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Date: | Mon, 1 Jul 1996 09:21:52 -0500 |
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Let me give you a "generally" as well as a "usually". In the US,
materials are generally cheaper than process; so the six layer board
may turn out to be cheaper. However, neither of these boards should
cost more than $15 ~ $50 depending on the size and shape and total
hole count. You may already be using the wrong vendor if you think
that 1000 holes is going to save you $100 per board.
Regards,
Roger Held
Hitachi Computer Products (America), Inc.
______________________________ Reply Separator _________________________________
Subject: Re: 4-layer vs 6-layer
Author: [log in to unmask] at Internet-HICAM-OK
Date: 7/1/96 9:32 AM
>Hi,
>My customer is curious as to what would cost more a 4 layer board or a six
>layer board. Here are the details:
>
>Board has 1 gnd layer an 1 vcc layer and is primarily surface mount and a
>digital circuit without any critical paths. These will remain constant. The
>board was autorouted for both a six layer version and a four layer version,
>so here is the difference of 2 signal layers or 4 signal layers . The 4
>layer was routed to 96% and 2500+ vias and the six layer routed to 100% with
>1450+ vias. We all can surmise that the six layer version will be more
>reliable in the long run. I am told that the cost is drilling alone is
>about a $100 difference per board. Can any body help with the cost analysis?
>
>Thanks in advance,
>
>Scott Shepard
>Interactive Design Solutions
>also at [log in to unmask]
>
Comments on the drill costs: a delta of 1000 holes for $100 ! Wow! Thats
ten cents per hole. I don't think holes cost that much...However, hole
density is another issue. I have seen a factor chart based on holes per
square inch.
# of holes per sq. inch factor
up to 40 +0%
40 - 50 +20%
50 - 60 +50%
60 - 70 +65%
70 - 80 +80%
100 holes per sq inch is having a hole every 100 mils.
As far as reliability goes, the simpler design is usually the more
reliable. The simpler the design, the lower the cost. So, if you are only
changing # of layers, routings, and trace/hole density, (and knowing
nothing about the design), I would quote the two designs from the same
shops and take the lower cost design. If I haven't said 'usually' enough,
I want to add that this usually works pretty good. (Don't forget to add in
the cost of assembling 4% of the connects in jumper wires.)
George Franck
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