Dennis,

You can probably get away with only calibrating features of the machine that
are "adjustable" which might not include e.g. air velocity, but I would
recommend a calibration strategy based on actual product temperature
for the following reason:

Reflow is a non-eqilibrium process so the product temperature is dependant on
belt speed and air flow velocities as well as zone temperatures so, for an oven
controller based calibration, all of these parameters should be calibrated.
Increases in surface emmisivities (due to flux build up or oxidation) could
also affect product temperature by increasing IR heat transfer (although I
have no evidence for this).


If you use a KIC system then again you are not checking the actual product
temperature.

A Datapaq or Mole system will give you actual product temperature and can
easily be sent away for calibration once a year. Another option that we have
developed in partnership with Quad, and which has just become available, is to
use an oven equipped with a line scanning infra-red sensor (which can again be
calibrated to the required standards) and which will monitor actual product
temperature board after board. (As this is a new concept in reflow process
monitoring I hope I will be forgiven what may sound like advertising.)

David Whalley
Manufacturing Engineering Department
Loughborough University
Loughborough
Leics LE11 3TU
UK

Tel. +44(0)1509 222930
Fax. +44(0)1509 267725

[log in to unmask]
http://info.lboro.ac.uk/departments/en/STAFF/David_Whalley/index.html



At 12:22 24/03/97 -0500, you wrote:
>I need to calibrate a conveyerized IR oven used for tin/lead reflow.  The
>calibration must comply with ISO and military calibration standards.  Until
>now we have been using an outside source to calibrate the oven.  I was not
>satisfied with the method they used.  I was wondering if other organizations
>are using reflow profiles, or physical calibration of the oven controls to
>meet military ans iso requirments. 
>
>Thank you for your replies
>
>Dennis
>

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