Printed Circuit Board Assembly & PCB Design SMT Electronics Assembly Manufacturing Forum

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Rippling effect of stencils

Jones

#18868

Rippling effect of stencils | 15 February, 2002

I've noticed that after we have switched to Transition Automation blades on our MPM screen printers that the stencils seem to be wearing out faster and I see a wavy rippling effect across the length of the stencil thats impacted by the squeege blade. Was wondering if others have had this problem. Some ideas into causes would be appreciated.

Some insite into our parameter settings. For a 12" blade on lets say a 6mil stencil:

Total force: 14 Balance 50/50 Downstop .0750 Attack angle 0 w/mechanical set up the same Stroke: Close to width of board

Thanks.......Jones

reply »

Dave G

#18870

Rippling effect of stencils | 15 February, 2002

What Snap-Off are you running ?

I've seen this happen when a large negative Snap-Off is used. If you "contact" print (I.E. Zero Snap-Off) this tends to minimize the stencil coining. We use a mix of MPM & Transition Automation blades. I have noticed that the stencils that we run the Transition Blades with do tend to have a different wear pattern than the Stencils used with the regular MPM blades. I'm going to look into this a little closer to see if ours are wearing faster as well.

Hope this Helps, Dave G

reply »

Greg

#18875

Rippling effect of stencils | 15 February, 2002

What about reducing your force and slow the blades down slightly

reply »


CAL

#18892

Rippling effect of stencils | 18 February, 2002

I have printed 1000's of boards with dozens of stencils with TA permalex blades and have not had the issue you speak of.

Sorry I was not much help.

Cal

reply »

dougk

#18945

Rippling effect of stencils | 21 February, 2002

Silly question, but, are TR blades 'exactly' the same size as MPM's and seat themselves in the holders just like MPM's? Also, different types of steel are harder (less flexable) than others. Are TR's the same? If harder (due to steel strength or coating), they will deflect less under same downstop setting, and a different strain on the stencil will result. We were thinking of going Permalex for our MPM's; would like to see what everyone here comes-up with.

reply »

#18946

Rippling effect of stencils | 22 February, 2002

O.K. Try this one on for size. I can't remember if I mailed this to someone privately or said it in the forum. I refuse to pay the exorbitant prices people are asking for squeegee blades.

You people are robbers and flim flam men.

I get my stencil manufacturer to make them. 0.010" thick s/steel with the bottom edge that contacts the stencil etched to 0.003" > 0.005" for a distance of 0.120". I supply the cad file - they supply the blades - SIX PER SHIM - $300.

Try it, you'll like it!

Take yer set of overpriced, dooverlacky, hoity toity, rickerpoodley and a fandoogally, titanium, teflon, whacko the diddle-o, whatever-o, "premium" blades to your stencil man and say, "duplicate that as closely as you can".

If it fails you've lost the price of a shim.

If it works you've got squeegee blades for 10% of the price these bozos are askin'.

You can do ten experiments, together, with different thicknesses, grades, cutaways etc. for the cost of ONE set of overpriced, dooverlacky, hoity toity, rickerpoodley and a fandoogally, titanium, teflon, whacko the diddle-o, whatever-o, "premium" blades.

I was gonna write a paper on this, but stuff it, let 'er rip.

reply »

Jones

#18947

Rippling effect of stencils | 22 February, 2002

There appears to be less of a blade sticking out of the holder than the MPM set up. Thats something we noticed recently. We have our mechanical attack angle set at 0 degrees right now, but we are in the process of changing this setting by 5 degrees to see what the results will be. Hopefully this will allow for more flexing of the blades. I'm not sure about the hardness of the metal as opposed to MPM blades, but since our Permalex setup uses two blades, one that contacts the stencil and the other that appears to re-enforce that blade, I'm sure theirs less give to the TR setup.

reply »

#18967

Rippling effect of stencils | 25 February, 2002

Jeezuz... Darby is right. High Tech Squeegee blades are a crock of BS.Don't belive the hype. Its a big scam to rake in your dough. We use .008" thick spring steel stock from McMaster. There is only one thing:The blades must be dried off thoroughly after use. I have used TA blades, don't get me wrong they work fine, but they are major expensive for what you are getting. By the way, I have also seen the wavy stencil thing. Do not confuse it with the coining term. Those are two different issues. Check your squeegee pressure,and verify that you are not pushing the board up into the stencil. Don't use snap off, thats old school stuff. Use the contact printing method.

Cyber

reply »

John

#22974

Rippling effect of stencils | 10 January, 2003

Hi. I am familiar with the Transition blades. Normally, when there is metal to metal contact, as in the squeegee-stencil situation, there will be scratches, or a "brush pattern". Sometimes it takes the pattern of the high profile surface elements under the stencil (like pc traces etc).

The Transition blades produce a "marble" pattern, after a few hundred strokes. If the board is very flat, and support is good, the pattern will spread out around the whole print surface. If the support isn't so good, the pattern may stay restricted to the areas of good support.

The Transition blades coating has a hard porous coating with Teflon trapped in it. At the begining, high points of metal contact the stencil and scratch. After the inintial "wear-in", there is essentially teflon contacting the stencil.

The marble pattern is actually the grain of the stencil metal showing after the polishing action of the squeegee.

I don't think your stencils are wearing out. I think they are exhibiting the polish pattern. TO BE SURE, YOU CAN CHECK THE STENCIL THICKNESS -OLD VERSUS NEW.

Finally, it is very important to know the vintage of your TR blades. If they are old and have a nicked edge, that will cause wearout.

Normally the TR blades will last 12 months of rigourous production. They are expensive. But who wants to be changing squeegee blades on a printer every three months?

Take care,

reply »

iman

#23055

Rippling effect of stencils | 17 January, 2003

wat angle of incline should the etched portion be? or am i missing something here?

reply »

PCB Soldering Tools

Flying Probe Tester