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

Printed Circuit Board Assembly & PCB Design Forum

SMT electronics assembly manufacturing forum.


optimized profile

Joe Cameron

#11744

optimized profile | 25 April, 1999

Hello all,

Our guys here still have some questions on the "optimized" profile which sees a more moderate ramp up straight to reflow temperatures versus the conventional profile which has a plateau at around 150 Celsius. If the optimized profile can really solve so many process problems, why was the convention profile used in the first place? What's your point of view on this issue.

BTW, we're using a convection assisted IR oven, or if you look at it the other way around, an IR assisted convection oven. We can't seem to adjust to the new profile without sacrificing on throughput speed. Is this type of oven suitable for this?

Thanks, Joe

reply »

Earl Moon

#11745

Re: optimized profile | 25 April, 1999

| Hello all, | | Our guys here still have some questions on the "optimized" profile which sees a more moderate ramp up straight to reflow temperatures versus the conventional profile which has a plateau at around 150 Celsius. If the optimized profile can really solve so many process problems, why was the convention profile used in the first place? What's your point of view on this issue. | | BTW, we're using a convection assisted IR oven, or if you look at it the other way around, an IR assisted convection oven. We can't seem to adjust to the new profile without sacrificing on throughput speed. Is this type of oven suitable for this? | | Thanks, | Joe | Just to add a thought. We use SBTU's (super big thermal units) machines. We run 9 different board types from single sided to those requiring flipping and flopping, SMT, through hole, and hole in the wall as well as edge. Our system is so "robust" (a term overused here) it requires only two profiles to do it all.

We do have an extra strong profile, but it's just for those boards deserving a special burning. We run air and nitrogen. Nitrogen, when required with each of the two profiles, is used with a specific paste type to ensure better thermal transfer and wetting on some board types. We don't use it with vias in pads as the solder drains off too fast.

Anyway, we have a luxury of first designing pads that are proven to work and we have an evaluation department that proves not only design rules but solder paste types (3 only). Then we have folks like myself who ensure the stuff is used properly.

Did I mention we make mistakes now and then. Oh well - who doesn't? However, we make very few when it comes to soldering except when one operator, who said we don't need no stinking pre-process audit check list, ran a batch all the way through reflow - up side down. That was fun. Wonder where she's working now - with any of you?

And on it goes,

Earl Moon

reply »

#11746

Re: optimized profile | 25 April, 1999

| Hello all, | | Our guys here still have some questions on the "optimized" profile which sees a more moderate ramp up straight to reflow temperatures versus the conventional profile which has a plateau at around 150 Celsius. If the optimized profile can really solve so many process problems, why was the convention profile used in the first place? What's your point of view on this issue. | | BTW, we're using a convection assisted IR oven, or if you look at it the other way around, an IR assisted convection oven. We can't seem to adjust to the new profile without sacrificing on throughput speed. Is this type of oven suitable for this? | | Thanks, | Joe |

In my opinion, the "soak Zone" profile that plateaus around 150 C is a throwback to the days of straight IR. That soak zone was needed to stabilize board temperatures before going into the spike zone. So all the paste manufacturers made pastes with fluxes that activated in this range. You'd hold for 60 to 90 seconds to activate the fluxes.

Then, one morning, someone woke up and siad "Hey, we got convection now. Why are we still heatsoaking?" and developed fluxes that don't need to dwell to work. And the benefits of this development are quicker throughput times and less thermal exposure to the assemblies.

So I went out and got me one of them "modern" pastes with the straight ramp profile. And in my convection ovens, my profile time dropped from about five minutes to about 3.5. The pastes in this "modern" category can ramp from ambient to peak at rates of 1 - 2 degrees C per second, which is the same ramp that you use in prehat and spike. So the new profile basically cuts out the soak zone.

I've realized higher throughput with the linear ramp. Boards that used to run at 80cm/sec belt speed are screaming through at 100 or 105 cm/sec in my 8-zone convection oven.

Now, about your oven. It is convection/IR assisted? This means IR panels and heat blowers? If the thermal transfer capability of the oven cannot heat the boards at reasonable belt speeds, then you are stuck with a soak zone. But on the bright side, you may be able to shorten the soak zone down to (mqaybe) 30 seconds instead of 60 to 90. And these newfangled pastes can take it. An Indium guy told me the flux in his SMQ92 will go up to 8 minutes without exhausing. So it doesn't matter what profile you use, although it does make a difference in the spread of residues.

So even if you can't run with the linear ramp, you can still upgrade your paste and reap all the printability, solderability, and testability benefits of this generation. And with a paste capable of linear ramps, you'll be able to cost-justify a new oven based on throughput increases.

reply »

Earl Moon

#11747

Re: optimized profile | 25 April, 1999

| | Hello all, | | | | Our guys here still have some questions on the "optimized" profile which sees a more moderate ramp up straight to reflow temperatures versus the conventional profile which has a plateau at around 150 Celsius. If the optimized profile can really solve so many process problems, why was the convention profile used in the first place? What's your point of view on this issue. | | | | BTW, we're using a convection assisted IR oven, or if you look at it the other way around, an IR assisted convection oven. We can't seem to adjust to the new profile without sacrificing on throughput speed. Is this type of oven suitable for this? | | | | Thanks, | | Joe | | | | In my opinion, the "soak Zone" profile that plateaus around 150 C is a throwback to the days of straight IR. That soak zone was needed to stabilize board temperatures before going into the spike zone. So all the paste manufacturers made pastes with fluxes that activated in this range. You'd hold for 60 to 90 seconds to activate the fluxes. | | Then, one morning, someone woke up and siad "Hey, we got convection now. Why are we still heatsoaking?" and developed fluxes that don't need to dwell to work. And the benefits of this development are quicker throughput times and less thermal exposure to the assemblies. | | So I went out and got me one of them "modern" pastes with the straight ramp profile. And in my convection ovens, my profile time dropped from about five minutes to about 3.5. The pastes in this "modern" category can ramp from ambient to peak at rates of 1 - 2 degrees C per second, which is the same ramp that you use in prehat and spike. So the new profile basically cuts out the soak zone. | | I've realized higher throughput with the linear ramp. Boards that used to run at 80cm/sec belt speed are screaming through at 100 or 105 cm/sec in my 8-zone convection oven. | | Now, about your oven. It is convection/IR assisted? This means IR panels and heat blowers? If the thermal transfer capability of the oven cannot heat the boards at reasonable belt speeds, then you are stuck with a soak zone. But on the bright side, you may be able to shorten the soak zone down to (mqaybe) 30 seconds instead of 60 to 90. And these newfangled pastes can take it. An Indium guy told me the flux in his SMQ92 will go up to 8 minutes without exhausing. So it doesn't matter what profile you use, although it does make a difference in the spread of residues. | | So even if you can't run with the linear ramp, you can still upgrade your paste and reap all the printability, solderability, and testability benefits of this generation. And with a paste capable of linear ramps, you'll be able to cost-justify a new oven based on throughput increases. | | Chrys,

Very wise stuff. We are now transitioning, while still keeping, from the SMQ62 to the 92. It does as the man says but we still need the old stuff for our stuffy old designs.

Earl

reply »

JohnW

#11748

Re: optimized profile | 26 April, 1999

| | Hello all, | | | | Our guys here still have some questions on the "optimized" profile which sees a more moderate ramp up straight to reflow temperatures versus the conventional profile which has a plateau at around 150 Celsius. If the optimized profile can really solve so many process problems, why was the convention profile used in the first place? What's your point of view on this issue. | | | | BTW, we're using a convection assisted IR oven, or if you look at it the other way around, an IR assisted convection oven. We can't seem to adjust to the new profile without sacrificing on throughput speed. Is this type of oven suitable for this? | | | | Thanks, | | Joe | | | | In my opinion, the "soak Zone" profile that plateaus around 150 C is a throwback to the days of straight IR. That soak zone was needed to stabilize board temperatures before going into the spike zone. So all the paste manufacturers made pastes with fluxes that activated in this range. You'd hold for 60 to 90 seconds to activate the fluxes. | | Then, one morning, someone woke up and siad "Hey, we got convection now. Why are we still heatsoaking?" and developed fluxes that don't need to dwell to work. And the benefits of this development are quicker throughput times and less thermal exposure to the assemblies. | | So I went out and got me one of them "modern" pastes with the straight ramp profile. And in my convection ovens, my profile time dropped from about five minutes to about 3.5. The pastes in this "modern" category can ramp from ambient to peak at rates of 1 - 2 degrees C per second, which is the same ramp that you use in prehat and spike. So the new profile basically cuts out the soak zone. | | I've realized higher throughput with the linear ramp. Boards that used to run at 80cm/sec belt speed are screaming through at 100 or 105 cm/sec in my 8-zone convection oven. | | Now, about your oven. It is convection/IR assisted? This means IR panels and heat blowers? If the thermal transfer capability of the oven cannot heat the boards at reasonable belt speeds, then you are stuck with a soak zone. But on the bright side, you may be able to shorten the soak zone down to (mqaybe) 30 seconds instead of 60 to 90. And these newfangled pastes can take it. An Indium guy told me the flux in his SMQ92 will go up to 8 minutes without exhausing. So it doesn't matter what profile you use, although it does make a difference in the spread of residues. | | So even if you can't run with the linear ramp, you can still upgrade your paste and reap all the printability, solderability, and testability benefits of this generation. And with a paste capable of linear ramps, you'll be able to cost-justify a new oven based on throughput increases. | | I found an article on this in the EP magazine a few month's ago and tried it out on a few product's....there were scream's of Blastphemy !!! from various quarters..haa no u need this nice flat soak bit ....I have to say I got grerat result's and the thru' put went up..the op at the end of the line complained that he wasn't getting his nap!!! I also found that a board we had a problem with the occational tombstone with came right. I'm still trying to convince people that this is the way to go...I actually have folk's trying to artifically create the soak zone by dropping the oven temp's in the 4th n 5th zones !!, anyway's I think I'm winning the battles but it's definately the way to go. BUT I'm sure u can only do it in a full convection oven, nota mix n match IR/convection....

reply »

pcb components vacuum pick up

Used SMT