Ingemar,
Maybe a nice piece of resilient, spongy silcone rubber foam cut into a square format snake format that could be inserted into the tube prior to reflow - stretch to insert through the square tube, then allow to relax to create outward pressure.
Steve
________________________________
From: TechNet on behalf of Hfjord
Sent: Sat 2/9/2008 5:23 PM
To: [log in to unmask]
Subject: [TN] SV: [TN] absolutely crazy dispenser question
Hi Wayne,
Preforms....hmmm.....you gave me a wink. Why not solder stripes, all four,
on a plastic paper, which could be wrapped as a square formed 'cigar' and
pushed into the tube, kind of a transfer. The solder melts and wets in the
corners and the plastic paper can be released in the washing machine. I'm
ready to listen to all kind of advice. Yours is a bit of realistic though,
Inge
-----Ursprungligt meddelande-----
Från: TechNet [mailto:[log in to unmask]] För Thayer, Wayne
Skickat: den 8 februari 2008 22:52
Till: [log in to unmask]
Ämne: Re: [TN] absolutely crazy dispenser question
Hi Inge!
I would get preforms made for this for production--very similar to the
wire solder, but flat to stay straight and hold in place easier.
Probably could get them stamped to have a few stringers between two so
you could put in two at a time. But maybe the solder in the stringers
would violate some aspect of your needs as it would be contamination
when it melts. Of course, you'll have plenty of contamination with the
solder paste anyway!
Wayne
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Friday, February 08, 2008 6:36 AM
To: [log in to unmask]
Subject: Re: [TN] absolutely crazy dispenser question
Four pumps would theoretically be better but, provided your needles had
a reasonable inside diameter, you could probably get away with one. Yes,
low-speed screw pumps would work, but you would probably do better with
the kind that has a chamber filled with paste and a plunger displaces
the paste along the needles (not a piston in a cylinder). The potential
problem with a screw pump is that the paste is subjected to considerable
shear as it is pushed along the rotor, making the chemistry quite
liquid, according to its rheological properties. This can cause metal
particles to come into contact with each other, coalesce and sinter into
clumps which could partially block the needles and then sinter further
onto other particles as they come along. The ideal is to disturb the
paste chemistry as little as possible, ensure a streamline flow along
the pipework, with no abrupt changes of diameter.
Brian
Hernefjord Ingemar wrote:
> You mean four needles in parallel with one and the same pump, or four
> needles with four pumps? Positive displacement, is that same as pumps
> with Archimedes's screws?
> Inge
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> Sent: den 8 februari 2008 09:59
> To: [log in to unmask]
> Subject: Re: [TN] absolutely crazy dispenser question
>
>
> Syringes, no; needles, yes. I suggest that a positive displacement
> dispenser feeding four needles that can be dragged through your
> assembly would not be difficult to contrive. You would probably need
> about 12 gauge Luer Lock needles, depending on the quantity of paste
> needed and the speed of withdrawal. This would not work well with
> electropneumatic
> dispensers: you must have the positive displacement.
>
> Any medical needle supplier will have something to suit: I used to
> have ad hoc needles made for me by one in Switzerland for
next-to-nothing.
>
> Brian
>
> Hfjord wrote:
>> Hi all,
>>
>> I have 100 mm long tube, quadratic cross section about 15x15 mm. It's
>> made up by 4 pcs double copper sided 'boards' put together to form
>> the
>
>> tube. I need dispense solder paste on INSIDE in all for corners and
>> all along the 100 mm length. Now, have you seen dispenser robotics
>> with syringes that long? I would like to dispense in all four corners
>> simultaneously, but that is probably to be a dream only.
>>
>> No, I can't buy ready to use molded stuff, or other tubular things,
>> nor cut-and-wrap, or any else products. The 4-piece design is given
>> and unchangeable. And..I can't print solder paste on the individuals
>> for later putting together.
>>
>> /Inge
>>
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