Monthly Archives: April 2018

PCB Industry on Fire — Literally

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The potential for fire is an occupational hazard of printed circuit board fabrication and assembly. Plating lines can be highly flammable, as can be ovens and the exhaust systems.

The deadly fire at Chin Poon in Taoyuan, Taiwan, over the weekend underscores how careful workers must be when building circuit boards — and how important it is for management to ensure safety practices are in place and followed.

The US tends to be reliable when it comes to fire safety. The last publicly cited incident was in 2016, when a minor fire broke out at TTM’s fab site in Anaheim.*

Overseas is a different story. Wurth’s plant in Neiderhall, Germany, was decimated by a blaze in 2014. The company rebuilt. Likewise, Unimicron spent millions to rebuild its site (the former Ruwel) at Geldern, Germany, following late December 2016 fire.

In Southeast Asia, blazes are all too common. Fires have been reported at ITEQ, Compeq Manufacturing, Gold Circuit (twice), Unitech (twice), Unimicron, Wus Printed Circuit and Tripod Technology (twice). Viasystems in Guangzhou was shuttered for a period of time following a 2012 blaze, and also sustained a fire in Zhongshan. Gold Circuit in Changsu .Taiwan PCB Techvest suffered a blaze in Suzhou, and Zhen Ding (ZDT) sustained one in Jiangsu.

And that doesn’t include another tragic incident which occurred last year at Unitech Printed Circuit Board in Taiwan, where four workers died after falling into a wastewater tank. They reportedly were overcome with fumes from the hydrogen sulfide present and lacked proper protective gear.

Assembly plants are risky too. Ovens and wave solder baths are potentially combustible, and it seems a cleaner explodes at least once a year.

A plant at EMS provider SVI Public Co. in Bangkadi, Thailand, burned to the ground in 2015. The last time we can recall a US assembly plant sustaining such damage was more than a decade ago, in 2005. That was a rough year for assemblers, as at least two were decimated by fires. Fawn Electronics, in North Carolina, chose to rebuild after a December fire leveled the plant. (It has since been acquired by ACDi.)

Workers at Mid-South Electronics weren’t so lucky: The EMS provider closed after a disastrous fire to its plant in Kentucky in January that year, leaving more than 700 workers out of jobs.

It’s commonplace to for management to say their workers are their greatest assets. We hope the tragedy in Taoyuan is a wakeup call for companies everywhere to review their safety practices and ensure the utmost caution is taken to prevent future disasters.

 

*Update: A good friend noted after this piece was published that ICM Controls’ captive board shop in North Syracuse, NY, was demolished by a fire in May 2017.

What is Your Supply Chain Telling You about Packages?

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Have you purchased any electronics components lately? Have you tried and failed to do so lately? Allocation is the word of the day and substitutions are your friend.

Many, many parts are in short supply, or unavailable with extraordinarily long lead times. Sure, that happens every now and then in this industry. It’s a periodic nuisance, but what should you do for the long term? We’re are getting some interesting stories from component suppliers that might help. 

What we’re hearing is that many passive manufacturers will be trying to move their customers to smaller sizes. They want to consolidate on as few packages as is possible. That means we may be seeing the end of 1206, 0805, and maybe even 0603 form factors for many passive values.

It kind of makes sense. Right now, there might be several dozen different varieties of 0.1uF, 16V capacitor. Does the industry need that? And if there isn’t enough fab capacity to make all of the variations, why not consolidate and run more of fewer variations? It won’t surprise me if we start seeing fewer voltage ranges as well. In most cases, a 16V part will be just fine if you’re calling for a 6V or 10V part.

The chip industry has been doing this for a while. Many of the newer components just come in BGA or QFN packages. Fewer and few leading edge parts come in large through-hole or SOIC packages.

Consider using smaller components, like standardizing on 0402 parts. I know it can be a pain to use smaller parts, but any potential for future proofing your design now can prevent delays or otherwise unnecessary redesign cycles. You might just be able shrink your board size and save some money on the board fab too.

Keep approved substitutions close by, and look for newer chips that are more likely to stay in production. For microcontrollers, pick parts that have multiple memory capacity or speed range variants all in the same package.

This looks to be a pretty extreme allocation cycle, and I have a feeling that the industry will be different when we come out of it.

Duane Benson
Which is worse
Being the missing link or the weakest link?

 

A Question on Schematic Style

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Just a quick question here…

I’m placing the components for my TinyFPGA based stepper motor controller board (see the prior articles here first, here next, and here last). Specifically, I’m finding places for all of the capacitors. That’s where the question of schematic style comes in. 

When I first started using CAD software, sometime shortly before the stegosaurus roamed the land, I would position component symbols on the schematic near the chips they belonged with. Doing so made it easy, come layout time, to remember which capacitors go where.

Since then, though — and I don’t remember when I started this — I’ve started following the practice of grouping capacitors on the schematic, as I’ve done on this sheet to the right. All of the capacitors are up at the top, shown connected to V+ and ground rails.

That’s not a problem when they’re all 0.1uf bypass capacitors and each chip just takes one. However, with higher speed and more complex chips, multiple bypass caps or different values are often required on each chip.

Now, when I go to layout, I need to go find my component data sheets again (they really should never be very far away) and re-figure out what combinations of bypass capacitors go to which pins on what chips.

I like the cleaner schematic that results from grouping bypass caps, but it’s adds pain and a bit of opportunity for error during layout.

What style do you use and why? Am I an idiot for doing it this way? Wait. Don’t answer that last question.

Duane Benson
Six of one and 12 × 5 × 10-1 of another

Does Solder Paste’s “Five Ball Rule” Remain Valid in SMT Today?

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Folks,

My good friends, Phil Zarrow and Jim Hall, in their audio series “Board Talk,” were recently asked about the “Five Ball Rule”. In the comments section for this session, one listener asked if this rule, created in the 1990s, was still valid. After all, the 1990s was the era of 0603 and 0402 passives; 01005 and even 008004 passives have arrived.

First, let’s consider what a “rule” is verses a “law.” As an example of a law, consider Newton’s Laws of Motion. At everyday speeds, these laws are shown to be accurate to within our capability to measure. As we will recall from Physics 101, these laws were superseded by Einstein’s Theory of Relativity, at speeds close to those of the speed of light. However, in our everyday world, Newton’s Laws are well … laws. They are, for practical purposes, exact.

What is a “rule” then? A rule is an expression that approximately fits some empirical data or the experience of experts. Moore’s Law is actually a rule, as it is not precise. The doubling of transistor density has varied from every 18 months to every two years. That’s why I call it a rule, a very useful rule indeed!

The “Five Ball Rule” is clearly a rule. It was likely developed a generation ago by some of the first SMT pioneers. It may be backed up by experiment, but I think it was likely more a consensus of SMT industry authorities from the 1980s and 1990s.

What is the “Five Ball Rule?” It states that the solder paste’s largest solder particle diameter should be such that at least five of these particle diameters would span the width of a rectangular stencil aperture (Figure 1).

Figure 1. The Five Ball Rule

 

 

 

 

 

 

 

When this rule was developed, stencil apertures were much coarser than today, and the finest solder powder was a Type 3, with Type 4 on the horizon. While it is true that stencil aperture widths are much finer today, solder pastes of Type 4.5, 5, and even 6 are now in use.

The particle sizes of different “Type” solder pastes are shown in Figure 2. Note that, for Type 4 powder, 80% by weight of the particle diameters are between 20 and 38 microns. 38 microns is considered the “largest particle.” So, from Figure 2, for Type 5 powder, the “largest particle” is 25 microns. For the sake of the Five Ball Rule, the “largest particle,” for each powder type are those shown in Figure 2.

Figure 2. Solder Powder Sizes.

 

 

 

 

 

 

 

 

 

So, is the Five Ball Rule still valid? It would be hard to argue that it is not. Hundreds of experiments have been performed using the Five Ball Rule, combined with the aperture ratio being >1.5 for rectangular apertures or the area ratio being > 0.66 for square or circular apertures, with successful results.

StencilCoach software now includes the newer (finer) solder powder sizes to 1) tell the user the fineness of solder paste powder for the Five Ball Rule, as well as 2) help with calculating aperture or area ratio. By the way, some have suggested that, for a square or circular aperture, an “Eight Ball Rule” is more appropriate. So, StencilCoach uses the Eight Ball Rule for such apertures.

Cheers,

Dr. Ron

 

PCB Chat: Are Designers Lazy, and is Automation All-Important?

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“Content is the most important aspect of the design world right now,” says Manny Marcano, president of EMA Design Automation. Over the past nearly three decades, he has grown EMA into the leading Cadence Channel Partner as the exclusive distributor of OrCAD in North America. EMA has also developed a series of its own software products for library management, component supply chain data, and conducts training.

Manny talks about the role of automation and whether designers are keeping up with their profession this week as my guest on PCB Chat.

In Acquisition Mode, Foxconn is Turning Up the Heat

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OEMs, beware: Foxconn is coming for you.

No, not just to buy your components, build your boards and run your logistics. Foxconn is coming for your data, your markets, and your customers.

We’ve been sounding the alarm about this for years. It’s not healthy for your primary supplier to be bigger than the nearly the entire rest of the market. Foxconn, pushing $150 billion in revenues, is as large as the next five EMS/ODMs combined, and more or less as large as numbers 7 through 500.

The 2016 buyout of Sharp could be chalked up to a desire by Foxconn to nab a key technology and supplier to Apple, it’s top customer. The just-announced deal for Belkin, however, coupled with its foray into developing 5G computing and cloud platforms,, suggest a drive to higher margin, branded products. Foxconn’s revenue is larger than almost everyone of its customers, and a new plan to issue $50 billion worth of stock could give it the capital it needs to go on a massive acquisition spree.

OEMs, beware.