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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


John

#10729

2 questions: via tenting and annular ring terminology. | 6 July, 1999

Q #1) Is it more reliable to have the mask tent over the vias or risk getting vias half filled with solder? These are vias with an .020" hole and .040" or .050" pad.

Q #2) When speaking of annular rings, I have always thought of them as minimums. Such as "hole registration should leave a minimum annular ring of .010". Anything else, I refer to as pads. I know that technically, to the letter, all pads are considered annular rings, but in real life aren't all but the smallest of pads referred to as pads, instead of annular rings? Thanks, John

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Scott Cook

#10730

Re: 2 questions: via tenting and annular ring terminology. | 7 July, 1999

| Q #1) Is it more reliable to have the mask tent over the vias or risk getting vias half filled with solder? These are vias with an .020" hole and .040" or .050" pad.

John, It depends......mainly on the via size. Tenting works on smaller vias. Tenting might NOT work well on .020" vias. What's the issue you fight here? Vacuum seal at ICT? There is another process which I've had done on larger vias--epoxy plugging. But it ain't cheap, It's a secondary process for the board house. NEGOTIATE pricing! And remember, only a good board house will do a great job at this.

| | Q #2) When speaking of annular rings, I have always thought of them as minimums. Such as "hole registration should leave a minimum annular ring of .010". Anything else, I refer to as pads. | I know that technically, to the letter, all pads are considered annular rings, but in real life aren't all but the smallest of pads referred to as pads, instead of annular rings? | Thanks, | John |

I'm no expert here....but I have dealt with a board or two in my career. I have always referred to the ring of a drilled hole as an annular ring, independent of size. Pads, to me, are metallized surfaces without drilled holes. The exception would be a pad with a via drilled into it (which we all hate).

Scott Cook

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Peter Brant

#10731

Re: 2 questions: via tenting and annular ring terminology. | 7 July, 1999

| | Q #1) Is it more reliable to have the mask tent over the vias or risk getting vias half filled with solder? These are vias with an .020" hole and .040" or .050" pad.

WIth regards to this question, and scott's follow up, I have used the "epoxy method" The issue at stake was corrosion on one side of the PCB. If corrosion is your issue, then tenting will NOT do the job, you need to plug the vias.

Regards Peter Brant

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John Thorup

#10732

Re: 2 questions: via tenting and annular ring terminology. | 7 July, 1999

| | Q #1) Is it more reliable to have the mask tent over the vias or risk getting vias half filled with solder? These are vias with an .020" hole and .040" or .050" pad. | | John, | It depends......mainly on the via size. Tenting works on smaller vias. Tenting might NOT work well on .020" vias. What's the issue you fight here? Vacuum seal at ICT? There is another process which I've had done on larger vias--epoxy plugging. But it ain't cheap, It's a secondary process for the board house. NEGOTIATE pricing! And remember, only a good board house will do a great job at this.

If you go for plugging be sure you have a protrusion spec that you can live with. This often results in little bumps of epoxy that can interfere with component placement. For us, tenting .015 vias usually gets us about 80% coverage from most of our FAB houses. You could also try dry film mask. John Thorup | | | | | Q #2) When speaking of annular rings, I have always thought of them as minimums. Such as "hole registration should leave a minimum annular ring of .010". Anything else, I refer to as pads. | | I know that technically, to the letter, all pads are considered annular rings, but in real life aren't all but the smallest of pads referred to as pads, instead of annular rings? | | Thanks, | | John | | | | I'm no expert here....but I have dealt with a board or two in my career. I have always referred to the ring of a drilled hole as an annular ring, independent of size. Pads, to me, are metallized surfaces without drilled holes. The exception would be a pad with a via drilled into it (which we all hate). | | Scott Cook | |

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#10733

Re: 2 questions: via tenting and annular ring terminology. | 7 July, 1999

snip | | If you go for plugging be sure you have a protrusion spec that you can live with. This often results in little bumps of epoxy that can interfere with component placement. For us, tenting .015 vias usually gets us about 80% coverage from most of our FAB houses. You could also try dry film mask. | John Thorup

snip

Liquid photomasks do a good job of sealing vias. Film masks do not.

Dave the design guy likes plugging from the secondary side. Dave the production guy like plugging from the primary side. They argue, but they don't agree.

Both hate plug material that become the high point on the board.

Ta

Dave F

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John

#10734

Thanks | 9 July, 1999

Thanks everyone. I appreciate the help. John

| Q #1) Is it more reliable to have the mask tent over the vias or risk getting vias half filled with solder? These are vias with an .020" hole and .040" or .050" pad. | | Q #2) When speaking of annular rings, I have always thought of them as minimums. Such as "hole registration should leave a minimum annular ring of .010". Anything else, I refer to as pads. | I know that technically, to the letter, all pads are considered annular rings, but in real life aren't all but the smallest of pads referred to as pads, instead of annular rings? | Thanks, | John |

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