Tag Archives: prototype pcb assembly

Importance of Good ESD Practices in SMT Assembly

Importance of Good ESD Practices in SMT Assembly

The management of electrostatic discharge is a crucial feature in the production, assembly, and maintenance of electronic equipment. If electrostatic discharges are not managed, they may destroy an electrical device at any step of its manufacture or use. Grounding any wires that come into touch with or are close to the electrical equipment is the main way of control. Humans, tools, ESD mats, various electronic equipment, boards, connections, packing, and other conductors are among them. Removal of extra insulators, shielding, ionization, pollution regulations, training, awareness, and highest level compliance are all part of a successful ESD management program.

What exactly is ESD?

The quick current flow between two oppositely charged objects generated by the response to an electric short or insulator breakdown is known as electrostatic discharge (ESD). Tribocharging via electrostatic induction may generate a build-up of high voltage. When different-charged items are placed near together, or the dielectric among them disintegrates, ESD develops, which typically results in a vivid spark. This could result in major part damage during the printed circuit board assembly process.

ESD may generate tremendous electric sparks and less dramatic forms, not seen or heard but strong enough for sensitive electrical equipment to be harmed. Electric sparks need a field strength in the air of more than 40 kV/cm, as seen in lightning strikes. Energy transfer from acute electrodes and brush discharge from flat electrodes are two further types of ESD.

Smt assembly
Smt assembly

What is the importance of ESD?

Exposure to ESD, or the abrupt passage of electricity over two electrically charged items, may cause any electronic device or part to deteriorate. When two differentially charged items brush against one other, an apparent spark is typically produced. Even easy movement on a workstation may cause ESD, which may harm a device’s sensitive electrical components. It may also have an impact on the functioning and quality of electrical devices and components. As a result, ESD protection solutions are critical for preventing the accumulation of electrostatic force in electronic devices. Their primary purpose is to limit the possibility of ESD-sensitive equipment being damaged. These protective solutions are particularly successful in preventing system failure and extending the life of fragile electrical devices.

A pro-EPA (ESD protected area) should be established for the safety of production facilities or pcb assembly workstations. EPA may be enhanced using ESD-resistant goods, including workbenches, commercial furnishings, trolleys, warehouses, etc. Wristbands, conductive straps, and other devices may be worn by persons working in the vicinity to safely disperse ESD. These items are wired to the ground, where an electrostatic charge is dissipated via earthing points and connections. This allows ESD to be dissipated more safely.

ESD Protection Zones in the Facility:

Electrostatic Discharge Shielded Locations (EPAs) prevent ESD-sensitive devices from typical electrostatic discharge sources by grounding conductive objects and personnel in ESD-prone production areas such as:

Pro mats, for example, are conductive surface materials.

  • Staff uniforms and clothing with conductive filaments
  • Optimal humidity levels

Circuits with built-in ESD protection:

When assemblies are most susceptible like during electronic assembly, built-in ESD protection decreases the danger of complete circuit breakdown or latent damage. The following are some of the best practices for ESD protection built-in:

  • Choosing the right short backflow prevention device for your Printed Circuit Board
  • Installing the isolator at the ESD contact site

What is ESD (Electronic Stability Device) Training?

Controlling electrostatic discharge requires ESD training. You recognize the significance of avoiding electrostatic discharge. You already know that in electronics assembly, an ESD control program is critical for quality and yield. Any successful ESD control program and vital to successful electronic manufacturing require an effective, systematic, and long-term ESD training, certification, and re-certification system.

What is ESD 20.20 Training?

Electro Static Discharge (ESD) is a typical phenomenon in which a person or almost any ‘charged’ item emits a brief electrical shock.

The multi-industry guideline for developing ESD management programs that safeguard today’s highly sophisticated electrical parts, assemblies, and machinery from expensive ESD damage and decrease downtime is ANSI/ESD S20.20. An organization may design an ESD control program that protects equipment down to 100 volts or fewer using the format’s control techniques and advice.

The S20.20 standard, which several multinational OEMs use and serve as a successor for MIL-STD 1686, has swiftly gained traction in the electronic, telecommunications, aircraft, automotive, and devices sectors. In reality, the S20.20 standard is included in the telecom industry reference TL 9000 as a recommended practice for addressing ESD control requirements.

A good ESD management program within a printed circuit board assembly facility may help you avoid expensive system failures while also improving customer service. Organizations may use NQA’s ESDA-accredited Site Certification program to guarantee that their programs satisfy the standards and give documentation of conformance for customer marketing reasons.

When it comes to ESD training, there’s a statement that goes something like this:

“Managing an ESD program is an important aspect of a full quality program in the modern electronics sector. Any electronics company that does not have an active ESD program is putting itself or its customers in danger.”

At PNC, all the employees receive annual ESD training based on ESD 20.20.

What Are the Advantages of ESD Training?

Improper handling of today’s electrical components may quickly harm or make them faulty. Furthermore, rejecting or fixing items affected by electrostatic discharge (ESD) may waste time and money for companies that handle electronic components.

  1. Raises ESD awareness in the workplace
  2. Enhances overall performance levels and product control
  3. Lowers the failure rate, lowers rework, and saves money.
  4. Aligns with peers in the electronics industry
  5. Provides consumers with clear evidence during site visits
  6. Controls for ESD (proper clothing, grounded tables, signage, etc.)
  7. Increases marketability and gives you a competitive edge.

What is ESD Audit?

A solid ESD control program should include an ESD audit. It audits all ESD-control processes and products, reminds employees of their obligations regularly, and provides management with the information needed to take remedial action.

An audit is conducted using an ESD control program that has been designed, authorized by management, and applied at all levels of the smt assembly area. In most cases, such software is based on industry-developed standards. ANSI/ESD S20.20-1999, produced and regulated by the ESD Association, is the cost of setting up a document for many programs and is a good option for a guiding standard.

ESD Audit Work Area:

The audit must ensure that the border between ESD-protected and non-ESD-protected locations is properly marked, e.g. signs, directional arrows, and floor markings. This reminds both employers and employees that they enter a critical control environment or leave it.

Supply carts to store or carry ESD-sensitive items should have electrically linked uprights and shelves mounted by a trailing chain to avoid tribo-loading. A floor snap is strongly suggested for strong grounding of the cart when fixed in an ESD safe location.

ESD Practices at PNC Online                           

During an audit at PNC, it was noted that all the employees themselves tested multiple times a day. The company follows all standard patterns for complete ESD audits on an annual basis. PNC employees wear ESD Smocks, wrist straps, foot Straps, and ESD shoes.

Minimizing Crosstalk in PC Board Layout

Minimizing Crosstalk in PC Board Layout

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

TOTAL-CONCEPT

Total Concept Company

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

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.