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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


Ryan Jennens

#12578

Squeegee Speed | 18 February, 1999

Hey all-

My question is this: My stencil printer operator has said that he has to wipe our 6-mil stencil each pass to get the paste in the 20-mill pitch aperatures for a QFP to release well. We are using Amtech NC-559 type 3 paste with 89.5% metal. The paste is not old. I considered using type 4 paste, which has a much finer powder in it. I was told by Amtech that this finer powder paste will pack more densly into the aperatures and I could get some bridging, unless I order a new stencil with aperature reductions. Our squeegee speed is 0.6 inches/s, or 15mm/s. Is this too slow? Amtech suggested that at this slow speed, the paste could be rising out of the aperature, as if someone pressed on a wet sponge and it rose back to its original shape. What is a good squeegee speed for 20 mil pitch parts? Thanks!

Ryan Jennens TelGen Corp.

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Tuffty

#12579

Re: Squeegee Speed | 19 February, 1999

| Hey all- | | My question is this: My stencil printer operator has said that he has to | wipe our 6-mil stencil each pass to get the paste in the 20-mill pitch | aperatures for a QFP to release well. We are using Amtech NC-559 type 3 | paste with 89.5% metal. The paste is not old. I considered using type 4 | paste, which has a much finer powder in it. I was told by Amtech that this | finer powder paste will pack more densly into the aperatures and I could get | some bridging, unless I order a new stencil with aperature reductions. Our | squeegee speed is 0.6 inches/s, or 15mm/s. Is this too slow? Amtech | suggested that at this slow speed, the paste could be rising out of the | aperature, as if someone pressed on a wet sponge and it rose back to its | original shape. What is a good squeegee speed for 20 mil pitch parts? | Thanks! | | Ryan Jennens | TelGen Corp. | | Ryan,

The type of squeegee you are using is a key factor, is it metal or rubber and if it's rubber how hard is it ? Your metal content may need to be looked at but most pastes today are recomending higher print speed's especially using metal blades - anything from 40 - 80mm /sec the other key factor would be the pressure you are using. It also depend's on how good your stencil is, laser etch and so forth. if your stencil wall's aren't right you wont get good paste release (seperation speed may also come into play here)the other thing to look out for is how close your appeture size matches you pad size , especially if you go to the finer paste.

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GORDON DURPHEY

#12580

Re: Squeegee Speed | 20 February, 1999

| Hey all- | | My question is this: My stencil printer operator has said that he has to | wipe our 6-mil stencil each pass to get the paste in the 20-mill pitch | aperatures for a QFP to release well. We are using Amtech NC-559 type 3 | paste with 89.5% metal. The paste is not old. I considered using type 4 | paste, which has a much finer powder in it. I was told by Amtech that this | finer powder paste will pack more densly into the aperatures and I could get | some bridging, unless I order a new stencil with aperature reductions. Our | squeegee speed is 0.6 inches/s, or 15mm/s. Is this too slow? Amtech | suggested that at this slow speed, the paste could be rising out of the | aperature, as if someone pressed on a wet sponge and it rose back to its | original shape. What is a good squeegee speed for 20 mil pitch parts? | Thanks! | | Ryan Jennens | TelGen Corp. | | RYAN, I HAVE NEVER WORKED WITH PRINTERS, BUT THE PROBLEM SOUNDS SO MUCH LIKE A MOLD RELEASE PROBLEM IN THE PLASTICS INDUSTRY THAT I HAVE TO ASK IF A GOOD LUBRICANT WOULD HELP?? GIVE ME A CALL AT 888 8286226 IF YOU THINK THAT'S A POSSIBILITY.

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Rick Wyman

#12581

Re: Squeegee Speed | 22 February, 1999

| | Hey all- | | | | My question is this: My stencil printer operator has said that he has to | | wipe our 6-mil stencil each pass to get the paste in the 20-mill pitch | | aperatures for a QFP to release well. We are using Amtech NC-559 type 3 | | paste with 89.5% metal. The paste is not old. I considered using type 4 | | paste, which has a much finer powder in it. I was told by Amtech that this | | finer powder paste will pack more densly into the aperatures and I could get | | some bridging, unless I order a new stencil with aperature reductions. Our | | squeegee speed is 0.6 inches/s, or 15mm/s. Is this too slow? Amtech | | suggested that at this slow speed, the paste could be rising out of the | | aperature, as if someone pressed on a wet sponge and it rose back to its | | original shape. What is a good squeegee speed for 20 mil pitch parts? | | Thanks! | | | | Ryan Jennens | | TelGen Corp. | | | | Ryan, | | The type of squeegee you are using is a key factor, is it metal or rubber and if it's rubber how hard is it ? | Your metal content may need to be looked at but most pastes today are recomending higher print speed's especially using metal blades - anything from 40 - 80mm /sec the other key factor would be the pressure you are using. | It also depend's on how good your stencil is, laser etch and so forth. if your stencil wall's aren't right you wont get good paste release (seperation speed may also come into play here)the other thing to look out for is how close your appeture size matches you pad size , especially if you go to the finer paste. | | I have to agree with Ryan- We have found that an increase in squeegee speed goes a long way toward eliminating bridging. We use DEK screenprinters with metal blades. Coupling the increased speed with a reduced separation speed (board separating from the stencil) usually will do the trick- assuming all else is well.

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Steve Schrader

#12582

Re: Squeegee Speed | 23 February, 1999

| Hey all- | | My question is this: My stencil printer operator has said that he has to | wipe our 6-mil stencil each pass to get the paste in the 20-mill pitch | aperatures for a QFP to release well. We are using Amtech NC-559 type 3 | paste with 89.5% metal. The paste is not old. I considered using type 4 | paste, which has a much finer powder in it. I was told by Amtech that this | finer powder paste will pack more densly into the aperatures and I could get | some bridging, unless I order a new stencil with aperature reductions. Our | squeegee speed is 0.6 inches/s, or 15mm/s. Is this too slow? Amtech | suggested that at this slow speed, the paste could be rising out of the | aperature, as if someone pressed on a wet sponge and it rose back to its | original shape. What is a good squeegee speed for 20 mil pitch parts? | Thanks! | | Ryan Jennens | TelGen Corp. | |

Your print speed is not out of line. You could probably raise it to 1.0 inch/sec. (we sometimes go up to 2.0 inch/sec). If your printer is not your line bottleneck, I would keep wiping after every 20 mil print (we do). We have an automatic wiper on an MPM-SPM and the printer is never the bottleneck in our process.

I would recommend reducing your apertures for 20 mil pitch. We use a 10% reduction on 20 mil pitch (6 mil stencil). We have found band-etch stencils to deliver results similar to laser etch at chem etch prices, so we use band-etch stencils on all of our fine pitch applications (chem etch otherwise) and reduce 10% on 20 mil and 15% on 25 mil.

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