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super fine pitch paste & dispensing questions

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#62443

super fine pitch paste & dispensing questions | 16 August, 2010

i would like to request some advice on manually dispensing paste for super fine pitch components.

first some background. i am a small design house and specialize in sub-miniature prototypes for avionics. so far, i have mostly used stainless steel stencils (0.07mm) to deposit paste onto my proto boards. i have been using pretty standard paste (kester R276) and that all works fine.

the problem with the stencils is that i sometimes have to do one-off designs and would like to avoid the cost for the stencil.

in addition to the cost issues for stencils, i would like to venture into the world ob BGA, WLCSP, and other super fine pitch footprints and have tried to dispense the paste i have thru 0.2mm needles but that didn't work due to mesh size and viscosity.

here now my questions:

can someone recommend some specific paste and source to dispense 0.2mm dot paste manually.

what i have found out so far is that there seems to be a type "6" paste with mesh size of 5-15um which should go thru a 0.2mm needle but i haven't been able to find a source for this paste in the US (small syringes).

any advice on this subject appreciated.

thanks in advance, -r

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#62444

super fine pitch paste & dispensing questions | 16 August, 2010

Hello, i don't know if is possible to dispense paste but for reduction of cost we use a diferent type of stencils, from aluminium of 0,2 mm, purchased from a typography of newspapers. Ofcourse the pcb for what we use this stencil are simple. But this stencil is very cheap because it is already used for newspaper template and then we make some drill for each pad of resistor, capacitor, etc. and milling for each pad of integrated circuit. If you want I could send some pictures.

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#62446

super fine pitch paste & dispensing questions | 16 August, 2010

CiXi Tian Hao Electric Technic Co.,LTD manufactures adhesive dispensing equipment and may be able to offer assistance with your application. Check out our product information at http://dispensing-th.com. We manufacture dispensing equipment ranging from manual dispensers to XYZ benchtop automated systems http://dispensing-th.com/Product.aspx for all types of fluids. In the meantime, I can send you product information or have an application specialist talk to you about your SMT application. Please provide your mailing address,and or you can contact us with trade@dispensing-th.com

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#62500

super fine pitch paste & dispensing questions | 21 August, 2010

The paste you dispense will not solder the same as the one you use with a stencil. The paste for the stencil will have a higher metal content. I was not working with dispensing as small as you are, but after evaluating the cost of the stencil vs. longer run-time on the machine when dispensing, keeping multiple viscosities of paste, and the cost of the dispensing equipment, I decided the stencil was still the best solution for me (even with proto runs). This is just what I decided for my shop and doesn't mean it is the best solution for yours.

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#62514

super fine pitch paste & dispensing questions | 23 August, 2010

Hi,

I have never been able to find an acceptable dispense process for dispensing small dots of solder paste. I currently have an auger screw automated dispense system and can not accomplish 0.010" dot sizes. In addition, stencil printing is much more reliable. Your pump or needle is going to plug up often. Maybe you can do it with a jet printing system from Asymtek or MyData. However, I still believe stencil printing is much better than any dispense process. We use electroformed stencils between 0.002" and 0.003" thick with apertures 0.004" to 0.006" square and type 5 paste -500/+635.

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