Thanks Mike. Exactly what I'm looking for--trying to see the limits of what can be gotten away with! I would NEVER have thought of using the CO2!
My thought with the vacuum was to get to a controlled inert environment quicker and to get the wind velocity near zero so the temperature of the work would be more consistent.
Thanks,
Wayne
-----Original Message-----
From: Mike Fenner [mailto:[log in to unmask]]
Sent: Wednesday, August 28, 2013 7:37 AM
To: 'TechNet E-Mail Forum'; Wayne Thayer
Subject: RE: [TN] Flip Chips
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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