Good old days 20 years ago, the coupons I saw were located on the panel cut off edge, and center, it consists of the critical design feature of the board: PTH, wire bendable gold pads, osp covered fine pitch, etc. You take the coupon, do 10 thermal shock, get open short electrical test followed by cross section . Some of virgin sample you do tg, cte measurements if it was a new design. Follow on shipments, you just need to do 10-15 wirebonds, match up with certificate from the vendor in term of wire pull strength, and electrical test. You random check for x-section and tg (use tma,so you get cte as well, any poor cured PWB would shown). Both party, the user and the supplier understood, the certificate is based on the cross section on file, ready for review on moment of notice. You pay a bit more to get it all in the contractual agreement, save a lot of money and you sleep well at night.   Hardly have any problem. However, the design also fully aware of not push boundaries.   Bleeding edge technology is not good practice. Both party make money, live happily ever after (allow you to work on some bleeding edge technology... otherwise, you just spent a lot of dough and try to catch your tails. - "pay me less, pay me now. Pay me more and pay me later... unless, some one just turn a blind eye and wait for field returns).

"All professional skills are mastered by critiqued practice" - by Schon.
  Original Message
From: Louis Hart
Sent: Tuesday, April 1, 2014 7:05 PM
To: [log in to unmask]
Reply To: TechNet E-Mail Forum
Subject: Re: [TN] PWB Microsection Report - Photos


Phil, interesting the questions you ask.

As someone who works on PCB fabrication, I have often wondered if any customers looked at the coupons and sections we send them.

Personally, I have been reluctant to send Compunetics' sections as I have told colleagues that these sections are the documents showing that, to all indications, the boards were built in conformance with requirements.  For that reason, if a customer requests a section of a single coupon, I tell our folks that we will prepare an extra one for the customer and keep our usual complement.  During the past few months a customer has been requiring all of our formerly internal sections, the sectioning and analysis by an external lab, plus any remaining coupons. (We have been sending everything - G, E, M, etc -  in the face of these imprecise requirements.)  Then we note in the microsection archive, and on the production records, that all coupons and sections went to the customer in accordance with the purchase order requirements.

The semiconductor detectors in the common lab microscopes cannot get an image of much more than one hole, and maybe not even that in a thick board, at the standard 100X magnification. The CCDs used in the big astronomical telescopes like those at Mauna Kea, the Canary Islands, or the European Southern Observatory high in the Chilean Andes, could capture more area, maybe. But the last I heard, which was 11 years ago, the price for one of those chips by itself was upwards of $70 000.

If I had the sections themselves, I would not bother with any photos.

I notice Vladimir at Sentec just posted something.  Let's see what he thinks....Louis Hart

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro
Sent: Tuesday, April 01, 2014 6:40 PM
To: [log in to unmask]
Subject: [TN] PWB Microsection Report - Photos

I have been trying to get my PWB Fabricators to include photographs of the cross sections that come in with our PWBs but have encountered resistance from some of them.  Some even say they cannot do this as they don't have the camera equipment. They always include a mount with a cert and spare coupons but no picture of what is already polished in the mount.

In my opinion, looking over a spreadsheet of check marked boxes for compliance to 6012 is important, but a picture of the mount(s) reveals more information.  And in my experience, when I go to a third party lab, I always get photos.


Am I asking for something that is not normally provided from a PWB Fabricator?

What do the rest of you do when it comes to inspection of microsection mounts?

Thanks in advance,

Phil
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