Pin-in-Paste Aperture Calculations Using Solder Preforms

Folks,

The pin-in-paste (PIP) process is often the best choice when the PCBA is a mixed SMT and through-hole board with a small number of through-hole components. However, ensuring that the correct volume of solder paste is printed to ensure an adequate amount of solder for a reliable thorough-hole solder joint can be a challenge. One tool to help in this regard is the Pin-in-Paste Aperture Calculator. This calculator is now online at http://software.indium.com/. The solder volume equations were developed by good friend Jim McLenaghan of Creyr Innovation.

To estimate the right amount of solder paste, we need to calculate the volume of the plated though-hole, subtract the volume of the component pin, and add the volume of the solder fillet. See Figure 1.

Figure 1. Solder volumes in the pin-in-paste process.

Let’s assume we have the PCB and component pin metrics, as seen in the left hand column of Figure 2, under the header “Input.” Blue cells are inputs, green cells are calculations by StencilCoach. Notice that, if you have a rectangular pin, the software will calculate the equivalent pin diameter for entry into the “Input” cells. The “paste reduction factor” is the fraction of the paste volume that is solder. Most pastes are about 50% by volume flux, so, typically, this metric would be about 50% or 0.50.


Figure 2. PIP metrics.

The “Output” calculations are not really necessary for the task at hand, which is determining the stencil aperture dimensions, but may be of interest. The important stencil dimensions are shown in the “Stencil Metrics” section. Note that in our example, even though we have a 7-mil thick stencil, we would need a square aperture with a side dimension of 93-mils to get enough solder paste. With a circular aperture the radius must be >50-mils, if the pin spacings were 100-mils, there would not be enough spacing between the printed deposits, they would overlap. So we must use square apertures.

As in this case, it is a common problem with the PIP process to deliver adequate solder volume. If the PCB and component metrics are such that obtaining enough solder paste is an issue, it can be helpful to use solder preforms to increase the solder volume. The next post will cover this topic.

Cheers,

Dr. Ron

Posted in Dr. Ron | Tagged , , , , | Comments Off

Optimal at Optimum

As corporate models go, Optimum Design Associates isn’t unique. Several firms have launched as design shops only to add EMS capability as they matured.

But one thing ODA does that I really like is provide a much greater level of detail about its financials on its website.  See below:

Financial Disclosure

Financials through 12/31/2013

Ownership Private
Annual Revenue $19 million
Credit Access $5 million
Loan Balance $133,000
Principal Payments $3,700
Access to additional financing Yes
Executive changes last 90 days No
Ownership changes last 90 days No
Return on Assets (last quarter) 3.6%
Current Ratio 2.2
Quick Ratio 1.21
Capitalization 23%
Cashflow 5.45
Debt to Equity Ratio .003

 

For a privately held company, that level of public disclosure is unusual. For a small business, it’s unheard of. Certainly any OEM worth its salt would ask for verification of financial stability prior to engaging, but having that data on hand upfront makes determining whether ODA is the right fit a little easier for potential customers (which could also be a time-saver for ODA), and moreover offers a high degree of confidence that ODA will be above board.

Perhaps that’s willingness to break the mold is why ODA is again on the Inc. list of the fastest-growing companies. (It also made the 2007 and 2008 rankings.)

Congratulations to Nick and the gang at ODA.

Posted in Hot Wires, Laying It Out | Tagged , , , , | Comments Off

VTP: Very Tiny Parts

A while back, I wrote about a new ARM Cortex M0+ chip from Freescale. It’s not the first M0+, but I do believe that it’s the smallest. I’ve been checking stock off and on and finally found the smallest package to be in stock and available to ship. 

I actually bought a couple of different types. First, there’s the WLCSP 20. It’s got 32K Flash, 2K SRAM and an 8K bootloader. The real kicker is that the package is only 1.6 X 2.0 mm. I also got a few in the QFM-16 package, which is a bit more workable at 3 X 3mm.

Finally, I bought a Freedom development board with the 4 X 4mm QFN-24 package. The dev board is hardware compatible with Arduino shields, so that will make for some interesting possibilities.

Anyway, here at Screaming Circuits, I’m most interested in that 1.6 X 2.0mm package to see how easy (or difficult) it is to use – see if there are any particular layout challenges. The other stuff is just for after hours play time.

Duane Benson
I’m not a number. I’m a free development board!
(Free, as in named “Free…”, not free as in “don’t cost nothin”)

http://blog.screamingcircuits.com/

Posted in Laying It Out | Tagged , , , , | Comments Off

The HP Split

Those wondering how the HP split might shake out should read this piece in Bloomberg today. In summary, HP’s PC group just lost some of its pricing advantage, as the servers and other business-oriented gear are going with the new Hewlett-Packard Enterprise company. HP is currently Intel’s largest customer, but that will change as the two primary hardware lines are separated. (HP’s server gurus have been working on a competitive line using Applied Micro chipsets, so that ranking might eventually have been in jeopardy either way.)

On the other hand, given HP’s deservedly stodgy reputation in tablets and handheld PCs — despite, or perhaps because of, its acquisition of Palm in 2010 — the shakeup could enable the new HP Inc. to focus on trendier designs for the mobile market.

What’s not clear is whether each group will retain a certain number of chip designers. This is an area of strength for Apple, and HP Inc. will need to ensure it has the internal talent to advance in the hypercompetitive PC space.

Posted in Hot Wires, Laying It Out | Tagged , , , , | Comments Off

Cost Reduction in Design — More Advice

If you’re looking for the absolute, cheapest possible assembly service, you’ll need to look outside of North America. If you really need a decent price with good quality and good service, you can keep your gaze West of the Atlantic and East of the Pacific.

Like everything else in the modern world, design decisions can have a pretty big impact on your cost. So, lets take a look at some design decisions that can make your manufacturing more affordable.

  • Accept longer lead times

Lead times are one of the biggest factors in electronics manufacturing. Screaming Circuits can turn a kitted assembly job overnight, but it costs a lot of money to do that. Screaming Circuits also has a 20 day turn-around that is much, much more affordable. Accepting longer lead times on PCB fab will drop your cost as well.

  • Avoid leadless packages like QFNs and BGAs

We build tons of QFN and BGA boards – even down to 0.3mm pitch micro-BGAs. That’s great if you need those packages. However, since all of the leads are underneath, we have to x-ray every part. That adds a bit of cost to the process. If you can, stick with TSSOPs and other parts with visible leads.

  • Use reels, or 12″ or longer continuous strips

We will gladly assemble parts on strips of almost any size. But, to save costs, use full or partial reels or continuous strips of at least 12″ long. It costs us less time to work with reels and continuous strips, and we pass those saving on.

  • Stick with surface mount

These days, through-hole components tend to be hand-soldered. That costs more than machine assembly, so use surface mount wherever possible. Surface mount components tend to be less expensive than through-hole too. If you do need a few through-hole parts, this is an opportunity to put in a little sweat equity by soldering the through-hole yourself and save a bit of money.

  • Panelize small boards

We can work with really tiny boards individually, but sticking with a larger size makes the job easier, and, again, we’ll pass those saving on. If your PCB is smaller than 16 square inches, panelize it. We put in less labor and you get a price break.

By following these guidelines, you get a decent price and really good quality and service.

Duane Benson
That would be telling

http://blog.screamingcircuits.com/

Posted in Laying It Out | Tagged , , , , | Comments Off

Red Makes Green

The arrival of India’s Mars Orbiter is an achievement on many levels. Much will be made of the fact that it is the first Asian satellite to reach the red planet’s orbit. That they accomplished it on their first try will open some eyes to India’s hardware capability as well, given than the success rate for the rest of the world is just 40%.

What I’d like to focus on is the price: India spent a reported $74 million on the Mars Orbiter Mission. That’s barely 10% of what NASA spent on the Maven mission.

Coincidentally, the F-22 Raptor saw action for the first time this week. But the fighter has been under fire for years for what critics call a bloated price tag and unmet performance objectives. The DoD has spent $67 billion for 188 planes, and no more will be produced.

Wall Street Journal

Should the US government wake up and realize that a huge price tag does not necessarily translate into performance, what will be the impact on the electronics supply chain, especially in the US where so much of it relies on military spending?

Posted in Hot Wires | Tagged , , , , , , | Comments Off

The End of the Viasystems Era

At long last, the hunter became the hunted.

TTM Technologies today announced its pending acquisition of Viasystems. The deal, expected to close in early 2015, will vault TTM to second place among the world’s largest PCB fabricators.

No matter how the deal turns out for TTM, Viasystems will remain one of the most talked about PCB companies in the industry’s history, held in awe for its audacity and blamed on multiple continents for nearly single-handedly devastating local supply chains.

For the entirety of its 18 years, Viasystems was worth 10 times its revenue in industry controversy and chatter. It sprung on the scene in fall 1996, the brainchild of New York investment firm Hicks, Muse, which in quick order bought up AT&T’s board shop in Virginia, Circo Craft, Kalex, Forward Group, ISL, Mommers and Zinocelere, plus several EMS and peripheral businesses. They were the Yankees of the PCB world, albeit without the same level of success.

Then came the Tech Recession of 2001, and Viasystems’ debt ballooned to over $1 billion. Two Chapter 11 restructurings and countless lawsuits later, the company stabilized and managed to spend the better part of the rest of the decade simply managing the business.

In 2010 the veil was lifted. Viasystems resumed its buying ways, snatching up Merix and then, two years later acquiring DDi (which in turn had gobbled up Coretec). Yet consolidation didn’t bring happiness. Over the years Viasystems found it nearly impossible to turn a consistent profit. Debt, a persistent problem dating to its Hicks, Muse days, now sits at $561 million.

TTM is getting Viasystems for $16.46 per share, or about 6.8 times adjusted EBITDA. You tell me if that’s worth it.

I would expect TTM will sell off Viasystems’ wire harness business, which is small ($174.6 million in 2013) relative to the rest of the business and has shown operating losses in five of the past seven quarters. Viasystems has already consolidated its China manufacturing base, so I would not expect much change there. TTM is running at 75% capacity in China but only 60% in North America. TTM has seven sites in North America and Viasystems has nine, including a combined three in the Silicon Valley and two in Orange County. Perhaps they will seek to consolidate here in order to boost rates.

Viasystems changed the way the world viewed the industry. It forced Wall Street to take notice. It laid waste to the regional landscape, ultimately closing millions of sq. ft. of some of the once-best shops in the world. Some will say this was inevitable. Viasystems bought plants that were obsolete or quickly headed that way, whose workforces could not change even while the technology was quickly shifting away from them. And the firm tied up enormous amounts of capital in dubious debt deals that may have enriched a few but certainly did not leave their business units with the balance sheets necessary to operate in such a cyclical market.

There’s still time for the deal to fall through, and it took about 18 seconds before shareholder lawsuits began piling up. No matter what happens on the ground, come next spring, Viasystems will again occupy the rarest air of the PCB world. It just won’t be as Viasystems.

Posted in Laying It Out | Tagged , , , , | Comments Off

QFN? QFP? QFWHAT?

The QFN (quad flat pack, no leads) has become my favorite integrated circuit package. It’s very compact, yet is easier to use than a µBGA.

µBGAs of 0.5mm and smaller pitch become a bit more difficult and costly with more than two rows of pins. At those geometries, escape routing can involve plugged and plated vias, which add complexity and cost to the fabricated board. QFNs can be almost as small, but have all of the pins exposed around the edges, so there’s no need for escape routing.

One thing that’s important to note is that despite sharing the first two letters (Q and F), QFP and QFN footprints are not interchangeable. We do, from time to time, see boards laid out for one along with the other form packaged part.

Take a look at this PCB layout clip from the Arduino Leonardo. It has both footprints on the board. You can see how much bigger the QFP package is.

They put down both footprints because the Atmega32U4 chip used in the Leonardo sometimes has supply issues in one package or the other. This gives them the flexibility to use either without making changes on the board.

You might consider this as an option if there’s space for a QFP and you are concerned about the availability of one package variant or the other. If you do, there are some very important things to check out:

  • Make sure the pin-outs match. Some parts vary the pin-out a bit between packages or have extra pins on one or the other.
  • Make sure the extra space won’t cause noise problems. Generally, bypass caps should be as close as possible to the supply pins. This amount of extra space probably won’t be a problem when using a QFN, but in some designs it might.
  • Make sure the board won’t be in an environment where unsoldered pads will be a problem. Some harsh environments could attack the unsoldered pads. If that’s the case, consider conformal coat.

Duane Benson
We’re always being pushed and shoved by people trying to beat the clock
But we like it – it’s what we do

http://blog.screamingcircuits.com/

Posted in Screaming Circuits Blog | Tagged , , , , , | Comments Off

Who Needs 2 Newspapers?

Juxtapositions can funny, even when the subject is serious.

From DigiTimes today:

Foxconn considering lawsuit over leukemia report

“Foxconn Electronics (Hon Hai Precision Industry) is considering taking legal action against UK-based Daily Mail for its recent report claiming Foxconn employees working in Shenzhen plants have developed leukemia.”

Foxconn promises assistance for ill workers in response to leukemia report

“Foxconn Electronics’ (Hon Hai Precision Industry) plants in Shenzhen, China reportedly have seen many of their workers develop leukemia because of long-term operations in the presence of electronic cleaners.”

 

 

Posted in Hot Wires | Tagged , , | Comments Off

Wave of Innovation

Old friend Jeff Miller (some readers may remember him from his ACT and Wise days)

3D printed car

3D printed car

took this photo of a 3D printed car this week while at IMTS in Chicago.

Meanwhile, while at PCB West earlier this week, we saw the row of Tesla demo cars on display and waiting for test drives in San Jose. A designer from Telsa’s Palo Alto R&D center (the former HP semiconductor plant) was at the show and was visibly excited talking about the range of electronics he gets to work on.

No one will confuse Tesla’s elegance with the admittedly rough model at the right, but there are some amazing things happening with both board technology and form factors right now, and we are lucky to get a front row seat for this latest wave of innovation.

Posted in Hot Wires, Laying It Out | Tagged , , , | Comments Off