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From:
"Woolley, Mark D. (Mark)" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Woolley, Mark D. (Mark)
Date:
Mon, 2 May 2011 08:15:47 -0600
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Sorry, Let me try again.  (I don't know what happened the last time.)

Being a slave to "Standards" is not where we should be as an industry.  The "standards" are, in reality, minimum acceptable criteria.  I often hear manufacturers state that they build to a standard or their product meets the "standards."  

However, as I inspect these products per the same standards (mostly IPC-A-600 and IPC-A-610), I see that while the product might meet the “Standards” it was manufactured along the minimum edge of acceptability per the standard.  

An example: Visible, opaque particulates embedded in the solder mask might meet the IPC-A-610 standard if they do not encroach on certain areas of the PWB.  But what does finding multiple occurrences of particulates in the solder mask mean in terms of the PWB manufacturing quality?  Unless you are dealing with military classes, in mass production a close visual inspection can only be performed on a limited number of units. If those units barely meet the standard what does that indicate about the remainder?  (How many particulates might be embedded within the PWB layers where they are not readily visible?  And of these how many could eventually cause a short?)  

Meeting the Standards is not sufficient to build a reliable product.  The standards must always remain as the minimum acceptable criteria not as the expected mean or median product.

The IPC committees put long hours into each specification to clarify points and make the items as understandable as possible.  IPC-A-610E (and later revisions) is a great asset.  Pictures showing both the good and the bad are presented.  But never is it stated in the specification (that I have read) that a process that consistently produces products at the edge of acceptability (per the standard) is acceptable to industry.

Having said that I must agree with Brian’s statement:

“In short, Standards, used appropriately, can help, as far as possible, 
to perfect reliability for a given application. Used inappropriately, 
they can drive up costs dramatically …” 

There needs to be common sense in the application of the standards, both from a user and a manufacturer point of view.  Customers’ don’t want manufacturers to hide behind the “Standards’ Wall” when confronted with issues with their products.  And the products should be manufactured in a manner that places only the smallest percentage, (ideally none) of products below these limits.



mark
Mark Woolley |PTRL Laboratory | Avaya | 1300 West 120th Ave | Westminster, CO 80234  USA |
Voice (Lab): (303) 538-2166 | email: [log in to unmask] |


-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Woolley, Mark D. (Mark)
Sent: Monday, May 02, 2011 8:13 AM
To: [log in to unmask]
Subject: Re: [TN] "The Curse of IPC-A-610 and IPC-J-STD-001" - opinion piece by James Smith


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7V7f"twithstanding, I believe - and I've proposed this idea before - that 

there is a too slavish adherence to standards rather than to common 

sense. This is because the standards exist and are used but are not 

applicable to many applications which do not require top quality 

reliability. Just the unnecessary inspection is costly, let alone the 

afterwork. It reminds me of one of my ex-customers making a lab 

instrument that is used only in comfortable room conditions. He was 

getting a lot of cratering on his wired through-hole SJs after wave 

soldering, and he had personnel reworking these joints (which 

plop-plopped for several seconds of applying the soldering iron). I 

asked why and he told me that the joints were faulty. I rejoined with 

something like BS. He gave me a board full of craters but which was 

otherwise faulty and I did microsections of half-a dozen "faulty" SJs, 

all of which showed perfect intermetallic formation along both wire and 

through-hole plating, with the craters and blowholes outside the 

intermetallics. This persuaded my client that the "fault" was cosmetic 

and he stopped the retouching except on grossly obvious faults. From 

that moment, the number of returns was reduced. For pointing out to him 

that he was wasting money by a too-solicitous inspection and retouching, 

he presented me with a bottle of Neuchâtel Oeil de Perdrix, which was 

delicious.

 

Incidentally, it was this case that inspired me to develop what became 

known as the "Plop-plop Meter" to measure the outgassing of PTHs. This 

never got beyond prototype stage, but it worked admirably and was able 

to distinguish between different causes of outgassing. However, I wasn't 

convinced that the market justified putting it into production; it 

remained a curiosity.

 

In short, Standards, used appropriately, can help, as far as possible, 

to perfect reliability for a given application. Used inappropriately, 

they can drive up costs dramatically and with no justification; this 

could drive the manufacture to E. Asia, at the cost of jobs. Maybe the 

author was expressing this sentiment, albeit unscientifically and too 

clumsily.

 

Let common sense prevail!

 

Brian

 

On 29/04/2011 19:15, Graham Collins wrote:

> Anyone else read this?

> http://www.assemblymag.com/Articles/Blog/BNP_GUID_9-5-2006_A_10000000000

> 001038283

> 

> All I can say is "wow".  Well, I could go on for hours, but...  wow.

> Not quite how I see these specs!  Working on military stuff I can attest

> that changing from MIL-STD-2000 to the IPC specs was a significant

> improvement in reality, reliability, and productivity, but that's not

> how he sees it.

> 

> regards,

> 

> Graham Collins

> Halifax Production Engineering

> L-3 communications Electronic Systems

> (902) 873-2000 ext. 6215

> 

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