ome 13 years ago, UP Media Group launched the first virtual trade show for the electronics industry. In some ways – most, probably – we were ahead of the times. People liked it because it was simple to attend, but the platform wasn’t ready for prime time.

That’s not to say it was technically subpar. You could pop in and out of booths and talk to the personnel waiting for you, and I still feel for those folks who, driven by caffeine and excitement (or just an affinity for self-abuse), kept vigil around the clock as attendees in different time zones came on line and into the show. And we held webinars and chats with high-profile experts like Dr. Eric Bogatin. But in the end, attendees seemed to prefer meeting with peers face to face.

By making face-to-face sales calls impossible, Covid-19 is challenging electronics manufacturing services (EMS) salespeople to work in new ways. Sadly, that challenge isn’t likely to go away soon. On the bright side, it opens the door to a more productive, less costly sales and OEM relationship, provided salespeople modify their approach.

In the normal flow of EMS selling, there is typically a lead follow-up phase that results in a face-to-face sales call. There may be an additional meeting to present a quotation, depending on the distance between the salesperson and decision-maker. There is also usually a plant tour. When all these activities are local, costs drop to the amount of time the individuals spend on the activity. However, the cost of a sales call that involves business travel may be $1,000 to $2,000, depending on mode of travel and how many sales calls are clustered into that trip.

Question: I am looking to add a flex circuit supplier to our vendor base and requested its technical roadmap. After review, it appears almost exactly as the two vendors we currently have. Is this a coincidence, or do most (or all) flex suppliers have the same technical capabilities?

A technical roadmap is basically a document that outlines what a company can and cannot do from a technical standpoint (e.g., minimum trace/space, layer count, pad and via size, overall circuit size, etc.). I have never been a fan of technical roadmaps. Virtually every flex (and rigid) PCB supplier is compelled by their customer base to provide their capabilities, and therefore also their limitations. The problem with roadmaps is twofold. First, every supplier advertises the absolute best it has ever done in every single category. This is true even if it only did it one time, on one circuit, and in a beaker. This is not a fair representation of what the fabricator can or cannot do on production quantities. The second problem is the real answer for what a supplier can or cannot do is “it depends.” Let’s look at a few examples.

Application notes describe how to save layers in a PCB by routing two traces between pins on a 1mm pitch BGA. A leading FPGA vendor recommends this practice to use its very-high-pin-count FPGAs in a low-layer-count PCB. When this approach is used for a high-layer-count PCB, the result is often, if not always, very poor yields, and the board is unreliable when used in a system under actual conditions, as opposed to in a laboratory or a prototype built in a small volume by a specialty shop. The following discussion will illustrate why this approach results in unsatisfactory yields when volume manufacture is attempted.

To understand the space used to route traces in signal layers of a multilayer PCB (this also applies to four-layer PCBs), it is useful to look at how plated through-holes (vias) are created and the various requirements that must be met by the finished PCB. FIGURE 1 is an illustrated cutaway of a plated through-hole showing signal and plane layers.

Like embedded resistors and capacitors, embedded magnetics provide a means for reducing system size and cost. Transformers and inductors used in power and telecommunication applications are often the more expensive devices in a system design. When realizing a power converter or RF module, cost and size reductions can be realized by combining the magnetics and PCB functions. This article provides an overview of embedded magnetics design and construction.

Inductors and transformers are basic building blocks of power and communication systems. A simple transformer or inductor can be implemented between two PCB layers. FIGURE 1 shows a cross-section of an embedded magnetic transformer. A cavity is milled into an FR-4 substrate. Ferrite cores are inserted and encapsulated in place with low-shrink epoxy. For those unfamiliar with ferrite material, it is a ceramic made by mixing iron oxide and metallic elements like manganese, nickel and zinc. The mixture is molded and fired to create a magnetic core. The materials are classified as ferromagnetic, meaning when a conductor is wrapped around the material and a current is applied, a magnetic flux will develop within the core and remain there as long as the current is applied. Permeability is a measure of the materials’ ability to build a magnetic flux. High permeability materials (5000 to 20,000) use a mixture of manganese and zinc (MnZn) and are generally used to produce RF inductors and transformers. Power applications also use MnZn, yet at a mixture that produces a much lower permeability, in the range of 1000 to 3000. RF and power applications also use inductors and transformers to filter noise. Nickel-zinc (NiZn) ferrites have lower permeability (800 to 2000), yet operate over a wider frequency band and are commonly used to filter noise. A system implementation may use a combination of ferrite cores. For instance, a power converter may use MnZn ferrites to temporarily store energy in a transformer or inductor, while also using inductors wound on NiZn cores to filter noise.

A small raised area was initially noted on the top surface of the plastic ball grid array (BGA) package discussed here. To learn whether there were other structural anomalies deeper within the package, it was imaged by both x-ray and ultrasound. The x-ray imaging was performed first, using a Nordson-Dage Quadra 7. When traveling through a sample, the x-ray beam is locally attenuated by the density and thickness of the material through which it passes. Very dense materials such as metals may limit the thickness of the sample that can be imaged, while materials such as plastic are far less attenuating. The completed x-ray image reveals in very high-resolution local changes of attenuation over the area being imaged.

FIGURE 1 shows one corner of the BGA’s die and the attached wires. All the wires are intact here and on the rest of the BGA. All features are encased in the nearly transparent (to x-ray) mold compound. The black circular features are the solder balls under the BGA. The indistinct gray fea-ture just above the edge of the die is caused by the variable thickness of underfill material extruded from beneath the die. Within the area of this image there could be delaminations or voids – i.e., air-filled gaps – on top of the die or in the die attach material below the die, but air attenuates an x-ray beam so slightly, and the gaps are typically so thin, that these gaps would not be imaged.

Faster, better, cheaper has always been a mantra in electronics manufacturing services (EMS) because leveraging the benefits of companies selling manufacturing expertise and infrastructure has been the primary motivation behind the growth of outsourcing. Improvements in computing technology, networking infrastructure and systems interconnection now give EMS teams unprecedented real-time visibility into the product realization process. But like the guy who buys a Porsche and drives mainly on city streets, these systems are rarely tested to their full potential. Firstronic’s new product introduction (NPI) team recently needed to break that paradigm when the Covid-19 pandemic drove a new customer to request a product ramp at high speed when other supply chain options were unexpectedly shut down.

A medical device manufacturer with an infrared thermometer had production shut down in its Tijuana-based EMS supplier as a result of Baja California-mandated Covid-19 restrictions. They needed to dual source as quickly as possible since this was a critically needed product.

A field programmable gate array (FPGA) is an integrated circuit configurable by customers in the field, making such devices desirable for space and defense applications. A fortified version, known as a Radiation Hardened (RadHard) FPGA, can withstand attacks from electromagnetic and particle radiation in outer space.

Columns, rather than solder balls, are a critical subcomponent in the final assembly of FPGA packages.

A sudden shortage of mission-critical FPGA devices could result in warfighters not flying and rockets not launching. This is not an exaggeration. But how could this be? Quite simply, makers of ruggedized FPGA devices depend on a single subcontractor to provide services to attach copper-wrapped solder columns.

While productivity – manufacturing more product, more efficiently in less time – has been center stage in electronics assembly for decades, today’s razor-thin margins, coupled with the requirement for limited human intervention, have put an exclamation point on managing output proficiency. (This is especially true as the world restricts building access and maintains safe personal distances.) An optimized stencil printing process, as I’ve said many times, comes down to depositing the right volume in the right place at the right time. These are the three pillars of the print operation. Ultimately, for maximum productivity, a manufacturing operation needs a stencil printer that is always available and, when it is available, efficient and reliable.

It wasn’t long ago the bottleneck on the production line was usually the placement machine, so the stencil printer was generally available and had plenty of time to run the print routine. With recent modular approaches to manufacturing line setups, however, this is no longer the case. Placement platforms have exponentially improved speed. The printer now must maintain a much faster pace; this starts with mechanics and cycle time. In mass production settings, getting a printer down to a core cycle time of five seconds has become a necessity.

Low-temperature soldering is a subject of considerable interest and development. Several forces are driving implementation of solders with lower peak reflow temperatures than SAC 305 and its variants. The most technically significant is reduced warping of component and substrates. Chip suppliers are particularly interested in lower reflow temperatures, as thinner components are needed to meet dimensional limitations of thinner, smaller and faster devices. When a component deforms during reflow, the solder interconnect may be compromised, resulting in non-wet opens (NWO). NWO defects are difficult to detect and may not manifest until after a product is in the field. Other advantages of low-temperature soldering include the incorporation of lower-cost plastics, component and laminate materials, and reduced energy consumption and related environmental benefits.

As a practical matter, SnBi alloys are the only elements available to reduce peak reflow temperatures. Unfortunately, high-bismuth alloys have a number of disadvantages compared with the tin/silver/copper alloys currently in use. Bismuth alloys exhibit poorer mechanical and thermal fatigue performance than SAC-based materials. Minor element additions and micro-alloy elements can improve the performance of SnBi alloys, but, in general, they will retain the properties of their main constituents and lack the reliability and performance of their SAC-based relatives. Even with these limitations, SnBi alloys can be adopted for use in SMT and through-hole, but the main benefits are derived in surface-mount assemblies.

Subtle component lifting can be an issue to find during inspection. Most modern AOI systems should be able to detect drawbridging on small passive and active parts. Old systems may struggle with defects like the two shown in Figure 1.

There are many papers on lifting of parts during reflow and many suggestions on the root causes. In our experience, the most common reasons are excess solder paste, an excessively thick stencil, or poor pad design. These issues are exaggerated by fast wetting, as seen in nitrogen and vapor phase soldering. To be clear, nitrogen or vapor phase do not cause lifting; they just increase the possibility of component lift.