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February 1998

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Subject:
From:
Ed Holton <[log in to unmask]>
Reply To:
TechNet E-Mail Forum.
Date:
Mon, 16 Feb 1998 14:01:50 -0500
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---------------------- Forwarded by Ed Holton/Hella North America Inc. on
02/16/98 03:04 PM ---------------------------


Ed Holton
02/16/98 12:52 PM

To:   [log in to unmask]
cc:
Subject:  Re: [TN] To On or Not to On  (Document link not converted)

Wow, isn't workplace politics fun!?!

I have to assume that the supervisor has experienced non-soldered boards
from the wave solder system, otherwise, there would not be a concern about
the sensor sensing the boards or not.  Remember, if it works, they don't
complain about it.  HOWEVER:  The sensor is there to activate the wave when
the board is present for soldering.  Without the sensor, the wave will run
continually, and the amount of dross generated will be increased.  The less
dross generated in the pot, the less it has to be cleaned, etc.  Everytime
you clean your pot, you run the risk of changing a variable (pot height,
wave height, solder level, etc.  This is why the newer systems have
controls on these features to they can be returned back to nominal
conditions)  SO:  review the sensor operation, the sensor may need to be
cleaned or adjusted.   Why disable something on the machine because you do
not think it works, FIX IT!!!!

The flux:  Cannont answer this without knowing what flux it is.  Everyflux
I have used has to be dry before it enters the wave.  Liquid entering the
wave solder process "spits" and creates solderballs, blowholes, voids, etc.
Of a greater concern is the temperature shock you are subjecting your
boards to;  I have always used the traditional 100?C jump from last preheat
to wave(bottomside temperatures) so that the components are not thermally
shocked.

Finally, process control.  Who is in charge of the process?  They should
have developed a wave solder process, including defining preheat
temperatures.  If these two people are changing the process, then there is
no control, and the quality of the process is suspect, beware of long term
failures.  The wave solder process requires a controlled process!  It
should not be changed by anyone, without the approval of the person in
charge.

The IPC and SMTA have numerous books in their catalog on wave soldering.
Your questions are basic and you will find these answers and many others
about wave soldering in these books.

Ed Holton
Manufacturing Engineer
Hella Electronics



[log in to unmask] on 02/13/98 10:23:27 PM

Please respond to [log in to unmask]

To:   [log in to unmask]
cc:    (bcc: Ed Holton/Hella North America Inc.)
Subject:  [TN] To On or Not to On




Hello,

Can anybody please help or advice.

I am trying to settle a dispute between my company's production
supervisor and the maintenance technician on the wave soldering
machine.

1) The maintenance technician insisted that the wave should be switched
on and off between boards to prevent/lessen "damage" to the wave
creation mechanism.
(The wave can be switched on and off automatically by a sensor on the
conveyor). My production supervisor think otherwise. She covered the
sensor so that the wave would not be off.(She says the sensor can
miss a board) So, who is right ?

2) My production supervisor sets the preheat to about 95 degree C so
that
the flux would not dry up when the PCB board reaches the wave and to
increase
solderability.(but this created a lotof residue on the solder
bath,according to maintenance).
My maintenance technician says the temperature should be about 120
degree C
so that it dry up the flux before the board reaches the wave. The reason
is so that
not much residue is created. Who is right again ??

Thanks in advance.

How Chee
Malaysia

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