Tag Archives: printed circuit assembly

Selective Soldering for PCB Assembly

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A selective soldering approach offers PCB connectors the perfect instrument to overcome a few of the challenges. Selective soldering is a robotic device that pushes hot solder from a tank via a nozzle to cover the conduits running from the ground of a circuitry

What is Selective Soldering?

Selective soldering is indeed the method of soldering components selectively onto electronic components and formed modules, damaged in conventional printed circuit board assembly or through-holes technology mounting procedures by heat from the heat exchanger or wavelength soldering. This normally involves an SMT refill operation; selectively soldered components are generally surrounded by elements that have already been supplied in a soldering process and must be accurate enough to prevent damage to them.

Benefits over wave soldering such as no solder pallets are needed:

Wave Soldering is the routine method used for soldering pieces on circuitry for many years. Although originally developed for boards having completely thru-hole parts, some SMT bits will also be soldered.

For TH components to be mounted on circuit boards while PCB manufacturing, selective wave soldering pallets are employed. The pallets are built of an isolated epoxy composites substance. Wave Solder Pallets simplify the production process considerably, removing the need for heavy human work and manual work.

Some situations do not allow wave soldering, and manual soldering is not successful. The only alternative left is to employ the selective solder technique in these circumstances. A few of these requirements include:

  • The high elevation of the component:

The solder wavelength has constraints, and certain components are large enough to obstruct the soldering of the wave.

  • Unanimous heating:

Thick boards, particularly boards with extensive copper layers, might issue manual soldering for power and neutral aircraft. It’s hard to get one molten metal in the board to heat all the electrically coupled metal enough because the solder flows via the holes to make an excellent solder bond.

  • The high-density accumulation of thru-hole connectors:

When big connections with tens of pins are utilized, a soldering iron may hardly be solder efficiently through each pin.

  • Tight spacing of the component:

When thru-holes are too near to SMT components, there may be insufficient space to install a safety fixture around SMT modules to provide efficient wave soldering during smt assembly.

Soldering technology is becoming increasingly 3D, with connections to multiple levels. The maximum temperature is restricted for wave soldering through pallets, and the slurry reflow pin is just a 2D solution with space limits.

PCB Assembly
PCB Assembly

Selective soldering unit with Nitrogen assisted for clean, shiny solder joint:

Introduction

In these technologies, the major objective of using nitrogen is to avoid creating additional oxide on the solder interfaces of the SelectWave and the MultiWave. Furthermore, nitrogen inhibits the creation of extra dross while cleaning the MultiWave nozzles.

The nitrogen supply surrounding the soldering bottle avoids oxide layer development on the wave exterior and supports the flux action during the soldering operation. The cleaning of the nitrogen must rely on the support needed for the procedure.

Naturally, nitrogen with the greatest purity provides the finest support for the lowest use. But on the other side, less pure nitrogen may also complete the task with greater nitrogen utilization and mass flow. Everything relies on the commodity and the flows utilized.

At PNC, our pcb assembly services will include selective soldering as we have an in-house unit that is nitrogen-assisted for clean, shiny solder joints.

Faster than manual human soldering:

The positioning and soldering of electrical equipment onto circuit boards are also largely dependent on robotics in modern circuit board manufacturing factories. Does it suggest they have passed on to qualified manual assembly engineers? Not really.

As with other production processes, selective soldering is the ideal way for reducing costs and speed. Manual installation needs much-experienced personnel to perform what an electronic soldering line can accomplish more quickly.

Large, dense electronics beneath their pins, including Ball Grid Arrays (BGAs), need automatic solder reflow because of the difficulties of soldering the pins beneath them manually.

  • Large quad flat packs featuring fine-width pins are planarity-sensitive when not all wires are on the surface exposed. This makes it hard to manually solder and prefers automated soldering devices.
  • On the opposite end of the size range, tiny chip equipment, such as resistors and condensers, are too hard for hand positioning and soldering in 0201 containers (or smaller).

ERSA Eco Select 2:

ERSA adds a small ECO SELECT 2 to the renowned VERSAFLOW range as a global expert in selective soldering systems.

This system is particularly suited for modular manufacturing lines and is the perfect answer for small and medium enterprises production when flexibility is vital.

The ECO SELECT 2 is fitted with a programmed elevated flux for specific lines or row flux application, as are other ERSA selective soldering solutions. An incorporated spray sensor monitors the location of the flux stream.

Quick-wave IR emitters on the bottom side enable short preheating procedures. The segments of the heating cassette may be triggered depending on the product. The optional top-sided convection preheater allows even complicated components to be homogeneously warmed up.

The soldering process is indeed the backbone of the ECO SELECT 2. ERSA’s ‘pel off’ effect enables 0° soldering without span development and ensures the minimum DPM rates.

At PNC, we have this facility available and you can even get it at very economical rates.

Features autoload and unload:

At PNC, the process work using the Autoload and discharge system quicker. Our automated smt assembly load/unload decreases the human operation of the worksheet by 80% to enable punching processes more efficiently. The material loads & unloads from the same side of the device to save space. Higher manufacturing stability makes production unattended. There are certain important characteristics;

  • Reduce handling periods by more than 80%
  • Full brush board setup
  • Grips of sensitive part nests.
  • Includes the interaction autoload.

The capability of using leaded solder and lead-free (Unit has two different solder pots):

Lead-free solder has a detrimental effect on connection reliability. In terms of mechanical effect, plumbing solder is tougher than plumbing solder. In addition, plumbing-free soil generates surface compounds, flux impurities, and deposits of alloys that may produce poor surface energy. For these reasons, the change from leading to plumbing-free electronic manufacturing is not a comprehensive substitution of electric and hydraulic features:

  • The lead is rather soft. You will discover that solder junctions without lead are tougher than solder junctions produced by lead. This increases the intensity and tiny changes, resulting in excellent dependability.
  • Free lead soldering creates poor weathering, causing other difficulties, such as vacuum and burial.

Leaded solder offers many advantages for electronic production, but the tides of revolution are furious. All sectors using solder in considerable numbers will probably change to plumbing free shortly if they’ve not yet done so.

Engineers at PNC are experts in designing, pcb assembly, and fabricating customized PCB designs with efficient soldering techniques which are pocket-friendly at the same time.

Contact us at sales@pnconline.com to get the customized quote on your requirements.

Advantages of Laser Cut SMT Stencils for SMT Assembly

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Laser Cut SMT Stencils:

Surface mount technology or SMT Stenciles is the procedure of mounting the electrical parts straightaway onto the PCB surface. SMT has replaced the through-hole technology technique of aligning parts with cable heads into holes in the PCB. The essential part of the SMT procedure is the covering of solder glue on the PCB. First, it is managed by screen impressing the solder glue with the assistance of solder stencils. Then, the solder glue is equally applied with the utilization of a squeegee.

Laser Cut SMT Stencils are laser-cut solder glue image stencils. It is organized for hand-operated solder glue impressing applications. These stencils are frameless, and it expeditiously eliminates the tiresome hand bonding of PCBs. Utilizing image stencils, you will be able to create your image on PCBs using your Gerber or CAD data file.

Five amazing properties of Laser Cut SMT Stencils:

  1. Laser-cut SMT stencils are created by utilizing the CAD data file that you provide. You can give a Gerber file for this as well. These data files are a two-dimensional graphic representation of every layer of a PC board where pads, vias, and tracks are presented with the assistance of different lines and figures. It depicts the electrical circuit board pictures, letting in the copper layers, legend; solder mask, drill information, and many more. These data files, either CAD or Gerber files, assists in producing the SMT image stencils for constructing a PCB board.
  1. Laser-cut SMT stencils typically bear a frame. Besides, it comprised of a sheet of stainless steel, in which the apertures are adequately organized. Utilizing it, they can squeegee the solder paste onto the PCB. Hence, it keeps the application of solder paste on amateur surfaces.
  1. The Laser cut SMT stencil generally is used on an full auto or semi auto screen printer using a squeegee blade. These blades traverse over the foil to deliver the potential paste volumes on the Printed Circuit Board surface.
  1. The laser-cut SMT stencils are usually stainless steel. It is utilized to assist the PCB operator in depositing glue or paste, onto the PCB surface. Steel stencils are more long-lasting and accurate than polyimide stencils. Often, other materials like mylar and nickel are used as well. Richly nickel substance stainless derivative has little grain, backing up better release attributes as the aperture surrounds are smoother. Precise release of solder paste through the aperture is essential. Additional solder paste deposition can make solder bridging. Lower solder deposition can make fragile solder joints that can involve the operation of the PCB.
  1. Laser-cut SMT stencils are laser-cut solder stencils. The laser-cut constructing technique improves the aperture definition and best dimensional leeways for more effective pitch apertures on the stencils. Hence, you will be able to have the best quality print with most minor faults. Laser-cut SMT stencils keep a precise and quotable solder deposition procedure. To utilize the laser-cut SMT stencils, set the PC board into the circuit board holder. Adjust the image stencil over the PCB SMT pads. Set the solder paste on the image stencil and disperse it through the whole width of the hole squeegee. Apply a squeegee to roll the solder paste over the image stencil coercing the solder paste through the image stencil on the PCB board surface.

 Advantages of Laser Cut SMT Stencils:

There are numerous advantages of Laser cut SMT stencils. Like:

  • Laser-cut SMT Stencils eradicates the mistakes that are expected to fall out in the hand soldering of image electrical circuit boards. The perfect laser-cut apertures enable fluent aperture sidewalls, hence bettering paste transfer. In addition, they are permitting post-processes of electropolish and nickel-metal plating to create the aperture walls articulate.
  • As laser-cut SMT Stencils are usually frameless, it reduces space requirements. Furthermore, it is significantly cheaper than framed image stencils.
  • These laser-cut SMT stencils are not glued in a frame, allowing optimal solder paste volume control.
  • Laser-cut SMT stencils can present fantabulous print performance and better the quality of your image Printed Circuit Boards.
  • Laser-cut SMT stencils are specifically organized to avoid the odds of whatsoever fault while using the solder paste on the PCB board. It also easy clean-up of the solder paste from the surface of the electrical board for quotable and precise solder paste deposition.
  • Laser-cut SMT stencils allow quick assembly with minimum cost. It brings down the PCB image assembly time. It is low-priced, concise, easy to handle, and easy to dispose of or recycle.
  • Laser-cut SMT stencils have a 24-hour turnaround standard.
  • Laser Cut SMT stencils have smooth inward pad walls, with geometrical fence changes of fewer than 3µm for best glue release features.
  • These stencils have aperture consistency for a decrease in expected defects.
  • These stencils have high pad positional conciseness for utmost good pitch accuracy in impressing. Tolerances of about 5um are possible with modern lasers.
  • Contrary to chemically engraved stencils, these stencils to Printed Circuit Board registration boast an exemplary circuit board to stencil registration.
  • These stencils have hyper delicate pitch designs less than 250µm can be recognized without problems letting you impress today’s challenging and outstanding pitch devices.
  • This stencil’s high accuracy of land visibility sound reflection in the stencil permits you to make an easy and authentic stencil position on PCB.
  • These stencil fabricating is performed straightaway from CAD/CAM data files eradicating problems with photo tool projecting and fictionalization quality and the caliber of surface planning and photoresist application to the queer as it is the same case with chemical engraving technique of stencil manufacturing.
  • These stencils bear chromium steel serving as ground material for these stencils has a high-potential rate. Hence, the stencil does not alter in size, and the aperture design is not disingenuous even after 10,000 impressing cycles that making the chromium steel stencil very authentic in usage.
  • Its smooth walls and pointed aperture profile. It was step-up the possibility of solder glue to pass over stencil apertures during every print cycle.
  • The laser-cut SMT stencils are easy to assemble and utilize.
  • These stencils create high-volume; chromium steel stencils are handy as they have a long span of life, allowing multiple utilizations for solder glue applications.
  • These same stencils permit you for on-contact and off-contact impressing on PCBs.
  • These laser-cut SMT stencils are efficient when utilized for multi-level impressing of PCBs.

How to check the size of the stencil?

The laser-cut SMT stencil size is compiled into 2 parts: inward size and general size. Inward size is the size well-matched, and that of PC Board set up to be collective, although overall size concerns the size well-matched with printer parametric quantity limit. As far as both sizings are precisely designed, the stencil will draw total usage of its functions.

Inward size of laser cut SMT stencil can be worked out adjusting to the following rule:

  • Width of Frameless stencil = width of PCB + 200mm while its Length = length of PCB + 200mm
  • Width of Framed Stencil = width of PCB + 100mm while its Length = length of PCB + 100mm

For instance, if one electric circuit board measure in size is 50*50mm, then the sizing of its bordered stencil should be about 150*150mm, and the sizing of its frameless stencil had better be about 250*250 mm.

It is comfy to remember and function, so it worked out for hand-operated solder glue printing in laser cut SMT stencils assembly before the coming of automatic printing machine. It can tell that different PCB sizings lead to propagations of different inward sizes of laser cut SMT stencils.

It derives from an automatic solder glue printing machine, all the same, relatively strong. The general size of these laser cut SMT stencil has to be ascertained by the parametric quantity limit of the printing equipment, that is, the printing machine, because stencil has to do work within the scope of printing machine with a frame. Diverse printing machines feature different parametric quantity rules. According to the conducted research, the stencil size congenial with our printing machine can be 650mm*650mm or 736mm*736mm.

PC Board designers have to focus on the internal size of the stencil; they don’t need to care about its overall size since it is generally determined by the parameters of the printer in your contract assembler workshop.

Final Words:

The laser-cut SMT stencils had better enable you to resolve your printing troubles to alleviate the PCB fabrication and assembly process. These stencils are well-suited for image fabrication, and the flapping helps keep the glue in an enclosed area during the impressing process. Furthermore, these stencils’ better accuracy saves time, and of course, step-ups yield. These laser-cut SMT Stencils are close-packed and easy to deal with. As an outcome, it has acquired popularity in offering faster and cost-efficient PCB prototyping.

These laser-cut SMT stencils that are decently designed enable highly effective PCBs that are uniform and quotable. This not just assists in saving up costs in the end, but it will also permit a higher-quality ultimate product. The team of highly competent technicians designs all the laser-cut SMT stencils with superior precision to assure you get the complete products that meet your requirements.

At PNC, you will get your design SMT Stencil’s requirements fulfilled at an affordable rate.

Importance of Good ESD Practices in SMT Assembly

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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

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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

PCB assembly Pre-Reflow FAI

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First article inspection (FAI) prior to SMT assembly is a design verification methodology that provides a reported verification and validation of details of a product on the shopfloor per its manufacturing procedure and requirements. There are various ways to perform FAI, from both supplier’s and customer’s side, making it a very dynamic process. This means that each organization can tailor its FAI method to benefit itself and consequently, its customer, yet maintain rigid performance standards at the same time. FAI involves qualitative and quantitative measurement. FAI is also highly effective since it can potentially fulfill process validation requirements of quality management systems like ISO9001 or AS9100.

In the PCBA manufacturing industry, FAI can be effectively employed in validating materials for manufacture, underlying technologies, manufacturing processes used, packaging, and equipment. It can also be applied to a batch of a given sample-size from a mass-production instead of just the first sample, as the name might suggest. At PNC, strict adherence to our manufacturing standards helps in production with better yield but at the same time, facilitating dynamic validation techniques in our manufacturing process allows us to reduce lead time. The focus of FAI in PNC assembly lies in validating the pcb assembly before reflowing so that the SMT team can make necessary adjustments for the next batch, saving time and effort during rework. They are also responsible for validating the correct loading of the right component in its allotted slot per the assembly program. This extra step helps in validating the placements of the components and improves the turnout rate for a successful production.

All aspects of reflow also must be amenable to improve solder performance and the same translates to our guideline where only the most recent batch of solder paste (with most activity) is permitted for use, which is validated by FAI. Apart from pre-reflow FAI, post-reflow X-Ray also helps validate the solder performance based on the reflow profile which can then be adjusted accordingly so that all components are successfully soldered. This can be similarly implemented at the rest of the printed circuit board assembly stages as well up to testing. But there is a necessity to establish a constant groundwork or point of reference in such a dynamic process to give each validation at a particular stage, the perspective of what changes were made before. This is achieved by using a single piece of documentation used to validate at every stage, wherever applicable, and that document reports any changes made to the processes or product, to the next stage.

pcb_assembly
pcb_assembly

PNC employs the use of AEGIS software to combine SMT assembly guidelines and inspection requirements into a single document (internally referred to as AEGIS). The AEGIS is used to report every single FAI validation to different stages of assembly. PNC’s FAI process for SMT starts with thorough solder paste FAI & its validation, which will be detailed in another post. For this post, let us consider pre-reflow FAI and highlight its validation process since it is the most crucial stage. The procedure is as follows:
1. The SMT team confirms the correct allocation of components as given in the assembly program. This is done by comparing each component with its description, measuring component value wherever applicable, and checking for physical marking on ICs. This helps in validating that the right component has been placed in its respective position on the board.
2. The next step involves checking for the polarity of components, wherever applicable. This is a two-step process. First, the supply angle of a component in the reel needs to be checked and second, the placement of that very component on the PCB needs to be verified.
3. Now, once the first board is assembled, the pcb assembly is put through FAI, where the placements of all components on the board are checked, any necessary placements that remain are placed manually and polarities of applicable components are checked and changed as per what is given in the AEGIS. The same changes are made in the assembly program to avoid the same occurrence in the rest of the batch. Components that are designated as DNP (Do Not Place) are also checked and finally, the solder paste information such as solder type, lot number, date of manufacture, and expiry are checked to ensure that the right solder paste has been used.
4. All these checks translate to notes, remarks, and checks on the AEGIS document, which can then be referred at later stages up to final inspection. If the job in consideration is a repeat job, it can be optimized to avoid any errors made in the first batch of production.
5. The board is then sent through reflow. Once reflowed, the board is extensively inspected under high magnification camera for quality of component placement, solder joints etc. yielded by SMT process.
6. Each section in the AEGIS is meant for FAI by a different team performing a different operation.

PNC has been able to reduce its lead time and increase customer satisfaction significantly and our personalized and successful FAI is a big factor contributing towards it. Further development to the FAI process is underway as much as it is needed to achieve better production yield over time for all the different types of PC Board assembly that are assembled at PNC.