Hi all
I have especially requested ALL my sales personnel to refrain from calling
customers Bozo's or NUTS. The customer is always right, always!
I just wish to thank all of you good folks for being so relaxed about being
referred to in such terms.
IF the field failure rate of the product is acceptable, and you used arc
welding to attach the thermo-couple, then fine...but aluminium - sorry
that's aluminum on that side of the pond - tape might be a more useful and
accurate method.
Is it Friday yet?
--
Regards Graham Naisbitt
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Concoat Limited - Engineering Reliability in Electronics
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> From: "Kerr, Bryan" <[log in to unmask]>
> Reply-To: TechNet E-Mail Forum <[log in to unmask]>, "Kerr, Bryan"
> <[log in to unmask]>
> Date: Mon, 25 Oct 2004 16:20:06 +0100
> To: <[log in to unmask]>
> Subject: Re: [TN] A poll of sorts...concerning thermocouple attachment
>
> Hi All
>
> The key to good, accurate thermal profiling is the thermal connection
> between the thermocouple and what you are trying to measure. The t/c
> junction must be at the same temperature as the solder joint you are
> measuring and there can be wide variation in the temperature of a specific
> joint depending on PEC design, e.g. a small chip cap joint to a large earth
> plane joint. After trying many techniques over the years, the one which most
> truly reflects the actual joint temperature is to use a high melting point
> solder and "envelop" the end of the 0.005" thermocouple. Try not to use too
> much solder otherwise you will add to the thermal demand of the solder
> joint. We often do not have scrap boards to play with either and find that
> we can, in these cases, use a bare board and fit a dummy component or
> components using HMP. You can then desolder and clean up afterwards. This
> means putting a board through reflow several times however they should
> withstand this OK.
> Best plan is to plan to measure components with both the highest and the
> lowest thermal demand to get a good picture of the delta T across the
> assembly.
> I would avoid the use of any tapes since this method of fixing is only good
> for measuring flat surfaces and not complex solder geometries.
>
> Bozo is a bit strong though !
>
> Cheers
>
> Bryan Kerr
> Principal Quality Engineer
> Process and Materials Laboratory
> AMS Hillend Scotland
>
> -----Original Message-----
> From: Dehoyos, Ramon [mailto:[log in to unmask]]
> Sent: 25 October 2004 15:00
> To: [log in to unmask]
> Subject: Re: [TN] A poll of sorts...concerning thermocouple attachment
>
>
> *** WARNING ***
>
> This mail has originated outside your organization,
> either from an external partner or the Global Internet.
>
> Keep this in mind if you answer this message.
>
>
> The trick is to make sure that the TC wires are molded by hand to
> lay by themselves on the board and secured with the Kapton or any hitemp
> tape. They should not by force down with the tape. When the TC stay put time
> after time through the oven the results will be about 2 degrees lower than
> if they are soldered with high temp solder. If they are forced down with the
> tape, the wires will spring up when the glue becomes weak by the heat. So
> Dr. ZapFart does not know what he is talking about.
> It is just my opinion,
> Ramon
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]]On Behalf Of Steve Gregory
> Sent: Saturday, October 23, 2004 12:10 AM
> To: [log in to unmask]
> Subject: Re: [TN] A poll of sorts...concerning thermocouple attachment
>
>
> Hi Phil,
>
> I guess I'm what you call a "Bozo". I use Kapton tape quite often when I do
> my profiling. I however, don't cover the thermocouple tip with it, but just
> use it to secure the wires.
>
> My thermocouple tip is shaped and placed with tweezers to be at the solder
> joint I want to monitor,and then the wire is secured along the assembly at
> places so as not to disturb the rest of the components. The thermocouple
> tip
> isn't covered by anything...high temp solder, epoxy, aluminum tape, or
> anything.
>
> Just because I use Kapton tape, doesn't mean that I'm a "Bozo"...
>
> -Steve Gregory-
>
> According to Dr. Zapfardt in the October issue of Circuits Assembly ("On
> The
> Forefront")attaching the TC with Kapton tape is for bozos who really are
> not
> interested in actually getting accurate profiles, but are just killing
> time.
> I couldn't have said it better myself.
>
> Phil Zarrow
> ITM Consulting
> Durham, NH USA
> www.ITMconsulting.org
>
>
>
>
>
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