Hello all again,
(for those who is just curious of who is who : the supervisor and the
technician
, read the end of the mail)
I have read through the numerous responeses and will be looking into
the problem very soon. But first, I'll be glad if anyone can provide me
with more data.
1) From the feedbacks, some switched on the wave all the time during
the wave soldering process and some mentioned the sensor is there to be
used.
Can anyone provide me the typical frequency between boards (going over
the solder wave) and turning the wave on all the time and also the
frequency when intermittent wave should be used. On my side, the
frequency is about 3-5 boards per minute.
What is the maintenance frequency of the wave solder machine also ?.
2) It is known also that the (at my place) boards coming out from the
wave machine
can sometimes have the corner sides not soldered (the rest is OK). This
I belief is due to wave height and conveyor height. Comments ? (The wave
is always on). Did
anybody face problem with wave height if the wave is switched on and off
?
3) People tell me also that manual solder touch up is necessary after
wave soldering.
What is the typical percentage of acceptable boards (no need manual
touch up) after
going wave soldering ?. I want to check whether we are doing too many
touch ups.
4) As for the flux, I'll be checking with the supplier. If I remembered
correctly,
they called it SP-42. Ring any bells ?. Whether the flux should be dry
or wet when
the board reaches the wave, most of the responses favours dried flux.
(At my place,
I am having wet flux when the board reaches the wave, this might explain
why quite a number of the boards have blowholes).
As for the preheat and flux activation temperature, contacting the
supplier should
solve the problem.
5) Determining the temperature profile for each board might not be the
solution for us,maybe it is possible to have a general preheat settings
or some formulas to
relate the preheat setting with the conveyor speed and PCB profile?.
Over at my side, there is only one wave solder machine and I suspose
that you need the wave machine to get the temperature profile , this
would sacrifice productivity.
6) My production supervisor also encountered PCB boards supplied by
customer
that had to go through the wave machine twice. On the first time pass,
insufficient solder resulted. On the second time, soldering is much more
acceptable. The PCB is not tinned but are fluxed. I felt it is
ridiculous for a PCB to go through the wave machine twice. This might be
due to the preheat temperature that is set too low.
(95-100 degree C). Any comments ? The diameter of the pads on the board
might be
too big compared to the hole diameter. (I read something relating the
pad size
and acceptability of soldering. IPC standards also, I think, has
recommendedations
for pad to hole size ratio.). Or is it another "not enough heat for flux
activation problem" ?
7) Has anyone face rejects (of LEDs) when 3mm round LED is mounted
directly to the board (its body touching the PCB) and is wave soldered.
I know that this violates the manufacturer's temperature rating but is
thare anyway
to solder the LEDs beside manual soldering ? (even manual soldering
might violate the
temperature specs.). There is no room on the leads for heatsinking as
the body is touching the PCB.
Hope someone can help.
How Chee
Malaysia
Note : I will not be able to see all your mail from Mon to Fri since I
have Net acess
only on Sat.
Who is Who ??
=============
p.s. : For those who are curious who is who. The maintenance technician
is not
under the production supervisor and all of us reports to the Operational
Manager and
NO roses are given. Over here, we are treated equally.
I apologized to all since I started this but I did get some laugh out of
it.
(some entertainment compared to the routine techical things).
>
> At 11:23 AM 2/14/98 +0800, you wrote:
> >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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