Victor,
You're on the right site. IPC-2221, 6.4 provides all the information known
to common man about impedance controls and associated calculations. Also,
the following is one of my Master Drawing notes concerning TDR findings with
MLB constructions:
7.0 Test Requirements
7.1 All electrical, including time domain reflectometry, and physical test
requirements shall be met in accordance with IPC-600F, IPC-6012, and
IPC-TM-650 test method requirements.
7.2 For all impedance controlled MLB?s, the fabricator shall provide
x-sectional correlation to TDR findings that clearly show and define each
dielectric thickness, glass style, copper foil thickness, plating thickness,
and laminate area and thermal zone evaluations as received and after thermal
stress ? as in 7.1.
7.3 Two photo micrographs shall be provided for each quality conformance
test circuit per lot. One shall show one hole on the ?A? coupon, in an as
received condition, and one shall show one hole on the ?B? coupon, after
thermal stress. This shall be done for each mutually agreed upon lot. Each
photo shall be taken at 40X and shall clearly verify the fabricator?s
microsection report, and shall directly correlate to the report?s findings.
Also, just about everything you wanted to know about TDR test methods is
presented in IPC-6012, with IPC-TM-650, number 2.5.5.7, therein.
Earl
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