In Table 8, there are three rows. Each row represents a thickness range of
the laminate to be measured. For example, the first range is 0.5-0.78mm
(~20mil to 30.7mil).
For each thickness range there a re 4 variants of sample : single / double
side and the dimension of the sample panel, since sometimes you will have
sample with 1 or 2 edges less than 200 mm.
Say you have a 0.6mm thick, 180mm x 250mm double side bow & twist sample,
then looking up the table you will see a value of '3.0'. This means that
with IPC-TM-650 test method 2.4.22, the calculation is as follows :
%Bow = 3.0mm / 30.5 cm = 3 mm / 305 mm = 0.98%
%Twist = 0.98% also
This is very similar to MIL-S-13949H spec. 1%, except for laminate > 1.68mm,
where the percentage values are slightly different.
Regards,
Darik Leung
Mica-AVA (Far East) Ind. Ltd.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]]On Behalf Of Richard Hamilton
Sent: Wednesday, March 17, 1999 3:23 AM
To: [log in to unmask]
Subject: [TN] IPC-4101 Help
Hello again gang,
In researching this idea of flatness or warp and twist, I have gone to the
IPC-4101 and have gone stupid!! So, HELP!!
On page 11, section 3.8.4.3 Bow and Twist Laminate Materials, it refers to
Table 8 on the next page. both my PCB designer and I are having a hard time
making out the proper way to use the chart. Can someone please render some
assistance on this, Please. I don't believe the conversion factor (metric to
inches) is the problem, but maybe we are making it since we don't seem to
come up with reasonable answers. An example would be great.
Thanks again in advance.
Richard Hamilton
Clemar Mfg. / Rain Bird
[log in to unmask]
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