What are the standards for EMI and EMC for PCB design? How to meet them?

By | Date posted: | Last updated: June 30, 2022
EMI EMC Standards for PCB Design

What are EMI and EMC in a PCB?

EMC or Electromagnetic compatibility refers to the ability of the electronic system to operate within an electromagnetic environment without generating EMI or Electromagnetic Interference. EMC ensures that the system performs as intended within defined safety measures.

EMI refers to Electromagnetic Interference or disturbance where when energy is transmitted from one electronic device to another, it corrupts the signal quality and causes malfunctioning of the device.

It is therefore vital to control EMI, a task that can be done in the early stages of the PCB design. In order that your board designing is EMC friendly, a fair amount of importance needs to be given to aspects such as component selection, circuit design as well as PCB layout design. It is when your product passes the necessary EMI/EMC standards that it can be market ready.

EMC/EMI Standards for PCB Design

When it comes to EMC standards there are two broad categories of standards to meet:

  • Regulatory Standards
  • Industry Standards

Regulatory standards differ from region to region. Early EMC standards were established by the US Federal Communications Commission. The European community, later laid down its own EMC standards which are today known as the EMC Directive.

Industry standards on the other hand as their name suggests are industry-specific. That way they ensure uniformity as well as interoperability. The US Military, for example, has its own set of stringent MIL-STD EMC requirements.

Broad requirements for complying with EMC standards

In order to comply with EMC standards designers, need to look at the following aspects:

  • You need to design for EMI immunity. This largely means paying attention to the right stackup & routing strategy.
  • The design needs to ensure that the device emits minimum radiation. For his factors such as layer stack, component placement, grounding strategy, and more play a role.
  • The device also needs to suppress conducted EMI which can take several forms such as switching noise from SMPS regulators, coupled common-mode noise, and more.
  • Fast transients or power fluctuations need to be taken care of. These can appear as voltage dropouts, power spikes or more. Such requirements are particularly applicable on designs with short cables or AC inputs
  • In order to comply with EMC standards, the design also needs to withstand surges & ESD.

Here are some effective strategies that help pass the EMC standard tests:

Stackup, Power, and Grounding

If the board is designed with a low inductance ground system, it tends to minimize EMI. In case of multilayer boards placing a ground plane below the signal layers minimizes loop inductance.

It is also a good idea to route signals on an interior layer. Placing traces between two ground planes & then placing the power plane below the bottom-most ground plane is of help. Placing the power plane close to the ground plane ensures capacitive coupling.

Tight coupling needs to be maintained when routing signals from an interior layer to the surface.

Shielding

Careful use of shielding is yet another method of follow. The easiest method to follow is to use grounded shielding that forms a Faraday cage around sensitive components & traces. However this may not be possible in all designs. A grounded via fence around the edge of the board & via stitching on copper pour regions can also offer protection.

Some common types of shielding for suppressing radiated EMI include:

  • Shielding Can
  • Conductive foam
  • Wire mesh material
  • Metallic tapes
  • Conformal coatings
  • Ferrites

Differential Pairs

Use of differential protocols to route the signals where possible is preferable. Differential pairs can produce some EMI & can lead to crosstalk however this is strong only when it is very close to the pair. A differential pair will produce less intense EMI as opposed to a single-ended interconnect.

Mixed-signal Layout and Routing

It works well to separate digital, low frequency analog and RF analog sections of the board. These sections in fact need to have their own dedicated areas in the ground layer. While you need to prevent interference between different board sections you also need to ensure that signals do not have loop inductances.

Bypass/Decoupling Capacitors on the Power Bus

Use of bypass/decoupling capacitors between the power pin of an active component & a grounded via, is advised. This ensures that the residual noise is passed to the ground.

It is important that the right tools as well as the right expertise be available to design PCBs so that they adhere to EMI/EMC standards. The right PCB assembly partner can create a compliant layout as also undertake any rework.

At Technotronix, we are fully equipped to handle your PCB manufacturing requirements. With state-of-the-art equipment, we deliver the highest quality boards that you can rely on. No matter how complex your requirement, you can count on us to deliver to your bespoke needs. If you have any requirements regarding PCB manufacturing or need urgent assistance, contact us at sales@technotronix.us or call us on 714/630-9200.

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What is PCB environmental testing? Why does it require in PCB manufacturing?

By | Date posted: | Last updated: June 27, 2022
PCB environmental testing

With PCB contamination on the rise especially in certain geographic locations, the need for PCB environmental testing is also increasing. Essentially if your PCB has to operate in harsh environmental conditions, it is imperative to test the PCB assembly under those conditions so that you can be sure of their performance & efficacy. It is a specialized process that requires you to go with an expert manufacturer who has the necessary expertise to conduct these tests. The tests also require specialized equipment; in choosing the contract manufacturer, therefore, this aspect needs to be kept in mind. PCB environmental testing is particularly recommended in some mission critical industries such as military and defense.

Types of PCB environmental testing

Typically, when you think of environmental tests you tend to think of testing the boards under high temperature & humidity alone. However, there are a wide variety of PCB environmental tests and protection ways that include shock, vibration as well as mechanical tests. These tests need to adhere to the IEC 60068 environmental testing standards.

There are also few tests which are known as Highly Accelerated Tests including:

  • Highly Accelerated Life test or HALT
  • Highly Accelerated Stress Screen or HASS

These tests assess the reliability of products in controlled environments. Essentially the aim is to simulate the conditions and ensure that the product does not fail under them. Typically, environmental tests are performed in a small environmental chamber.

Sometimes though product engineers are wary of accepting HALT/HASS test results as they feel that the stresses placed on the system may be more than what is found in the actual environment. However, the disadvantage of ignoring these test results is that you can encounter product failure at a later date on account of these same reasons.

PCB Test for humidity & corrosion

A water absorption test is an important aspect of environmental testing as the PCB may often be deployed in an environment that is humid. For such a test the PCB is put in an environmental chamber with controlled humidity, The weight of the PCB before putting it in the chamber, and after, is taken. Any change in the boards weight is on account of the water that has been absorbed by the PCB. It is also important to see that the exposed conductors do not corrode. Corrosion is the exact reason why copper is normally plated with an alloy that is oxidation resistant.

Thermal Shock and Cycling

A thermal test is an extremely important test & involves simulating the operating temperature under which the PCB must work. The testing involves changing the board temperature and seeing how the expansion and contraction affect the reliability of the board. An extended form of thermal testing is thermal shock testing in which the board is rapidly subject to two extremes of temperatures. While the low temperature is below freezing; the high temperature is typically above the glass transition temperature for the substrate. The board, therefore, expands or contracts accordingly. During expansion high stress is placed on the conductors & the solder point. The mechanical failure points can thus be easily identified & any such areas can be addressed in advance so that you do not have to deal with costly errors later.

To sum up

While not all PCB assemblies need environmental testing, it is a prerequisite for those which are used in extreme environmental conditions where temperature, humidity, shocks, and more are primary risks that can affect the working of the PCB. Therefore, It is important that; working conditions are simulated and the PCB testing is robust.

The other important thing to note is that environmental testing requires specialized expertise as well as equipment. Hence the right contract manufacturer who has the necessary skills needs to be chosen. Sometimes there is the fear that environmental assemblies can affect PCB appearance. However, this fear is unfounded as your professional contract electronics manufacturing partner can offer a reliable cleaning process post the simulation. It is also important to check if the contract manufacturer offers batch-testing or offers environmental testing on all boards bases.

Done correctly, environmental testing can ensure product reliability, like little else.

Technotronix is an ISO 9001:2015 certified company who delivers one-stop PCB manufacturing services with specialized support, reliable testing, and multi-functional features. Our consistent quality and quick turnaround time captivate us with our customers, who look on us as a one-stop-shop for all their PCB requirements. If you have any requirements regarding PCB manufacturing or need urgent assistance, contact us at sales@technotronix.us or call us on 714/630-9200.

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How do the unique features of Polyimide PCBs make them beneficial for certain industrial applications?

By | Date posted: | Last updated: June 14, 2022
Polyimide PCBs

When it comes to PCBs, there are a whole lot of PCB materials that are used to make these PCBs depending of course upon the application and the environment in which it will be used. Some of the popular materials include:

  • Epoxy Resins
  • FR4
  • Polyimide
  • Teflon

What really is Polyimide?

Polyimide is a high-performing polymer, which is made up of imide monomers. Polyimide occurs naturally and can also be manufactured synthetically. Polyimides are broadly of three types:

  • Aliphatic
  • Semi-aromatic
  • Aromatic compounds

The most common way of production of polyimides is through a reaction between dianhydride and diamine.

Polyimides are known for their heat and electrical resistance as well as their high mechanical strength. They are ideal for use in flex and flex/rigid circuit boards.

Beneficial Features of Polyimide PCBs

Below are some features of polyimide that make them extremely useful in certain PCB applications:

Durability

On account of high resistance to physical stress, Polyimide PCBs are extremely durable. They retain their shapes even in extremely harsh environments.

Thermal Stability

Polyimide PCBs can withstand a wide range of temperatures. In fact they are known to support operations with temperatures up to 260℃.

The other advantage with them is that they can resist any thermal damage during production or repair.

Flexibility

Known for their extreme flexibility, they are suited for use in rigid-flex as well as flexible printed circuit boards.

Resistance to chemicals

Polyimides are also known for their chemical stability. If they are exposed to corrosive materials, they do not show any adverse effects. In applications where the PCBs are likely to be exposed to chemicals, Polyimide works best.

Tensile strength

Known for its tensile strength, polyimide PCBs can support high load without any fracture. Also, when it comes to warping, Polyimide PCBs are resilient. They are therefore widely used in applications where physical strength and durability are a must have.

Some of the other important features of Polyimide PCBs include:

  • They have an arc resistance of almost 143 seconds.
  • Ehen it comes to integration & mounting of components, it is far easier with Polyimide PCBs than FR4.
  • They act as natural adhesives and even at high temperatures are know for their bond strength.
  • They are known for their tight tolerances.
  • They can be made moisture resistant using oligomeric dianiline.
  • They have a specific gravity of up to 1.6 g/cm cube.
  • At 1GHz, they have a dielectric constant of 4.2.

Difference between Polyimide PCB & FR4 PCB

Some of the differences between Polyimide & FR4 PCBs include:

  • While Polyimide PCBs are highly resistant to chemicals, FR4 PCBs are moderately resistant.
  • The tensile strength of Polyamide PCBs is 231MPa, that of FR4 PCBs is 70 MPa.
  • Polyimide PCBs show higher thermal cycling than FR4.
  • In terms of durability, Polyimide PCBs are far more durable than FR4 ones
  • Polyimide PCBs can operate in temperature ranges of -200 to 300 degrees Centigrade. The corresponding range for FR4 PCBs is -50 to 110 degree Centigrade.
  • Polyimide PCBs have a Glass Transient Temperature range of 195 to 220 degrees centigrade. For FR4 PCBs it is 135 degrees Centigrade.

Polyimide PCB Applications

Little surprise then that Polyimide PCBs are used in a wide variety of PCB industrial solutions, including but not limited to:

Medical Industry

Polyimide PCBs find application in:

  • Magnetic resonance imaging equipment
  • Ultrasound equipment
  • Flex and rigid-flex interconnects for sensitive equipment

Industrial Equipment

  • Power inverters
  • Motor Controllers

Automotive Industry

  • Engine management systems
  • Antilock braking systems
  • ADAS vehicle systems

Telecommunication Equipment

  • Phone switching systems
  • Cell towers

Military Applications and Aerospace Industry

  • Power distribution systems
  • Communication and Defense navigation systems
  • Electronic flight instrumentation systems
  • Digitized signal and microwave processing systems

Consumer Products

  • Televisions
  • Consoles for video games

Telecommunication Equipment

  • Phone switching systems
  • Cell towers

To Sum Up

Polyimide PCBs work as a very good alternative to FR4 printed circuit boards on account of the features that Polyimide PCBs offer. These mainly include flexibility, thermal resistance, quality and reliability.

It is important, however, to use your PCB partner with care as they can offer a wide variety of customized PCBs that suit your industry and their bespoke requirements.

At Technotronix, we combine state-of-the-art technology with our advanced engineering to offer you the highest quality PCB manufacturing services. With over four decades of experience in delivering high quality, on-time, price-competitive products, you can rely on us for your PCB requirements. Also, you can drop an email to sales@technotronix.us or give us a call at 714/630-9200 to solve your queries or to get a quote.

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What is BGA Reballing? Why does Ball Grid Array require Reballing?

By | Date posted: | Last updated: June 7, 2022
BGA Reballing

What is BGA Reballing?

BGA Reballing refers to changing every soldered ball on a grid array circuit. Essentially, a ball grid array circuit is established to make an accurate connection between the PCB & the chip. Very often, it will involve extracting old solder balls and replacing them with new ones.

To offer an example, Video Graphic Chips or VGCs as they are popularly known as, are particularly prone to solder joint breakage and need reballing. Every so often, you would have encountered a situation where your computer screen goes blank. This is often a result of poor solder joints and needs BGA reballing.

Why is BGA reballing needed?

There are several reasons that necessitate BGA reballing. Let us look at them in detail:

  • Overuse – The overuse of a graphics chip can often lead to reballing. With time, the solder joints between the PCB and the chip become loose and this could lead to issues that could progressively worsen.
  • Faulty Chips – When BGA chips become faulty, there is the need to replace them. Also, sometimes a PCB motherboard may require a chip upgrade to deal with new software.
  • Overheating – Overheating can also lead to the need for the BGA chip to be reballed. On account of the heat the ball loosens and can even be dislocated. Overheating can also result in the formation of a solder bridge that can prove to be fatal to your PCB equipment.

BGA Reballing Process

In order to effectively undertake the reballing process and for it to succeed, you need adequate experience and expertise and the right tools. Let us look at some of the tools that are needed for reballing:

Soldering Iron

A soldering iron is a hand-based tool that sends heat to the solder metal. Its melting can optimize flow into the broken joints between the component and the BGA PCB assembly. It is important for the soldering iron to have a heated metal tip as well as a well-insulated handle.

Desoldering Wire

A desoldering wire is required to solder wick or to desolder it. It is beneficial to remove the solder from the joint by soaking the metal solder in it. It is usually braided with 18 to 42 AWG copper wire that is insulated with leading-edge rosin flux.

Chip Stencil

A chip stencil is essentially a metal sheet with holes that allows solder balls to be fitted. Made of high-quality steel, you can heat it with the BGA machine or a hot air gun. It ensures that the ball soldering process is quick and hassle free.

Solder Balls

As the name suggests, these are small balls of solder strewn on the SMT board surface. Essentially, they offer a point of contact between the multichip modules and the stacked packages, as also between the PCB and chip package.

BGA Reworking Machine

It generates copious amounts of heat and is required to finalize the BGA reballing process. It also comes in handy to remove or attach BGA chips.

Steps in the BGA Reballing Process

The essential steps in BGA Reballing include:

  • Preparing the BGAs. This involves removing existing components and ensuring the surface is clean.
  • Securing the units.
  • Introducing the stencil to match the space and sizing of your BGA.
  • Securing the stencil by screwing a ring on top.
  • Shaking in solder balls.
  • Reflow soldering with a reflow oven that offers temperature control.
  • Post process inspection to see that the balls are secure and in proper place.

Choosing the right services for BGA reballing

It is imperative to choose the right PCB services when it comes to BGA component reballing as there is almost no margin for any error. You need to work with a company that has the right experience and expertise to offer accurate, high-quality work. You need to look for high yield, cost-effective BGA reballing services. The right company will be able to offer you the ability to reball BGA devices of every size, pitch and package style. From low volume to high volume BGA re-balling, the partner should be able to meet all your requirements.

The other aspect to look for is the ability of the company to offer robust customer support and to handhold you through state-of-the-art solutions.

Technotronix offers professional PCB assembly services with 40 years of expertise. Our accurate PCB assembly process meets the quality standards, including ISO-9001:2015, RoHS, and more. Our superior engineering capabilities mean that each board matches your exact requirements and technical specifications. If you have any questions or any requirements related to PCB assembly service, please feel free to contact us via email at sales@technotronix.us or call 714/630-9200.

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