Hi all, even him hanging up and down in Sydney,
interesting to see someone going even deeper into the dispensing marshland, 80 microns, wow x exp 2! If I appear less in the fiber just now, it depends on a mountain of jobs.
Now, dispensing 150 microns is enough headache. We have found that, except for needle and pump problem, we have to rebuild the machine itself, also have to do some software adjustments. As dear Aussilek correctly pointed out, the pump must make a small reverse movement between every dispensing operation (dots, lines, evenso the pressure should go down at the same time. If these two facts are neglected, the adhesive will form into small drops hanging on the needle's tip, causing wrong amount of adhesive here and there. In our case correct dot size is very important, as chips are extremly small GaAs transistors.

Following, is also a need for checking the dot quality in terms of wetting and enclosed airbubbles etc. For studying that, we have ordered dummy chips of transparent 0.1mm glass on blue tape. So, the PP picks the dummys and places them like the semi chips, afterwards we can check if the PP tool pressure was correct, also study the wetting mechanism just through the glass. Finally, we have made some syringes ourselves, because we are not satisfied with the inside conditions (no, Aussilek, I don't mean my head). Without much rheology knowhow, we can still see that the inside walls are too rough, there are mechanical discontinuities that catch bypassing silver flakes and build up small amounts of adhesive that will sooner or later cause clogging...etc. What we talk about is a rather complicated process window, I have announced the parameters in earlier mails, and, as clever Aussilek also told me: eliminate one problem at a time, don't mix with all in one sweep. There we are just !
!
now. We CAN dispense, we could certainly depress the line's start button and run some assembly, but not with the parameter spread we need to have (6S).

Also going on, is a study of the used adhesives. Particle size and shapes together with tixotrophy and viscosity are major parameters. These factors have to match the needle and pump conditions. Have in my hand an EU investigation of most known silver epoxies, from this you can get some insight in the mystery of different manufacturing of adhesives and their applications. All this takes time, more time than we are happy with, but the alternative is a rope, which seems to be less attractive.

When all obstacles are removed, I will come back to you with more vitamins.

By the way, Steve, if you read this, I can tell you that your Nova Scotia pumkin recipe was a success. Yum-yum on icecream, good as marmelade and cakes, splendid on musli etc. However, couldn't be dispensed with a 150 micron syringe. But a bycycle pump did the work pretty well. Could hit my musli plate across the kitchen.

Ingemar

-------------------------------separator-------------------------------------------

object: Re: [TN] Dispensing of conductive adhesives for flipchip attach


Paul,

I certainly will talk to Ingemar.

You said that "the outer chamfer must be ground = evenly sharp exit".

Could you expand on this as I'm not sure what you mean.


Thanks for your input

Gareth Jones
Celestica Ltd
[log in to unmask]

------------------------------------------------------------------------------

Gareth, check our past correspondence with Ingemar on this subject (IPC
archives)
If your gold particles will be as flaky as Inge's silver you may find it
interesting to talk to him;
I think he's just nearing to some resolutions .
Otherwise pending the machine used (camelot/asymtek/[both have web
sites]etc.);they will make you custom needle .
Sometimes I found custom carbide needles from adjacent industry like Nordson
(hot glue jets),
http://www.nordson.com ;
much more precise with low impedance of flow (inside polish):
If Inge won't reply to this one (seems flat out somewhere)I'll mail you the
crosscut picture of a standard needle to see what you're up against (not a
pretty sight).
Nordson can also supply the cleaning broaches you need for cleaning of this
micro's ,
I think Martin just contacted a fellow there (Steve) for the same .

Paul Klasek
ResMed

PS
You may know this ; the outer chamfer must be ground = evenly sharp exit .


-----Original Message-----
From: Gareth Jones [mailto:[log in to unmask]]
Sent: Wednesday, 27 October 1999 3:09
To: [log in to unmask]
Subject: [TN] Dispensing of conductive adhesives for flipchip attach


Hi Netters,

I'm looking for a needle capable of dispensing 80 micron blobs of conductive
adhesive. The adhesive is epoxy based with 5 micron gold particles. Does
anybody
know where i can buy a needle with a 80 micron bore.


Thanks very much for your input

Gareth Jones
Celestica Ltd

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