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September 1999

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Subject:
From:
Michael Fenner <[log in to unmask]>
Reply To:
Michael Fenner <[log in to unmask]>
Date:
Sat, 11 Sep 1999 13:32:15 +0100
Content-Type:
text/plain
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text/plain (126 lines)
Theoretical dispense needle:
The people I knew at the company are no longer there, I outlined your interest in
dispense needles to who ever I spoke to and gave them your Email address, so they may
or may not contact you. The guy said so far as he knew they were made by a local
company to their design, but some time ago. It's a two piece design, consisting of a
machined fitting with the ferrule/needle let in to it flush. The internal hemisphere
is an exact match for the end of the material container. The ferrule has quite a
thick cross section which is profiled at the dispense end.
The reason they use these things incidentally is that on their (in-house made) high
speed lines they got blockage in the needles and on their air driven system the
operators tended simply turned the pressure up to clear it. This resulted in a couple
of explosions....

I did speak to a couple of other people in tracking this guy down and offer their
suggestions/observations as a result :

If you are worried about blockages in the dispense path why not make it as short as
possible and stencil/screen the adhesive on......

Try contacting the needle orifice to the substrate and dispense very lightly as you
lift off. This will pull a very small bead volume from the needle and allow a bigger
dispense ID.

I pass these on with no particular commendation or thoughts other than to comment
that the second idea is closer to transfer printing than dispensing, and that
transfer printing adhesive is a recognised process for volume production and of
course has no blockage problems.



Mike Fenner



-----Original Message-----
From: Ingemar Hernefjord (EMW) <[log in to unmask]>
To: 'Michael Fenner' <[log in to unmask]>; TechNet E-Mail Forum. <[log in to unmask]>
Date: 09 September 1999 13:42
Subject: RE: [TN] Clogging dispensers soon...


>
>
>Mike, your help is of same high standard as is Aussilek's (yes, Aussilek, you must
accept even english are bright, rembember the Piltdow man, Nelson, Newton,Thatcher an
d Kermit),
>now, Mike,
>------------------------------------------------------------------------------
>A:
>It sounds from this and previous postings "that in view of your demanding
application
>it might be better to use a higher specification needle than the standard type
>normally supplied". Or whatever your present supplier is saying.
>
>Such a higher specification might be one in which the moulding around the steel tube
>does not have sudden cross sectional changes and no internal reverse re-entrant
>shapings.
>RE: exactly what we will do, we have cross sectioned and seen what you mean. We have
a reputation for making tough specs, we will use that from now on.
>------------------------------------------------------------------------------
>
>B:
>You can get these OK from people like EFD. So far as tube length is concerned these
>suppliers also make a shorter length, but still long to allow manual access. No
>reason why you should not cut them down, provided you can get a good finish. I
>suggest a length no greater than 5-6mm.
>RE: please explain who EFD is, we will call immmediately.
>-------------------------------------------------------------------------------
>
>C:
>It just might be worth investigating the type also supplied for solder paste
>dispensing. These are made entirely of polysomethingene. And are a conical cross
>section from fitting to dispense end. The problem is they can be flexible and may
not
>give precision placement accuracy.
>RE: good idea! May be a little bit cheaper also, ours cost 200GBP each!
>----------------------------------------------------------------------------------
>
>D:
>Reverting to your question on internal finish of needle:
>From what little I know about laser machining I suspect you would have great
>difficulty making a smooth hole of this size and length. Irrespective of that,
>whatever method you use to correct the internal finish it would be especially
>difficult to build a tool to hold the needle and get the alignment you require.
>
>So as an alternative you could make your own theoretically perfect ones. These would
>consist of a hemisphere internal shape with a projecting tube just long enough to
>clear the external body of the hemisphere from the substrate surface to prevent
>smearing.This would be much easier to make.
>RE: Also good idea, like putting a fine needle into a wider, and the finer only a
millimeter ore two long. THEN you may be able to use laser.
>-----------------------------------------------------------------------------
>
>E:
>I now recall visiting a company once that is using these, or at  least was about 18
>months ago, in high speed component manufacture, I believe they made them themselves
>but if you become convinced this is an answer then I will try to remember where and
>who they are and see what I can find out.
>RE: please, look once more in your drawer.
>-----------------------------------------------------------------------------
>
>F:
>waiting for pumkin wine recipe, you just opened a new file, I need something to pour
into it......
>
>CU
>
>Ingemar Hernefjord
>
>
>

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