Hi, Steve,
Yup! We've taken the plunge and bought one after getting the rep to
demonstrate the removal and replacement of all kinds of things from 2 inch
square PGA's to plastic and ceramic BGA's, plastic and ceramic LCC's - even
plastic connectors! We were hugely impressed with it. The guy even showed
that you could leave the system cooking away while going for a cup of
coffee and you wouldn't come back to find everything cooked to a crisp.
Many folks avoid IR because of the misconception that it's not controllable
- but it is, isn't it? I'm looking forward to having some fun with it once
it arrives.
I'm interested on your take regarding the thermally consuctive tape. I was
going to buy a couple of reels of the stuff along with the machine, but was
told that the tape's function is not actually to transmit heat. Rather, its
purpose is to improve the emissivity of things like metal-bodied components
for the feedback sensors that control the amount of heat being put into the
component. Our rep uses the machine himself for his core business of
repairing elderly comms equipment cards, and is thus quite an expert in
using it. It was he who also re-designed the original controller. His
explanation is that it's component emissivity to the sensors that indicates
the component temperature and governs the amount of heating that a
component receives. His experiments have shown that even using the tape,
indicated temperatures can be out by 20 or more degrees compared with
actual temperatures. His approach is not to use the tape at all, but to use
the natural emissivity of the component and derive a number of profiles for
different component body materials using thermocouples and noting the
temperature reading on the controller. So if the thermocouple reading shows
the component is at 190 degrees, for example, but the controller only shows
150, that's OK. If you like, he's calibrating the controller readings to
suit a range of component body material types. It makes sense in theory,
but I don't have the benefit of practical experience yet to prove to myself
that what he says is valid. It means, though, that I'll have to sit down
and tabulate what the controller readings should be for the components we
rework where they're metal or ceramic - the systems "naturally" works best
for plastic-bodied devices. WHAT D'YA THINK?
I'm relieved to hear that you're still enthusiastic about your machine.
Maybe we can compare notes from time to time on our findings and
experiences.
Peter
Steve Gregory <[log in to unmask]> 10/12/2002 08:34 AM
Sent by: TechNet <[log in to unmask]>
Please respond to "TechNet E-Mail Forum."; Please respond to SteveZeva
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cc: (bcc: DUNCAN Peter/Asst Prin Engr/ST Aero/ST Group)
Subject: Re: [TN] Table Top Static Reflow Ovens
Hi Peter!
So, you guys are buying one? Pretty cool, ain't they? I've had mine for
about 10-months (or there abouts) now, and love it!! One part that
sometimes can be a problem I've found out, is PLCC sockets. Just gotta make
sure that the thermal conductive tape contacts, and is seated well against
the leads at the top of the sockets so that you get good thermal transfer
down to reflow the joints.
But otherwise, I haven't run across a part I couldn't rework...even with
boards being bonded to big, thick, heatsinks. Couldn't even get the solder
plastic with hot air systems.
-Steve Gregory-
Hi, Bev,
Not a reflow oven, but a rework station if you're interested in such a
thing as an adjunct to your main oven. We have just ordered a PDR
Lightmaster IR component rework station from a local company here in
Singapore. They have redesigned the controller unit and the operating
principle so that it now has a proper feedback loop that controls the
power
being put into the components very nicely, and doesn't involve all those
nozzles that are required for a hot air system and which can cost quite a
bit.
The basic system costs about US$14K and seems to handle just about
anything
once you understand about the emissivity of the different component body
materials. The company selling the re-modelled systems is Vanco Pte Ltd,
but they don't have a website. Contact me off-line if you're interested
and
I'll give you more details.
Peter
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