http://www.circuitnet.com/articles/article_83073.shtml as a response to an Ask the Expert Question. We think it’s worth repeating here as well.

Subj: Unusual Component Lead Contamination

We suspect the issue visible on the attached image is due to contamination on this component lead. We only see this issue on one component type, and only on one side of the component.

Can you offer any comments? E.W.

REPLY FROM PAUL AUSTEN, OF ECD:

Here is one possible cause to check on before you apply the failure to the component.

As with most solder quality problems, it is best to make sure the solder thermal profile, as required for good soldering for you specific solder paste, is being met. Do not assume that a general thermal profile for this board is the same everywhere on the board.

Make sure the thermal profile on or very near each end of this component is as needed. I have heard of components as small as this stand up on one end and then lay back down again during the solder transition into the liquid state (AKA: liquidous, or liquidus) because one end of the part heated faster than the other by a few fractions of a second. By the time the component lays down again, it is too late for best wetting.

To look for this possible time delay in the heating of the component’s ends with your thermal profiling software, make sure the profile peak alignment tool in the profiling software is turned off so you can see instant by instant the temperatures measured at each end of the part through the liquidous point of the solder. If one end is hotter than the other during this time, this may be part of the problem.

The cause of the temperature difference may be because one end of the part was on a pad that had no (or poor) thermal relief compared to the other. Typically, you need both pads of a component to be thermally equivalent. It may be that the board design needs to changed, or it may be as simple as running the board through the oven process turned 90 or 180 degrees to the current orientation.

However, turning the board 90 to 180 degrees may introduce other production or thermal issues on other components. None the less it may be worth trying.

Paul Austen, Senior Project Engineer

Electronic Controls Design Inc

paul.austen@ecd.com

Paul Austen is a 30 year veteran Senior Project Engineer with ECD in Milwaukie, Oregon. Paul has seen and worked with the electronic manufacturing industry from many points of view, including: technician, designer, manufacture, and customer.

This month ECD announced availability of the new 2.20a version of M.O.L.E.® MAP software.  Introduced in 2007, MAP (Machine-Assembly-Process) received multiple innovation awards, and is now the software platform for ECD’s entire line of thermal profilers: SuperM.O.L.E.® Gold 2, MEGAM.O.L.E.® 20, V-M.O.L.E.®, SuperM.O.L.E.®, Gold and PTP® VP-8

This version release coincides with the new SuperM.O.L.E.® Gold 2 availability and implements inputs from our Software Advisory Board (yes, we have one!)  So without further ado, here are the top 5 new features and benefits of M.O.L.E.® MAP 2.20a.

1. AutoPlay

This new feature auto-detects your M.O.L.E.® type and quickly links your plugged-in M.O.L.E.® to perform these basic tasks:

• View the status of your M.O.L.E.®
• Setup your M.O.L.E.® to perform a data run
• Download your most recently recorded data
• Start M.O.L.E.® MAP

This instant USB access eases the learning curve for the novice and focuses the operator on the basic profiling tasks at hand, shielding them from the full feature set of the software.

2. Improved Navigation

When you do open MAP, the “Welcome” screen now displays links to recently used Directories and recently viewed Profiles.  Quickly resume your previous work session by clicking where you left off with this convenient new feature.

3. Bulk Import of Previous M.O.L.E.® Files

Speaking of Profiles, you will probably want to import your libraries of SuperM.O.L.E.® Gold profiles (from SMGSPC) into MAP, which converts the .mdm file into the new .xmg format.

This MAP version implements group importation of existing .mdm and collaborative .xmg profile data. With a simple click-shift and drag, you can now move the contents of old Workbooks (an SMGSPC term) into new Directories, M.O.L.E.® MAP’s term for the currently viewed data in the Spreadsheet Tab.

4. PDF Printing to File and Email

Another way to collaborate your process engineering work between EMS/OEM is to provide documents to operators in PDF format.  The new MAP integrates PDF printing with an improved Print Selection dialog to accomplish portrait or landscape orientation directly to Email or a File. Great when your customer demands hardcopy proof!

5. Free Self-Serve Web Authorization and Automatic Upgrade Notification

Last but not least, licensing fees and pay authorization have been replaced with free “Self-Authorization” through the ECD website.  We give you a 31-day window to go to the Help menu, select “Authorize” then click on “Web Authorize”.  After you fill out the web form and agree to standard terms, our site sends you an email with your software unlock key.

It’s as simple as that!  Plus, you will be notified of new releases in the future.  We always want you to have the advantages of our current release.  Thank you for reading this month’s What’s New!

Free MAP 2.20a download is available at ECD DOWNLOADS.  (Check out the Readme file for the entire list of Rev 2.20a M.O.L.E.® MAP improvements!)

Till next time,
Ray Pearce
ECD Sales Engineer
ray.pearce@ecd.com

Energy needs a conductor in order to flow

1) An energy difference between two objects. 

and 

2) There is a conductor to act as a bridge enabling the energy to flow. 

Energy always flows through a conductor from an object of high energy to an object of low energy. In this illustration, the high-energy object is a moving hammer, the low energy object is the table and the conductor is a block sitting on the table. 

When you hit the block with the hammer, the energy contained in the moving hammer is transferred to the block when it hits. Some is also conducted through the block and transferred to the table it is sitting on. However, because the block is not a perfect conductor, which is true for most things, some of the energy stays in block. That energy bounces between the molecules of the block like balls on a pool table. 

Because the molecules rub up against each other, and there is friction between them, some of the moving energy of the hammer is converted to heat energy, which causes a rise in the block’s temperature. It all comes down to molecular motion in an imperfect conductor creating friction that raises its temperature. Therefore, temperature increase is a way of observing energy flow, and energy flow that causes a temperature rise is called heat flow. 

What Affects Heat Flow? 

Heat "flows" from hot to cold

The amount of heat that flows is dependent on the same basic things as energy flow, only we sense its effects by measuring temperature difference. As with high-energy objects imparting their energy to low-energy objects through a conductor, heat flow happens when a hot object transfers its heat through a conductor to a cold object. The quality of the conductor determines how quickly, and how much of the heat is transferred. If no heat is lost to the outside, the objects and the conductor in the above illustration would settle to a temperature 1/2 the value of their difference above the cold object, or below the hot object. The quality of the conductor would then only affect the time it takes for the heat flow to even out the two temperatures. 

Heat flow, therefore, is affected by the temperature difference between the Hot and Cold object and the quality of the conductor. The higher the temperature difference, the faster the heat flow and the higher the conductivity of the conductor, the faster the heat flow. 

Methods of improving this conductor have been played with by oven manufactures for many years. Three common ways to conduct heat between the oven heater (the heat source) and your circuit boards (the heat sink) are: 

1) Infrared Radiation (IR) 

IR depends mainly on the “sun-like” conduction of heat via electromagnetic radiation. Although some conduction occurs due to heating of the atmosphere surrounding the circuit board, it plays a lesser role than the radiant energy. This is useful when the entire surface being heated will absorb the radiant energy in exactly the same way at exactly the same rate. The main drawback is that in order to make up for the inefficiencies of this method of heat transfer, the heat source is often set to temperatures much higher than the required melting temperature for the solder on your circuit board. In addition, the components on your circuit board each absorb radiant energy at different rates, aka emissivity. While one component may heat very little, another may be over-heated because it absorbs radiant energy very well. This uneven heat absorption makes it very difficult to choose a heat-source temperature that will meet the varying absorption rates of the variety of components on a typical circuit board. 

2) Vapor Phase (hot liquid) 

Vapor phase heat conduction is one of the best around because of its high conductivity and heat capacity, which is released as the vapor changes from gas (vapor) to liquid. Plus, it has the ability to conform to the irregular shape of your circuit board. This method of conducting heat in reflow soldering machines is currently enjoying a comeback. 

3) Convection (hot air) 

Convection has been very popular because it provides “vapor like” conformance to board shape, but does not require much more than electric power to function. Here hot air (or nitrogen) is used as the conductor, but with an extra kick: convection fans that move heated air from the heat source to the heat sink. This combination of an air conductor and air movement is called convection. The greatest asset of convection is that it allows you to lower the temperature of the heat source because the movement of the air creates a more efficient heat flow system. 

4) Direct conduction (metal plate) 

Using a direct conductive medium, like a metal plate, is efficient, but is only practical when the surface being heated is flat. 

What about my boards? 

In a convection oven, heat is "hammered" into your circuit board by moving air

So heat flow causes circuit boards to get hot within an oven. In this case, the oven is the heat source (like our hammers); moving air is the conductor that delivers the energized air (like moving the hammers) and pounds the heat into the circuit boards (the heat sink).

Because of the increased conductivity that the moving air creates, lower oven temperatures still allow a circuit board to reach the required temperature, and more evenly because conducted heat is not as dependent on a component’s ability to absorb radiant energy. The heat is conducted to the circuit board as fast as the moving air can deliver it. 

So, if you want to increase the heat flow, you just turn up the temperature, right? That is correct, but this creates a potential hazard for your circuit boards. Given enough time, your circuit boards will reach the heat source’s temperature. If that temperature is significantly higher than the specified limits for your components, you will damage them. Another way to increase the heat flow is to set the temperature at an acceptable level and only increase the airflow. In other words, add more hammers. This forces the heat into your circuit board components much more evenly and at a rate that meets your component specs. You can accomplish this at your desired process speed while lowering the risk of component damage due to over-temperature. 

How can I measure heat flow?

  

Heat flow is easy to understand, but difficult to measure. This is because the conductor of the heat flow (air) plays as big a role as the temperature in determining how much heat actually flows. For heat, everything is a conductor. There is no simple way to say where heat is going; it goes everywhere. So you cannot know how much of the energy consumed by your heater actually gets to your circuit boards, even though heaters are nearly 100% efficient at converting electrical energy to heat. Therefore, energy into an oven is not energy transferred to your circuit boards, because a lot of it is going into the room, up the exhaust, and some into you.

As a result, heat flow measurement has taken the form of very sensitive probes that measure the temperature difference between the surfaces of thin films. These measurements translate into the amount of energy in watts per square centimeter. Typical values for heat flow in a reflow solder machine from the top heating zones to the surface of a circuit board range from 0.1 to 0.7 watts/sq. cm. This value drops as it proceeds through the oven because circuit boards heat up and reduce the temperature difference between the heater and the circuit boards. This naturally reduces the heat flow because heat flows from hot to cold and if there is no more cold, there is no place for the heat to flow – no heat flow. 

Problem Solved 

Convection plays an important role in heat flow

Understanding that oven temperature alone “does not a temperature profile make” is vital toward making your oven consistently reproduce a good temperature profile. The temperature profile your circuit board experiences as a result of your oven settings is dependent on the temperature settings AND the heat flow capacity of your oven. To illustrate this fact, two thermal profiles were run on the same circuit board where the speed of convection air in the oven was the only parameter changed. As you can see, the thermal profile at low convection is dramatically lower then the same profile at high convection, while the oven’s zone temperature settings remained the same.

This does not mean that the heat flow capacity should be large, but it must be consistent hour-to-hour, day-to-day, and week-to-week. Small variations in heat flow can cause temperature variation on your circuit board, even though the oven temperature remains the same. A measuring device that can produce meaningful information relative to heat flow in addition to the temperature will give you a complete understanding of your oven and its performance over time. Of course I would not tell you this if I did not know of the tool that can measure your oven’s ability to “hammer heat” into your boards; that being the OvenRIDER. 

Conclusion

 

Controlling the reflow oven soldering process requires monitoring not only temperature but also heat flow. Since heat flow is what causes objects to increase in temperature, measuring your oven’s ability to increase the temperature of fixed thermal mass objects will allow you to detect variation in heat flow. By observing the temperature rise in the mass over a fixed amount of time, you can discover if the same amount of heat has been transferred into the mass. Such a measurement, combined with ambient temperature, yields a much more complete profile of a reflow oven. Only by knowing the heat flow capacity of an oven can you be assured that the oven will heat your circuit boards at the same rate and to the same temperature, every time.

Calibration of electronic measurement instruments is a necessary process, even though most electronic equipment is very stable and somewhat “resistant” to the effects of environment and changes due to aging.

Q: So why calibrate if my MOLE is “in spec” every time I send it in for calibration?

Because calibration is not so much an adjustment process but rather a proofing process that shows, over time, that your MOLE has been in calibration and thus should remain in calibration, because you have a track record to prove it. Documented history of a MOLE’s performance is the only way to claim your MOLE is in calibration at any given instant.

Most good labs will tell you that when your MOLE is calibrated, it is compared to standards , typically standards that have traceability to NIST, and if it is shown to be measuring within its specified accuracy they will not make any attempt to “adjust” it. Only if it is “on the edge,” which usually means it is getting to the last 10% to 20% of the specified accuracy limit, will they make any adjustments. Your MOLE may still be “in spec” and thus “in calibration,” when the lab received it, but getting close, so they will adjust it closer to the middle of the spec. range.

If it is out-of-spec when received by the lab, then a red flag goes up and calls into question every measurement made since the last calibration! The lab will tell you how far out of spec it is, and you can decide if its measurements during that time affect the quality of the measurements made more than can be tolerated, or if they are “close enough” to still be acceptable.

Q: So, when should the MOLE be calibrated?

The number one best time to calibrate the MOLE is on a regular time-based interval, which is recommended once a year. However, there are other events which may cause you to want to seek calibration at other times of the year, such as:

1. When the MOLE is subjected to rough treatment like a fall to the floor,
2. When your MOLE is accidently “over heated” ,
3. When you are starting a new product introduction and you are characterizing an oven and new assembly to find the right recipe,
4. When a new customer’s contract stipulates you use equipment that has been recently calibrated,
5. When your in-house quality program requires a calibration interval.

Getting your MOLE calibrated is easy and we want to make sure you are always making the highest quality temperature measurements.

1. “I’m from the Metrology lab and it’s time for the annual calibration of your reflow oven.” We’ve got an app for that.  After you’ve finished with the oven’s calibration procedure, you can run the MegaRIDER-20 with a Process Test Pallet to see if the machine is uniform across the conveyor width and has the same heating capacity as it did the last calibration or maintenance.

2. “I’m the Manufacturing Engineer and our QC Department wants me to show that this oven is in control.” We’ve got an app for that. You probably need more information than the once a year Metrology profile can provide. So weekly you can an OvenRIDER and see that every zone in the oven is performing the same using X-Bar R charts to prove it.

3. “I’m on the New Product introduction team and I need a good recipe to solder a new board without killing the parts.” We’ve got an app for that. The Super M.O.L.E.® Gold thermal profiler will let you connect T/Cs to the board to see exactly what’s going on, thermally, on the areas where you and the designer have the most concern. Use the Prediction tools in the new MAP software to lock in the perfect recipe.

4. “I’m a Line Technician and I have to know my reflow oven is ready to run product without all the wires and circuit board stuff.” We’ve got an app for that. OvenCHECKER is one pallet loaded with the most powerful profiler on the market today. It takes no more time to run than the first production board and it lets you know if the reflow oven is ready or not. No downloading, no comparing numbers on a chart, just Go, or No-Go.

The ECD V-MOLE with patented one button “OK” profile evaluation

(The OK Button is also available on the 20-channel MEGAM.O.L.E.™ thermal profiler, and OvenCHECKER™ )

Taking only seconds, the MOLE can tell you and your oven operators if the profile just measured is in or out of specification with the universally understood Green for good (GO!) or Red for bad (STOP!).

You get to set the specification limits for any or all of the four most popular profile parameters:

• Ramp Slope
  
• Time Between temperatures
  
• Time above Liquidous
  
• Peak Temperature
  

…and you can choose which of the MOLE’s input channels to include, up to 20 channels on the MEGAM.O.L.E.™, and three on the V-M.O.L.E.™ thermal profilers.

The Specification Table in MAP Software

Using the MAP™ Profiling software, enter your specification limits for the four profile parameters in the Upper and Lower Limits table in the “Target-10 OK” tab. These values will automatically be sent to the MOLE profiler when you use the Verify Process Wizard to confirm that a previously characterized oven recipe is still performing within specification.

MAP™ Profiling Software Target-10 OK Profile tab

Once programmed, the MOLE profiler can be used many times (up to 96 times) to Verify your oven is producing the same profile, without reconnecting to your computer. Simply run the profile and press the “OK Button” on the MOLE. No more running back to the PC software to download to see the results. One push of the OK button, and you get your answer…Go, or No-Go. It’s that simple!

*U.S. Patent Number 7653502.

You might ask, why should I perform an Oven HealthCHECK? In other words, why should I run a rather sophisticated measurement system through my oven to produce a rather nice looking 3-D plot of the cross belt temperature uniformity?

Figure 1: An example 3-D plot of the oven with very good cross belt uniformity, < 3ºC

I may not like the answer because I might find out my oven has a problem that I cannot fix? Sounds like a “head in the sand” sort of excuse to me.

I would ask a different question: “Why do you calibrate your bench test instruments?” Is it to find out that the instrument is out of spec? Heavens no!! That would be a nightmare because it would call into question everything that instrument was used to test since the last time it was calibrated. So why do you calibrate if the results could be so disastrous? Simple, it allows you to show and document that the instrument is and always has been “within specification.” So when the auditor asks, how do know your instruments are in calibration, you pull out the Certificates of Calibration.

Figure: What’s the first thing you check after you receive your Certificates of Calibration? The “As Received: Within Tolerance”

ECD’s Oven HealthCHECK is designed to certify and document your oven’s performance or health. It is a “calibration” done on a regular interval, say once a year, to show that the oven performance is within specification and not changing over time. It can also provide a baseline level of performance around which you can compare into the future. Further, if you have several ovens, the HealthCHECK can show you which ovens are best for applications where oven uniformity is critical.

Back this up with much simpler and more frequent verification profiles of your oven using OvenRIDER or OvenCHECKER, where simple software-generated Xbar-R control charts show daily indications of a thermal process that is “in control,” and you will no longer have to steer the auditor around your reflow oven. You can proudly show that you know your oven’s performance level and that it is consistent because you have taken the steps to measure your oven’s health as part of your Thermal Quality Management program. Such a program should be marketed, since it shows you commitment to understanding your oven’s thermal nature and you have the data to show it. This sure beats the “head in the sand” quality program which may characterize your competition.

1. (Max preheat) How hot the board is just before it hits the wave
2. (Dwell time) how long do you spend in the wave
3. (Contact temp) Temperature of the solder at the contact surface with the board
4. Conveyor speed

All the rest of the many measurable parameters are secondary to these in my opinion. Let’s talk a little about each of these as measured by the WaveRIDER SPC software:

Figure 1: WaveRIDER SPC Software

Max Preheat temp (Preheat Max Temp) is really the temperature of the board (solder joints) just before it hits the wave so you can understand the “shock” the solder joint will get when contact with the wave forces it to melt the solder in a quick few seconds. This temp may NOT be the max preheat temp applied because most wave machines have a large gap between the pre-heater and the solder wave so the board will loose some of the heat during that space/time.

The Dwell time is how long the solder will be above liquidous, all said and done, and this time needs to be consistent across the width of the wave (AKA: parallelism), but you can see consistency across the wave just as easy by setting a min/max spec for the three dwell times. How long you must dwell is a function your solder joint requirements and components ability to withstand the wave temp. Most component specs say they can take 10 seconds or less and most solder joints need only a second to form. The longer you spend above liquidous the more time you give to form the brittle “intermetallic” alloy between the not molten metals. So the only reason you dwell at all is to get the heat to travel up the lead to the board top (on through-hole parts), which may take a few seconds depending on the thermal conductivity of the board and its thickness. A pot of liquid solder has plenty of heat to force into a board, so it depends mostly on the thermal conductivity of the board material itself. You will have to watch/trial your assembly (board) to see just how long that takes so you can set a minimum dwell time. The Dwell time is usually about 2.5 seconds for most 0.062″ (1.6mm) thick boards and this can vary +/- 10% to 15%.

Figure 2: Wave crest pattern

Pot temp at the solder contact surface (Contact temp) does vary depending on the load (your board) places on the surface of the solder wave. It is not the same as the solder pot temp, since that temp is controlled by a Thermocouple deep in the core of the solder pot and not the surface where the board skims across. This temperature should be maintained at least 20ºC or more above liquidous and no more then the maximum temperature allowed by the component specifications.

The conveyor speed is measured by dividing 9.75″ (distance between C and Speed sensors on the WaveRIDER pallet, see Figure 4) by the time measured between the C and Speed sensors hitting the main wave. It is easy to see why this is an important measure since ALL other values will be altered if the conveyor speed changes. Most solder machines can maintain speeds within +/-0.1 ft/minute (+/-1.2 in/minute, +/-3cm/minute)

Immersion depth is only important to prevent solder from spilling over the top of the board during wave contact. The absolute setting is not critical provided it is NOT spilling over the board and its depth is affording the dwell time one needs. However, it is easier to adjust the conveyor speed to control dwell time then the board’s immersion depth and risk a spill over. This is usually controlled by pump RPMs and how full the pot is of solder. If these change over time, the dwell times slowly change and thus is be one of the reasons for dwell changes. However, neither can be directly measured by WaveRIDER which has no chance to access the pump’s RPMs or the amount of solder in the pot.

Conclusion:
Focus your efforts on the critical WaverRIDER measurements by setting reasonable specifications. The many other things the WaveRIDER measures are not as critical, and can be used to diagnose a problem if there is one rather then used to prove there is NO problem. Use the WaveRIDER SPC software to set Spec limits and plot X-Bar R charts for these critical parameters. (Figure 3)

Figure 3: X-Bar R charts

Figure 4: Keep the WaveRIDER pallet contacts clean using a fine wire brush. This will reduce oxide build up on the sensors which can cause the Dwell times vary beyond normal.

Reach For the Sun

Solar Cell manufacturing has been around for a long time; however the materials and process have changed drastically in the past few years and will continue to evolve as the technology and need for Renewable Energy grows. The costs of manufacturing and the risks associated with the ever changing processes can strain  the ability to maintain yields and improve quality. Proving these new manufacturing processes, then achieving the repeatability and yield needed for production have always been a challenge.

ECD’s suite of profiling tools allow detailed Characterization of these advanced processes  during the R&D phase.  During production ramp-up good thermal thermal profile data drives yield improvement leading to maximum profitability.   In  production these same tools can quickly Verify that the optimum manufacturing  process is being maintained.

Thin Film Solar

ECD has many types of customers in the Solar Cell manufacturing industry.  They include start-ups, university research departments and production facilities, located around the globe. 

The application areas that we have been able to identify are among the following:

Silicon Metallization:
   Thermal profiling is used to optimize the drying, rapid firing and following cooling process in the oven.

Silicon Diffusion:
   Thermal profiling is used to optimize the heating, high temperature diffusion and cooling process in the oven.

Thin film Solar Cells:
Done on glass and other substrates, this process is similar to Diffusion process, but at lower temperature.

Profiling Equipment Requirements:
Minimum profiler thickness is important – Many of the ovens designed for solar manufacturing provide little vertical clearance for the profilers.   Thermal barrier requirements vary and in some cases, time and temperature do not allow pass-thru profiling.  In most cases 3 channels of thermal data are sufficient for process verification as all areas of the silicon heat similarly.   Thermocouple attachment can also be tedious, with mechanical pressure being the most common contact method.

We look forward to the continued growth and success of the Solar industry and we would like to invite all solar industry participants to work with us and discover how we can help you reach your performance goals.

A good Thermal Quality Program (ThQM) demands consistent oven verification to show that the reflow oven is reproducing the same thermal environment as it has in the past. The OvenRIDER is a good way to verify oven performance. How do you make best use of these tools, both the OvenRIDER pallet and the OvenRIDER SPC (ORSPC) software?

There are five basic steps:

• Set up the Oven, Workbook and MOLE
  
• Model the oven
  
• Collect a base set of OvenRIDER runs
  
• Set the spec limits
  
• Monitor of verification

Let’s get right into it:

Set up the Oven, Workbook and MOLE

1. Place a magnet at the beginning of zone one. The OvenRIDER came with at least three magnets. This is not because we think you only have three zones, but because we figure you may have more then one oven, and you only need one magnet per oven to mark the start of zone one and let the OvenRIDER measure conveyor speed for you. The software detects this magnet in the profile and uses it automatically place the start of the oven model on the profile’s time axis. It does not matter where you put this magnet as long as it is on or before the beginning of zone one. You can even put it outside of the oven so it can be removed when you are not using OvenRIDER. Just be sure you always put it back in the exact same spot.
2. Set the oven’s recipe you plan to use for this OvenRIDER run. It can be the same recipe you are now using to solder boards. In fact, you may want to start an OvenRIDER collection of runs for all your different recipes. This does need to be a big one time effort for all your recipes. You can do this slowly for each recipe one at a time as you do line change over. In time you will have enough runs for each recipe to begin useful oven Verification.



3. Start the OvenRIDER software and select the Workbook you wish to save these recipe runs. If this is the first time you opened the software, a sample work book will be opened. Go to the file menu and close this Workbook. Then open the file menu and start a New Workbook or open an existing Workbook you previously created. The Workbooks can help you group like OvenRIDER runs. Having a work book for each oven recipe is the best for Oven Verification. You can name Workbook the same as the recipe name to help keep it straight.�
    
4. To make sure the MOLE is ready, connect it to the PC via the communication cable and run the Configuration Wizard in the OvenRIDER menu. This will find the MOLE and set it’s clock and other settings.

 



 

5. Load the MOLE into the OvenRIDER barrier and connect the configuration plug

 



 

6. Make sure the oven is up to temperature and ready to receive product. Also make sure the conveyor width is set the OvenRIDER’s width.
7. Start the MOLE, close and lock the lid, and load the OvenRIDER pallet onto the oven conveyor.
8. When it gets through the oven, open the barrier and stop the MOLE by pressing and HOLDING the button until the Status LED turns off by itself.

Model the oven

Oven modeling is critical. This tells the software how big each oven zone is and where each zone is on the thermal profile so it can correctly show which zone had what effect on that portion of the profile.

Above is a typical Oven RIDER thermal profile with an oven model (vertical dashed lines) in place. Each zone influenced the “shape” of the thermal profile of the OvenRIDER’s sensors as it passed through oven. The amount of influence depends on the oven recipe temperature set point for each zone, the conveyor speed and the convection rate (fan or air speed). The temperature set points and conveyor speed has a straight forward and expected effect. The convection rate is a little different. Some ovens allow this to be changed and may be measured in several ways like: velocity, pressure, percent, Hz or RPMs. In some ovens, the convection rate is not adjustable or has two or three settings like: Low, Medium, and High. In either case, convection rate changes are one of the leading causes of profile changes when neither the conveyor speed nor zone temperature set points have been altered. So understanding what part of the profile each zone influenced is critical to pin pointing where problems in the oven have occurred.

Here is the best way to model an oven, any oven:

1. After the profile run, connect the MOLE to the PC via the communication cable and press the Read OvenRIDER button.

 

2. The software will as you how much data you want to use from the previous run, if there is a previous run. This time, the first time don’t select anything by un-checking all three.



3. The OvenRIDER profile will look something like the profile below. Because you installed a magnet, the start of zone 1 is in place on the profile, and that’s it. It is ready to Model the oven.

 

4. Start the Manual Zone Definition by selecting it on the Manual Zone menu.
5. Select the number of zones check boxes on the let that your oven has. Name them if you like. Leave the values it defaults for Zone Lengths and Units. We will take care of that next. Note it has the measured conveyor speed already calculated and entered in as the conveyor speed value.



6. Enter the Zone Temperature Set Points in the Top column. Note the Bottom values copy from the Top values as you enter them since most oven use the same Top and Bottom values. Enter the bottom values, if different, after you enter the Top values. When done, click OK.
7. You will now see all of your zone boundaries located in the default locations, but not in the right locations. Note the small boxes at the top of each boundary. This is a handle for you to grab and move the boundaries to the right locations. The right locations are in that little dip that happens between zones you can see in the Ambient sensors, the Red, Blue, and Green profile lines (Channels 1, 2, and 3). So start moving the zone boundaries into place. Remember, don’t move the start of the first zone, this was set for you by the software when it detected of the magnet.



8. Your profile and oven model should look like mine below. This is the “thermal” Model of your oven. It’s already saved with this profile, but let’s save it for future use with other recipes used in this same oven.



9. Go to the Manual Zones menu and select Setup Zones.



10. This will re-open the Oven Zone Setup dialog box. Hit the save button and name your oven model. I recommend using the Oven or line name. This model can be used for other OvenRIDER profile runs using the same model of oven, but with different oven recipes later on. Use the Load button to recall this oven model on future runs.

Collect a base set of OvenRIDER runs

You now have a good oven model and your first run at this recipe. You need to collect at least three runs at this same recipe before enough data is collected to meaningful, statistically. This can be all at once, but this take a big chunk of time from production, and most don’t have that kind of time. I recommend you take an OvenRIDER run at the beginning of each day or shift, while you are running the same recipe, for several days. You will have 3 or more runs in less then a week.

If you don’t run the same recipe for more then a day, you can set an “Oven RIDER Recipe” near the recipe setting you use most often. Start the day with that recipe, take the run, and then move to the “real” recipe you plan to use that day.

If you want to do three or more Oven RIDER runs all at once, just be sure to cool the MOLE and the Pallet to room temperature between runs. Do NOT short cut this critical cooling process. This will save the MOLE from possible over heating and assure the pallet temperatures are consistent run to run. 20 minutes on a nice fan will be enough in most situations.

Once you have several runs, you Spreadsheet will look something like this:

Make use of the user columns, the Green ones. This is where your can name the column anything you like. At least make a column for Recipe, and maybe the Machine or line name. I also have a Part Number column to identify the part or assembly soldered using this recipe.

Set the spec limits

With a good set of OvenRIDER runs collected under the same oven recipe, at least three, but five or even 10 is better, you can now set limits on the average of these runs. Do the following:

1. Select the Spreadsheet tab and filter out or “hide” the runs that are NOT part of the base OvenRIDER runs. If you named each base run like I did in the example, this is easy. Select the filter dropdown arrow in row 4 of the column where you named the base runs, n my case column E, and select the name that you used to name the base runs. I used “Base Runs,” for simplicity. This hides (temporally) all the other runs. If you don’t have any other runs yet, then you don’t need to do this. The statistical data at the bottom of each column is now calculated only from those runs still visible.



2. Now select the Admin tab and click the drop down arrows in the LSL and USL columns. Select the -10% and + 10%. This will set as upper and lower spec limits +/- 10% of the Average values for your base line runs showing on the Spreadsheet tab for ALL the values OvenRIDER measures. These will be good starting values to see how your oven is doing.





3. Optional – You may want to select +/- 5% later on after you have a few more runs, if you wish to run tighter specs. Or, you may want to change the conveyor speed spec limits to a little tighter because you know you machine can do better then 5% or 10%. Finally you may want to remove some of the specs because you are not concerned with those measured values. To start with, it will not hurt to keep all the values.

Monitor of verification

Now each time you run the OvenRIDER at this recipe, you can see in a flash if the ALL of the measured values are within the specs you set. Simply select the OvenRIDERData tab and give the values a look.

If any of them are Red (above spec) or Blue (below spec), then there may be a problem in this portion of the oven. The values of most concern are the Average Temperatures and Process Delta per zone. If these begin to fall out of spec, then you know there may be a problem in that zones ability to heat.

All black, as in this run, the oven is ready to roll.

Any parameter out of spec should be examined to see if it’s a concern or not.

If you wish to get deeper in the SPC control you can create. Xbar-R Charts for any of these values as well. Simply drag and drop any measured value in the column to the left into one of the SPCA, B, C… boxes. Check the box to add that SPC group of charts to the tabs pages below.

Select the tab to see the X-bar R charts. Here are many production runs of the oven ruder captured of time.
These chart use all the typical SPC rules to determine process control.