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Adhesive Application by Stencil

rwilliams

#5701

Adhesive Application by Stencil | 22 March, 2001

In regards to SMT adhesive application by stencil:

Can anyone make any recommendations for: SMT Adhesive Material itself? Squeegee Blade Material? Stencil Material? Characteristics/Features of your Stencil? E.g., thickness, aperture ratios, etc... Printer Set-up Parameters? E.g., Print Gap, Squeegee Pressure, Squeegee Speed, etc...

Any recommendations or suggestions at all would be appreciated...

Thanks,

RW

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kaopsahl

#5703

Adhesive Application by Stencil | 22 March, 2001

Yes, there are adhesives designed just for stencil application. Usually plastic squeegee blades are recommended for best printing results. Plastic stencils are also available for this application. Both Alpha Metals and Loctite have articles on this subject in PDF form on their websites. The articles are fairly detailed, and give guidelines on stencil design (apertures, squeegee speed, etc.). One thing that is supposed to make a big difference is the ability to control snap-off on your printer-if you have a Fuji GSP with a Motion-Pak controller or similar set-up this should help. I have never actually tried using a stencil adhesive process, but good luck to you. Post your results if you get a chance!

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Mike Naddra

#5723

Adhesive Application by Stencil | 23 March, 2001

RW,

I have Screened Adhesive on to several different assemblies and have found that when it is possible I get a much better result than with a dot deposition process (The green strength was greatly improved), the biggest issue I ran in to was the profile of the component (or distance from the bottom of the component to the surface of the board), as the printed adhesive brick does not have the height of a dot created by a dot deposition process. So in some cases I had to combine a print process with a dot deposition process (For the high profile components). To get on with it, I used a stainless stencil and printed with stainless blades (Using an MPM AP series vision aligned printer), the adhesive I used was Heraeus PD955PY (Probably not the best choice but it worked). My stencil design was 8mil Stainless stencil laser cut and electropolish all aperatures ; I maintained a minimum aspect ratio of 2.0 ,(I found that if I got below 2.0 I started to expierence release problems, this could also be possibly attributed to the adhesive I was using), The stencil was backcut 50% for each pad on the board and the backcut increased 10% larger than the pad size. This gave me a better gasket to the printing surface and minimized under side stencil bleed, I used a wet stencil wipe after each print, I used a print speed of 2.5 inches per minute and a snap off of 0.

Hope this helps, Mike

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Verm

#5740

Adhesive Application by Stencil | 27 March, 2001

I am currently depositing adhesive for mixed technology PCB's with both axial and radial inserted components. The stencil is plastic and has underside relief for the clinched components (not possible with a metal stencil), rather than go any further. Is this what you are looking to implement?.

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JohnW

#5754

Adhesive Application by Stencil | 27 March, 2001

RW,

I've been printing glue by stencil for a while. Like the other guy's say there are various method's and material's that you can use but then your printing paste so the ideal is for as little change as possible to the method's your already using. Hereaus PD955PY is what I'm using and it's pretty good, also Hereaus have a really good back up on printing glue, on the stencil requirements and the appeture types and dimensions that work well. In term's of stencil's I'm using your std lazer cut vintage, I'm still not sure wether it's teh best but it's working pretty well, as for squeegee blades, they're metal too, and I have to say compared with rubber it's a dream to work with. I've alway's been a tad concerned about using plastic stencil's and rubber squeegee's or for that mater meltal on plastic...I know there was initially an issue with static and I know my company banned it as an approved method but taht was a while ago and I don't know the lastest on those. So summary, Metal Stencil, Metal Squeegees ' 60 deg, hereaus PD955py along with they're appeture selections and you should be laughing...you 'll even find that they will come and help. Typically I'm using 8 thou' stencils but occassionally I do 10 thou' as well. Another thing to check, look at the archives, about a year or so ago I did a big bit on printing glue and how to set it up, or at least how I was setting it up...

JohnW

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JohnW

#5755

Adhesive Application by Stencil | 27 March, 2001

RW,

I've been printing glue by stencil for a while. Like the other guy's say there are various method's and material's that you can use but then your printing paste so the ideal is for as little change as possible to the method's your already using. Hereaus PD955PY is what I'm using and it's pretty good, also Hereaus have a really good back up on printing glue, on the stencil requirements and the appeture types and dimensions that work well. In term's of stencil's I'm using your std lazer cut vintage, I'm still not sure wether it's teh best but it's working pretty well, as for squeegee blades, they're metal too, and I have to say compared with rubber it's a dream to work with. I've alway's been a tad concerned about using plastic stencil's and rubber squeegee's or for that mater meltal on plastic...I know there was initially an issue with static and I know my company banned it as an approved method but taht was a while ago and I don't know the lastest on those. So summary, Metal Stencil, Metal Squeegees ' 60 deg, hereaus PD955py along with they're appeture selections and you should be laughing...you 'll even find that they will come and help. Typically I'm using 8 thou' stencils but occassionally I do 10 thou' as well. Another thing to check, look at the archives, about a year or so ago I did a big bit on printing glue and how to set it up, or at least how I was setting it up...

JohnW

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Chinaren

#5763

Adhesive Application by Stencil | 28 March, 2001

we use the screen glue AMICON D125 F5 from Emerson company of Belgium and stencil is Varidot stencil from Loctite with thickness of 250 micrometers The squeegee is also from loctite, previously we use squeegee of material PU, it is easy to be broken,so later we change to compound squeegee a new product from Loctite

For the aperture ratios, the Loctite has theire regulations, you can ask for this and modify according to your own status.

we now use the adhensive screnn printing without problems. The set up parameters such as speed and pressure should adjusted acording to your own machine status. For the Gap we set as 1.5mm

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