few of my personal preferences regarding test coupons:
(1) place the test coupons on center and the four corners of the pannel (top
two corners of the pannel normally have less plating due to field
distorsion, insufficient stir and "dead corner of the plating tank"). Check
for uniformaty.
(2) all the surface finishing shall be well showcased on the test coupon,
e.g. wire bonding pad (soft Au), ZIF edge (hard Au), HASL or OSP, etc.
(3) the feature of the test coupon should be the finest of the circuitary,
sufficient for SIR testing (with the solder mask).
(4) there should be an area (0.5 x 1.0 cm) with minimum cupper layer for use
as weight loss test (outgas test).
(5) coupon shall have wire bonding pads and die attach pads for wire bonding
test...(if you have enough Au on the coupon, you will be fine for the PWB
for wire bond..see item (1)...
(6) PTH and vias of the smallest feature of the design...including via plug,
if it is required.
(7) all the other goodies IPC and Mil wants (representing the designed
c.c.t, etc. etc.)
Warning: such "fussy" only worked with some vendor who willing to improve
the process and understand the needs to go through the "hell"...I have
someone roll his eye balls to almost completely "white"...also some sales
and purchesing guys say: "how much you will pay?" and some shake their
heads to the stage I start to worry about to pay some HMO fees...However,
who ever did it with design and qualification hardly have any problems
during the production...
If you are going to use the "fussy" methods, be ready to face some "life or
death" threat.
jk
At 08:40 AM 10/14/99 +1000, you wrote:
>Hi Jim
>You got good feed from Alain, Earl and Kelly .
>That is from the fab side of the story .
>
>You can double edge this (coupon) tool ;
>if you integrate to fab coupon (bare board) also your troublesome component
>mountings (say caps).
>Than you can on the same coupon analyze metalography of joints ;
>use them for cycling tests ;
>comparative shear tests (process stability on the same/different parameters
>[say different effects of various cooling profile scenarios]).
>The population (pads/component) you can alter say with any new bare board
>revision ;
>that way you can plan to target your various woes (say cap pad geometry's) .
>Obviously you parallel check your field as well , say cycling your coupons
>will give you warning way ahead before it hits you = you can walk to MD
>office and tell him he'll have a problem with this batch in 2 years or so
>time,
>because of this and that = supply service fellows with more clever
>alternative before the tsunami in on them .
>Concurrent engineering can be warped to limitless scapes ; often you need to
>step back to see it .
>Something about the trees and forests............
>
>cu
>
>Paul Klasek
>http://www.resmed.com
>
>
>
>-----Original Message-----
>From: West, Jim [mailto:[log in to unmask]]
>Sent: Thursday, 14 October 1999 0:23
>To: [log in to unmask]
>Subject: [TN] Specifying test coupons
>
>
>Hi all,
>
>Thanks to all that responded to my earlier test coupon question. I have a
>few more question, how do you specify test coupons? What do I tell the
>board layout guy? What do I tell the board house? Does everyone have test
>coupons on all boards or only multilayer? Any good advice on how to specify
>would be great!
>
>Thanks,
>
>Jim West
>Manufacturing Engineer
>
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