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Main aspects of the PCB industry – PCB Design, Manufacturing & Assembling

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In this article, you’ll get to know the fundamentals of PCB manufacturers and how our company “PNC Inc.” is unique from other manufacturers in the United States.

What are the three main aspects of the PCB industry?

According to our experience of more than 50 years as the leading PCB Company in the industry, we can easily write that three main aspects in the PCB industry for which most clients look for are:

• PCB Design
• PCB Manufacturing
• PCB Assembly

Design, Manufacturing, and assembling of PCB is a systematic method for examining the parts and components which is needed to execute. It included obtaining costs of a commodity and seeks to cut costs before actual development begins. There are specific manufacturing, design, and assembling principles required to be following during the PCB process execution of any electrical or electronics part. Eventually, a final design concludes the series with a review among the most common issues related to the PC Board or Printed Circuit Board.

Until continuous description, it is important to explain how the word ‘manufacturing design’ is used when speaking more generally and when talking more directly about PCB output. In general, design for manufacturing and assembling may lead to the simplification and optimization of a model or theoretical design in anticipation of their production. As these words are used to describe PCBs, they also imply a more straightforward study of possible production problems.

Ideal Design can Help PCB Fabrication:

The purpose of addressing the nature of manufacturing and assembling, in general, is to decide how a commodity can be produced and installed most cost-effectively. Manufacturing is to be done in a way to reduce the total cost and, more evidently, assembly design is required to be done to reduce commodity inputs, capital operating costs, and labor reduction. The emphasis is both on applying standards to lower manufacturing costs and also aim to shorten the product creation period. The fusion of these methods is often widely called manufacturing and assembly design for Mil-Spec PC Board.

Rules of PCB Manufacturer and Assembly:

After the conceptual Circuit Board Fabrication design has been developed, the company is required to research opting towards the most economical way of executing the PCB fabrication. The construction of a prototype or the development of a new version of a product could require a conceptual design. Once a conceptual design has been developed, a designer review will analyze the design’s bill of materials.

Try to use fewer parts in a design:

Reducing the number of components in PC board manufacturers is a simple aim with clear advantages. It would minimize construction costs and assembly difficulty, while not as obvious, it is of great advantage. When PCB assemblies are supplied using devices, for example, they are restricted to the number of modules they may be supported in a single port.

Being aware that if use many parts are used by pick and place machines in circuit boards fabrication will contribute to non-assembly. Cost savings are obvious. For example, if a design needs a resistance of 20K ohms, and 10K ohms resistance has been already used in the design, it might also be easier to use two 10K ohms resistors in sequence if this reduces the amount of time the computer picks and places simulation.

In the same way, you can speed assembly time up and transfer portions of the test requisites to the IC maker in search of regularly integrated circuits that can combine part of the specification into one IC. Having in mind the number and form of PCB components is perhaps the most significant move towards reducing total PCB manufacturing costs. In a term, the elimination of a component for the final design would decrease BOM costs, minimize purchase costs, production time, test time, and workload assembly feedback.

Use Original Components:

The use of composite materials will dramatically reduce construction time and expense. It goes without saying that defining a specific custom approach would significantly raise the initial cost of every product which may render a concept unfeasible. In addition, the use of more generic materials will shorten the supply chain of a commodity and mitigate supply issues. The fact that their measurements are easier checked until they are included in a PCB design specification is another advantage to prefer electronic interfaces.

Use Multifunctional Parts for Printed Circuit Design:

When an electric power part may be used for many uses in a model, the designer must take account of it. For instance, utilizing a container that can also act as hot in a design can give considerable cost control. A further definition of a dual-use mechanism through the use of a blockade as a link to ground from PCB board assembly.

Install all PCB Assembly Directions:

If practicable, all the board companies would plan all pieces to be assembled from the same side of an assembly around one axis. This is also referred to as a “Top Down” assembly in which all parts from top to bottom are placed. The use of this kind of single-sided assembly method saves time when a product is turned and rotated during assembly. As for all of the design choices, PCB design engineers would then have to consider whether producing a smaller PCB fabrication with components placed on every s sides of the board safer is compared with developing a larger PCB.

Advantages of PCB Manufacturers and Assembly:

• Fewer pieces ought to be handled and recorded.
• The expense of billing products should be minimized.
• The cost of handling can be reduced to some degree.
• Labor and input of electricity should be reduced.
• The total production period may be reduced to significantly increase manufacturing productivity.
• Lower sophistication results in greater efficiency.
• Increasingly competitive products should be.
• High Replacement margins are achieved.

The Circuit Printed Boards Manufacturers and prototype PCB manufacturers should have a simple way to reduce the next design bill. The advantages of reducing the number of designs are evident. Materials will become more viable as they are cheaper and less vulnerable to loss, however by lowering the number of materials used in the production of product costs, paperwork needs will be decreased and the work required for SMT assembly. All these factors contribute to lower manufacturing costs and encourage either better commodity or price profits at more affordable prices.

In addition, the processing period is shortened so the goods can be delivered to customers in less time. An optimal printed circuit board may be built with the right PCBA assembly considering all the above implementation of these objectives.

At PNC Inc., You’ll get your PCB done from any of the following design tools of your choice as we have an in-house facility available for all the tools.

• Cadence Allegro v16
• OrCAD Capture v16.3 & OrCAD PCB Designer v16.3
• PADS v9
• Signal Integrity Analysis: Hyperlynx

You will get the following deliverables from us:
• Gerber, drill files & PCB File
• Assembly and fabrication files
• Formal drawings on your (client) desired format

Why you should choose us & why we are better than others in the Market?

At PNC Inc., we have got the facility of executing all the design, manufacturing, and assembling in the same building. In this way, you don’t have to visit different places to check the progress of your work. You’ll get all the things done in the same building at our Nutley, New Jersey facility. That’s why we are a “one-stop-shop” and providing all the services under the same roof.

Work with PNC to Reduce PC Board Costs

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When it comes to reducing the manufacturing cost of a PCB, it is important to remember that a significant part of the cost of a PCB assembly is already baked in at the design concept stage.  The product concept defines the PCB size and shape, while the performance of the system dictates the microprocessor, memory and other functional elements of the circuit.

However, some of the assembly cost can still be affected by design choices made by the PCB designer.  A PCB that is designed for manufacturing (DFM) can reduce both the fabrication cost of the PCB and the costs of component assembly and soldering. A DFM approach to design can also reduce the likelihood of the hidden costs of poor yield in production.

The best way to achieve the lowest cost, most manufacturable design is to work closely with the prospective  manufacturer, since the way to maximize DFM cost savings is to design for a manufacturer’s specific equipment and technology, rather than to rely on general rules.

Reducing PCB Fabrication Costs

The first step to reducing costs in PCB fabrication to reduce the number of operations performed by the manufacturer.  The second step is to optimize the PCB design to leverage a manufacturer’s particular fabrication technology.

One way to reduce costs is to eliminate or minimize the amount of machining required around the board edge or within the PCB itself.  Rectilinear PCB outlines without internal slots will minimize machining, and the rectangular shape allows the PCB to be grouped in larger panels that are separated after assembly.  These large panels streamline assembly by allowing a several PCB to go through component assembly and reflow at the same time, improving throughput. For example, PNC can process a maximum panel size of 18” X 24.” To ensure that the components on the PCB are not damaged during the scoring and separation from the panel, components should be kept 200 mil from the board edge.

Reducing board layers to reduce fabrication costs

The generally accepted rule that reducing the number of PCB layers in a stack-up will reduce cost has become more complicated with the advent of HDI technology.   The reason is that the cost of an additional Printed Circuit Board layer is not linear, so a cost calculation needs to be made for each jump in the number of layers. Is it cheaper to use finer trace widths and buried vias to reduce the layer count from six to four?  Only the manufacturer is going to know.  However, as a board gets past eight layers costs increase non-linearly with each additional layer.  The aspect ratio of the through hole vias begin to become a factor, as well as the sheer number of vias that need to be drilled and plated to connect all those layers.   At an eight layer stack up or above, the additional cost of HDI technology begins to make economic sense if it is used to reduce the number of stack-up layers required.

Respect drill to copper clearance and aspect ratio design rules

Respect the design rules for hole sizes and hole to copper clearance.  If the real estate on the PCB allows it, selecting hole sizes clearances and annular ring sizes larger than the absolute minimum will improve fabrication yield. Here are the through hole design rules for PNC:

Non-Plated Through Hole (NPTH)
● Finished hole size (minimum)= 0.006″
● Edge to edge clearance (from any other surface element) (minimum)= 0.005″
Plated Through Hole (PTH)
● Finished hole size (Minimum) = 0.004″
● Annular ring size (Minimum)= 0.004”
● Edge to edge clearance (from any other surface element) (minimum) = 0.009″

PCB assembly
PCB assembly

Reducing PCB Assembly Costs

To reduce assembly costs the objective is the same as reducing PCB fabrication costs; reduce the number of operations, and optimize the PCB design to leverage a manufacturer’s particular fabrication technology.

One easy way to reduce assembly costs is to stay away from the smallest passive packages.  0603 passives are easier to place than 0402 or the almost invisible 0201.  If possible, chose active parts that have leads rather than ball grids, because they are easier to place, they can be visually inspected instead of x-rayed, and they are easier to rework.

Avoid parts that have to be manually soldered.

Manual operations are always expensive, and the designer should do everything they can to avoid the need for them.

Component manufacturers have recognized this and now offer through-hole components (typically connectors) that can be reflow soldered.  This technology called “Through-Hole Reflow” allows through-hole components to be soldered in the same reflow process as the SMD components, eliminating a pass through the wave soldering machine or manual soldering.

Finally, if possible, avoid putting components on both sides of the board.  The cost of a higher density PCB with components on one side may be cheaper than a lower density PCB with components on both sides.

Don’t wait until the PCB design is finished before talking with PNC

The best time to talk with the PC Board design experts at PNC is early in the layout process.  They can tell you when to use HDI to reduce costs and can advise on how to optimize panel size. The experts in the assembly department can also work with you to select components that will reduce assembly costs and increase yield.

Give PNC a call today.

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

Beyond PCB Assembly Services, Board Support Package Development

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What is a Board Support Package?

A board support package (BSP) is a collection of essential low level software applications configured for a specific microprocessor and its associated hardware. It supplies the drivers for all the hardware in the system andcontainsa bootloader to initialize the microprocessor and hardware prior to loading the operating system. The package may contain additional low level software to assist the developer in initializing the operating system. The BSP can also include a root file system, and a utility to configure the microprocessor and other hardware.By using PNC to develop the BSP, it will allow them to design around their circuit board fabrication capabilities and process.

Board Support Packages are specific to a family of microprocessors and to a specific operating system.  A typical BSP may contain drivers and initialization code for:

  • Initializing the microprocessor
  • The parallel and serial buses
  • The volatile and nonvolatile memory
  • The display and graphics card,
  • Digital and analog I/O
  • Camera, wireless modules, user input devices etc.

While a BSP for the hardware is the first requirement for developing a product with embedded software, this doesn’t mean that every company developing embedded software needs to develop their own BSP with the drivers for their specific hardware configuration. There are five reasons to let an outside BSP developer like PNC develop the BSP for your embedded application.

1. The BSP supplied by the microprocessor manufacture is an incomplete solution

The microprocessor manufacturer will typically supply a rudimentary BSP with their evaluation board.   This is because manufacturers know that making it easier for the developer to work with the microprocessor is helpful to being selected for the final design and pcb assembly process.   However, the manufacturer’s BSP may not have the drivers for the specific hardware in your design – the only way to ensure a BSP fully supports your hardware design is to have it customized for you.

2. Developing device drivers is a specialized skill

Developing the drivers and initialization code BSP requires detailed knowledge of the microprocessor and its peripheral hardware.  Most developers writing applications running on an OS do not have the requisite expertise to write the hardware driversunderneath that OS.  On the other hand, a group focused only on BSP development like the team at PNC obtains that expertise by working with many hardware platforms every year, and by developing robust tested reference code for common peripherals such as displays and USB ports.

3. A BSP is needed only once for a product

A BSP is needed near the beginning of an embedded software product to allow the developers to work with the target hardware instead of an evaluation PC board or emulation software. Once all drivers are debugged, however, the BSP rarely needs to be touched again except for occasional updates to address hardware end-of-life issues.  This is different than the product’s application, which may see multiple releases over the life of the product.  Since BSP updates are so infrequent it does not make sense for an organization to maintain that highly specialized expertise for the months or years between BSP updates.

4. The BSP and associated drivers are invisible to the customer

Application software that meets customer needs is a close collaboration between developers, product management, marketing, and sales.  Any time spent by the in-house team developing a BSP is time not spent developing features the customer will see and use.  Outsourcing the invisible aspects of the product like the BSP allows the development team to stay focused on the customer.

5. Outsourcing the BSP can accelerate product development

Handing off the BSP to an outside supplier like PNC means that the team’s developers are not tied down developing it internally.  The BSP supplier can develop the BSP incrementally starting with core functionality followed by drivers for some of the less critical hardware once the development team is ready for it.  The outside supplier also brings deep expertise to the driver development, meaning driver development takes less time, and works the first time. The most beneficial reason for PNC to develop your BSP is that they can also fabricate PCB’s as well having in house pcb assembly services.

Talk to the software team at PNC the next time you have a time critical embedded project.  Let PNC help you with your Board Support Package, device drivers, operating systems porting, or protocol stacks development.

PCB Design, Selecting the Right PCB Trace Widths?

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Every PCB designer has a series of decisions to make PCB Design as they translate an abstract schematic into a functional, reliable, and manufacturable PCB assembly. Placing the components on the    PCB is usually the first step, connecting those components with copper conductors to create the circuit is the next.  To connect the components, the layout designer must interpret the circuit netlist and turn that netlist into actual copper traces, subject to constraints of both manufacturing technology and the laws of physics.  One of the most important considerations for the designer is the appropriate trace width for each of those connections. The width of each trace determines both the real-world performance of the circuit and the overall size and number of layers of the PCB.

To balance circuit performance and PCB size, the designer needs to balance four considerations:

  • The manufacturer’s minimum trace width and spacing
  • The size and pitch of the component pads that the trace will connect
  • The amount of current flowing through the trace
  • Whether the trace is part of a controlled impedance circuit

Minimum Trace Width and Spacing

The manufacturer’s minimum trace width and trace spacing will define the smallest trace width that can be used for all signal traces that do not carry significant current or have impedance constraints.  The minimum trace width is typically used as the default for the layout, since using the minimum trace width will result in the smallest possible PCB and the most flexibility in routing.

For a standard Printed Circuit Board, fabrication minimum trace widths/spacing is typically 5 mil (.127mm). PNC’s High Density Interconnect (HDI) PCB trace width/spacing can be as narrow as 3 mils (.076mm)

Trace Width vs Pad Width

Another consideration when selecting trace widths is that the trace should be smaller or equal to the pad width. For the most part, if working with the minimum trace widths, this will not be an issue, however, care must be taken when laying out the traces and pads for high current applications.

High Current Traces

Once a designer has placed the components in the layout, they will often focus next on creating the power and ground traces to the active components.  This is because the current carrying traces need to be appropriately sized and routed.   Signal traces, which are typically at the minimum trace width, can be more easily routed around the larger power traces.

Copper PCB traces, like any conductor, have an internal resistance that is proportional to the conductor length, and inversely proportional to its cross-sectional area. Since the copper on a layer is of a uniform thickness, the width of the trace determines its cross-sectional area.  There will be both a voltage drop along the trace as well as heating of the trace due to the power dissipation.  If a PC Board trace is not sized appropriately to carry the current required by the circuit, the trace can fail due to overheating, or the high voltage drop along the trace can cause intermittent circuit problems as the current and thus the voltage drop in the trace varies over time.

Designers often create an internal copperlayer with multiple buses of various voltages.  Since that layer consists only of power busses, the buses can be quite wide.  The designer will then connect the individual components to the bus using vias rising to the component’s power pins.  A bus based design reduces voltage drop at far from the power supply while reducing the width of the short connector trace to the same size as the component pin pad.

In the days before the internet and sophisticated PCB layout software,  designers would use the pages of current vs trace width tables  in IPC 2152 “Standard for Determining Current Carrying Capacity in Printed Board Design”  Now there are online calculators  based on those tables that take in to consideration all of the factors involved in determining the appropriate trace width for a specific current and allowable temperature rise of the trace due to the power dissipation. Many full featured Printed Circuit Board layout applications have the calculations embedded in their design rules.

If a PCB is intended for high power applications such as motor control or an LED power supply, a copper layer thicker than the typical 1 oz can be used but note that it is difficult to etch fine traces and pads in thicker copper.  Make sure to check with the PCB fabricator about their capabilities. PNC has experience with thick copper layers and can provide advice to the designer about what is possible.

Controlling Trace Impedance

The last consideration in selecting trace widths is the impedance of the trace, which becomes a factor in high frequency signals such asDDR busses, video such as HDMI, and high speed serial communication like USB and Gigabit Ethernet. At these high frequencies, not only the trace resistance, but the capacitance and inductance of the trace become significant factors.

Designing controlled impedance (CI) circuits is beyond the scope of this post, because designing a controlled impedance circuit requires taking into account the dielectric constant of the PCB, the length and routing of the trace in addition to the width of the trace.  However, trace width is one of the most easily controlled elements of impedance controlled circuits,so the trace width on individual controlled impedance circuits may be different from the width of other low frequency signal traces, and those traces may be finetuned after the prototype PCBs are tested.

The design of controlled impedance circuits is described in detail in IPC-2141A “Design Guide for High-Speed Controlled Impedance Circuit Boards”, and many of the formulas are available in online calculators or as options in PCB layout applications. When designing high speed circuits, it also pays to work with a PCB manufacturer like PNC that has expertise in fabricating PCBs with precise and consistent dielectric properties.

Schedule a Design Review with your PCBA manufacturer

 The designers at PNC have experience with both high power and high-frequency RF and microwave PCB layout designs.  Because they work closely with the manufacturing team, they know what is possible to achieve with the thick copper layers used in today’s compact LED and motor controllers,  and they know what it takes to maintain consistent dielectric properties in the substrates, needed for predictable RF performance. Let them help you with your design.