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April 1999

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Subject:
From:
Jorge Engenharia <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 26 Apr 1999 14:59:25 -0300
Content-Type:
text/plain
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text/plain (75 lines)
Poh,

  If the boards are HASL ( Hot Air Soldering Level ) the difference is
probably in the quality of HASL process, some vendors gives irregular
surface finish and when stencil contacts with that irregular surface
gives more height from board level, so you are measuring
HASL irregularity with solder paste deposition, thats explain the
difference in height.
  You can examine the surface finish with microscope or using the solder
paste height toll to check the differences between the 3 suppliers.
  You will be able to note also that is difference in height between
vertical and horizontal pads

Thanks
Jorge Santana
Process / Maintenance Engr
Microtec - Brazil

> -----Original Message-----
> From: Poh Kong Hui [SMTP:[log in to unmask]]
> Sent: 26 de Junho de 1999 16:57
> To:   [log in to unmask]
> Subject:      [TN] Different Paste Height
>
> Hi,
>
> Have anyone encountered that PCB from different suppliers give
> different
> paste height.
>
> We are using 3 PCB suppliers for one of our product, and the average
> paste
> height we are getting (on 2 suppliers), using 6 mil stencil with
> rubber
> squeegee (70 durometer) gives an average paste height of 6.5 mil.
> However,
> there is one supplier's PCB that gives the average paste of 8 mil.
>
> We need to double the squeegee pressure to achieve the paste height of
> near
> 7.0 mil
>
> Could anyone advise me the cause to such issue.
>
> Thanks
>
> Poh
>
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