Monthly Archives: March 2011

Which Surface is Best?

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RoHS has been in effect since, when, 2006? Pretty close to five years now. It’s been around long enough that there’s even talk of follow-on legislation. All of the PCB fabricators have pretty much figured out how to deal with RoHS. There are Pb-free versions of every PCB finish at this point. But, we still get questions about the best choice of PCB finish.

I don’t think industry has selected one PCB finish as the “standard” preferred choice. A lot depends on the application and the componentry being used. For large parts, HASL, leaded or lead-free, is a good choice. It’s inexpensive and works well. For leaded work, HASL still seems to be the most common finish. We don’t see quite so much Pb -free HASL, though.

If you’re working with small geometry parts, then you really need to go to immersion silver or ENIG. The consistently flat surface of those finishes will help keep the small parts on the pads where they belong. The disadvantage of silver is that it requires a little more care in handling and storage. It can oxidize which will make soldering more difficult. ENIG is more expensive, but it tends to work real well and is easier to store. Fingerprints can be a problem though. We’ve seen the oils from a fingerprint essentially etch the gold surface off. Weird.

OSP becomes a viable choice with high-volume, cost critical applications. It used to be very sensitive to storage and handling, but has gotten a lot better over the last few years. We don’t see immersion tin much at all. It apparently is harsher on the environment to produce than other finishes.

All that makes it more understandable that we don’t have one preferred finish. It seems confusing, but really it’s not that different than any other product. There certainly isn’t just one preferred style of tire for all motor vehicles.

Duane Benson
Gotta have those monster truck tires if you live in Kelso

http://blog.screamingcircuits.com/

An SPC Rx

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It was Wednesday evening and I had just finished a brief pitch on applications of SPC to a group of 20. I was followed by Jim Hall, who spoke of process mapping using SIPOC.  So did these folks have solder paste under their fingernails, or wave solder flux stains on their shirts, or, perhaps, a solder preform or two stuck in their pant leg cuff?

No — none of these souls would have had any of this type of trace evidence of electronic assembly on their person. You see, they were all medical doctors and students at Harvard’s famed medical school (see image below).  (I hope it is OK that the proud dad shares that my daughter Jessica is a colleague of these folks.) 

Jim and I were presenting to the doctors, because they are interested in process optimization in the healthcare industry. The event was hosted by Dr. Andy Ellner.  He is a professor and doctor at the medical school and is a focal point for these process improvement efforts. I was introduced to him in the summer of 2009 by Dartmouth’s new President Jim Kim.

In November 2009, Jim, our colleague Larry Parah, and I facilitated Andy’s team in dramatically improving the prescription refill process in Brigham and Women’s Hospital Clinic.  Jim and I plan on working with Andy in similar efforts over the next year or two.

The most striking thing that Jim and I left with on Wednesday evening was how profoundly interested these doctors and students were in healthcare process optimization. The Q&A session lasted nearly an hour.

Ah, yes, would that our many colleagues in electronic assembly were as interested in optimizing their processes!

Cheers,

Dr. Ron

Something Free at ESC

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My post title rhymes. I’m a poet and don’t even know it.

So, what about that free thing at ESC? And is there a catch? Of course there’s a catch. There’s always a catch. This is a good catch, though.

If you are an electrical design engineer and are at ESC this May, come to our booth and see if you make the cut. The first 50 qualified electronic design engineers will get one of these things.

Yes, I’m being non-specific about the details. That’s a technique. It’s supposed to make you more curious. That’s what they tell me anyway.

The details:

  • Embedded System Conference, Silicon Valley
  • McEnery Convention center
  • San Jose, CA
  • May 3-5

    • We’re in booth 823.

    Duane Benson
    Robots for world domination!

    http://blog.screamingcircuits.com/

    Icahn’s Next Move?

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    It comes as no surprise to this blog that Mentor Graphics is rejecting Carl Icahn’s offer to buy the company. After all, Mentor has in the past turned down bids that valued the company at roughly the same amount as did Icahn’s.

    But there is a distinctly disengenuous flavor to Mentor’s reasoning. In a statement, the company insists that the company is worth more than Icahn is valuing it. Specifically, it claims, “Our share price has grown by more than 70% over the last year, for a two year aggregate growth of approximately 200%.”

    True, that, but what the company fails to acknowledge is that Icahn’s accumulation of Mentor stock is likely the main driver behind the upswing. One year ago, Mentor’s stock was trading at under $8 a share. It’s now almost twice that. During that time, Icahn boosted his holdings from under 5% to almost 15% of the company. The combination of his large purchases and the inevitable ride on his coattails some speculative investors are taking has no doubt strongly influenced that jump in value. Despite a $125 million jump in revenue, Mentor has lost an cumulative $14.2 million over its past three fiscal years: to suggest investors are simply thrilled by its performance is a difficult assertion to prove.

    The company also speaks of — but doesn’t elaborate on — regulatory risks that come with Icahn’s proposed buyout. It’s not clear why a sale to its largest shareholder, one who is tellingly not a competitor, would run afoul of SEC or other rules. 

    The relationship between Mentor and Icahn has clearly soured. That was predictable: Few companies welcome Icahn’s type of shareholder “interest.” What’s less clear is what happens next. Will Icahn fold his flag and start selling? Or will he redouble his efforts to pressure the company into a sale?

    5 Case Studies on REACH Compliance

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    For companies still wondering how their situation fits into REACH, the following case studies may help. These case studies address compliance in a variety of scenarios. The five instances of how-other-companies-did-it represent common situations. The case studies address both upstream and downstream scenarios.

    1. Downstream user under REACH (with confidential uses)
    A medium sized company supplying preparations to the marine sector consider implications of keeping this use of a substance confidential from their suppliers; find out what further action they may need to follow as a downstream user under REACH.

    2. Global manufacturing company seeks to automate the collection of supplier data for REACH
    A Fortune 500 manufacturer and retailer with operations worldwide seeks to automate supplier chemical data collection as much as possible for compliance with REACH.

    3. AstraZeneca, a pharmaceutical manufacturer, and famous furniture company Herman Miller along with an automobile agency voice software testimonials on software products they use to manage substance-level compliance with substances under REACH and similar regulations.

    4. An alloy producer (see also RoHS) clarifies duties under REACH
    A producer of alloys determines that under REACH it is the component metals that constitute the alloys they manufacture that are within the scope of registration and for one of these that they import they will have registration obligations.

    5. REACH and a company importing a solvent from the US
    A company importing a solvent for the first time from outside the EU is concerned about having missed the preregistration deadline but finds they can pre-register and get help from other SIEF members.

    These case studies — unless otherwise indicated and linked above — may be found on the web (at the time of this posting) at the following URL:  hse.gov.uk/reach/casestudies/index.htm.

    That Final Check

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    I’m not talking about the final check that you get from an employer laying you off due to outsourcing. That’s a bummer of a final check. The final check I’m talking about is a good thing. It always pays to do this kind of final check. Of course the other kind of final check pays too, but only once. This kind can pay off numerous times.

    Here’s the scenario: I have an MCU board that can take 5v power from either USB or from a dedicated power source. I want part of the board to receive power all the time and one small high-current section Schematic wrong pwr source to receive power only from the dedicated power source. I don’t want to suck too much current out of a poor little USB.

    My circuit has three different power busses: USB regulated 5V, on board regulated 5V, on board 9-12V. I even fabbed up some PCBs and built a first prototype. It needed a few mod wires, but I missed this problem. After my mods shown on the older posts, the circuit still worked, so I stopped looking for problems.

    Fortunately, I took one last look before sending off for v2 PCB. Two of my bypass caps went to the wrong supply (they were supposed to go the “BRD5V” instead of “5V”). Not a huge deal and in my test set-up, it didn’t prevent the circuit from working, but who knows what would have happened in real use. In any case, it would either resulted in another board spin or left the potential for intermittent problems when in use.

    Duane Benson
    Once again, time for oatmeal

    http://blog.screamingcircuits.com/

    Bouncing BGAs

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    I dropped my cellphone on the pavement the other day. That’s bad enough, but in my instinctive attempt to catch it, I actually hit it and increased its downward velocity. Luckily, everything still works. The odd thing is that I just assumed that it would still work. No real questions or doubts on that thought.

    That realization got me thinking. (It happens now and then.) What other devices do I have that I automatically expect to survive a drop onto concrete? I have a carpenter’s hammer. I expect that to survive a drop intact. I would not expect my camera to survive such a drop intact, and have empirically verified that fact. A little car GPS? Probably not. Laptop; uh … no.

    I’m sure there are some other devices that would easily survive. I just can’t think of any off the top of my head. I suspect that there are a lot of factors that go into making cellphones survivable. The case, the overall mass, the quality of solder joints.

    Along those lines, some folks use an underfill glueish type substance to hold BGAs more securely. Some designers use pick and placeable solid underfill. Some just rely on extra good soldering and some leave it to luck. Of course, not all BGA installations require much shock resistance. How do you secure your parts when shock or vibration are serious concerns?

    Duane Benson
    Quick, where’s Henry? I need an inductor.

    Virtual Questions

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    Here’s a question I received during my Virtual PCB chat session on March 8:

    • From Jack: “Here’s my default question (as a designer), what is your biggest headache from designers?”

    My answer: “Probably the most common difficulty has to do with CAD library footprints. That’s really a headache caused by the CAD software”

    • Jack: “Ha, well it seems like the majority of problems stem from incorrect library footprints (including mask, silk, etc.). Maybe we just need to get together and make a universal library for everyone, eh?”

    I’ve been hearing a lot of lamentations over the last year regarding CAD library footprints. It seems to be one of those issues that has been around long enough and is now reaching a critical mass of attention. There are a few partial solutions in the works. PCB123 is trying to make the most complete set of libraries possible. NXP has been supplying factory libraries to PCB123. There is the IPC-7351B land pattern generator. Some manufacturers give good footprint guidance at least (TI, Freescale). Sparkfun and Adafruit are supplying libraries for most of the components that they use and sell.

    All good things and all in the right direction, but still not a consolidated universal effort. There’s also talk floating around of crowdsourcing libraries. I can see that working for Eagle and a few other packages, but I question whether large companies using expensive CAD systems would rely on such a thing. I guess that all means that we don’t have a solution in sight, but if the problem is getting broad-based visibility, than maybe someone will come up with an actual complete answer.

    Duane Benson
    Esperanto for CAD libraries

    http://blog.screamingcircuits.com

    IPC Responds to EPA on Electronics Stewardship

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    On March 11, IPC responded to a US Environmental Protection Agency (EPA) request for public comment. EPA’s request for comment was regarding its embryonic National Framework for Electronics Stewardship.

    IPC responded by first saying that it appreciated the opportunity to comment on EPA’s Solicitation of Input from Stakeholders to Inform the National Framework for Electronics Stewardship (Docket ID # EPA-HQ-RCRA-2011-0185).  Then:

    IPC believes that EPA’s goal of encouraging the design, manufacture, procurement, and use of greener electronics should begin with a definition of a green electronic product.

    This is in fact an excellent point.  At a recent high-level symposium for “Green Chemistry,” roughly 500 managers and executives gathered to share ideas on the subject of green chemistry.  In my working group, 250 well-educated individuals sat in a large conference room to discuss the business implications of Green Chemistry.  Very quickly it came to light that almost no one present agreed on what Green Chemistry meant.

    Definition of green in manufacturing. Some, myself included, thought “green chemistry” would be a topic as defined by Paul Anastas and J.C. Warner, and a discussion of green product manufacture would be about materials and finished goods screened against the original 12 principles of Green Chemistry.  A few folks thought we would discuss law in terms of state-level green chemistry legislation, risk and litigation.

    The slight majority in the room had never heard of the 12 principles of Green Chemistry; these folks thought Green Chemistry was synonymous with Sustainability, itself an undefined term.

    Truly:  no definition is correct until we define these terms once and for all, and then continue to define our terms consistently as we go along.  Upshot:  the conference collateral and agenda should have defined Green Chemistry on every page.  In fact, every Sustainability conference or paper ought to do the same until we all know the definitions without thinking.

    With that said, we can only applaud IPC for its sensible call for definitions of “green electronic product,” as the term will be used in the new national framework for electronics stewardship.

    IPC’s letter to EPA on electronics stewardship. The IPC letter articulated that before developing a framework for electronics stewardship, the EPA ought to establish a definition for a green electronic product. Defining a green electronic product, it said, ensures that all impacted stakeholders will be working from a common starting point. Yes!

    There is no need to recreate the entire document here, but there is a second particularly relevant point:  the need to consider the fact that some attributes may be less damaging to the environment in one way, say sourcing or end of life, but be more damaging in another way such as in processing emissions and waste. In IPC’s words:

    For example, as shown in EPA’s lead-free solder study, the substitution of tin-lead solder for lead-free solder resulted in increased energy use associated with the higher operating temperatures required for manufacturing electronics with lead-free solder.  This increase in energy use was projected to cause higher air pollution, acid rain, stream eutrophication and global warming impacts.

    That study serves as an important reminder that there are environmental trade-offs when substituting one substance for another. The EPA must lead the way in determining what attributes are of most importance in defining a “green electronic product.”

    IPCs letter is signed by Stephanie Castorina, manager, Environmental Programs for IPC.  The entire document may be viewed here.

    Green manufacturing index. Perhaps a hierarchal, ranked, feature set matrix would be a good start.  If the major electronics associations, industry consortia, EPA, and the new Task Force for Electronic Stewardship could agree on a ranking system to establish a green index in manufacturing, that index could be used to determine and define “green electronic products,” also to ensure that one evil wasn’t swapped for another.

    With a Green Manufacturing Index we could move forward with a unified theory of electronics recycling, which would simplify a lot of things. Stay tuned.