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'Re[4]: UV Pic problem (use a hairdryer!!!)'
1996\12\20@123519 by Craig Knotts

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    The distance from tube center to silicon on my dinosaur-era eraser is
    about 1.5 inches... draw your own conclusions :)


______________________________ Reply Separator _________________________________
Subject: Re: Re[2]: UV Pic problem (use a hairdryer!!!)
Author:  spam_OUTlrichTakeThisOuTspamQNI.COM at internet
Date:    12/20/96 5:23 AM


There's considerable variation in eraser UV intensity, distance from the
bulb surface to the silicon is critical.  The $39.95 DataErase (?) from
DigiKey puts the chip on top of the bulb, separation about .05 inches, and
will take about 4 minutes to make a 16C71 read erased but you should give
it an extra 4 minutes to get a good erase.  The older style erasers had
the bulb about a half inch above the chip and would take 30-45 minutes to
get a read-back as erased, so 60 minutes isn't out of line here.

The low presure mercury vapor bulbs used in most erasers will last several
thousand hours.  The Xenon flash erasers which can erase an eprom in
5 to 10 seconds use bulbs with a few hours lifetime.



On Fri, 20 Dec 1996, Jim Robertson wrote:

{Quote hidden}

1996\12\20@132059 by Craig Knotts

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    OK, you talked me into it... I did some tests on a pair of 16C57's
    with the following results.

    2 minutes in my old eraser - part read back as not erased
    2 more minutes - parts read back as erased!

    I think in the future I'll give the 5x parts about 6-8 minutes unless
    I start having trouble erasing parts.  Also, I think I was
    over-estimating the time I was taking before, instead of 45 minutes it
    was probably more like 20-30 minutes.  I never really paid attention
    to how long it took.


______________________________ Reply Separator _________________________________
Subject: Re: Re[2]: UV Pic problem (use a hairdryer!!!)
Author:  .....lrichKILLspamspam@spam@QNI.COM at internet
Date:    12/20/96 5:23 AM


{Quote hidden}


'Re[4]: UV Pic problem (use a hairdryer!!!)'
1997\02\05@123216 by Brian Boles
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    At any temperature that is within the storage specification, you are
    looking at years and years.....

    Kinda makes sense doesn't it.  After all, if there was some reasonable
    erasure time at a resonable temperature, you would be very worried
    about those OTP devices that are running at 85C!

    Rgds, Brian.


______________________________ Reply Separator _________________________________
Subject: Re: Re[2]: UV Pic problem (use a hairdryer!!!)
Author:  Mike <erazmusspamKILLspamWANTREE.COM.AU> at Internet_Exchange
Date:    2/5/97 8:44 PM


At 08:48 AM 4/02/97 -0700, you wrote:
>     One minor problem with erasing OTP with a 450 deg bake...
>
>     You'll have a puddle of melted/burned plastic package and aluminum
>     leadframe at the bottom of your oven!
>
>     Rgds, Brian.

OK then but, what is the situation if we select a temperature just below
the Epoxy melt and the bond soldering etc. Will the device still erase
over a 'longer' period of time ?

Could you provide us with a graph of the diminishing return ?

Rgds

Mike

1997\02\05@152814 by Joe Dowlen

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    Mike and Brian,

    In the old days when I used to do high temperature validation of
    design we noticed that electron activity would double for every 23 deg
    C change in temperature.

    The most temperature that I would ever subject a packaged IC to would
    be about 300 deg C.

    So, it would take about 92 times longer to erase an IC at 300 deg than
    at 450 deg.

    Joe


______________________________ Reply Separator _________________________________
Subject: Re: Re[2]: UV Pic problem (use a hairdryer!!!)
Author:  pic microcontroller discussion list <.....PICLISTKILLspamspam.....MITVMA.MIT.EDU> at SMTP
Date:    2/5/97 6:43 AM


At 08:48 AM 4/02/97 -0700, you wrote:
>     One minor problem with erasing OTP with a 450 deg bake...
>
>     You'll have a puddle of melted/burned plastic package and aluminum
>     leadframe at the bottom of your oven!
>
>     Rgds, Brian.

OK then but, what is the situation if we select a temperature just below
the Epoxy melt and the bond soldering etc. Will the device still erase
over a 'longer' period of time ?

Could you provide us with a graph of the diminishing return ?

Rgds

Mike

1997\02\05@232343 by aab

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>OK then but, what is the situation if we select a temperature just below
>the Epoxy melt and the bond soldering etc. Will the device still erase
>over a 'longer' period of time ?

    > At any temperature that is within the storage specification, you are
    > looking at years and years.....

    > Kinda makes sense doesn't it.  After all, if there was some reasonable
    > erasure time at a resonable temperature, you would be very worried
    > about those OTP devices that are running at 85C!

Maybe that's one reason the storage temperature is set where it is. :-)

Do you happen to know the lowest melting point of the various
substances in the package? Its worth a few cents of electricity to
see if anything happens.

What is the max storage temperature BTW?

Let see, solder melts at 450 F IIRC. Maybe a day in the oven
would do something...

Or the oven on self-clean (> 500 F)

Propane torch?

1997\02\06@025445 by Shel Michaels

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aab@cichlid.com writes, in relation to erasing OTP parts:

<< Or the oven on self-clean (> 500 F) >>

I tried a 16C74 in my oven at 550 F for two hours - didn't see any bits in
the first 16 go back to 1s!!  Plastic didn't melt, though it did burn off the
paper label I had on top.

Shel Michaels
Massachusetts, USA

1997\02\06@030519 by Mike

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At 02:53 AM 6/02/97 -0500, you wrote:
>EraseMEaabspam_OUTspamTakeThisOuTcichlid.com writes, in relation to erasing OTP parts:
>
><< Or the oven on self-clean (> 500 F) >>
>
>I tried a 16C74 in my oven at 550 F for two hours - didn't see any bits in
>the first 16 go back to 1s!!  Plastic didn't melt, though it did burn off the
>paper label I had on top.

Hi Shel,

Someone back when on this thread said it was 10mins at 450deg C and 92 times
longer at about 250deg C or something like that, could you put it in dah oven
for say - 24 hours but, not just looking at first 16 since the 'hit' rate
might be less than playing lotto ?

I presume you let the device cool down gradually to below 40 deg C before
applying any power to the chip - we killed a couple of 27C256 EPROMS a few
years ago when we put them in the programmer soon after our UV eraser...

Rgds

Mike

1997\02\06@082450 by David Nicholls

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On Thu, 6 Feb 1997, Mike wrote:

{Quote hidden}

Hi there,
       Would I be correct in assuming then from that last comment that it
is not recomended to program PICs directly after removing them from the UV
eraser ??? Even when your not overheating them beforehand ??

Dave.

1997\02\06@092605 by Mike

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>> I presume you let the device cool down gradually to below 40 deg C before
>> applying any power to the chip - we killed a couple of 27C256 EPROMS a few
>> years ago when we put them in the programmer soon after our UV eraser...
>>
>> Rgds
>>
>> Mike
>>
>
>Hi there,
>        Would I be correct in assuming then from that last comment that it
>is not recomended to program PICs directly after removing them from the UV
>eraser ??? Even when your not overheating them beforehand ??

Hi Dave,

We had to let the devices cool down gradually - hopefully to room temperature
otherwise they tended to fail quite quickly. Also it didn't help if we put them
in the fridge, the thermal stress probably broke a few bonds...

Rgds

Mike

1997\02\06@143949 by )

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Is there anything analogous to this for EEPROM devices (i.e. the PIC
'84)? After programming (say an '84), is there any problem with
immediately putting in a circuit and powering up?

In working with EPROMS years ago, I also noticed the problem Mike talks
about below. At the time, I blamed it on the surplus EPROMS I was using.


Frank Richterkessing
Experimental Methods Engineer
GE Appliances

@spam@FRANK.RICHTERKESSINGKILLspamspamAPPL.GE.COM
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