Hi Poh Kong Hui,

I do agree that the manufacturing process of the PCB has a great effect on
it. But the duration and method of storage also plays a part in it.
There is a possibility that the boards were not baked properly by the
manufacturers or not sealed properly.  

I would like to tell you my experience in this matter. During summer I did
a defect reduction study for a company in upstate NY. They had
similar problems. Did number of experiments. 

We found that it was because of the following 2 reasons.

1) Too much of moisture in the boards, this was due to bad sealing during
transportation and storage. Solved by backing the boards before wave
soldering.

2) Due to the manufacturing process. After drilling the boards were not
cleaned properly. This was solved by introducing a hot air cleaning
process after drilling. 

I don't know  if this helps. If you need more info on the experiments that
i did, i would be glad to tell you. 

Regards
Raj
------------------------------------------------------------------------------
Raj
Graduate Student
State University Of New York
Binghamton NY 13902
Phone: (607) 797 6821
email: [log in to unmask]
-----------------------------------------------------------------------------   

On Sat, 3 May 1997, Poh Kong Hui wrote:

> Hi  Technetters,
> 
> I would like to tell about my personal experience with different PCB
> suppliers.
> 
> One of our part number, which was given to 4 PCB manufacturers, and all 
> PCB were kept in the store for more than a year. 
> 
> Supplier                        Length of storage
> 
> A                                       55 weeks
> 
> B                                       59 weeks
> 
> C                                       76 weeks
>  
> D                                       64 weeks
> 
> >From each of the PCB suppliers, I took 5 boards each, and wave-soldered all 
> the boards. The result shows that Supplier D has least blow-hole, followed by
> supplier B, supplier C and supplier A.
> 
> >From the result, it showed that the datecode, or length of storage, does not
> determine the PCB quality, but rather the manufactiring process and the 
> qualityt of the raw material used.
> 
> I am not too sure whether I have concluded it correctly. Would any please
> comment. Thanks..
> 
> 
> Poh
> 
> 
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!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! 
 
   RAJKUMAR  B. RAJ                Residence : (607) - 797- 6821
   41 Floral Avenue, Apt # 7       e-mail:[log in to unmask]
   Binghamton, NY 13905            

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