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SMT electronics assembly manufacturing forum.


Pin Hole/Blow Hole - Causes and cure please

Vinesh Gandhi

#10868

Pin Hole/Blow Hole - Causes and cure please | 24 June, 1999

Recently, there has been an upsurge in the Pin Hole/Blow Hole problem in our wave soldering process. We are baking the PCBs for 2 Hrs. at 125 degree C. The Wave Soldering profile seems to be O.K. Still the problem is persistent. Can somebody help me on this!!!....

Also, as per IPC-610-B Class 2, upto 270 degree coverage on soler side of the board is acceptable, but if I have about 20-30 joints with about 20-70 degree coverage, is that acceptable by normal standards. Please elaborate.

Thanks & Regards Vinesh Gandhi

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Earl Moon

#10869

Re: Pin Hole/Blow Hole - Causes and cure please | 24 June, 1999

| Recently, there has been an upsurge in the Pin Hole/Blow Hole problem in our wave soldering process. We are baking the PCBs for 2 Hrs. at 125 degree C. The Wave Soldering profile seems to be O.K. Still the problem is persistent. Can somebody help me on this!!!.... | | Also, as per IPC-610-B Class 2, upto 270 degree coverage on soler side of the board is acceptable, but if I have about 20-30 joints with about 20-70 degree coverage, is that acceptable by normal standards. Please elaborate. | | Thanks & Regards | Vinesh Gandhi | | Pin holes and/or blow holes are effected by causes as poor drilling (rough, gouged, etc) followed by poor hole wall preparation (epoxy etch back and/or smear removal, and/or poor glass fiber removal after the foregoing effecting glass fiber protusion into the hole wall reducing the subsequent copper plating below specified minimum, etc.), poor electroless copper deposition, poor copper electro-plating and, in general, poor process management in the board shop of choice.

All the baking in the world will not cure the problem. Only effective process management within the board shop will do that.

Earl Moon

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John Thorup

#10870

Re: Pin Hole/Blow Hole - Causes and cure please | 24 June, 1999

| Recently, there has been an upsurge in the Pin Hole/Blow Hole problem in our wave soldering process. We are baking the PCBs for 2 Hrs. at 125 degree C. The Wave Soldering profile seems to be O.K. Still the problem is persistent. Can somebody help me on this!!!.... | | Also, as per IPC-610-B Class 2, upto 270 degree coverage on soler side of the board is acceptable, but if I have about 20-30 joints with about 20-70 degree coverage, is that acceptable by normal standards. Please elaborate. | | Thanks & Regards | Vinesh Gandhi | | Vinesh I'm not sure I understand the second part of your question but if you are referring to the circumferential fillet and wetting on the solder side, 270 degree coverage is the minimum acceptable and 20-70 degrees sounds like a recipe for solder joint failure. With good boards and components you shouldn't have any trouble getting 360 degrees. Blow and pin holes are acceptable as long as they do not create a violation of the minimum requirements for wetting but Earl is correct about your likely having poor quality fabs and if your vendors processes are that out of control you are likely to have other problems with these boards as well (like your wetting problem?) Did this start when a new vendor's board was introduced? Baking wont help because your fluxing operation is squirting fresh fluid up into the hole every time. Just to cover all the bases, have you checked your pre-heat profile? If something is amiss here you might not be evaporating all the flux carrier before the wave, especially if you use a water base flux. Guaranteed to cause blow holes. This might cause insufficient flux activation and your wetting problem as well. good luck John Thorup

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Earl Moon

#10871

Re: Pin Hole/Blow Hole - Causes and cure please | 24 June, 1999

| | Recently, there has been an upsurge in the Pin Hole/Blow Hole problem in our wave soldering process. We are baking the PCBs for 2 Hrs. at 125 degree C. The Wave Soldering profile seems to be O.K. Still the problem is persistent. Can somebody help me on this!!!.... | | | | Also, as per IPC-610-B Class 2, upto 270 degree coverage on soler side of the board is acceptable, but if I have about 20-30 joints with about 20-70 degree coverage, is that acceptable by normal standards. Please elaborate. | | | | Thanks & Regards | | Vinesh Gandhi | | | | Vinesh | I'm not sure I understand the second part of your question but if you are referring to the circumferential fillet and wetting on the solder side, 270 degree coverage is the minimum acceptable and 20-70 degrees sounds like a recipe for solder joint failure. With good boards and components you shouldn't have any trouble getting 360 degrees. | Blow and pin holes are acceptable as long as they do not create a violation of the minimum requirements for wetting but Earl is correct about your likely having poor quality fabs and if your vendors processes are that out of control you are likely to have other problems with these boards as well (like your wetting problem?) Did this start when a new vendor's board was introduced? Baking wont help because your fluxing operation is squirting fresh fluid up into the hole every time. Just to cover all the bases, have you checked your pre-heat profile? If something is amiss here you might not be evaporating all the flux carrier before the wave, especially if you use a water base flux. Guaranteed to cause blow holes. This might cause insufficient flux activation and your wetting problem as well. good luck | John Thorup | | John added some good stuff. To find the cause of the effect, X-Sectional analysis is in order. Go to your local lab and cut up one of the pin holed holes. If the pin hole does not propagate from the hole wall, through the plating, it is as John said. This means something is wrong with your process, not the board shop's. Somehow, I doubt it, though hopeful, but we'll never know until you.

Earl Moon

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Vinesh Gandhi

#10872

Re: Pin Hole/Blow Hole - Causes and cure please | 25 June, 1999

| | | Recently, there has been an upsurge in the Pin Hole/Blow Hole problem in our wave soldering process. We are baking the PCBs for 2 Hrs. at 125 degree C. The Wave Soldering profile seems to be O.K. Still the problem is persistent. Can somebody help me on this!!!.... | | | | | | Also, as per IPC-610-B Class 2, upto 270 degree coverage on soler side of the board is acceptable, but if I have about 20-30 joints with about 20-70 degree coverage, is that acceptable by normal standards. Please elaborate. | | | | | | Thanks & Regards | | | Vinesh Gandhi | | | | | | Vinesh | | I'm not sure I understand the second part of your question but if you are referring to the circumferential fillet and wetting on the solder side, 270 degree coverage is the minimum acceptable and 20-70 degrees sounds like a recipe for solder joint failure. With good boards and components you shouldn't have any trouble getting 360 degrees. | | Blow and pin holes are acceptable as long as they do not create a violation of the minimum requirements for wetting but Earl is correct about your likely having poor quality fabs and if your vendors processes are that out of control you are likely to have other problems with these boards as well (like your wetting problem?) Did this start when a new vendor's board was introduced? Baking wont help because your fluxing operation is squirting fresh fluid up into the hole every time. Just to cover all the bases, have you checked your pre-heat profile? If something is amiss here you might not be evaporating all the flux carrier before the wave, especially if you use a water base flux. Guaranteed to cause blow holes. This might cause insufficient flux activation and your wetting problem as well. good luck | | John Thorup | | | | | John added some good stuff. To find the cause of the effect, X-Sectional analysis is in order. Go to your local lab and cut up one of the pin holed holes. If the pin hole does not propagate from the hole wall, through the plating, it is as John said. This means something is wrong with your process, not the board shop's. Somehow, I doubt it, though hopeful, but we'll never know until you. | | Earl Moon |

Dear John/Earl

Thanks for your clarifications. To me also the problem does not seem to be linked with the PCB. The Pre heater temp. is set at 450 degree C. We are using Alpha Aq. cleanable flux. Can you elaborate on the Desired profiling required.

Best Regards

Vinesh Gandhi

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#10873

Re: Pin Hole/Blow Hole - Causes and cure please | 25 June, 1999

snip | | Dear John/Earl | | Thanks for your clarifications. To me also the problem does not seem to be linked with the PCB. The Pre heater temp. is set at | 450 degree C. We are using Alpha Aq. cleanable flux. Can you elaborate on the Desired profiling required. | | Best Regards | | Vinesh Gandhi | Not your mamma's preheater, is it?

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C.K.

#10874

Wave Solder Profiling Basics | 25 June, 1999

| Dear John/Earl | | Thanks for your clarifications. To me also the problem does not seem to be linked with the PCB. The Pre heater temp. is set at | 450 degree C. We are using Alpha Aq. cleanable flux. Can you elaborate on the Desired profiling required. | | Best Regards | | Vinesh Gandhi |

Let me elaborate and put my 2 cents in, please. Your preheater is set @ 450 C, but at what conveyor speed? How fast you run your conveyor speed will affect what your thermal profile looks like. Is it just one zone of preheat? Profiles depend on lots of things, such as what types of devices you have, the thermal mass of your PCB, required flux activation temperatures, etc. Typically, on mixed-technology boards you'll want a no greater than 2 degrees celcius per second rate-of-rise, and around 100 to 130 deg. C top-side board temperature before your board hits the wave. You want to minimize the temperature delta, or the difference between your top-side and max. board temps. It's up to you what combinations of conveyor speed and preheat settings will achieve this profile. That's the tricky part of developing your wave process.

I recommend that you "revisit" your profile...run a MOLE through and slap 6 T/C's on that troublesome board of yours. Or for "quick-and-dirty" profiling, use a WaveRIDER or Wave Optimizer. Both devices have a thermal sensor board consisting of 3 T/C's embedded in the board. The output from either device will get you pretty close to the profile that you'd run most of your production boards. For even quicker and dirtier profiling, try temperature stickers, and you'll see right away if your board is getting hot enough.

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Earl Moon

#10875

Re: Wave Solder Profiling Basics | 25 June, 1999

| | Dear John/Earl | | | | Thanks for your clarifications. To me also the problem does not seem to be linked with the PCB. The Pre heater temp. is set at | | 450 degree C. We are using Alpha Aq. cleanable flux. Can you elaborate on the Desired profiling required. | | | | Best Regards | | | | Vinesh Gandhi | | | | | Let me elaborate and put my 2 cents in, please. Your preheater is set @ 450 C, but at what conveyor speed? How fast you run your conveyor speed will affect what your thermal profile looks like. Is it just one zone of preheat? Profiles depend on lots of things, such as what types of devices you have, the thermal mass of your PCB, required flux activation temperatures, etc. Typically, on mixed-technology boards you'll want a no greater than 2 degrees celcius per second rate-of-rise, and around 100 to 130 deg. C top-side board temperature before your board hits the wave. You want to minimize the temperature delta, or the difference between your top-side and max. board temps. It's up to you what combinations of conveyor speed and preheat settings will achieve this profile. That's the tricky part of developing your wave process. | | I recommend that you "revisit" your profile...run a MOLE through and slap 6 T/C's on that troublesome board of yours. Or for "quick-and-dirty" profiling, use a WaveRIDER or Wave Optimizer. Both devices have a thermal sensor board consisting of 3 T/C's embedded in the board. The output from either device will get you pretty close to the profile that you'd run most of your production boards. For even quicker and dirtier profiling, try temperature stickers, and you'll see right away if your board is getting hot enough. | Everything said is true and good. I must take exception to those damn stickers. Don't trust 'em based on too many errors found when using other profile methods to "calibrat" the little bastards.

If you want cheap and dirty, while getting accurage readings in real time, use an IR profilometer - if you don't need a top preheater cover. If you do, measure the board just coming out of the tunnel before wave contact.

Earl Moon

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C.K.

#10876

Re: Wave Solder Profiling Basics | 25 June, 1999

| | | Dear John/Earl | | | | | | Thanks for your clarifications. To me also the problem does not seem to be linked with the PCB. The Pre heater temp. is set at | | | 450 degree C. We are using Alpha Aq. cleanable flux. Can you elaborate on the Desired profiling required. | | | | | | Best Regards | | |

| | | Vinesh Gandhi | | | | | | | | | Let me elaborate and put my 2 cents in, please. Your preheater is set @ 450 C, but at what conveyor speed? How fast you run your conveyor speed will affect what your thermal profile looks like. Is it just one zone of preheat? Profiles depend on lots of things, such as what types of devices you have, the thermal mass of your PCB, required flux activation temperatures, etc. Typically, on mixed-technology boards you'll want a no greater than 2 degrees celcius per second rate-of-rise, and around 100 to 130 deg. C top-side board temperature before your board hits the wave. You want to minimize the temperature delta, or the difference between your top-side and max. board temps. It's up to you what combinations of conveyor speed and preheat settings will achieve this profile. That's the tricky part of developing your wave process. | | | | I recommend that you "revisit" your profile...run a MOLE through and slap 6 T/C's on that troublesome board of yours. Or for "quick-and-dirty" profiling, use a WaveRIDER or Wave Optimizer. Both devices have a thermal sensor board consisting of 3 T/C's embedded in the board. The output from either device will get you pretty close to the profile that you'd run most of your production boards. For even quicker and dirtier profiling, try temperature stickers, and you'll see right away if your board is getting hot enough. | | | Everything said is true and good. I must take exception to those damn stickers. Don't trust 'em based on too many errors found when using other profile methods to "calibrat" the little bastards. | | If you want cheap and dirty, while getting accurage readings in real time, use an IR profilometer - if you don't need a top preheater cover. If you do, measure the board just coming out of the tunnel before wave contact. | | Earl Moon |

I've forgotten many-a-times to take a reading before wave, or just plain leave the wave off, and have witnessed that sticker "blowing up" right in front of me! Talk about "stepping on your own d$!&" !

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