Daan,
since we deal with many different customers, I can tell you that the most important thing in passing boards is how knowledgeable they are in terms of IPC-610 and assembly processes. The more they know, the better the communication and the less time you spend over inspecting, cleaning no-clean flux, making sure that TH components are all on the same line, etc.
So I guess the answer should be the well-known "it depends". Just kidding, not really "it depends", but "inspect it all". In the consumer goods world there is no way to segregate products and say: this one sees 100% inspection and touch-up, but this one no. The assemblers will always change, the shifts will have an impact, no matter how good your instructions are. So some people will comply and inspect less, but somebody will re-check their work and compare it with the work of a 100% inspection team. You see the picture, "why do you guys have poor results and the others are doing so well?" Nobody will bother to compare the actual cost per piece.
I know it is not what you wanted to hear, but this is my opinion. Maybe in your world, hi-rel, avionics, etc. it would be easier to control output. Also, the number of customers is important, less you have, easier to control. So, in your case, maybe, with a good production preparation engineering you could try to segregate the products. You will not be able to apply a common inspection rule to all of them. Some might be less inspected, but you will need to determine which ones. Do you have the manpower to do this?
And by the way, where did you get this report from? I would like to read it. If free download, could you add a link to your site?
Good luck,
Ioan
> -----Original Message-----
> From: TechNet [SMTP:[log in to unmask]] On Behalf Of Daan Terstegge
> Sent: Monday, April 25, 2005 6:22 AM
> To: [log in to unmask]
> Subject: [TN] Inspection and touch-up of visual defects
>
> Hi Technet,
>
> I have a question about inspection, touch-up, and how far you need to
> go to get a product that meets the required IPC-spec.
> According to some reports (i.e. "New Study Reveals Component Defect
> Levels" by Stig Oresjo of Agilent) the average defect level in PCB
> assembly is around 1100 dpmo. Even with much better dpmo-figures it is
> easy to see that except for very simple boards almost every one of them
> will have one or more defects before touch-up. A significant portion of
> these defects will be visual defects like an isolated spot of flux
> residue, overhang of an occasional bent lead, micro-solderballs, an
> occasional insufficient solder, an overlooked spike from handsoldering,
> etcetera. Although these are all actual defects according to
> IPC-A-610,the chance that they will cause the product to fail during
> their service-life is minimal.
>
> Now the point of this posting is: how much effort do you need to put
> into finding and correcting visual defects.
>
> You could argue that every board that still has a visual defect simply
> does not meet the IPC-requirement, and therefore every boards needs to
> be 100% visually inspected until you can be sure that you have found and
> reworked all visual defects. Subsequent to the 100% touch-up inspection,
> another 100% inspection by quality control might be needed to achieve
> this. The result is a nice-looking product which meets all the
> inspection requirements of IPC-A-610, but unfortunately it will be an
> expensive board.
> Another approach is to visually inspect the boards mainly for the
> purpose of feedback to the assembly process (on sample basis), and rely
> on electrical tests for finding defects to be reworked. Quick and
> effective, but only some of the visual defects will be found and thus,
> formally, the product (or at least some of them) will not meet the
> inspection requirements of IPC-A-610.
>
> I try to convince others that we spend more time on inspecting than we>
> should, but so far every visual defect that is found is seen as proof
> that I am wrong. I am interested to hear how others are coping with this
> issue.
>
> Best Regards,
>
> Daan Terstegge
> Production Engineering
> Thales Land&Joint Systems
>
> Tel: +31(0)35 524 8297
> Fax: +31(0)35 524 8181
> Unclassified Email
>
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