Apparently Poh Kong Hui has received printed boards that are out of 
specification (too thick).  It strikes me that either the board fabricator made 
an error in determining the construction of the board or there is a difference 
in how Poh Kong Hui and the board fabricator are measuring the thickness of the 
board.  The original message did not specify how or where the thickness was 
measured.  Specifications exist which require measurement of the board after 
lamination and before subsequent processing, over bare laminate on the finished 
board, over solder resist, over everything (maximum thickness), and I probably 
forgot a few others.  Often there is a lack of understanding (wasn't specified 
clearly or didn't read the specification) regarding how the thickness is 
measured.

Any boards that are do not meet specifications require a wavier from the 
customer.  In this case, Poh Kong Hui and the board fabricator should determine 
how the thickness of the finished board is being measured before the boards are 
rejected or the end user is contacted for a wavier.

Don Vischulis
[log in to unmask]
_______________________________________________________________________
[log in to unmask] wrote:
> 
>      There are many other considerations which should be weighed
>      prior to accepting these boards. First any Fabricator should
>      not make judgements on the acceptability of product which
>      doesn't meet a Customers specifications. The Customer, in
>      most cases, has reasons for his specifications. There could
>      be a height issue, component lead issues, UL agency, designed
>      in capacitance ect.... The best course of action is to notify
>      your Customer and discuss the variation.
> 
> ______________________________ Reply Separator _________________________________
> Subject: Re[2]: Assy/Fab: PCB Thickness
> Author:  [log in to unmask] at Internet
> Date:    6/3/96 12:38 PM
> 
>      I believe that the additional thickness will do very little to the
>      electrical performance nor its reliability. Your vendor did a poor job
>      in material selection and his up front engineering stackup. The
>      problems in assembly would be if the axial leaded devices do not have
>      long enough leads to properly protrude through the board for good
>      solder connection practices.
> 
> 
> ______________________________ Reply Separator _________________________________
> Subject: RE: Assy/Fab: PCB Thickness
> Author:  [log in to unmask] at SMTPpost1
> Date:    6/3/96 11:51 AM
> 
> 
> Dear Technet,
> 
> First, please bare with me my inexperience in PCB fabrication.
> One of our customer's requirement for their PCB's thickness, ranges from
> 1.55 to 1.60 mm. However, our PCB manufacturer supplies us the thickness
> ranges from 1.70 to 1.77 mm.
> 
> As our customer requires this board to be assemblied and shipped urgently,
> I would like to know
> 
> a.      how this happens ,
> b.      whether this difference in thickness will affect the assembly process,
> c.      whether it will affect the reliability and the electrical performance.
> 
> as to decide to use this board or to delay the shipment..
> 
> I thanks you in advance ...
> 
> 
> Poh Kong Hui
> Nera Electronics
> Email: [log in to unmask]
> 
> 
>