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Embedded software development along with PCB Assembly

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No company can excel at every aspect of new product development and trying to do everything can dilute an organization’s focus on the tasks that are essential to its success. For example, most companies have long ago outsourced the PCB design and fabrication steps of new product development. This same need to focus on the essential is true of software development too. It is difficult for a software company to excel at every type of software development because of the ever expanding universe of software languages, operating systems, and architectures.  A cloud based SAAS or PC based application is very different from embedded software running C on a 16-bit processor, and it takes very different software development skills to develop that kind of embedded application.

Unlike cloud based or PC based applications, embedded software is optimized to run on a specific custom hardware platform with limited processing power and memory.  It often runs on a real time operating system or no operating systems at all, and the interface of an embedded device may consist of only a small display, or just a few buttons and LEDs.

The unique challenges working with embedded systems is why many software companies outsource their embedded software projects to experts like PNC.  Here are three reasons why they do.

The embedded system is not the organization’s primary product line.

Many products on the market require options or accessories that are important to the customer, but not are not similar technically to the primary product. A cable set top box remote is a good example.  Customers expect a cable set-top box to have a remote, but the low power microcontroller embedded in the remote is likely to be completely different from the high power processor and OS driving the set-top box functions.  Similarly, Industrial or commercial equipment may have optional modules to provide additional functionality like a cellular modem.   These optional modules have independent processors and embedded software which is unrelated to the primary product software.

In these cases, software companies will choose to focus their development resources on the primary product, recognizing that it is more cost effective to outsource the software development for the ancillary embedded products to a company that is familiar with embedded microcontrollers and the constraints that come with low power operation. If that company can design the hardware and perform SMT assembly too, it becomes an even better value.

Embedded software development along with PCB Assembly
Embedded software development along with PCB Assembly

The software is deeply embedded and invisible to the user

Successful software companies are highly focused on the customer experience with their product. They are constantly refining the look and feel of the industrial design and user interface to make the product more attractive, and easier to use.  But what if the product doesn’t have a user interface?   What if it is a router or a motor controller?  Products like these need a simple interface for initial configuration, but they typically operate in the background, invisible to the customer.  In this case the goal is to optimize for cost and performance rather than user experience.  Deeply embedded applications without a sophisticated customer facing interface  are ideal to outsource to a company like PNC because the product requirements are centered on the embedded functionality – there is no need to maintain the same look and feel as the company’s customer facing products.

The application requires specialized expertise

 Sometimes a software company needs embedded expertise that it just doesn’t have in-house.  For example, they may need a Zigbee or Bluetooth RF stack, or expertise with digital signal processing on low power Digital Signal Processors DSP.  In some challenging embedded applications, a company may need a partner with the expertise to  iterate the design of both the hardware and software simultaneously to arrive at an optimized embedded solution.  In that case you need a full service provider like PNC.

PNC offers the full solution to developing embedded products

When it comes to product development, PNC is not just a PCB manufacturer.  The engineers at PNC can work with you to design and manufacture the product hardware, and then develop the embedded software to run on that hardware.   If you have a challenging embedded software or hardware project, contact PNC today and find out how they can help.

Minimizing Crosstalk in PC Board Layout

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In this ongoing series on PCB layout from the design team at PNC, previous posts have looked at some of the initial steps to turn a circuit schematic into a manufacturable, reliable PCB. These posts have looked at  component placement, selecting appropriate trace widths, and BGA routing.   In this post we are going to take a deeper dive into methods for reducing crosstalk in the PCB design. After the power and ground have been routed, the next task is to route high speed signal traces, and the traces that could either generate or receive crosstalk.

 What is Crosstalk?

Crosstalk occurs when the signal on an aggressor trace on a PCB appears on a nearby victim trace, due to capacitive and inductive coupling between the two traces.  Typical aggressor signal traces are:

● High speed digital signals, especially clock signals
● Noise from switching power suppliers
● High frequency RF.

Victim signal traces, on the other hand, carry high impedance signals like op amp input lines or reset lines, or low impedance signals with long loops.   Low amplitude signals such as a sensitive analog measuring circuit traces are also susceptible.

Crosstalk occurs when aggressor trace and victim trace are close together and run in parallel for a distance.  The aggressor and victim(s) can be side to side on the same layer or on top of each other on adjacent signal layers. Coupling between traces on adjacent layers separated by just a thin section of laminate is called broadside coupling.

Minimizing Crosstalk in PC Board Layout
Minimizing Crosstalk in PC Board Layout

 

 

 

 

 

Printed Circuit Board Design guidelines to reduce crosstalk

There are several design rules to reduce crosstalk between signal traces.  Before applying these rules, the first step is to use the general guidelines described above to identify and flag any potential aggressor signal traces and their potential victims.

Since crosstalk occurs between two traces running in parallel, try to reduce the distance that the aggressor and victim traces run in parallel. Unfortunately, this may be difficult if the signals originate and terminate from the same locations.  To minimize broadside coupling try to orient the signal traces east-west on one layer and north-south on the second layer.

It is essential to have a broad contiguous ground plane directly under (or over) the signal layer.  A ground plane located between two signal layers can prevent broadside coupling. However, make sure that ground planes located on adjacent layers but not electrically connected do not overlap.  The overlapping ground planes separated by a dielectric form a capacitor, which can transmit noise from one ground plane to the other. This can defeat the purpose of separate ground planes if they were created to isolate the noisy elements of a circuit from the noise sensitive ones.

Increasing trce spacing

The most effective method of reducing crosstalk is to increase the spacing between the aggressor signal trace and the potential victim traces.  Like all electromagnetic radiation, electrical or magnetic coupling between the two traces drops with the square of the distance between them.  The amount of spacing required between the traces is dependent on the height of the traces above the ground plane.   The formula defining this relationship is from Douglas Brooks “Crosstalk Coupling: Single-Ended vs. Differential”   The coupling between two traces is proportional to:

Where S is the spacing between traces, and H is the distance from the trace to the ground plane.  Once H is defined by the lamination stack-up, the relative change in coupling can be easily plotted as a function of S.  Douglas Brooks looks in detail at the coupling between traces under several scenarios.  For those looking for some general guidance, a spacing of 5H is considered conservative.  The PC Board design team at PNC can assist designing a PCB stack up that will minimize the spacing needed between coupled traces, ensuring that crosstalk is minimized while maintaining routing density.

Finally, for very high speed digital signal traces, consider the use of differential pairs.  For many designers, the most common applications for a differential pair is for a high speed serial bus like USB, SATA, or HDMI.  The design rules for the layout of differential traces is beyond the scope of this post.

The most important part of reducing crosstalk in your PCB design is to first recognize in which signal traces crosstalk is likely to occur, then follow the guidelines above to minimize it.  PNC’s Printed Circuit Board designers have experience with high speed digital and RF circuits and can help you select the correct PCB layer stack-up and review your designs for areas where crosstalk is likely and suggest ways to minimize it. Request a design review from PNC today

What’s a HDI Printed Circuit Board?

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HDI stands for High Density Interconnect. HDI PCBs have finer traces and trace spacing, laser drilled micro vias and higher connection pad density. Its two chief advantages are that it permits the use of fine pitch BGAs and it reduces the number of PCB layers required because the finer traces and smaller vias allow more circuitry in a smaller area.

Narrow trace widths mean higher circuit density

At PNC standard PC Board fabrication uses a minimum trace width of 5 mil, with a 5 mil space between traces (5/5mil) PNC’s HDI trace widths can be as narrow as 3 mil with 3 mil spacing.  These finer traces allow 160% more traces in the same real estate. 3/3mil spacing will also allow two traces to escape between pads of a standard BGA, meaning less PCB layers are needed to fan out the pins from the BGA.

Microvias are the enabling technology for HDI

Narrow trace widths used in HDI PC Board are a result of the gradual refinement of photolithography and etching technology.  Microvias on the other hand, are a revolutionary innovation driven by the development of high powered lasers that can be controlled accurately enough to ablate a 3 mil hole through the surface layer of copper and underlying laminate, without damaging the underlying layer of copper.

The minimum hole size for PNC’s laser drilled microvias are 3 mil and the minimum pad diameter for the microvia is 7 mil.  Pads for laser drilled holes can be smaller than for mechanically drilled holes because of the location accuracy of the laser drilled hole.  There is no mechanical deflection of the drill bit to account for.  The laser drilled holes can be fully copper filled and planarized flat, so they can be used as pads for fine pitched BGAs with 0.4mm or smaller spacing. Using microvias as pads allows the signal trace to fan out by going straight down and out to an inner layer of the printed circuit board.

The biggest limitation with microvias is the aspect ratio of the holes.  Where a drilled through hole can have a 10:1 depth to diameter aspect ratio, a laser drill can achieve no more than around a 1:1 aspect ratio.  This means that the smallest microvia can only connect two adjacent copper layers. A larger diameter microvia can penetrate two layers. To connect deeper layers, the designer must stack vias one directly atop another.

Laser drilling of the microvias changes the way PCBs are fabricated and gives the designer flexibility that they do not have with through hole vias.  In a standard drilled PCB, via holes are drilled and plated after the PCB fabrication stack-up is completed.  Because the microvias can only bridge two or three copper layers, the microvias must be drilled and plated at each lamination step.  This means that microvias can be fully buried between layers, stacked or staggered to allow the microvia to connect multiple layers of the stack up.

The major space saving advantage of the microvia technology is that vias can just connect traces that need to be connected, rather than taking up real estate all the way through the PCB the way a through hole via does.

The Printed Circuit Board designers at PNC take advantage of this by locating the power and ground layers at the top of the stack up.  Since all active components access power and ground, sometimes through multiple pins, having the power and ground layers directly below the component layer allows all those connections to be made directly by microvias.  This leaves the component layers and layers beneath the power and ground layers completely unobstructed for signal routing. This has the added advantage of reducing parasitic capacitance because it eliminates the circuit stubs caused by plated through holes.

Two sided boards are typically fabricated with a combination of through holes and microvias.   Though holes can be drilled just through the core, connecting the stacks on the top and bottom of the board from the lowest layer, or through holes can be drilled through the entire stack directly connecting the traces on the top and bottom component layers.

 

HDI PCBs are a necessity when using fine pitched BGAs, but they can also reduce cost on PCBs without fine pitched BGAs because of the reduced layer count.  On your next PCB design, talk to the experts at PNC.  They can help you determine if HDI technology is can reduce your PCB cost by reducing layer count and shrinking the PCB size.

TOTAL-CONCEPT

Total Concept Company

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PNC’s expertise in design, manufacturing printed circuit boards, PCB assembly, and Box builds in one 70,000 sq./ft. facility makes us the ultimate total concept company. PNC’s unique manufacturing facility is just that, a PCB assembly usa manufacturer located in Nutley, New Jersey. PNC has been a vital supplier of electronics in the PCB industry for over 50 years and serves the military/defense, medical, aerospace, automotive, RF/Microwave, industrial and consumer sectors. Having these capabilities all in-house stream lines the turnkey process under one PO which is invaluable to our customers.

ELECTRONIC DESIGN

Being able to design in-house has its importance when designing for PCB manufacturing as well as prototype pcb assembly and production PCB assembly. Our designers have an edge in designing for PCB manufacturing since they are knowledgeable of the PCB manufacturing process. Designing for manufacturability eliminates defects, delays and process issues. Our design tools used are Cadence Allegro, OrCAD Capture, OrCAD PCB Designer and PADS. Our deliverables are Gerber, drill files, PCB File, schematics, Assembly and fabrication files and Formal drawings on customer format.

Having the capability to manufacture printed circuit boards, pcb contract manufacturing, in the same facility also has its benefits for prototype pcb assembly and production PCB assembly. While the printed circuit boards are in process of being fabricated, our pcb assembly division can work in parallel creating pick & place data, SMT Stencils, work instructions, AOI programing, selective soldering programming, and pre-pare testing procedures to expedite the PCB’s once the hit the SMT assembly floor. The work in parallel process makes for an efficient seamless transition from PCB manufacturing to Assembly.

TOTAL-CONCEPT-PCB
TOTAL-CONCEPT-PCB

After the PCB’s clear final inspection, they are transferred to the PCB assembly department. For a pcb assembly manufacturer in a total concept configuration, logistically you gain 1-2 days shipping time, since you do not have to outsource the PCB’s as well as a time savings of not have to perform an incoming inspection. PNC’s Assembly division is comprised of multiple high speed SMT lines with 13 zone re-flow ovens, 3d AOI, 3D X-ray, thru-hole stations, selective soldering, and rework stations. If required, PNC can perform Flying probe, ICT and functional testing to ensure a robust and error free PCBA.

Another SMT assembly service with-in our total concept company is box building. The PCB assembly never leaves the facility eliminating any ESD issues from incoming inspection handling. Our expertise in box building varies from small plastic snap together housing, medium sized metal enclosures to rack builds. If provided with a system test procedure, PNC testing engineers and technicians can perform the functional and burn in testing. When looking for total concept printed circuit assembly companies, we are here to help.

pcb manufactuter USA

Let PNC Simplify Your Printed Circuit Board Design With, CPLDs

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New product designs continue to get more compact, while the performance and the number of features that customers expect continue to increase. To the engineer, this means higher PCB circuit densities and less room on the PCB for just-in-case design, such as unallocated I/O, or 0 ohm resistor networks to allow for reconfiguration of the PCBs at PCB assembly.

Meanwhile, new product prototype cycles are also getting faster. 3D printed mechanical parts are available within hours, putting pressure on electrical engineers to work faster and get their PCB designs right the first time. Even the fastest PCB fabrication, such as PNC’s 24-hour fabrication turn-time can’t help if the PCB has to be redesigned to fix errors.

The answer to both problems may be the CPLD. PNC’s CPLD programmers can help engineers reduce PCB size and allow on the fly circuit reconfiguration. Most people know that PNC specializes in fast PCB prototyping, but PNC is more than aPCB Manufacturer, PNC can speed prototyping by designing PCBs that replace inflexible circuit designs with PCBS that can be reconfigured to remap I/Os or change the order that circuit elements power up. A CPLD design developed by PNC can also allow the same PCB to be reconfigured to be used for the next generation product.

When it comes to programmable circuit elements, FPGA and microprocessors get all the good press. They are powerful, versatile, and generate more revenue for the manufacturers than workhorses such as CPLDS. Even though CPLD capability has improved dramatically over years, while both cost and power consumption have dropped, they are still often considered only for low level tasks such as “Glue Logic.” PNC designers can tell you that even a CPLD used for “low level” glue logic is appreciated when a late breaking design change means that two outputs now need to be two inputs, and one input needs to be inverted. All in a day’s work for PNC.

A PC Board Manufacturer, such as PNC can help you use these new, more capable CPLDs in places that can solve tough problems, replacing more expensive, complex and power-hungry solutions. Here are four examples.

I/O expansion

One of the most common CPLD applications is to expand the number of available microprocessor I/O ports. The CPLD I/O can either be multiplexed to the microprocessor or controlled via a serial interface. The advantage of a serial bus interface is that it allows you to locate this extra I/O anywhere, even on another Printed Circuit Board through a compact two or three pin connector.

The CPLD combinational logic architecture allows the creation of either a big fan-in or fan-out (over a hundred ports in some cases), and the outputs have enough current to drive small LEDS, a great way to create an array of circuit status LEDS.

When the CPLD output is used in conjunction with a CPLD’s internal clock the CPLD can also drive multiple PWM outputs allowing it to control things such as LED brightness, cooling fan speed, and simple sound producing devices.

The CPLD’s architecture gives it another useful capability for I/O expansion, the ability to accept inputs and drive outputs at different voltages. This multi voltage capability is often utilized for another common application; the communication bridge.

Bridges

CPLDs are often used as a bridge between one or more bus protocols, potentially at different voltages. They can support

  • serial to serial
  • serial to parallel,
  • parallel to parallel

They can even be used to drive an LCD. Because of their simple architecture, they have a low pin delay, making high speed synchronization possible.

Power Management

Another one of CPLD’s features is that they retain their programming and will boot within 500 µs. This means that the CPLD is the first programmable element to wake up on power up, so that it is awake and ready to manage the power up of power supplies and programmable devices ensuring they start in the right order.

Safety Systems

Because of the CPLDs simple architecture and 100% deterministic behavior CPLDs are often used in safety critical systems. One example application is to monitor interlocks, ensuring that the system is in a safe condition before the system can begin operation.

CPLDs pack a lot of capabilities into a compact package, they can reduce PCB complexity and allow reconfiguration on the fly. If you have never considered a CPLD in your design, the designers at PNC can help you with the CPLD circuit design, CPLD programming and Circuit board fabrication. Talk to PNC today.