmask]
Subject: [TN] Laminate question

Got a spec with the following information;


Type FL-GH or FL-GB,

Does anyone know what these refer to???

Thanks


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Franklin

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