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August 2013

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From:
Mike Fenner <[log in to unmask]>
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Date:
Wed, 28 Aug 2013 12:36:41 +0100
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Why are you thinking vacuum? If your flux type requires an inert atmosphere
you could run bottle nitrogen into a small enclosure placed over the work.
It won't be very efficient use of gas, but you should be able to get down to
say 50ppm easily enough, maybe better. 
Done that lots of times in small scale trials, used a metal frame about 1"
tall big enough to surround the work with a Kapton film glued on top to make
a windowed chamber. Just rests on hotplate, you might need to drill a few
vent holes for exhaust. OR I suppose you could use your bell jar.
The 50 ppm number is an estimate derived from comparing results from a
proper nitrogen inerted oven to the inerted hot plate.(in subsequent line
trials). If you run a high gas flow this can cool the work. Just use high
temp silicone hose wound around the hotplate to take the chill off. The hose
size can be quite small - around 0.1-0.15" ID. Actually with a long enough
hose you can run the enclosure down a conveyor machine - not forgetting it
will be very hot when retrieving it :)
If you don't have a nitrogen cylinder you could use a small CO2 cylinder of
the type used to make homemade fizzy pop (soda in US Speak). Done that. You
can get them at a supermarket. The hose size is about the same as that used
in car windscreen washers. Done that too!

Best Wishes
 
 
 
Mike

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Tuesday, August 27, 2013 6:25 PM
To: [log in to unmask]
Subject: Re: [TN] Flip Chips

I forgot to mention that I have no nitrogen oven.  I am thinking of buying a
rapid response hot plate and putting that inside of a big vacuum bell jar.
If I go through several vacuum purge cycles I should be able to get to
100ppm O2 in less than a half hour.  Anybody done that?  Recommendations for
hot plates?  How about recommendations for O2 meters which go down to that
level?

Wayne

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Wayne Thayer
Sent: Tuesday, August 27, 2013 1:00 PM
To: [log in to unmask]
Subject: [TN] Flip Chips

OK, Inge, you've inspired me to share what I'm up to presently:

I'm trying to prove out an in-house flip chip attach/underfill process.
I'll get the die from Practical Components and/or Topline, most likely 10mil
pitch full array, although Practical also reps a PacTech 200x400 micron
array which sounds pretty good too.  Looks like SnPb would be special order,
so I'll do SAC305.

I'm disappointed to see that the boards they stock for these are all OSP,
which means that in initial development anyway, that I'll have to cut the
test board in sections.

Any advice from the "school of hard knocks" for me?  Preferred
fluxes/underfills?  Good stories maybe?

Wayne

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
Sent: Tuesday, August 27, 2013 12:47 PM
To: [log in to unmask]
Subject: Re: [TN] test

What is (not) going on?  No conversation. No problems. No fun stories.
Nothing at all. Technet's death-throes?

Inge


On 26 August 2013 15:26, Steven Creswick <[log in to unmask]> wrote:

> Ah, but here in the mid-west, the cicada's are rubbing their legs 
> together ...
>
> Steve C
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge Hernefjord
> Sent: Monday, August 26, 2013 6:21 PM
> To: [log in to unmask]
> Subject: [TN] test
>
> Silent as Nevada desert.
>
>
> ______________________________________________________________________
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