Hi Dave:

Let me ask YOU these questions: When you say that specifications should 
not be set in concrete, is that because the specifications are
themselves
circumspect? Shouldn't specifications provide the necessary information
for companies to meet the level of quality and reliability demanded 
of their products? If not, why call them specifications, and why involve
reputable organizations such as IPC and ANSI to mandate them? 

I think that the role of standards is to set precise criteria based on 
a thorough analysis of the associated parameters and to reduce the 
misinterpretation that arises out of differences of opinion. No company 
should find it necessary to conduct experiments to prove that its 
assembly will perform reliably in its designed environment. 
This should be provided by an industry specification such as 
J-STD-001 or IPC-610. (of course, not every company is capable of 
such research and a new service industry could be spawned off as a
result!!!)

Inspection and rework are costly and should be based on a commonly 
accepted norm that is flexible to the extent that it tells you the 
related variables that influence or  are impacted by the one being 
verified. It may take many years to understand the true impact of 
the variables and settle upon a range of limits that make better sense. 
But once established, they should serve as a self-contained reference 
for BLIND implementation so that the INDUSTRY as a whole will 
benefit from it. The ANSI/ASME Y14.5.1M for dimensions and tolerances 
is a classic example of such a well supported standard.

So instead of belittling the current standard by asking
people to disregard the wording (in which I think you played an
important
role), I strongly urge you to stimulate a discussion of how to make the
specifications more meaningful. This TechNet forum is possibly the best 
place to communicate our thoughts freely. Moreover, there seem to be 
more people on Technet who are knowledgable about the
process-shape-property 
relationship than at any meeting. We can provide the continuous 
improvement that is a natural characteristic of the technologies in 
electronics manufacturing.

Regards,

Vijay Sankaran
Research Associate
Center for Integrated Electronics and Electronics Manufacturing
Rensselaer Polytechnic Institute
Troy, NY 12180
Ph: (518) 276-2721
Fax:(518) 276-2990

ddhillma wrote:
> 
>      Hi Phil -
> 
>      Let me ask this question: When you do put adhesive on a MELF for wave
>      soldering purposes, do you have an failures? I would put forth that if
>      you have sufficient documentation showing that your procedure results
>      in no reduction of reliability for the use environment the assembly is
>      going in then ignore the "specification". Specifications are not
>      (well, should not be anyway) set in concrete - JSTD 001 is an example
>      of a specification that allows for processes to be fit to their use
>      environments. I wouldn't get wrapped up in the specifications words if
>      you can show proof that a process/assembly method is reliable.
>      Hopefully your customer will look at the situation the same way. Good
>      luck.
> 
> 
>      Dave Hillman
>      Rockwell Collins
>      [log in to unmask]
> 
> 
> ______________________________ Reply Separator _________________________________
> Subject: melf's
> Author:  [log in to unmask] at ccmgw1
> Date:    1/16/97 9:23 AM
> 
> Technetters
> 
> I have a customer who asks?
> 
>      How can you apply adhesive to MELF's that will be wave soldered,
> when section 2.4.2 of IPC-610 states that "Adhesive contacts an
> unsleeved glass body component." is a nonconforming defect.
> 
>      I say that there is a difference.
> Adhesives used to bond a component in section 2 is for mechanical
> holddown and the component could crack if it were applied to the
> glass body.
> 
> Adhesive used for staking in section 10 has very little strength and
> used only to hold the part until it is soldered.
> 
>      anyway thats my story and I'm sticking to it.
> 
> 
> Phil Belliveau
> Sippican, inc.
> 7 Barnabas Rd
> Marion, MA 02738
> TEL: 508-748-1160 x379
> FAX: 508-748-3086
> EMAIL: [log in to unmask]
> HOME PAGE : HTTP//WWW.SIPPICAN.COM
> 
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