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Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Apply glue with a stainless stell stencil

Francois Racine

#1930

Apply glue with a stainless stell stencil | 12 February, 2000

First I'm a french people so excuse my bad english writing. I have a complete smt production line. First a screen printer DEK 240, a chip shooter PANASERT MVIIV, a multifonction machine MULTITRONIKS EP6000, a reflow oven at the end of the SMT line and I have a dual wave solder machine after the manual assembly line. Now with my DEK machine, I apply solder paste on the pads of my SMT component then I place the SMT components with SMT machines. But on my design, I have a big XFO, a lot of relays and I dont have enough space to place other SMT components.My idea was to place all SMT components on solder side and thru hole components on other side. My problem at that time was : How can I solder the thru hole components? With that process, it's impossible to pass the PCB in the dual wave because the SMT components on solder side will fall in the dual wave. So i think it's possible to apply glue instead of paste with my DEK machine but I don't find any information concerning the quantity to place under each quind of component and what are the rules about that process.

If you have info about that, I'll appreciate it.

Thank you

Francois Racine

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Jackie Hsieh

#1931

Re: Apply glue with a stainless stell stencil | 13 February, 2000

First I'm a Taiwanese people so excuse my bad english writing. On my experience, The process of double side SMT procedure with two methods ---First one is appling the glue on the solder side, and placeing the R,C,L chips components on it.and 2nd one is appling ROT(Reflow of Thru Hole),pin in paste, in yur process. but it should see as the temp.spec.of your thru-hole componets. According to the quantity to place under each quind of component, the rule is that 0.3 to 0.4 mm width and 0.7 to 0.8 mm in length (just over the component)in the shape of bone. The stress of decouple is over 2.2 to 2.5 kg. The process I prefered is the 2nd one, because the FPYR is higher than first one.

Thanks

Jackie Hsieh

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#1932

Re: Apply glue with a stainless stell stencil | 14 February, 2000

Francois: Sound like a messy process to me.

Choice #1: Put only SMT parts on the primary side Choice #2: Put only SMT parts on the primary and secondary sides Choice #3: Put only SMT and PTH parts on the primary side Choice #4: Put only SMT and PTH parts on the primary side and small SMT parts on the secondary side Choice #5: Other combinations of parts

Good luck

Dave F

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Dane Stokes

#1933

Re: Apply glue with a stainless stell stencil | 15 February, 2000

Also in some instances a 10% decrease on glue size would be needed for the smaller S.O.T. sizes out there. If you are dealing with a good company to make your screen they should send you back a preliminary art work file on the Screen to be made so you can make and overlay to review the placements before ordering the final Stencil for production.

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Rob Fischer

#1934

Re: Apply glue with a stainless stell stencil | 15 February, 2000

Don't feel alone. Many assemblers have the same problem but aren't fortunate enough to have say in the design of the board. They're either have a capital invedtment in a selective solder machine or pallets designed to mask bottom-side SMD. The pallets are widely available in the states but I only know of one option in Europe, Murphy Engineering in Galway, Ireland. You may need a few to keep up with production but the cost vs. benefit factor more than pays the expense.

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MARK ALDER

#1935

Re: Apply glue with a stainless stell stencil | 16 February, 2000

Please refer to the archives on SMTNET date 02/19/1999 on aperture sizes for printing SMD adhesives.

Regards Mark Alder

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sin

#1936

Re: Apply glue with a stainless stell stencil | 16 February, 2000

Why don't you have stencil house make a selective wave fixture for your product so that you can avoid the glue problem. If it's a must for your process to have glue, you just add extra work and glue tended to contaminate.

Just a suggestion..if you think there's a mistake somewhere please let me know..

late

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Jim N

#1937

Re: Apply glue with a stainless stell stencil | 17 February, 2000

We bulid many boards with fine pitch on solder side and then wave. We use a wave fixture that is custom for each board. The fixture covers the SMT components and only exposes the PTH lead during the wave process. It requires about .070 to .100" clearance around PTH pads for the fixture to seal against the board so there is no bridging of SMT. There are several wave pallet vendors out there. Search the web and you can probably find one near you.

Regards Jim

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