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Air Bath Rework System


CJ

#29539

Air Bath Rework System | 16 July, 2004

Hello! I am an Electrical Technician with Filtronic Comtek. I am responsible for all of the Engineering changes and rework done to prototype and pilot run PCB's. My current rework equipment includes: Soldering irons, heat gun, and hot plate. Considering that the work that I do goes to the customer, I am looking to update the rework equipment that will allow me to be more insync with the production equipment on the manufacturing floor. The only system that I have found that fit my needs is the Zephyrtronics Air Bath System, because it is an bench top rework system.

Majority of the PCB's that I rework are single-sided, with a board thickness of about 1.50mm to 1.70mm

Does anyone know if there are other systems like the Zephyrtronics out there?

Also, is there any information available that will prove that an air bath rework system is better than using the standard soldering iron and heat gun. I need to put together a proposal to present to my boss.

Thanks for your help in advance!

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Steve

#29647

Air Bath Rework System | 24 July, 2004

I would contact my local distributor. Using a Heat Gun is not the best method for rework. Using the Air Bath depending on board specifications also may not be the best method. Try a small distributor rather than a catalog house. Usually the small distributors have a better understanding of process related questions.

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CJ

#29649

Air Bath Rework System | 24 July, 2004

Thanks for the assistance.

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Cal

#29689

Air Bath Rework System | 27 July, 2004

CJ- If I am not mistaken the Zephytronics machines have a money back guarantee if not satisfied. We have boards with huge ground planes and the air bath is the only rework that can do this. We also have found heat guns get hot enough but the heat is localized and the ground planes act as big heatsinks and wick away the heat.

Cal

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CJ

#29692

Air Bath Rework System | 27 July, 2004

Thanks for your input Cal! It is very helpful. The PCB's that I work on also have large ground planes. I was wondering if the Zephytronics could handle it. It is also good to know that they have a money back guarantee.

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Chris

#29761

Air Bath Rework System | 30 July, 2004

The Zephytronics unit does not have the power you need. Their process is based on low temp soldering. Companies like PACE have preheat units that will give you more power and control. I see more Zephytronics on the shelf in my travels than any other piece of rework equipment.

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CJ

#29762

Air Bath Rework System | 30 July, 2004

Thanks for your input Chris. I have also seen the preheater units from Pace. I value all information pro or con, because the last thing I need is to purchase something that will not do the job.

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Paul

#30024

A Completley Different Experience Than You. | 13 August, 2004

Funny how these things are. I see more PACE equipment on the shelf and on EBAY. I've seen hundreds of the Zephyrtronics units in Raytheon myself...all being used and on very, very large boards. I believe that they actually have a far larger selection than what they post on their website.

In any event, you must know that Zephyrtronics has an entire line of preheating units and typcially they introduce them only to have the other company follow their lead. Another company, other than Zephyrtronics that makes pretty darned good preheaters would be APE. They don't have the selection or established reputation for preheating that Zephyrtronics does, but I'd recommend either A.P.E. or Zephyrtronics preheating units over PACE anyday.

By the way, if anyone wants to pick up PACE equipment cheaply, go to EBAY...you'll save a bundle. And the DENON BGA Split Beam BGA System, I think is far superior than the new PACE one, but that's my opinion.

Chris, you seem to know a lot about PACE and I have a question for you: Didn't PACE originally market the DENON products with the PACE name silkscreened on it --- until the PACE President left PACE to go to work for DENON in Japan??

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Hi CJ.

#30025

Air Bath Rework System | 13 August, 2004

Don't be discouraged about the Zephyrtronics Air Baths from Chris' comments. I'm sure he means well, but I've seen these units being used by people who swear by them.

You might also look at the APE preheating units and the Zephyrtronics...but you should try contacting Zephyrtronics directly as I think that they have a larger line of preheating equipment than they post on the web...and I do know that they offer the money back on a thirty-day trial (which I don't think anyone else does).

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CJ

#30036

A Completley Different Experience Than You. | 16 August, 2004

Thanks Paul and Hi CJ for your input. I appreciate it very much. Do you have an website address for APE?

Thanks

CJ

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sly

#30043

Air Bath Rework System | 16 August, 2004

Hi CJ, if you need a rework station for any SMD's (fine pitch, BGA's, chips, SOT, ...), maybe you should also check ERSA that offers rework stations with computer controlled thermal profile (meaning you can apply a typical profile for each typical rework you need to do); this systems can also be equipped with a very good video placement system, allowing you to place a BGA or any fine pitch IC with a lot of precision to their attaching position.

Brgds

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CJ

#30045

Air Bath Rework System | 16 August, 2004

Thanks for your input Brds.

CJ

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Paul

#30051

Links | 16 August, 2004

You are welcome. I typically just read here and try not to post, but the other post was unfairly negative and seemed to be biased to a single supplier...which I always find suspect.

Here are the links to APE and ZEPHYRTRONICS which I hope you find helpful.

APE: http://www.ape.com

ZEPHYRTRONICS: http://www.zeph.com

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CJ

#30069

Links | 17 August, 2004

Thanks for the website addresses Paul

Regards, CJ

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James Dornan of APE Inc

#31818

Air Bath Rework System | 22 December, 2004

A little late but if this subject is still of interest the following paper from APE may be of interestwhen considering IR to Air Bath:

HOT AIR versus IR and other convection Rework Systems

HOT AIR is the most popularly chosen method of rework in the industry, with many varied configurations of equipment that can be utilized in a manner best suited for many different types of applications.

There are several important differences between the HOT AIR Vision rework systems and those that use IR technology. Primarily, they are: 1. Profiling and soak programming to create a pattern. 2. Temperature control. 3.Repeatability. 4. Controlled Convection. 5. Process time and 6. Ease of use. It is widely accepted in the industry that forced air convection is the preferred method for both rework and production environments. IR ovens are no longer used in production.

An HOT AIR system can be easily programmed to match any profile with up to 16 segments of ramp soak within a pattern. The system can virtually duplicate the original manufacturing profile for maximum safety for both the PCB and components. Accurate profiling with ramp soak is not possible with an IR system. An IR machine programs the percentage of power (light) rather than temperature. This requires a much higher level of operator skill because it is so easy to burn the boards when using IR.

Shadowing is an issue that occurs with IR systems. If the light source does not hit the board evenly then the heat will not be evenly distributed throughout the board and or the component. This can cause a number of problems with BGA�s including land-sliding, bridging and component warping, which can result in open circuits.

The HOT AIR temperature control is extremely accurate (within +/- 25 degrees F). Controlling temperature with an IR system is a hit or miss proposition, too much light and the board will turn black.

Repeatability is another important advantage that HOT AIR has over an IR system. Once the profile is established it is possible to literally rework hundreds of thousands of components without the need for alignment or calibration. The HOT AIR Sniper II placement accuracy is 0.001�. HOT AIR can report that two important HOT AIR accounts stated that after 24/6/300 and about 100,000 placements, no realignment was required.

A recent discussion with a client who was using two IR systems before switching to a HOT AIR machine had these comments about their IR system:

1. The system can't soak - all it can do is ramp and continue ramping. 2. There's no feature in the software or technology for soaking 3. IR heats the component not the air - this sounds an effective method but if the IR thermal couple (TC) is directed either on the component or on a lead/sphere of the component the air has to increase at least 30% over a convection system � usually resulting in scorching. An HOT AIR rework system monitors the air and its relay is switching many times a second controlling the air whereas an IR system reads the component, opens the relay and just lets that air temperature escalate, which can cause damage. 4. The IR TC is not a laser - it's like a torch light - the nearer the object the more focused the beam - the greater the distance the less focused the beam, this principle only heats up the object of focus - it doesn't heat the environment and if the red dot of light is off it's target, which it often is, it isn�t accurate - it will focus its heat where it comes into focus - before or after the subject or to the side - another important point in this is that the actual TC sensor isn't the light you see, it's a dark piece of the IR spectrum that may not be where the light appears to be focused. 5. Because the system is programmed to reach temperature when the object flows and doesn't consider the environment - it's not repeatable. 6. For the system to work the operator has to focus the IR beam and the camera very accurately on the component leads (in the case of a CSP this is very difficult, the operator has to endeavor to direct a TC light spot and a camera on the leads under the CSP and of course it�s impossible to direct these to the center sphere under a die) the programmer has to be extremely cautious and certain program was halted during the set up at exactly the right time and that this set up was in someway repeatable. 7. The same hit and miss procedure must be gone through for each component. 8. Large boards are a problem and the board holder supplied is problematic. 9. The machine is described as flimsy and fiddly - more of a toy in the opinion of the client 10. In a practical reworking environment reworking different components was impossible. 11. IR systems burn or scorch boards because of insufficient power and the necessity of having to focus the heat on the component body or leads unlike a convection system that heats the air replicating the oven environment. 12. IR has warp issues. 13. Different reflective component surfaces (Shadowing) will distort an IR systems ability to accurately recognize the component and maintain a even temperature distribution.

Other comments were: �There is no such thing as repeatability with IR machines. Results on exactly the same type of component and board were vastly different, for example: Four minutes the 1st time and six minutes the 2nd time etc.� It is extremely easy to burn the boards and there is not enough power to rework boards with heavy ground planes. Warping was a serious issue with IR systems.

As for the argument put forward by IR manufacturers against Convection Rework machines, one of the claimed advantages of an IR system over convection hot air is that nozzles are expensive and hot air machines blow off surrounding components. HOT AIR systems are often delivered complete with nozzles and a lifetime nozzle exchange program. In addition nozzles are designed so that you can use the same nozzle for many different types of components. As will be discussed in more detail below. Be sure to select a HOT AIR machine that has a very low air velocity replicating a convection oven, similar to the ovens used in the original production of the board. This airflow is extremely gentle so that the surrounding components are not disturbed during reflow.

Controlled Convection � Power and Velocity in a Lead-Free Environment:

In considering one manufacturer their Optimum Heater Wattage or Power is an advantage HOT AIR has over IR and other rework systems. The feature that gives HOT AIR greater flexibility and ease of use in reworking components and handling lead free environments is the optimum Wattage of the reflow heater coupled with a carefully controlled constant Velocity of the convective air carrying the heater energy. This combination of Power and Velocity has been proven over 20 years to provide an optimum transmission of Joules (calorific) energy so that the component and PCB is reworked without scorching or disturbance.

Since 2003 other convection systems have endeavored to follow a leading supplier and may claim increased power in response to lead free solders that require higher temperatures to reflow, coupling the power and velocity in a carefully controlled manner is crytical in ensuring that lead free and eutectic solders are reflowed using a reflow pattern that is at an optimum temperature in all segments, never having to increase the ramp rate or temperature above that recommended for the component.

The 1200Watt phenomenon (The importance of not �going over the top�)

It is important to note that a few manufacturers of higher power systems use higher air velocity in an effort to increase the life of their heaters and to transmit the energy through smaller focused nozzles. For these systems to operate at the optimum controlled air velocity would burn out the heaters because of the attenuated airflow through the nozzle. Using a power rating for a heater above 1200Watts results in problems for the reworked subject and also the heater components in a machine.

There is another important issue, which we call the �1200Watt Phenomenon� Using a reflow heater above this Wattage has little or no effect on the energy carried in the air flow � all that happens is that the air runs hotter and the airflow must be increased to allow the heaters to remain functioning. Using a heater below 1200Watts results in insufficient power and the same compromises are installed to overcome the problems that are also associated with higher power heaters � namely increased airflow and higher temperatures.

HOT AIR systems replicate the oven environment allowing it�s low velocity to carry the energy to the component environment gently ramping and soaking the component through it�s programmed pattern until it is either removed or replaced using the lowest possible air temperature to reflow the solder.

This design means that regardless of the density and /or relative weight of the PCB, the machine will achieve the reflow with the minimum temperature input. Typical reflow cycles mimic actual convection oven profiles used in production. Machines that use lower wattage heaters (1200Watts) increase the temperature due to the velocity carrying the energy � of course with lead free solders higher temperatures are desired but in a highly focused design high velocity needs to be applied so that the heaters do not burn out � this results in air an temperature much greater than the reflow temperature of lead free solders and the result is scorching and degradation.

Typically a HOT AIR profile will not require any more than 250c in air temperature to achieve reflow on any board. The machine controller itself will store up to 16 different profiles, and each of those profiles can have as many as 16 heating zones for your use. With a minimum of training, even the most complicated reflow profiles can be run at the touch of a button.

Preheat

We have been discussing reflow temperature and primarily a top reflow heater above the component, it is important to briefly mention the necessity of a pre-heater that can either follow a profile or apply a constant temperature evenly under the subject. These pre-heater or bottom heaters are generally of less power and apply a reduced background temperature to thermally blanket the subject and reduce stresses in potential warping.

HOT AIR systems are equipped with Pre-heaters designed either for 110V (maximum 900Watts) or 220V (Maximum 3600Watts) the former for general rework and the latter for larger infrastructure reworking.

Conclusion

The primary focus of HOT AIR from day one has been �Ease of use� as well as a rugged and reliable construction. As IC devices get smaller and more complex, straightforward processes can be documented using the many optional fixtures and tools available using HOT AIR.

It is interesting to note that those companies that operate as a contract rework business, such as Cable and Satellite Set repair operations choose HOT AIR first. These companies repair several million boards per year at various locations where HOT AIR machines will be seen quietly, quickly and efficiently handling the load - keeping their uses ahead in their industry.

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Mark

#31819

Air Bath Rework System | 22 December, 2004

LOL . . . shameless plug. I wonder who came up with the 1200 Watts theory (not a watt more and not a watt less)?

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#31820

Air Bath Rework System | 22 December, 2004

Shameless? In APE's experience not so - air velocity/power is extremely important in carrying energy to the board and close loop control of that energy is crytical in maintaining a controlled environment - if a machine design requires that air is forced through at a high velocity then the obvious will happen. APE can go to any wattage heaters desired in multiples of 600 watts - within reason, say 2400 watts (top) 3600 watts (bottom) - but when APE conducted practical tests measuring energy carried by a certain air velocity within a constricted and attenuated nozzle arrangement it had little effect on the energy getting to the board - around 1200 watts seemed to be the optimum (I'm sure there was a watt or two that could of been included). With bottom heating the heat is less focused and the power is spread over a larger area in fact higher power will provide a more efficient blanket of energy to the substance of the board from the underside reducing the necessary reflow temperature at the top, because the heaters are spread over a large panel arrangement and not attentuated to any extent. With Lead Free solders bottom heat becomes more important in reducing the necessary top reflow temperature and once again hot air is a better method of transmission and control.

These are APE findings and since 1994 APE has been working with higher power technology so they have a good grasp on getting energy to reflow solder using an air bath.

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Mark

#31824

Air Bath Rework System | 22 December, 2004

Yes, shameless. You could have come out and said that APE's equipment is the best thing since sliced bread but . . . you had to get all scientific with us. We already get bombarded by subliminal messages in commercials now, tech forums. In all seriousness, just a few points which I found interesting.

1. You don't state what IR system (make, model) your customer has X-ed in such a detail. Better yet, is this customer made public in your paper? Without this info, you are comparing an ambiguous product in detail to your system (don't see how thats possible).

2. The whole watts theory

"air velocity/power is extremely important in carrying energy to the board and close loop control of that energy is crytical in maintaining a controlled environment - if a machine design requires that air is forced through at a high velocity then the obvious will happen." Agree, but the same applies to probably any forced air rework system.

"APE can go to any wattage heaters desired in multiples of 600 watts - within reason, say 2400 watts (top) 3600 watts (bottom) - but when APE conducted practical tests measuring energy carried by a certain air velocity within a constricted and attenuated nozzle arrangement it had little effect on the energy getting to the board - around 1200 watts seemed to be the optimum"

Ok, for the APE system this may be so but in your original post you are comparing your system to all the others. If I recall, 1200 watts is stated as being the optimal, anything less is a no no, anything more is even a bigger no no. Again, for the APE design where you are adding power in increments of 600 watts (by the way, huge jump) 1200 may be best, but I am sure it is not so for all the rest.

"With bottom heating the heat is less focused and the power is spread over a larger area in fact higher power will provide a more efficient blanket of energy to the substance of the board from the underside reducing the necessary reflow temperature at the top, because the heaters are spread over a large panel arrangement and not attentuated to any extent."

Agree, to an extent. If your preheater is 2" x 2" whether the bottom heater is 1000 watts or 3000 watts would not really make a difference. More powerful heater will allow you to ramp up to the desired temperature faster buts thats it . . . once the temperature is reached, the relay will simply control the heater to keep the temperature constant. Faster ramping is good but to a point. With 1000 watts lets say the air will ramp at no more than 4.5 deg C/sec, with 3000 watts it could be 7deg. C/sec @ a specific air flow rate. I think 7 deg C/sec will do more harm than good. Besides the high probability of board / component damage, the problem with a more powerful heater in this case is that it is less sensitive than lower power heater thus, tolerance of the air temperature will be wider (i.e. +/- 5 deg. C with 1000 watt heater / +/- 10 deg. C with 3000 watt heater). On the other hand, if your preheater is 10" x 10" 3000 watts will certainly be much better as you have more volume of air to heat up. When we are comparing 1000 watt heater to a 3000 watt heater we are comparing the energy output not transfer (transfer is specific to a machine design). The coils/heating element of a 1000 watt heater will be cooler than that of a 3000 watt one, with a air flow being constant.

Based on your original post, your system is better than say Pace or Metcal since it has 1200 watts. To me, that just isn't so.

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