This chart just shows how different prepreg glass styles (construction) are
used to build up different dielectric thicknesses.  FR4-04 is .11mm or
.0043", FR4-06 is .0051".  -17 is .0122" thick.

From a cost point of view, prepreg costs are basically the same per sheet
regardless of thickness.  The exception is 106 which has a slight premium
because it's so thin there's always an associated amount of handling damage.
When building up a specified thickness, the fewer sheets of prepreg that are
used, the cheaper the construction.  Compare -19 and -20.  Both are .37mm
thick but one is 2 plies of 7628 while the other is a 3-ply mis of 2113 and
7628.  -19 is cheaper becuase it only has 2 plies.

The downside is that the 7628 glass has relatively large bundles making it
difficult to drill.  It also has a lower resin content which can limit it's
use in some stackups.  There are also other drawbacks to using 7628 is some
applications.

Of course the main driving force in specifying materials is what dielectric
thickness do you need.  If you need have 10 layer board .062" thick you're
not going to be able to use -17 or-19.  It just won't fit.

Your trusty fabricator should be able to walk you through selecting the
appropriate thicknesses and constructions.

> ----------
> From:         ATI ProcessGuy[SMTP:[log in to unmask]]
> Reply To:     TechNet E-Mail Forum.;ATI ProcessGuy
> Sent:         Monday, February 18, 2002 3:10 PM
> To:   [log in to unmask]
> Subject:      [TN] FR-04 questions
>
> Per IPC 2222 (Feb 1998):
>
> Page 6, table 4-2 lists a selection chart for various Registered FR4
> types.
> I am familiar with FR4-04 and -06, however, it appears that for boards
> requiring to be very flat while still trying to watch cost, I would be
> better off specifying something like FR-4-17 or -19.
>
> It appears that the cost for 17 is middle of the road and cost for 19 is
> good.  The kicker is that the farther down the table I go, it appears that
> the minus is the laminate is more difficult to drill.
>
> Is there articles anywhere out there regarding costs once we leave the
> FR-04-06, FR-04-04 material and start going into the -17 or 19 etc?
>
> What about the accuracy of the chart?  It states material availability is
> good.  Anyone out there had experience with this?
>
> Reason I ask, I have a 488 pin BGA 1 inch square I have to solder and they
> are asking me what to spec.  Thanks in advance.
>
>
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