Ramon

Depends on your application but we have 1 product at 26DegC, another at
71DegC and another (which is actually the best, but read Per-Erik's comments
first) that has a Tg of 0DegC. Temperature ranges for product 3 is -65DegC
to +200DegC.

What are you looking for Ramon?

Graham Naisbitt

>
> Hi Graham:
> The operating temp ranges for the Humiseal urethanes and acrylics are -65 to
> 125. The tg for acrylic IB31 is 14 deg C, what is the transition temperature
> for the urethanes?
> Regards,
> Ramon
>
>> -----Original Message-----
>> From:    Graham Naisbitt [SMTP:[log in to unmask]]
>> Sent:    Thursday, March 25, 2004 1:43 PM
>> To:    [log in to unmask]
>> Subject:    Re: [TN] acyrlic coating deformed BGA balls
>>
>> Hi everyone,
>>
>> I have been in France for the past couple of days, so did not respond to
>> everyone earlier.....but here goes the duel! (You can't get rid of me that
>> easily!)
>>
>> The subject in question is David's oft repeated reference to low Tg....and
>> for the record the Tg of 1B31 is 14DegC not 15.
>>
>> So what?
>>
>> As Dewey said, and is no doubt backed-up in the Collins report submitted by
>> Dave Hillman, this is not necessarily a bad thing.
>>
>> Circuits exposed to wide temperature variations, coupled with high levels of
>> humidity are quite commonly conformally coated. The coating MUST therefore
>> be capable of surviving temperatures commonly down to -65DegC and up as high
>> as +125DegC or more.
>>
>> I have the distinct impression - and David please correct me if I am wrong -
>> that David thinks that an acrylic coating such as 1B31, permits external
>> "stuff" to descend through the coating and hence onto the circuit surface.
>> Whilst this might be the case, there are most certainly many other forces at
>> work or conditions that must be considered and it is inappropriate to
>> zone-in on one issue in isolation.
>>
>> Definition of Tg: The temperature at which an amorphous polymer changes from
>> a hard and relatively brittle condition to a viscous or rubbery condition.
>>
>> A simplistic view of a material's glass transition temperature (Tg) is the
>> temperature below which molecules have very little mobility. On a larger
>> scale, polymers are rigid and brittle below their glass transition
>> temperature and elastic above it.
>>
>> The Space Shuttle Challenger disaster was caused by a rubber O-ring that was
>> below its glass transition temperature and thus could not flex adequately to
>> form a proper seal around one of the two solid rocket boosters.
>>
>> So how about a coating that has a high Tg, Would this be better David? In a
>> purely high temperature environment the answer would be a definite maybe!
>> However, below its Tg it is brittle, therefore the lower the temperature the
>> more brittle it becomes and hey presto - the coating shatters allowing all
>> that nasty stuff to get in through the cracks!
>>
>> So, as stated by Dewey: The key is to understand the end use environment and
>> choose the coating that has the widest processing window, tolerates rework
>> and functionally does the job.
>>
>> You will now have to excuse me for saying so, but this is the very reason
>> why we have so many different coatings in our range - "horses for courses"
>> or, as Dewey so poetically referred to it: We have a huge selection of
>> quality Dust Bags whatever your needs - we even do latex but I don't want to
>> go there right now....
>>
>> TTFN everyone
>>
>> Graham Naisbitt - with a little (lot!) of help from Phil Kinner.
>>
>>> To all,
>>> I thought for a moment we were going to have an old fashioned duel between
>>> David and Graham.It would have been a shame to loose all that intellect and
>>> humor in one fell swoop.We would have missed Graham, also( just kidding
>>> Graham).
>>>
>>>
>>
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>

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