How do Circuit Boards Work

How do Circuit Boards Work?

Whatever electronic equipment or device you are using, there is likely to be a circuit board inside. Most of us use our equipment or device without any thoughts or considerations about what lies under the hood, or how the computer circuit board works. In this blog, Rush PCB UK explains the basics of the circuit board or printed circuit board (PCB), the components on it and their functioning, to give you a better idea of the PCB electronics you are using regularly.

You can consider the electronic circuit board as the heart of an equipment. Basically, the simple circuit board is made of glass fibers with copper tracks and pads on one or both sides. The copper tracks act as conductors of electricity between tiny PCB components mounted and anchored on pads on the board. If you look closely, a grey-colored material known as solder anchors the components in place.

circuit board

PCB Construction

A glass fiber board with copper tracks on one side forms the PCB construction. A slightly more complex type of PCB electronics can have copper tracks on both sides, while still more complex boards can consist of multiple layers, with copper tracks on each layer.

A designer uses a computer and a special program like a PCB CAD for designing the PCB electronics. Depending on the complexity, the PC-Board may be single-, double-, or multi-layered. Once complete, the designer outputs the entire design in the form of a standard file format, commonly, the Gerber format. The designer sends the Gerber file to the PCB manufacturer.

The manufacturer fabricates the printed circuit board design following the Gerber files. They build the PCB in layers with copper traces on each layer. Vias make the interconnections between the layers. A green mask covers the two outermost layers, thereby insulating and protecting the copper from tarnishing. The pads remain exposed as they are necessary for mounting the components. However, a layer of surface finish protects them from tarnishing, until soldering. To help and guide operators mounting components, a silkscreen printing displays the part number of each component in white.

Electronic Components

A multitude of circuit board components are available for use on PCBs, depending on their individual functions. Some of the most circuit board parts are:

Switch: Allows two circuits to interconnect electrically or remain isolated. Once interconnected, a switch allows current to flow.

Battery: Supplies the circuit with electrical energy at a defined voltage level.

Resistor: Controls the amount of current flow in a circuit by offering electrical resistance.

Capacitor: These components store and release charge as necessary

Inductor: These also store and release charge, but in an opposite manner to that by capacitors.

Diodes: These components allow current to flow only in one direction, blocking it in the other.

LEDs: These are diodes that can emit light in many colors.

Transistors: Active components with ability to amplify charge

ICs: Integrated Circuits are active components with multiple functionalities.

PCB Assembly

A PCB assembly consists of mounting and anchoring circuit parts on the PCB, with machines doing most of the work. A solder paste dispensing machine places small amounts of solder paste on the pads of the PCB. Next, a pick-and-place machine takes the surface mount components from reels and places them at specific places on the PCB. This combination of components and PCB then passes through a reflow oven where heat melts the solder paste and anchors the components on the PCB. After testing for shorts and opens, the PCB assembly is ready for use in a device.

Conclusion

We, at Rush PCB UK, have presented only a very brief overview of PCB circuits and how do circuit boards work with components. Although the basic principles remain the same, the complexity increases with the size and number of layers of a PCB, and the type of components it uses.

Call Rush PCB today or visit our website for all your PCB requirements.

PCB

PCB Assembly Fabrication Methods

PCB or Printed Circuit Board assembly at Rush PCB UK Ltd involves combining the bare PCB, electronic components, and other accessories effectively to allow the assembly to function as the designer intended. Broadly, the fabrication methods involve a number of major steps:

  • Component placement
  • Soldering
  • Cleaning
  • Inspection
  • Testing

However, depending on the nature of the PCB undergoing the assembly, above steps may involve further activities.

Component Placement

Methods of placing components on the PCB depend on several factors such as:

  • Single or double side component placement
  • SMD components only
  • Through-hole (TH) components only
  • Mix of SMD and through-hole components

A PCB may have components present only on one of its sides or on both, although assembling a PCB with through-hole components on both sides is a rare occurrence. Single side component placement with either all SMDs or all through-hole components is more common, while single sided PCBs with a mix of SMDs and through-hole components is also to be found.

For assemblies requiring SMDs on both sides of the PCB or a mix of SMD and through-hole components on the top and only SMDs on the bottom, the PCB assembly process must be broken up into several intermediate steps, and the assembler needs to take special precautions for each of them.

Single-Side Component Placement

This type of PCB may have only SMDs, only TH components, or a mix of both. If it is only SMDs, the necessary steps for assembly are:

  • Solder paste printing
  • SMD placement
  • Reflow soldering
  • Manual Inspection
  • Electrical and Functional Testing

When the PCB has only TH components, solder paste printing is not necessary, in place of SMD placement, there is either manual placement or machine placement of the TH components, and wave soldering replaces reflow soldering. For a mix of both components, the assembler places TH components after anchoring the SMDs to the underside using adhesive and follows it up by wave soldering. This is because SMD components at the bottom of the board require to be held in place, while component leads extending on the underside of the PCB are undergoing wave soldering.

Double-Side Component Placement

Similar to the single sided PCBs, double sided PCBs may have SMDs alone, TH components alone, or a mix of SMD and TH components. Although it is usual to mount SMD components on both sides, mounting TH components on both sides is not feasible. However, it is possible to have a mix of SMD and TH components on top, and only SMDs on the bottom side of the PCB.

With both sides of the PCB holding components, multiple steps are necessary for the placement and soldering of the individual sides. SMDs on the underside need anchoring to the bottom side of the PCB to prevent them from falling away. Assemblers use a glue dispenser or a glue stencil to deposit a small drop of glue at the coordinate where the pick-n-place machine will deposit the SMD on the bottom side of the PCB. Baking is necessary to allow the SMD to permanently stick to the board before the soldering process.

The top side of the board may have only SMDs, only TH components, or a mix of the two. If the board has only TH components on its top side, the assembler inserts them and sends the board for wave soldering. However, if there are only SMDs on the top or a mix of SMDs and TH components, the assembler mounts the SMDs first, solders them with reflow, mounts the TH components and then wave solders the bottom side of the PCB.

Soldering

Soldering is the process of joining two dissimilar metals using a molten filler metal alloy. The molten metal alloy enters the joint, and as it cools and solidifies, bonds with the adjoining metals. Primarily, there are three common ways of soldering:

  • Manual Soldering
  • Wave Soldering
  • Reflow Soldering

Manual Soldering

Manual soldering requires the use of a soldering iron whose tip is heated either by gas or electricity. The pcb assembler applies the hot tip to the component lead and pad to heat them up. Solder held on the heated junction melts and solidifies to form a joint. The assembler may apply flux to the surfaces to help the process of soldering.

Wave Soldering

Wave soldering is a bulk soldering method. The PCBs to be soldered pass over a bath of molten solder. The bath has a pump to create a wall of solder that washes the underside of the PCB as it passes over the wall, effectively soldering the components to the underside of the PCB.

Temperature of the molten solder in the bath and the time the PCB is exposed to the solder are the two important parameters governing the quality of the solder joints formed. It is also necessary to preheat the board mounted with components to allow proper wetting. Although wave soldering is primarily effective for TH components, it can solder SMD components anchored with adhesive on the underside of the PCB.

Reflow Soldering

Assemblers use reflow as the most common method for soldering SMD components to the top side of the PCB. However, before they can solder the components, they must deposit solder paste and mount the components in place. The sequence they follow are:

  • Solder Paste Printing
  • Mounting SMD Components in place
  • Passing the assembly through a Reflow Soldering Oven

The assembler first deposits solder paste using a prefabricated stencil onto the pads of the PCB. Instead of using solid solder, SMD assemblers use a paste of solder and flux, which they draw with a squeegee over a stencil placed on the PCB. Appropriate cutouts in the stencil allow the solder paste to deposit onto the pads. On removing the stencil, the pads that will hold the components only retain the solder paste.

A pick-n-place machine then places respective SMDs onto their locations on the PCB. A pre-assigned program on the machine allows it to pick a specific SMD component from reels or cassettes and position it on a predefined position on the solder paste.

This assembly of PCB, solder paste, and components then passes through an oven on a conveyor belt, where heat melts the solder paste, effectively soldering the SMDs to the board. The speed of the board through the oven and the oven temperature are very important settings for achieving a good quality of solder joints.

Cleaning

After soldering is over, some flux residue may remain on the printed circuit board. Over time, this can turn acidic, and corrosively damage solder joints. The flux residue can also attract fingerprints and make the PCB look unclean.

For cleaning and removing flux residue, Rush PCB UK Ltd prefers washing the PCB assembly with high-pressure deionized water. A quick drying cycle with compressed air removes all traces of water, and the PCBs are ready for inspection and testing.

Manual Inspection

Inspection is necessary at various stages of assembly. For instance, one stage of inspection is necessary when the operator has stuffed TH components into the board, and again once the assembly has undergone wave soldering.

Likewise, for reflow soldering, inspection is necessary once after solder paste printing is over, then again after mounting the SMD components, and once again after the boards have exited the reflow oven.

Also Read: PCB Assembly Compatibility with In-Circuit Testing

Inspectors in both cases above look for missing components, wrong components, wrong polarity, solder bridges, excess solder, inadequate solder, dry joints, and many more defects. For minor faults, a touch up station is enough to rectify them, but for more severe and persistent faults, a change in process parameters is the solution.

AOI & X-Ray Inspection

For large batches of PCB assembly, the manual inspection process may be too slow. A faster process is the Automatic Optical Inspection or AOI process. AOI machines have video cameras to capture images of the PCB, the components, and the solder quality, and they can compare the images with standard images in the machine’s memory. The AOI machines work at high speed processing a large number of PCBs within a relatively short time.

Fine pitch components such as BGA conceal the solder joints under the component body, preventing manual or automatic inspection. The only way to assess the quality of solder joints hidden under such components is by passing the board through an X-Ray machine, capturing the images on camera, and examining the results.

Electrical & Functional Testing

Electrical testing may be necessary after the assembly has passed through the above stages, to test whether the assembly functions as intended by the designer. This may involve programming the board, or calibrating certain components before the actual testing can begin.

Electrical and functional testing involves applying specific voltage/voltages to the circuit on the PCB and looking for normal/abnormal behavior at predefined outputs. Some tests may require a voltmeter and ammeter, while others may need more sophisticated instruments such as an oscilloscope or a waveform analyzer to complete the testing.

Conclusion

PCB assembly is a complicated process involving several technical processes with important setup parameters. Eminent assemblers such as Rush PCB UK Ltd are always careful with these setup parameters to allow the final product achieve the desired quality

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PCB Assembly Compatibility with In-Circuit Testing

RUSH PCB UK Ltd wants all its clients to be assured that we ship all products from our production facility only after testing them to be in perfect working condition. For this we have a variety of strict quality control procedures at each stage of our PCB assembly process. This includes not only standard services such as visual inspection and automated optical inspection, but also advanced test procedures such as X-ray inspection, and functional circuit testing or FCT. Although each method has its own advantages, for the most meticulous testing method, RUSH PCB UK Ltd recommends In-Circuit Testing or ICT.

In Circuit Testing (ICT)

Working at component levels, ICT allows localizing issues that may be present on the board under test. For instance, ICT can point to a specific device as the cause of the problem. With ICT, it is possible to test the individual voltage and current levels on the PCB, while including a step-by-step program execution.

The above helps in troubleshooting complex boards where the board is still a prototype and the design is not totally verified. Boards not passing the test may need reworking at component level to potentially save the batch. When this happens, our test engineers generate a Design for Assembly (DFA) recommendation to the client.

At RUSH PCB, we work closely with our clients and provide them flexible services tailored to their individual requirements. We have an engineering team to review the specific test requirements for a project, recommend the necessary equipment, and develop the test workflow. We even design test jigs if necessary. We have equipment to handle any type of project.

One of the advantages of using ICT is its speed of test. For instance, a few seconds is all it takes to test a complicated board. Therefore, projects involving large volumes of PCBs benefit exclusively from ICT. Apart from the speed of testing, detection of faults at component levels makes the diagnosis process faster and at the same time, does not involve a skilled operator.

However, for the ICT to be effective and accurate, the process requires a dedicated test fixture and a program. In addition, the PCB design must also allow the test machine and fixture to interface properly with the assembly. To maximize the test coverage and find the maximum number of potential faults, our clients must consider some points when designing the layout for their PCB assemblies. This not only reduces the redesign steps necessary at the prototype stage, it also helps in producing boards that perform right at the first attempt.

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Making PCB Assembly Compatible with ICT

Test Pads—have a test pad on each electrical network on the PCB, including on unused IC pins. It should be possible to connect to the test pad via a spring-actuated test pin in the test fixture. For through-hole technology, the test pin can engage the component leg on the solder side.

It is usual to place 0.05-inch (1.27 mm) diameter test pads on a 0.1-inch (2.54 mm) grid, with the test pads spaced 0.1 inch (2.54 mm) from any component, and 0.125 inches (3.18 mm) away from the edge of the PCB. The above dimensions allow using long-lasting standard test pins. RUSH PCB UK Ltd does not recommend using test pads of reduced diameters, as thinner test pins are generally more expensive, requiring more frequent replacements.

Probing—place all test pads ideally on the solder side of the PCB to allow the test pins on the jig to access them from the bottom side. While it is possible to place test pads on the top, the construction of the test jig will become more complicated and expensive as it will require additional transfer probes and wiring.

Solder-Side Components—it is preferable to have no components on the solder side, other than small SMDs. Test fixtures usually have a vacuum plate to hold the PCB assembly from the bottom. It may be necessary to mill the vacuum plate for accommodating components on the bottom side. As milling is an expensive process, it is necessary to restrict the milling for bottom components to only a few millimeters.

Locating Holes—add locating or tooling holes to the PCB (not in the panel), to allow the test jig to locate the PCB in the fixture. Preferably use non-plated holes of 3 to 4 mm diameter. Locating two tooling holes in diagonally opposite corners will allow the test jig to accommodate the PCB unambiguously. Keeping a free space of 5 mm around each hole will ensure the tooling pins of the fixture will not cause shorting of components or tracks during the test.

Pull-Up Resistors—use pull-up or pull-down resistors on all floating pins, rather than connecting them directly to the power rails. For pins that hold other devices to a reset state or high impedance state, the presence of these resistors allows the test jig to control the pins. Tying the pins through pull-up or pull-down resistors also helps in product functioning, as the circuit can reject spurious signals. These resistors also help the test jig in isolating individual components when locating a fault.

Space for Pusher Rods—these are necessary to push down on the PCB when testing. ICT jigs usually have fixtures with 2 mm diameter pusher rods and necessary space should be available between components on the top-side of the PCB under test. Spacing them evenly around the PCB helps the jig manufacturer locate individual positions for the pusher rods.

Programming Devices—although capable of programming devices such as EEPROMs during testing by ICTs, the cycle time per board may go up. RUSH PCB UK Ltd recommends pre-programming such devices before assembly, and allowing the ICT to control them during testing.

Batteries—preferably, fit batteries only after the testing is over. As an alternative, use a removable link to connect/disconnect them during the testing.

Review—reviewing the design to ensure proper functioning is important before committing to a fixture. Moving test pads or components on a PCB can mean a new fixture, leading to time and cost overruns, as an ICT jig can be expensive and take some time to prepare.

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Conclusion

We at the Electronic Manufacturing Services (EMS) from RUSH PCB UK Ltd offer advice to our clients on the above points and help them to design their PCB properly for compatibility with ICT. However, once the design meets DFA requirements, ICT provides fast and accurate testing, making the returns worth the investment.

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PCB Design

Up and Coming PCB Designs

We know the importance of PCBs in our tech-savvy world. The continual advancements in modern technology creates a need for continual advancements in printed board circuits. There is a demand for smaller, more elegant, and dependable PCB designs. These new designs are used from PC manufacturing to new medical technology. The constant development of new printed board circuit designs allows the technology industry to keep inventing new ways to make our lives a little easier and in some cases healthier. Today, we are going to explore some of the advancements that we are already benefitting from and what is in store for the future of the PCB Fabrication Industry.
Board Cameras are now being used in medicine to make diagnostic testing much more comfortable for patients. Instead of a large, uncomfortable scope or camera being inserted into the area of the body that is being examined, the patient can now swallow a camera that will collect the necessary information that a physician needs to make a diagnosis. One example of this is called Capsule Endoscopy, the patient will swallow the disposable “pill” which will take up to fifty thousand pictures of your digestive tract. The pill travels out of the body through a bowel movement and can be flushed away.
Vertical Conductive Structures (VeCS) is the invention of Joan Tourné will offers a less expensive alternative for challenging fan-out projects to fine-pitch grid array components. Although still in the testing phase of development, Tourné states “Not only can we achieve higher interconnection density by packing more vertical connections in a smaller space, at the same time we can increase conductor router channel density under grid array components.” He continues to explain that PCB Fabricators will not experience additional cost with this method since the technology required is already being used by high-end shops after the appropriate training and licensing. We will have to wait and see if this new method will prove beneficial to the PCB Fabrication industry.
GaNonCMOS project consortium is currently working on a project that will use energy efficiency using GaN power switches and CMOS drivers. Collaboration on this project began in January 2017, the goal is to work with optimized embedded printed circuit boards creating integrated power components for less expensive, better-functioning systems. That sounds wonderful, let’s hope that it works!
Newer, better, stronger. PCB designs are the backbone of any electronic device. They provide us the ease of access to information around the world, they allow us to stay in constant contact with our loved ones and are beginning to play a vital role in medical technology. Smaller, elegant, smarter. PCB Fabricators are constantly challenged to create innovative boards to further our thirst for the technological and make our world an easier place to live.

References
Starkey, Pete. 2017. Vertical Conductive Structures–a New Dimension in High-Density Printed Circuit Interconnect Accessed March 9, 2017
Prophet, Graham. 2017 Consortia to develop GaN processes and PCB panel-level packaging Accessed March 9, 2017

electronic-components

Understanding the Basic Aspects of Electronic Components

If you are not sure what an electrical component is rest assured, you are not alone.  For those of us who love our devices, but have no idea how they work, sit back, relax and get ready to learn!  Electronic components are the meat and potatoes of the electronic devices we use every day and can’t live without.  They are not flashy and are usually quite easy to overlook.  However, without them, we would literally be back in the dark ages. Today we are going to discuss some of the most basic electronic components.  Some examples include parts like resistors, capacitors, LEDs, transistors, and integrated circuits.  So, let’s get started with the basics.

Resistors

Resistors have been named for their function, resisting the current.  The resistor is responsible for managing the volts and current in nearly any device that requires electricity.  It is the resistor that allows your device to continually operate without overheating or worse.  By controlling the voltage, it allows just the right amount of electrical current that is needed to operate the device, if it did not do this, then the device would receive too much electrical current and then overheat or in technical terms fry.

Capacitors

Capacitors are used to store an electronic charge for a small period which is released when the charge is needed.  The capacitor will release the stored-up charge when there is a disruption in the circuit of the device resulting in the need for additional power to keep it running.  Kind of like a backup battery, or you can think of it in terms of a generator.  When there is a blackout, facilities or homes that are equipped with a backup generator will not be left in the dark, the generator will save the day by providing electricity to the building.

LEDs (Limiting Emitting Diode)

Although this sounds like something that Luke Skywalker would use, LEDs are routinely used.  LEDs are used to provide light.  That little light that comes on when your cell phone is charging or the power light on your personal computer is the LEDs in action!

Transistors

Transistors are a little more difficult to wrap your mind around.  They are made of three terminals;

  • Base: Voltage goes through first, it makes the collector “turn on”
  • Collector: Receive voltage from base has a positive charge
  • Emitter: Receives voltage from collector has a negative charge

They work together as a switch to turn the circuit “on”.

Integrated Circuits

An integrated circuit is a tiny component that may contain some of the components you have just learned about.  They are the cornerstone of the devices we know and love ranging from cell phones to our home and work personal computers.  Without them, we would not be in the age of technology that we currently enjoy!

So, there you have it!  Your first lesson in the basic aspects of electronic components is now complete!  We hope you have found this information valuable and informative.

Assembling Wearable Electronics

Assembling Wearable Electronics

Rush PCB Uk engineers know the importance of keeping up with all of the latest technological advances of the times.  With the constant introduction of new technology staying current in the contemporary market is a necessity for our customer’s satisfaction and our continual growth.  For example, the demand for wearable electronics is at an all-time high, with such popularity it is necessary to be constantly on the look-out for new and better ways of improving functionality as well as the assembly process.  Whether we are assembling smart watches, tracking devices or medical alert devices, Rush PCB experts understand their complexity and the precision necessary to successfully assemble the device to function correctly.  As a matter of fact, the assembly of wearable electronic devices does not differ greatly from the assembly of other types of printed circuit boards with the exemption of the size.

Aside from their difference in size, wearable PCBs can also come in various shapes and sizes, which can make the assembly process a bit more challenging.  Their smaller size requires much more attention to detail and exact precision.  Our engineers love challenges, we are ready to begin any wearable electronic assembly and guarantee that you will be satisfied regardless of the shape and size of your PCB.  By using a heat-curing adhesive to join the flex circuits to a rigid board our engineers ensure that the difference in the coefficients of thermal expansion are balanced so the sensors will operate as expected.  The final product will provide a flat even that provides enough surface tension to control solder paste spilling while including techniques like overprinting and under-printing.

Understanding the importance and sensitivity of sensors PCB engineers design soldering pads which enable the sensors to come in contact with skin so they can collect the information they were designed for.  This is just one consideration in our process.  Other factors included in assembly are the direction of the bend of the circuitry, degree of bend, number of fold cycles, application type of the device.  When assembling wearable electronics, our experts provide quality devices guaranteeing that they will bend and twist so the wearer of the device will be able to perform their normal activities without damaging it.  From stencil printing to the thermal profile or reflow, Rush PCB UK  provides quality devices that you can count on.

During the stencil printing phase our engineers guarantee that the distribution of solder paste is perfect ensuring that the appropriate electrical connection is achieved.  When we move on to the pick and place phase, we precisely position the components, the surface of the flex-circuit, surface mount pads through the use of specifically designed fixtures and special tooling.  Shields and cages are delicately placed during the pick and place phase.  For the thermal profile or reflow phase, the most challenging one of all, our engineers lower the temperature of the conduction oven, using special profiling care for lead-free wearable electronics.  Contact us today to find out how we can help you.

PCB Assembly Methods

Printed Circuit Boards Assembly Methods

A PCB offers mechanical support and connects electronic components electrically using conductive tracks and several other features etched from copper sheets illuminated onto non-conductive substrates. PCBs are assembly and design defines the type of final PCB product; that is, single sided PCB, double sided PCB or multilayer PCB.  Modern PCB assembly processes are extremely complex and automated thus high speed which might lead to component failures.  This is due to lack of sufficient understanding of the concept of design for assembly (DFA). Manufacturing and assembly should be considered during the design stage of every PCB. We are professionals in PCB design, assembly and manufacturing. Please join us as we discuss the various methods of assembling your PCB and the relative advantages of each method. To learn more about PCBs, PCB outsourcing and manufacturing, you can visit our blog https://www.rushpcb.co.uk/blog/. However, as already stated, in this article we shall only discuss the PCB assembly methods.

To begin with, the first critical process this occurs before PCBs are manufactured is contacting the assembly house or company and discussing your project with them. Communication is crucial throughout the product’s life and the 2 parties should participate relevantly. Uniquely, its house has its own strengths, methods and requirements and as their customer, you should be familiar with them before outsourcing their assembly services. Some of the important components needed for PCB assembly are:

  • Printed Circuit Boards
  • Electronic components
  • Soldering materials-solder wire, paste and solder bar.
  • Soldering flux
  • Soldering equipment like soldering station and SMT equipment

On the other hand, before submitting the PCB for assembly, there are some tools that you should provide to the PCB assembler. These items include the BOM (Bill of Materials) which should categorically state the parts numbers, description, reference, value, package type and number. Please always ensure that this information is accurate and each detail that you would wish included in the PCB is included to avoid assembling a PCB that doesn’t meet your specifications. However, after detecting confusion or a missing part, most PCB assemblers will stop the process and seek for clarifications. This can lead to late delivery of your final PCB. Sequentially, the centroid or X-Y rotation side (XYRS) file is required since it clarifies the rotational angle, X and Y coordinates and the side of the board each of the parts is placed. Computer-aided design programs used for the PCB design process can export any XYRS file directly and those that cannot have an extension that gives them the capability. As if that is not enough, you should also provide the Gerber files for the PCB.

After receiving the requisite information, the PCB assembly company will review what you send and rectify the obvious errors before getting back to you for clarification. Some of the above files and processes are automated in software and machines in most of the companies thus the process is not much complicated. The initial physical assembly begins with the setting up of the pick and place machines by loading the XYRS files and various parts to be used in the machine. However, some assemblers populate a board manually but scan it into the pick and place machines for proper component placement. This might take longer and it can lead to large setup costs of the Printed Circuit Boards. Pick and place machines can only place parts on one side of the board and then they are ejected, soldered and then run through the pick and place process to take care of the back side. The sequential procedures that follow this process are soldering, testing and shipping.

PCB assembly with thru-hole electronic components

Electronic components with leads coming out inserted through tiny holes in a PCB for soldering are known as thru-hole electronic components. The assembly process for these components when used in PCBs requires the use of hand soldering and wave soldering. Moreover, the temperature range used in this process depends on the solder type used. In these soldering processes, the solder is usually in the form of solder bar and it is put in a high-temperature bath. Moreover, the PCB with all its thru-hole components in holes is the passed over the molten solder using a conveyor belt. The soldering process involves the following procedures: inserting the electronic components in the molten solder, flux application, cleaning and testing. However, sometimes hand soldering is carried out in assembling companies with less with little work load or in repair work. However, a quality soldering station or solder wires and flux are use in this process.

PCB assembly using Surface Mount Technology

The SMT (Surface Mount Technology) is a PCB assembly process for SMD electronic components. Unlike thru-hole components, SMDs don’t have legs or leads but they are instead mounted on the surface of a PCB. The electronic components and soldering materials used in this process are also different from those used in the thru-hole soldering process.Surface mount parts are held in place by the tension of the solder paste which is allowed to be flow continuously. This is in a bid to prepare them for the process of wave soldering. On the other hand, as the pieces are placed on the PCB, there is a literal push as the pick and place inserts them in the board. The downward pressure acting on the board can cause board flex in panels with bare minimum connecting tabs between the boards. As the pick and place moves away, the board snaps to its original position and sometimes this might flick pieces off the board.

Are you interested in acquiring high quality PCB assembly services for your PCB? With over 20 years’ experience in the PCB design, assembly and manufacturing world, all our products are unique and tailored to meet customer specifications. We are proud to be the preferred PCB provider and manufacturer to millions of lovely customers from all over the world. You can also join us today by visiting us at https://www.rushpcb.co.uk/. Our team of experts will work with you from the start until the final product that meets your specifications is achieved. Please try us today.

Errors which cause PCB Assembly Holds

Mistakes Which Cause PCB Assembly Holds

As an international PCB manufacturing and design company, RUSHPCB is determined to ensure that its boards adhere to customer’s specifications. Such specifications determine the applicability thus the general operating characteristics of a Printed Circuit Board. To do this, we ensure that we understand what each customer wants. However, to avoid discrepancies and poor work output due to wrong designs, we hold a job if there are any differences between an order and the parts or files which the customer provided.

This protocol is used in the entire PCB design and manufacturing industry since all PCBs design demand explicit precision. Moreover, Design Rule Check (DRC) errors should be avoided to ensure specifications like minimum via hole diameter and copper-to-copper spacing are given. It is for this reason that we recommend that you double-check your order to prevent delays due to holding in the assembly stage. Fortunately, we are all proud when your product is delivered to you on time with no errors at all. This is why we came up with some of the most common errors which lead to PCB assembly holds. Please join us as we discuss or visit us at https://www.rushpcb.co.uk/blog/ for questions or to place a quote. We are always ready to serve you.

  • Mismatch between the footprint and the BOM

In this case,a component placed in the Bill of Materials (BOM) happens to be too small, too big or simply the wrong component for the designated position. This could include the size of a drill bit to be used to create holes or the size of copper layers to be used. The BOM is usually accompanied by the Excellon drill file which defines the drill. The drill file specifies where the holes are to be placed. In some cases, there is a conflict between the components in the BOM and what the design needs. To avoid confusion and design of the wrong board which does not meet your specifications, we hold the assembly process until clarifications are made.

  • Mixing different orders

As an international and one of the best PCB manufacturer, fabricator and designer in the world, we deal with thousands of orders in a day and we welcome customers to place as many orders as they can. However, care should be taken to ensure that the components in one order in the Bill of Materials are clearly differentiated from the others by marking by a tape or a reel or placed in a single troy come bag. This eradicates chances of confusion which may lead to PCB assembly holds since we cannot design a PCB whose components are not clear. Do you have any question so far or would you wish to know us better? Please Contact Us .

  • Missing components

Customers provide the list of tools or components which they need the manufacturer to use in coming up with their design product. A tool list is embedded in the Excellon drill file or it can be sent as an independent file. Using the tool list which is provided on the fabrication is not professionals since it eliminates automatic verifications and may cause some errors in data entry. We highly recommend that you provide minimum overages so as to compensate for any assembly attrition. Failure to do this might lead to holding of the assembly of the board.

  • Failure to update the Bill Of Materials to meet recent design changes

After coming up with a clear idea of what one needs to design, there are some changes which one might need to incorporate in the design to make it more appealing or effective. We welcome any design changes from our customers provided they don’t interfere with an already ongoing PCB assembly for the same board. We, therefore, encourage our customers to ensure that design changes in the BOM, assembly files, materials and instructions are updated on time so as to give us humble time while designing the board. However, we consider the interests of our customers so in the event that you find yourself in such a situation, we will listen to you and find the best way out.

  • Non-marked polarities

In PCB assembly, there are many components used like the diodes and batteries which have polarities. These polarities ought to be clearly marked so that our experts might distinguish between the cathode and anode. This is because connecting the wrong polarity to the wrong terminal leads to a short-circuit which might blow up the whole circuit or destroy some components due to thermal discharges. Always ensure that the polarity of each component you provide is clearly marked. Please note that we have most of the PCB assembly components in our stores so to avoid such dubious mistakes, please pay us a visit at https://www.rushpcb.co.uk/ and place your quote.

  • Insufficient inner clearance

Inner clearance is the minimal distance from the edge of any hole to the next unconnected inner layer of copper. In PCB design, it is vital to ensure that inner clearances are sufficient so that the drill does not short the inner copper layers which might lead to wastage of copper. This applies for both non-plated and plated holes. Most of the inner clearances are 0.010-inch inner clearance

Inner Clearance = Spacing+ Annular Ring

If you provide the above specifications, please ensure that they fit your board precisely otherwise we will have to hold the PCB assembly process. However, we advise our customers in advance if we see some of such errors.

  • Missing Aperture List and Excellon File

The aperture list gives a specification of what shape and size of an object should be drawn in a given Dcode (location). A comprehensive aperture list doesn’t have to be in the 274X format files. Different from that, the Excellon file is majorly accompanied by the drill file. This is crucial in identifying the areas which need drilling. It is significant that you provide these files to avoid the holding of your PCB in the assembly stage.

Please don’t be scared by the above points and procedures which one should adhere to so as to ensure that their board is manufactured without delays. We are professionals in the Printed Circuit Boards world thus we assure you of the best. Our team of experts goes through your orders, BOM and design specifications to ensure everything is in order. They contact you and clarify and confusing procedure before the final assembly commences. Serving you is our pleasure and we will always focus on quality and uniqueness.

Please pay us a visit at https://www.rushpcb.co.uk/ or contact our sales team [email protected] or 0203 750 0201