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Reflow Temperatures and speed for a 7 zone top/bot for conceptro

James

#24839

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 16 June, 2003

Could anyone give me a basic profile temperature settings for a conceptronics 7 zone oven and speed? I have the first couple of zones ramped up to get to the soak temperatures. Is this correct or should I start out with low temperatures and gradually work my way up? ex set now 165 165 150 150 150 210 250 at 35 inches per minute or set at 120 130 135 150 165 210 245 at 25 inches per minute. Which is preferred, I just need somewhere to start and then go from there?

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Stephen

#24841

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 16 June, 2003

The second one is typical. The important temperature is the temperature of the joint, not the setting of the oven. The oven setting are only important because they determine the temperature of the joint. If you set the oven to 150, that will be the temperature of the oven thermocouple, and the board itself will be less than that. How much less depends on many factors. You will need to put thermocouples on the board itself to measure the actuall temperatures of the board. Start with your second set of settings and profile the board then adjust the settings untill the actual temperature profile of the board matchs the solder paste manufacturers recomendations. Also take into consideration any thermal shock restrictions for components.

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James

#24849

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 17 June, 2003

The main problem I am having is getting the Rising slope 1-3 degrees. If I slow the conveyor down then I have too long of a reflow and if I speed it up then my ramp rate is too high. I was not sure if I need my first zones at a low temp or higher temp and then soak time. Thanks for replys.

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#24940

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 24 June, 2003

Hi

The temprature for the first zone should be more as the PCB entering the oven from the ambient shop floor temprature needs a higher temp.Next zone could be lower than the first zone.The ramp is a relation of conveyor speed and the temp profile.This can be done by experiance or by hit and trial basis.

Sanjeev

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Stephen

#24943

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 24 June, 2003

The temprature for the first zone should be less as the PCB entering the oven from the ambient shop floor temprature would suffer a thermal shock from a higher temp. Experience must be gained from profiling a board with thermocouples, otherwise you don't know what is happening to the board. To do otherwise would be like teaching yourself the violin by not taking lessons and playing it with earplugs in. Even by a hit or trial basis you need to use thermocouples on the board during reflow. Visual inpsection of the joint is not sufficient to say if you have a good recipe for your oven.

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James

#24947

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 24 June, 2003

So which one is it? I am getting confused a bit because there are so many people doing it different ways. I know with higher temperatures at the begginning you have a chance of shocking the parts but if you dont have the higher temperatures at the beginning then it is hard to get the soak temperature where you want it. Eveyone has a different way I guess. I do appreciate your info on this. Thanks for the help.

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Stephen

#24966

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 25 June, 2003

We have a 5 zone oven and were starting at 150 which brought it up too fast. Even with only a 5 zone starting at 140 we get the temp up to soaking temp fast enough. ( I think too fast actually) What kind of oven do you have anyways? And I can't stress enough you need a read out from thermocouples attached to the board. There is no other way to know what is happening to the joint temps.

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RDR

#24968

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 25 June, 2003

This may make it easy, Do you really need soak? Or can you just ramp to reflow. Most pastes that I am aware of perform just as well using the linear ramp as opposed to the ramp/soak /spike.

Now, out of curiosity how are you attaching the thermocouples? If you leave the tip exposed it will give you higher more aggressive readings than what is actually happening on the board since you are measuring air temp instead of joint/board temp. If not already, I would recommend that you use hightemp solder to attach the T/C to your components.

Russ

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Brian W.

#24970

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 25 June, 2003

Water soluble pastes generally work best with a ramp-to-spike reflow profile. Check your paste manufacturer's recommended profile. There are many factors that impact your profile; board thickness, component density, buried thermal masses, board size, etc. That said, my experience has shown that starting lower and gradually increasing usually keeps my ramp rate at less than 2.5�C/sec. I strongly believe in the Ramp-To-Spike instead of the Ramp-Soak-Spike. On a 7 zone oven, I typically start at 100� or 120� and increase from there. Conveyor speed is typically around 30 in/min. I aim to get my above 180�C time to be 40 to 60 seconds, and my above 200�C time to be 20 to 40 seconds. 99 times out of 100, if I achieve those times, my soak time is fine.

Hope this helps, Brian W.

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#24974

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 26 June, 2003

Hi James, I saw very good posts here.Now I will give you one more practical way:

1. My advice is to encrease the temperature(like your first sidgestion). Termostress is important thing so your first zone should be 120-150C. 2. The paste profile. If Sn62Pb36Ag2 or similar the reflow temp is about 183C. If leadfree paste its higher.That's very important for the profile.(You could tell us the type of the paste) 3.First 2 zones - preheat.Next 3- soak and at the and reflow. When you go to the soak zones their values should be closer and the last one could be even with higher temperature then the reflow temperature of the paste.Then the reflow zones must be much higher(30-50C depending on parameters of the oven) 4. The speed from 30 to 70 cm/min (3-6 min). If about 3 min: preheat 30-60sec soak 60-100sec reflow 30-60sec If about 5 min: preheat 60-90sec soak 90-150sec reflow 45-90sec

Wish you good luck!

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James

#24978

Reflow Temperatures and speed for a 7 zone top/bot for conceptro | 26 June, 2003

To Brian W. I think I will use your concept thanks for the help and from all the others that gave me suggestions. I seem to get best results from a Low temp at first with hardly no soak and just a ramp to spike. Thanks again.

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