Unusual Component Lead Contamination
Posted by Paul Austen in M.O.L.E. MAP, Reflow Profiling, Thermal Profiler, Thermal Profiling on August 26th, 2011
Today’s blog post originally appeared in Circuitnet on August 22, 2011
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.
What’s New – July: M.O.L.E.® MAP 2.20a Release
Posted by Ray Pearce in M.O.L.E. MAP, Ray's Blog, Reflow Profiling, Thermal Profiler, Thermal Profiling on July 29th, 2011
Since the advent of the CPU, electronic products have been getting “smart.” And now, to the extent that software and an internet connection make it possible, even appliances which most of us would consider to be a block of steel and plastic with a singular function, such as a refrigerator, are now capable of keeping inventory, reminding you to go shopping – even placing delivery orders to restock! Yes, when you really think about it, it’s often the software that enables and drives product innovation and answers the question “What if we could….?” The latest ECD software is a perfect example. It allows us to give our profiling equipment the very capabilities that customers have had on their wish lists. A M.O.L.E.® can’t order you lunch, but here’s “What’s New.”
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.
- 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.
- 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.
- 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.
- 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!
- 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
Heat Flow Happens
Posted by Paul Austen in M.O.L.E. MAP, OvenCHECKER, OvenRIDER, Profiling, Reflow Oven Verification, Reflow Profiling, Thermal Musings, Thermal Profiling on May 24th, 2011
An often misunderstood concept is heat flow and how it can influence the temperature of the product being heated so here is Wikipedia’s definition of heat flow, followed by a discussion of our own on the subject.
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. Read the rest of this entry »
Thermocouple Attachment in Vapor Phase Soldering
Posted by Paul Austen in Epoxy, Kapton Tape, Thermocouple Attachment, Vapor Phase Soldering on February 8th, 2011
Attaching thermocouples in Vapor Phase Soldering (VPS) presents a potential problem that’s often overlooked. To illustrate this potential problem, let’s look at how VPS works. All the work needed to heat the components and solder joints to the melting temperature of the solder take place in the very thin “condensate” layer of liquefied vapor phase fluid. This 0.2 mm layer is very much like the layer of water that forms on a cold drink on a humid summer day. (See figure 1.) The vaporized fluid (cloud) is at or very near the boiling temperature of the fluid, which is typically 200ºC to 240ºC, depending on the fluid you choose to use.
Figure 1 – Vapor Phase Soldering and the condensation layer
When your room-temperature assemblies are immersed in the vapor cloud, the vapor quickly condenses onto the cold surfaces of all the parts, releasing the heat of vaporization, or the heat energy that was put into the liquid to evaporate it into a vapor. This energy release begins heating your assembly rapidly toward the 200+ºC vapor temperature.
To measure the thermal profile of the process to prove you are staying within the components’ thermal limits, (always a prudent step) you must attach a thermocouple to the component or solder joint you wish to profile. Here is where you must take care. (See figure 2)
Figure 2 – Typical thermocouple attachment to component lead
The thermocouple may be attached with solder or epoxy. However the thermocouple wires extend away from the point of measure and may be exposed to the vapor. The vapor will condense onto the thermocouple wires in the same way it condenses onto all the parts. Exposed bare wires will heat quickly because they are very small. These heated wires will conduct that heat toward the thermocouple bead, where it is sensing the temperature, and artificially heat the sensing point. This will actually show as a “false” temperature rise in the early part of the ramp up in temperature because the heat is conducted in to the part by the thermocouple wires. The insulated part of the wire will not heat as fast because the insulation slows the heat flow of the condensing vapor. .
So when connecting thermocouples to components to measure the thermal profile, it is very important to insulate any exposed thermocouple wire beyond the thermocouple sensing bead. (See figure 3)
Figure 3 – Insulated thermocouple wire
This is best done with a thin layer of epoxy covering the exposed bare wires of the thermocouple, up to and a bit past the insulation on the thermocouple wire, being careful not to cover the sensing bead of the thermocouple. The epoxy does not need to be very thick, just a thin covering. Using too much would have the “chilling” effect of preventing the heat from getting to the component or solder joint, giving an artificially cooler profile result.
You may also try Kapton® tapes or high-temp heat shrink around the end of the thermocouple. These may shrink back or come loose, however; and if you plan to profile more than once, these methods may not hold well over time.
References:
SMT Magazine, “Vapor Phase Soldering: The Comeback Kid” by Ray Prasad
Thanks to Kevin Syverson, Silicon Forest Electronics, Inc., for the use of their Vapor Phase soldering system.
Total Heat – Another way to analyze your thermal profile
Posted by Paul Austen in Extracting Parameters, M.O.L.E. MAP, Reading Profiles, Reflow Profiling, Thermal Profiling on January 21st, 2011
One of the most popular ways to determine if a thermal profile of an electronic assembly is within specification is to consider the limits placed on four measurements or parameters: Initial Ramp Slope, Soak time, Time Above Liquidus and Peak temperature. Keep these four parameters within the specified (solder paste) limits and you can be assured that you are soldering the parts without damaging them.
Figure 1 Typical thermal profile with the four traditional parameters within spec
There are other ways to look at a profile which can be helpful in determining if the profile may threaten components and showing if it is consistent, both across solder joints, and over time.
In the profile example above, the Time Above Liquidus (TAL)on solder joints 1 and 3 are within 2 seconds, yet channel 3 (from the data; plot not shown for visual clarity) had more readings at higher temperatures. This means that although this part may have the same time above 183ºC, more readings were at temperatures higher than channel 1; higher risk of damage. Also note that the peak temperatures were not far apart; 222.2ºC vs. 223.5ºC.
So we added a new measurement to the MAP software to not only show Time Above Liquidus, but also consider the temperature values during the TAL portion of the profile. This new measurement has several names: “Total Heat,” ” Area Under the Curve,” or “Stress Integral.” It combines the time element of Time Above Liquidus with the temperature measurements during that time to give the Total Heat the component experienced, expressed in degree-seconds.
Figure 2 Total Heat measurements (component 1 only shown for clarity)
In this case, even though the Time Above Liquidus values are within 2 seconds and the peak temperature is less than 2 degrees apart, the Total Heat values are 2278º-sec and 2628 º-sec which differ by 350 º-sec! This clearly points out that component 3 had to withstand more Total Heat than component 1 and this simple parameter can now be examined in an instant, using the latest; version 2.18j of MAP software.
The Cooling Zone
Posted by Paul Austen in Profiling, Reflow Profiling, Thermal Profiling, Wave Solder Profiling on November 18th, 2010
A sometimes forgotten fact about reflow and wave soldering is that anywhere from 25% to 50% of the time a solder joint spends above its melting temperature, aka: time above liquidus (TAL), takes place in the “cooling zone”. Much time is spent getting the heating portion of the oven recipe finely tuned to produce a robust thermal profile, only to toss the product, covered with liquefied solder into a cooling zone where the solder joints must return to a solid state. The rate at which this occurs (cooling slope) is even more critical using lead- free solders. Giving the cooling zone some well deserved attention when defining the requirements of the thermal profile is essential to a good Thermal Quality Management program for your soldering process.
The cooling zone is where the quality of the solder joint is defined, with the cooling slope influencing the joint strength, and overall longevity. These two qualities are often at odds with each other because strength often comes from slower cooling rates, while longevity results from faster rates. Different cooling slopes have been tested to try to find what rate produces the best combination of strength and long life when subjected to accelerated thermal-cycling. These studies have concluded that slow cooling rates (1 to 2 °C/sec) allow too much time for intermetallic alloy growth, a strong but often brittle alloy prone to cracking when stressed. Faster cooling (5 to 7 ºC/sec) can form a softer solder joint with less overall strength, not to mention possible component damage. Cooling slopes between 3 and 4 °C/sec were found to be the best at producing a solder joint with both good strength and overall longevity.
So… don’t forget the cooling zone when developing the best thermal profile for your solder process.
References:
“Cooling Rates in Lead-free and Tin/lead Reflow”
SMT Magazine
by Denis Barbini, PhD.; Ursula Marquez
“Accelerated Thermal Fatigue of Lead-Free Solder Joints as a Function of Reflow Cooling Rate” Journal of Electronic Materials
by Qi Y; Zbrzezny A R; Agia M; Lam R; Et al
“Proceedings of 2005 International Conference on…” Asian Green Electronics
by Qiang Hu; Zhong-suo Lee; Zhi-li Zhao; Da-le Lee
Thermal Profiling and Vapor Phase Soldering
Posted by Paul Austen in Vapor Phase Soldering on September 9th, 2010
There has been some new talk by some of the best quality conscious electronic manufactures about the many benefits of an older soldering process: vapor phase soldering. Vapor phase soldering has a lot of good things to offer, now that we have gotten past the stigma of the old CFC fluids and moved on to newer chemistries. The maximum temperature that the assembly can be subjected to is dictated by the boiling point of the fluid being vaporized. Because the boiling point of the fluid is a physical constant, you might think, “Why bother running a thermal profile on the assembly being soldered.”
This idea should be considered carefully, and here are some reasons why thermal profiling in vapor phase soldering is still a very good idea:
1. Although the boiling point of the vapor phase fluids is a physical attribute that limits the maximum temperature, the condensation of the fluid onto the components can impart a lot of heat, real fast. This can subject components to the old thermal shock problem, and unless this heating rate is carefully controlled by the vapor phase machine, you may well be shocking the components. Thermal profiling is the only way to show this is under control.
2. The maximum temperature is a function of the fluid type, and one needs to be sure the correct fluid is being use. There is a fluid whose boiling point is hot enough for lead free soldering, and not too hot for leaded soldering, about 230ºC. This “happy medium” is a good compromise, so one does not have to own two different vapor phase machines, or change fluids from one process to the other, but it is another reason why thermal profiling is a good idea: to prove that the process is meeting the need of the solder paste and the limits of the components.
3. A process undocumented is a process out of control. Unless you have some evidence that the thermal profile is meeting the requirement of the solder paste and the limits of the components, you cannot prove the process is in control statistically. You can’t make process control charts if you don’t measure the process. This is at the heart of a good Thermal Quality Management (ThQM) program.
4. Your customer still wants to know what the thermal profile looks like. No matter how you solder your customer’s boards, they still want to know what they were subjected to, thermally. This is your assurance to them that you have treated their product properly.
Lead-free in Mission Critical – Failure Is Not An Option
Posted by Grant Peterson in Thermal Musings on August 19th, 2010
The following is an excerpt from an article by Grant Peterson, V.P. of Marketing & Sales at ECD, which discusses the use of lead-free in mission critical hi-rel applications. The article originally appeared on August 11 in SMT Online. The link at the end of this excerpt will take you to the complete online article.
Lead-free in Mission Critical – Failure Is Not An Option
A mission-critical industry can be defined as one in which product failure can be catastrophic: threatening life or critical infrastructure, causing unacceptable collateral damage, and resulting in liability for OEM and/or EMS. Generally included are the military/aerospace, aviation, medical, and automotive industries. To confidently use lead-free in those high-reliability applications, especially considering the EU drive to impose RoHS on some areas currently exempt, it seems prudent to step back and determine where we are, how we got here, and what remains to be done.
RoHS was implemented in the consumer sector before hi-rel industries for two reasons. First, consumer goods made up most landfills. But more importantly, it was initially assumed the lifespan for items like cell phones would give us approximately ten years to encounter and solve any lead-free related problems before moving into mission-critical areas. Life span, however, was greatly overestimated. Cell phones, computers, etc. are now replaced sooner and with greater frequency than originally anticipated. With this reduced time frame, we have neither seen the full extent of lead-free reliability problems, nor developed means to fully combat those we have. Can we really proceed to mission-critical areas with full confidence? Click here to go to the full SMT Online article.
MOLE® Thermal Profiler Calibration – Why and When?
Posted by Paul Austen in Thermal Musings, Thermal Profiler, Thermal Profiling on July 26th, 2010
MOLE® Thermal Profiler Calibration – Why and When?
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:
- When the MOLE is subjected to rough treatment like a fall to the floor,
- When your MOLE is accidently “over heated” ,
- When you are starting a new product introduction and you are characterizing an oven and new assembly to find the right recipe,
- When a new customer’s contract stipulates you use equipment that has been recently calibrated,
- 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.
MOLE Talk
Posted by Paul Austen in Thermal Musings on June 28th, 2010
Yes I know, I’m ripping off the Car Talk radio program name, the truly funny call-n show where two well educated brothers have the best of fun giving advise (correct for the most part) to their call-in victims about everything from car repairs to personal relationships. If you’ve not heard the program, find your local NPR radio station and check it out. And also, I’m following on the heels of Board Talk, a web based collection of questions and answers by two respected members of the electronic assembly community who do a nice job (in a “Car Talk” like format) of answering many common questions submitted by followers of the Circuitmart web based electronic assembly resource.
So why take the risk of being yet another abuser of the “Car Talk” theme? Well because I have been asked this question many times: “Why did you call it a Mole?” Call what a Mole?
You know the M.O.L.E. ® Thermal Profiler, that pocket sized 6-channel temperature measurement logger used to see if you are getting the right temperature to your solder joints without overheating your thermally sensitive components (J-STD-075) in reflow or wave soldering machines.
There is a mouth full! Well, to answer this question I thought I’d take a look at the many really cool things a Mole can be. Here are a few:
A Mole of any substance shall have the same number of atoms, molecules, ions, or other elementary units, as the number of atoms in 12 grams of carbon. That number is: 6.0225 × 10^23, AKA: Avogadro’s number. So if you want to calibrate your scale, simply pile up 602,250,000,000,000,000,000,000 atoms of carbon and you’ll have 12.001 grams.
An annual celebration of the date and time represented by the numbers 6.02×10^23 or October 23 from 6:02 a.m. to 6:02 p.m. There is a cool web site in honor of this important number in the world of chemistry and physics. Check it out.
A small gray burrowing mammal, that is for the most part blind, although they probably can tell night from day. Moles tunnel through dirt and eat small worms living mostly underground. Moles can be found in most parts of North America, Asia, and Europe, although there are no moles in Ireland.
What do you call a Mole’s baby? Yes, a Pup. A female Mole is called a sow and the male is called a boar. And if you have more than one Mole you have a “company” of Moles.
A benign skin tumor found on human skin appearing as a small, sometimes raised area, with darker pigment.
A Mexican sauce made from chili peppers, other spices, and chocolate. However, it’s pronounced “Mole-Ay” and I often take service calls from Spanish speaking customers who say they have a “Mole-ay” that is due for calibration. I recommend this dish at your favorite Mexican restaurant. However, there are many different ways to make it so if you don’t like it at one restaurant, don’t be afraid to try it again at another.
A spy who has worked their way into an organization or country for the purpose of getting information. Wasn’t there a TV show?
A pier, jetty, or junction between places separated by water. I did not know this could be called a Mole until today.
A complete line of stage and production lighting products made by the Mole-Richardson Co I’m into theatrical lighting so naturally I’d know about this one.
OK, so this has been fun. Can we get on and just answer the question, “Why did you call it a MOLE?” Taking from the best parts of the many uses of the word Mole, we grabbed the following:
- A Mole crawls through tunnels.
- A Mole secretly spies on the goings-on of something or someone without detection
- A Mole of something is a number that starts with the number 6 (6.02…)
- A Mole is a delicious Mexican sauce. OK, we took nothing from this possible definition of Mole.
Put these together and you get an instrument that goes through the dark tunnels of many different thermal processes, measures the temperature of that process without disturbing it, and does it in 6 (or 3, or 20, since the original naming of the brand) locations of that process. Only a M.O.L.E. ® can do that. So that is why we called it a Mole. So what does the acronym M.O.L.E. stand for?
M = Multichannel – more than one temperature measurement input
O = Occurrent – events that happen (or occur) at the same time
L = Logger – a recording instrument
E = Evaluator – one who makes a judgment, as in the “OK” button on the new V-M.O.L.E. and MEGAM.O.L.E.
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