Test coupons comprise quality conformance test circuitry. This circuitry,
and their coupons, represent important PCB, especially multilayer, features
as holes, plating, shorts, opens, impedance, laminate integrity, etc.
Quality conformance test circuitry, and their coupons, are attached to PCB
panels and are detached when required to verify product quality. IPC's new
2221? and the old D-275, and the older MIL-STD-275 provide requirements for
this circuitry and coupons.
As an example, if you wanted to determine hole wall quality as received from
a supplier, you could X-Section (a destructive process used on the coupon
but not the expensive board) a coupon and determine its quality assuring the
specified laminate was used, the drilling process was well managed, the
specified plating thickness was present, voids did not exceed specified
requirements, and other physical requirements were met, etc.
Another example would be examining the "B" coupon after thermal stress
testing simulating assembly soldering operations. If defects were found, as
delamination, hole wall cracking, pad lifting, etc., corrective action could
be taken and process improvement could be effected and ensured.
There are many coupont types comprising the quality conformance test
circuitry. Some exist for plating adhesion. Others exist for continuity, as
shorting or opens, testing, and others are provided for impedance or solder
mask testing. In fact, anything you want to know about a PCB, especially
about a multilayer type, is apparent in a coupon or many. After all, more
than 90% of a PCB lies hidden in its Z axis so why go anywhere without them?
Earl Moon
----- Original Message -----
From: West, Jim <[log in to unmask]>
To: <[log in to unmask]>
Sent: Tuesday, October 12, 1999 1:00 PM
Subject: [TN] What are test coupons?
> Hey Techno's,
>
> I see people talking about test coupons and I'm not sure what this is all
> about. Could someone explain to me what they are, how are they used, and
> what do they do?
>
> Thanks,
>
> Jim West
> Manufacturing Engineer
>
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