The Ideal Bill of Materials

Posted on by

A good portion of a quality build is simply the result of clear information. One of the more important pieces of information we deal with is the bill of materials, called “the BoM.”

The BoM is a list of all the components to be placed on the PCB. The file typically includes an index number, the number of times a specific component will be used on the board, the reference designator from the schematic, the component manufacturer, and the manufacturer’s part number.

If a specific component is used more than once – a common bypass capacitor, for example – it will still only take up one line in the BoM. One field in the BoM will list the number of times the component is used, and another field will list all the reference designators for that part number.

For example, line 5 in my BOM on this slide, is a 0.1 microfarad, 10V capacitor.

The first field in the table has a line item index, 5, because this is the fifth unique part number in my BoM. The next field has a quantity of this component used on the board, which is 5. Field three holds reference designators C1, C2, C3, C4 and C5. The next field has the manufacturer, and the final field has the manufacturer’s part number.

You will likely have additional fields, such as a distributor part number, a description, the package type and other tidbits, as I have here.

But the first five columns in this example show what is generally considered to be the minimum data set for a good bill of materials.

Note the three lines at the bottom highlighted in red with the label “DNS” in the Type column.

DNS means “do not stuff.” That’s an instruction to the manufacturer to not install that component during the assembly phase. Some people use DNP, for do not place, or DNI, for do not insert. It’s always best to consult with your manufacturer to get their preferred labeling.

You may also want to include alternate parts for components likely to go out of stock. Passives, such as capacitors and resistors, are notorious for going out of stock without notice. Invariably, though, a half dozen nearly identical parts will fit the bill just as well.

Create an alternates list so the purchasing folks or manufacturer won’t get stuck not knowing if a substitute is valid or not.

Duane Benson
In the 90’s, when people said good things were “the bom”, this is what they were talking about

 

PCB Chat – Joe Fama

Posted on by

Joe Fama is an expert in electronics manufacturing services with more than 30 years helping OEMs and EMS companies, particularly in southeast Asia. Joe specializes in taking relatively unknown electronics companies and linking them with key OEMs. His career has taken him to Singapore, Malaysia, China, Mexico and the Philippines. He also writes an occasional column. He talks with Mike Buetow about setting up three-way program among a Western OEM and NPI EMS and a Southeast Asian volume EMS that can generate a recurring revenue stream for the US-based EMS.

2 Sides to the Border

Posted on by

Writing in Circuits Assembly this month, our longtime columnist Sue Mucha explains the forces that set the wheels in motion for Foxconn’s much-discussed deal to put a new campus in southeastern Wisconsin.

Some of the impetus starts, oddly enough, in Mexico, where a 2014 change in the status of flat-panel displays made them subject to that nation’s 16% value-added tax. The TV assembly industry crashed. Writes Sue: “In short, tax policy in Mexico appears to have contributed to a changed investment strategy in the TV assembly market. That didn’t just impact TV manufacturers; it also impacted the EMS companies they outsourced to.”

The gate swings both ways, according to a  Reuters report today. The wire service says Amazon, Facebook and Oracle, among others are leading the way south, expanding operations and hiring engineers in Mexico, where the cost of living is lower, access to talent is rising, and US immigration laws (and attitudes) aren’t in play.

Could this be the tip of a coming iceberg?

 

The Return of PCB Chat

Posted on by

After a hiatus, we have relaunched PCB Chat as a podcast.

Our first guest is Mike Konrad of Aqueous Technologies, who shares his experience with what happens when a contract manufacturer follows its customer’s instructions to the detriment of the product. The outcome: Product failures, blame, drama, and a really big lawsuit.

We apologize in advance for the imperfect audio; we are still getting up to speed on the editing tools. But we think you’ll enjoy this, the first in what will be a regular series of interviews and conversations.

Orders, and Prices, Peaking

Posted on by

Peak manufacturing season is upon us, stretching component and raw material lead times and supplies. Lead times for some passives are now more than a year! We also are hearing price increases are greater than usual, and fabricators are getting notices from raw material suppliers about possible shortages or even allocation.

Moreover, transportation costs tend to get higher this time of year and a new wave of environmental inspections in China have shuttered some factories there.

Supply chain sources indicate these situations will become worse over time this fall.

Sorry to be the bearer of bad news.

Fabrinet’s Changing of the Guard

Posted on by

Were you as surprised as I was at Fabrinet’s choice of a new CEO?

During the 17 years of its existence, having been formed in 2000 when ex-Seagate exec Tom Mitchell took on the lease of his former employer’s plan in Chokchai, Thailand, there has been no EMS company so successful over the past two decades. That initial $21 million investment is now worth $1.35 billion in market value, not to mention the consistently most profitable business in the industry.

It would have been conventional, then, had Mitchell chosen longtime No. 2 Harpal Gill to assume the mantle. Dr. Gill has been Fabrinet’s chief operating officer since 2009 and president since 2011.

Instead, Mitchell went outside for Grady Seamus from rival Sanmina, where he headed the  Mechanical Systems division.

Some analysts believe the move foreshadows a coming diversification from fiber optics into non-optical manufacturing. Writes Stifel Nicolaus’s Patrick Newton:

[W]e see Seamus as having extensive leadership experience with both optical manufacturing (background at Lucent; Mechanical Systems Division at Sanmina manufactures the cabinets/chassis/frames/racks/ and storage cabinets integrated with electronic components and sub-systems that optical components are supplied into) and non-optical manufacturing (focus Medical experience at Sanmina). We view this competency in both optical and non-optical manufacturing as likely to be an aid in helping the company move beyond its optical focus to a 50/50 optical/non-optical mix long-term. We emphasize that our recent conversations with Fabrinet’s management highlighted that Fabrinet was targeting its next CEO to have a combination of operational excellence, deep technical expertise, and strength with customers as they will have to be customer facing.

Mitchell set the bar so high, any successor would be challenged to maintain it. Seamus is widely seen as a talented executive. But will he attempt to write Fabrinet’s next chapter with — or without — the team Mitchell put in place?

Mistakes Were Made — Too Much Ground Isolation

Posted on by

I recently ran a batch of my Neo Pixel clock boards through the factory here. It’s an Arduino UNO-based design that I made for myself not long ago. It sports an Atmega328P, with bootloader, an FT231X USB chip, and a DS3231 real time clock (RTC) chip. Pretty standard stuff. It doesn’t even use small parts. All the passives are 0805 size. There’s nothing exotic here. So, where did I go wrong?

I also used my 3D printer to make a clock frame to hold this board and a 60-pixel ring of NeoPixels, from Adafruit. I found that with the micro USB connector on the top of the board, it’s a little awkward to plug in the USB cable, so I put pads for the connector on the back side of the board. Depending on exactly where and how the board will be used, the micro-USB, button switches, and clock backup battery can all go on either the front or back surface of the board.

Programming the bootloader worked as expected, so I assumed it was just a job well done. Except it wasn’t. When I plugged in the micro USB cable, the RX and TX LEDs flickered briefly, but the board wasn’t recognized by my PC.

Take a look at the back side of the PCB and see if you can find my mistake (spoilers after the photo).

I ran a 24 mil trace around the back side of the board to supply power to the NeoPixels. That’s not a problem, except that I closed the loop on that trace, and didn’t put a path for the ground to get across the trace.

Follow it around, and notice that the ground connections to the u-USB connector don’t go anywhere except to this part of the plane. Ugh.

Duane Benson
Cassini’s gone now.

When Fake Buys Make Real News

Posted on by

M&A specialists in the electronics industry seem to have caught a case of merger mania. In the process, they unfortunately have seem to have learned the worst traits of the buyout crowd.

A pair of unsolicited bids were announced this week. In one instance, a small EMS company announced its interest in a much larger competitor. In the other, a Chinese connector manufacturer made a play for a smallish Canadian EMS/ODM.

What makes these cases interesting are the details.

In the former, Cemtrex, a company with trailing four quarter revenues of $125 million and a market cap of $31 million, made a play for Key Tronic, a top 50 worldwide EMS that reported sales of $468 million for its just completed fiscal year. Key Tronic’s market cap is $74 million, so Cemtrex’s offer of a one-for-one stock swap was a huge discount to Key Tronic’s value.

Not only that, says Key Tronic, it wasn’t really even  an offer:  “Based on (Cemtrex’s) current SEC filings, Key Tronic understands that Cemtrex has not commenced a formal exchange offer and that any such offer would require additional SEC filings by (Cemtrex),” Key Tronic said.

In the latter, Shenzhen Kaizhong Precision Technology made a written offer for Pacific Insight Electronics. The wrinkle here is, not only was Pacific Insight taken by surprise, it is already under agreement to be purchased by Methode Electronics.

The ODM today confirmed receipt of a written buyout proposal from Chinese connector maker. However, Pacific Insight has already agreed to be acquired by Methode Electronics, whose offer Pacific Insight says is superior to Kaizhong’s. Pacific immediately urged shareholders to reject the unsolicited bid.

Publicly traded companies such as Key Tronic and Pacific Insight have a fiduciary responsibility to their shareholders. However, from time to time outsiders try to make waves or generate publicity by pulling stunts like these. I’m not saying the interest communicated by Cemtrex or  Kaizhong is false, or even misplaced. But in both cases, I think the suitors are overplaying their hands.

 

Dont’ Forget PCB West Next Week!

Posted on by

Next week is the 26th annual PCB West, the preeminent trade show in the Silicon Valley for the electronics supply chain.

As those who have attended before know – and there are quite a few of you – PCB West focuses on the design and manufacture of PCBs, HDI, electronics assembly and printed circuit board test, and gives engineers, designers, fabricators, assemblers and managers an opportunity to improve skills, increase knowledge and network with peers, colleagues and experts. With an emphasis on training – half the presentations
are at least 2 hours in length – there is no place better to get real, practical, in-depth information.

Our three-day conference features:
• More than 70 presentations on the hottest topics, including noise control, flex circuits, and diagnosing assembly defects. This is our largest conference yet!
• More than 15 day-long tutorials or half-day seminars

• Sessions for all levels of experience and training, from novice designer and engineer to seasoned pro
• Speakers from Analog Devices, TTM Technologies, NXP Semiconductor and many more top companies
• The ever-popular Rick Hartley, Doug Brooks and Susy Webb
• An all new PCB/EMS Management track with special sessions aimed at helping executives make the capital investment and hiring decisions that shape their companies
• Three free day-long tracks on Sept. 13, with topics ranging from signal integrity and IoT PCBs to 3D printing technologies.

Also next week, a special 2.5-day IPC Designers Council Certification Program powered by EPTAC.

All conference attendees receive free admittance to the one-day exhibition Wednesday, Sept. 13, which includes a complimentary luncheon and evening reception, both on the show floor.

For more information or to register, click here.

Looking forward to seeing you at the show! And as always, please feel free to share your thoughts.