Save 15% in 15 minutes on your reflow’s energy consumption

Topic: 15% electricity savings in 15 minutes

Save Electricity in 15 mins. R0909B DRAFT

Date: Friday, September 25, 2009
Time: 1:00 pm, Pacific Daylight Time (GMT -07:00, San Francisco)
Meeting Number: 336 789 255
Meeting Password: (This meeting does not require a password.)

To join the online meeting
1. Go to https://kicthermal.webex.com/kicthermal/j.php?ED=107946437&UID=1013415122
2. Enter your name and email address.
3. Enter the meeting password: (This meeting does not require a password.)
4. Click “Join Now”.
5. Follow the instructions that appear on your screen.

Topic: 15% electricity savings in 15 minutes
Date: Friday, September 25, 2009
Time: 1:00 pm, Pacific Daylight Time (GMT -07:00, San Francisco)
Meeting Number: 336 789 255
Meeting Password: (This meeting does not require a password.)

——————————————————-
To join the online meeting

——————————————————-
1. Go to https://kicthermal.webex.com/kicthermal/j.php?ED=107946437&UID=1013415122
2. Enter your name and email address.
3. Enter the meeting password: (This meeting does not require a password.)
4. Click “Join Now”.
5. Follow the instructions that appear on your screen.

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Running lead free and eutectic PCBs simultaneously on the same reflow oven

Surface Mount Technology ran a piece titled Parallel Processes: Simultaneous Lead and Lead-free Soldering with a Single Reflow System written by Hans Bell of Rehm Thermal Systems GmbH.  Hans details a study where by controlling conveyor speed of each lane of a dual-lane system, it is possible to run both a lead and lead free product simultaneously.

The devil of course is always in the details:

Definition of the process window must always be based on the “weakest link,” namely the component with least amount of thermal stability during the soldering process. If two different processes are to be set up next to each other in the same reflow system, and if thermally sensitive components are included on the PCB, great flexibility is required for parameters configuration.

The ability to develop process windows for each product leaving enough room for each to call upon the same oven zone set points is key and of course taking into account special temperature tolerant components on each board.  Hans’ idea is intriguing.  Based on my experience in a world were many PCBs manufacturers struggle to profile or perhaps do not profile at all,  this is certainly a tall order.  Nevertheless his idea is do’able for perhaps many processes, since changing just the conveyor speed to reduce product changeover on a single lane oven is being done today (click here for an excellent application note using KIC product’s to achieve this end).  Why this couldn’t be adopted to a dual lane system running both lead and lead free simultaneously has its merits.

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No Waste: Beyond PCBs in Reflow Profiling

Article is from SMT Magazine

In many situations, EMS providers cannot waste a PCB for thermal profiling. Some ovens are equipped with profiling tools to generate an accurate reflow recipe without thermal profiling. This saves time, labor, money, and materials, but there are limitations.

By Brian O’Leary, KIC

There is a right way and a wrong way to set up a reflow oven to manufacture a new PCB assembly. This article suggests using the wrong method, but for the right reason. If an electronics manufacturer is prevented from following the correct method for setting up the reflow oven for a new production run, does a fallback position exist where they can still expect good results? For example, contract manufacturers find themselves in a not-so-uncommon situation where the manufacturer receives 100 boards and is expected to give a 100 assembled boards back. Sacrificing a single PCB to the profiling process is not an option. In another example, a manufacturer has PCBs that run in the several thousands of dollars. A suitable scrap board is not available for profiling, due to the cost incurred for the lost PCB.

Advantages and Disadvantages of Traditional Reflow Oven Set-up

The traditional method for setting up a reflow oven to manufacture a new PCB assembly is to attach thermocouples (TCs) to the PCB and run a series of profiles. Multiple profiles are usually required for the technician to adjust the oven recipe until an in-spec or deep in-spec profile is found. The introduction of lead-free assemblies has made this task more difficult and time-consuming. However, automatic prediction software and process optimization software have significantly cut down on the number of profile iterations required to determine the oven recipe that provides an in-spec process.

The benefit of this conventional reflow profiling method is clear: It achieves a deep in-spec and therefore stable process that is fundamental to good end-product quality. It also provides documentation to the client that proper process development work was performed.

These procedures, however, tend to sacrifice one or more PCBs. One reason for this concerns the TC attachment method. There are several TC attachment solutions, some more destructive to the PCB assembly than others. The use of high-temperature solder wire is a reliable method, but tends to damage the PCB assembly. Aluminum tape is also a reliable and repeatable method with the added benefit that the tape can be removed after the profile without damaging components.

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A second cause of PCB damage is the fact that each subsequent thermal cycle through the reflow oven raises the risk of latent or real defects as solder joints are re-reflowed, components are exposed to multiple reflow cycles, and the properties of the substrate changing. The PCB gets lighter, discolored, and more brittle with multiple profiles. Therefore, even with non-destructive TC attachment methods, such as aluminum tape, the PCB may need to be discarded when several profiles are run.

A final risk is that the technician selects, often guessing, a wrong initial oven recipe prior to the first profile. The initial recipe could damage the PCB. This could happen when the peak temperature is too high, the slope too steep, the soak prematurely dries out the volatiles in the paste, etc.

Profiling the Reflow Oven, Not the PCB

Modern reflow ovens are a far cry from their legacy siblings. Each oven model produced in volume tends to have very tight and similar thermal characteristics to each other. Equally important, these properties do not change over time as rapidly as in the past due to better flux management, improved oven control systems, more precise mechanics, etc. This enables new thermal process tools that “learn” the behavior of each oven model. To capture the thermal properties of a specific oven model, numerous profiles are run on a variety of PCB assemblies under differing process windows. This database will cover all but the most unusual applications encountered in SMT production. Once this work has been done, it is a simple matter of copying the information onto all the similar oven models. At that point, the operator could simply enter the basic information of the application, such as the length, width, and weight of the PCB assembly as well as the appropriate process window, and the oven will find its suitable recipe (zone temperatures and conveyor speed). This recipe will yield an in-spec profile in the vast majority of the cases without the need to run a profile or attach TCs. Experience with such technologies also suggests that when the recipe generated by the new thermal process tools does not yield an in-spec profile, it is usually very close.

Some U.S. oven manufacturers have completed this work. These reflow oven makers ship ovens with a fully functional database that essentially allows their customers to set up for new production runs without the need for profiling and sacrificing PCBs.

These systems do have limitations. The first was alluded to above, namely that there will be a small percentage of the applications that will not be processed in-spec. The fail-safe method is to wait for the oven to stabilize on the suggested recipe and then run an old-fashioned profile to verify whether it is in-spec. If out of spec, it should, in the vast majority of the cases, be close enough to achieve an in-spec profile on the second try. One profiling pass through the reflow oven, with aluminum tape used for TC attach, should not damage the PCB assembly.

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Another limitation is that an oven will, given enough time, eventually change its thermal properties. Wear and tear, changes in exhaust conditions, preventive maintenance, and a host of other factors will have an accumulative effect on the behavior of the reflow oven. Therefore, the initial database will need to be updated. This can be achieved by running some real-life profiles from time to time, and feeding this fresh information back into the database.

The final limitation is the fact that a system that eliminates profiling, by definition, does not have a profile recorded for the specific assembly. This means that there is no documentation or evidence that the PCB was indeed processed in-spec. Some customers will accept this, while others will not and require reflow profile documentation.

Conclusion

The correct method for reflow oven set up with a new application is to profile the PCB and dial the processed deep in-spec using prediction software. If the electronics manufacturer either cannot or will not perform this task, there are now thermal process tools available that achieve a more than 80% effective solution. Oven-inherent programming produces an in-spec recipe in the vast majority of the situations with no need to profile or sacrifice a circuit board. This technology also saves set up time and associated labor.

Using a profiling technology without an actual PCB profile run is also far better than doing nothing. Many manufacturers in our industry currently do not profile at all, or they limit their profiling to a single application a few times a year. If you do not want to do traditional profiling at all, oven-generated recipes can be an intermediary, rather than blindly reflowing.

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Plugging the Hole in the SMT Reflow Inspection Process

MB (Marybeth) Allen, General Manager of KIC Europe in an interview with Globalsmt.net makes a terrific case for RPI (Reflow Process Inspection). MB_Allen

Here are some excerpts:

Q. 2009 saw the introduction of your RPI In-Line Process Inspection System for SMT reflow ovens.  For manufacturers currently relying on AOI and X-Ray systems to carry out inspection functions, can you explain how this system works and why RPI should be the choice for this process?

Automated inspection systems have become critical in controlling quality throughout the manufacturing process.  SPI (solder paste inspection) and AOI (automated optical inspection) are excellent defect detection tools, within the limitations of their design.  The RPI (reflow process inspection) inspects the reflow process for each and every manufactured PCB.

The quality of a solder joint is not only a function of whether there was adequate solder, accuracy of placement, missing components etc., but that the solder was processed correctly.  For example, the peak temperature needs to be high enough, but not too high to damage the component; the time above liquidous must be within the required range etc.  The AOI machine is not designed to check for these critical events.

KIC’s RPI verifies that the PCBs have been manufactured within the required thermal process window.  Perhaps the best example of where RPI complements AOI is in the soldering of BGAs and other Area Array Packages, where the AOI machine cannot see the solder joints as they are hidden from view by the component body.  RPI even complements X-Ray machines as these inspection systems cannot tell whether the solder joints were processed in accordance with the required profile specs.

Q. So KIC RPI offers both oven and product data in one solution, this obviously enables the operator to harness this key data and use the yield charts to refine the process. What type of data do they receive and how easy is this to understand?

RPI automatically generates both Yield and DPMO (Defects Per Million Opportunities) production charts.  There’s really nothing for the customer to do as the information on all boards produced is captured automatically.  You’ve seen these charts in many factories showing product data for many steps in the manufacturing process.  However, previously data from the reflow process was missing.  Only reflow oven machine data was available.  KIC’s RPI now provides this missing key product process data, providing another key link to product quality.

Q. This product offers a timely solution for manufacturers in this tough climate and I understand it has already received awards for its innovation. What has been your feedback so far?

Yes, RPI has already received several awards around the world.    People are looking for a solution to save money and ensure continued quality control.  When I visit customers and prospective customers their initial questions or requests can be taken care of by using RPI.  It’s wonderful to be able to say “Yes, RPI can help you with that” to most of their requests.  We have plugged the hole in the inspection process.

For the full interview go to: http://www.globalsmt.net/content/view/7583/70/

Awards:

2009 EMAsia Innovation Award in the category of Process Control Software for its RPI in-line inspection system.

2009 NPI Award in the category of Process Control Tools for its RPI in-line inspection system.

Innovative Technology Center Award at Apex 2009

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Profiling BGA Webinar

Profiling BGA Webinar Supplemental (July 1, 2009):

Component Specific Specs

We discussed the need to define BGA specs separate from other components that have different reflow requirements.   BGAs typically require more heat to reflow properly but typically there are many other “smaller” components that also populate a PCB that will overheat if you develop your process solely around the BGA.   The following 2:40 min video reviews how you can bring both your BGAs and other temperature sensitive components into spec, striking a thermal balance that results in quality products.

Thermocouple Attachment

The following 1 min video shows one of the most reliable direct methods of TC attachment for BGA profiling.

…..but, who can always sacrifice a PCB in the process?   We talked about some indirect/non-destructive methods for profiling BGAs that are suggestive, but inconclusive.   In the fall I hope to have some results of a study that will help our industry come up with solutions that one can reasonably predict the temperature/profile of a BGA without destroying the PCB in the process or worse the BGA!

BGA Inspection

First there was SPI (solder paste inspection), then there was AOI, now there is RPI (Reflow Process Inspection)

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You can see a prior blog posting discussing RPI at:   https://profilingguru.com/reflow/what-is-reflow-process-inspection/

RPI works in the world of continuous reflow monitoring, where a profile is created for each and every production board.

In order to automate reflow profiling, a baseline/virtual profile is first established, where one runs a traditional profile with PCB, TC attachment and profiler while the on-board system of 30 thermocouples gathers the same profiling data and reconstructs and converts the traditional profile to a virtual representation. Once a virtual profile has been established, profiles can be collected for all production boards.  SPC charting, cPk, traceability and process control are all possible.

So rather then the reflow process being a black box, where anything and everthing can go wrong…..

illustration_5….alternatively, do you not only know what is going on continuously, but your BGAs using the techniques above are being monitored on a continuous basis.

reflow-yield_3in_nk

Your Questions:

Q: Doesn’t the thermocouples utilized by the oven itself (assuming that they are calibrated and verified) provide the same basic information as the secondary set of TCs you are referring to?

ANSWER:  No, the oven thermocouples and the secondary KIC  TCs have completely different and separate functions.  The oven TCs are typically located close to the heaters since their job is to turn the heaters on and off as the temperature drifts from the set points.  The KIC 24/7 (or KIC Vision) TCs, located along the conveyor, help to automatically measure the profile that each PCB experiences as it is processed through the reflow oven or wave solder machine.  This function is called Virtual Profiling.

Virtual Profiling (VP) provides process traceability as it logs the profile for each PCB, along with information on how this profile fits the established process window.  The VP works in real time and offers instant alarm when the process (profile) drifts out of spec.   Because it provides basic SPC charting, it acts as an early warning system for trouble ahead.  Think of the KIC24/7 or KIC Vision as an automatic profiling system in real time.

Q:  I encountered wetting issue with CSP and BGA, how do I solve them?   /   Q: How about wetting issue?

Answer; In some cases, but of course not all cases, wetting issues are a result of incomplete flux activation in the solder paste and an overall low temp soak, where the components did not reach sufficient energy levels before entering the reflow, TAL stage of the process. Many of these issues are related to Pb – free solder pastes, mixed RoHS components or a number of other variables.

I suggest that the best answer is to research the publications available on the Web for the most relevant solution. The following is a link that closely resembles the issue, but again, you will need to research the most relevant to your situation.

http://www.emsnow.com/cnt/files/White%20Papers/Henkel_Leadfree_Designing_Reliability.pdf

Q:  How do you take measurements on each board without TCs?

Answer: KIC software algorithms compare what was observed at the time of the Baseline Profile to what is present within the oven during production. Using the 30 thermocouples in the oven, this data is communicated to the eTPU and the output is the PWI based on the specific process and the specification of that process.

Q:  How well does the DPMO relate to the actual defect where there could be placement defects interacting with reflow?

Answer: DPMO is a parameter of only the thermal reflow process. If issues exist in placement or screen printing, it will not be reflected in the DPMO, since KIC is only monitoring the thermal process. Given that all other aspects of the SMT line is functioning properly, DPMO will give an assessment of the thermal defects assuming that the proper solder paste and placement is present at the time the product enters the oven.

Q:  What about paste formulations?

Answer: KIC works with any solder paste manufactures to build the solder paste library that is present in the KIC software. This library is updated periodically and verified by the solder paste manufactures in most instances. The library however does not at any one time contain all information about all possible solder pastes. We try our best to be certain the information is present, but changes in formulation and engineering at the solder pate manufactures sometimes causes gaps that are beyond our control.

Q: How important is it to drill into the BGA ball and put the TC in it, vs. putting on the package, slip under the package, and on the bottom side of the board?

Answer: There are many variables in PCB design and component placement that directly and indirectly affect other components, in this case BGA. The best possible answer to this question is in the amount of data that is collected, how it is collected and how this information is applied to the specific PCB and BGA directly. Gathering as much information as possible, charting this info and drawing data driven values is the best possible formula for successful BGA reflow. Using all available data collection methods and positions aids in successfully reflowing this package.

As indicated during the webinar, we are currently commissioning a study to see if non destructive methods can be used in place of drill a hole.

Q: Does your software always choose an extended peak recipe?

Answer: No. Based on the type of recipe and profiles that are part of your normal production determines what path the KIC Navigator (auto-prediction) directs the profile. If your profiles are mainly RTP, the software looks at the values of the library data and suggests set points that will lead to a RTS profile. If your profiles are largely RSS, then the suggested set points will tend towards a RSS profile.

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