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pcb design guide

How to create a PCB Layout Creating the files for a PCB design can be complicated and it's important each stage is completed accurate to ensure there are no issues with the files that are used for manufacturing the PCB. This guide demonstrates the latest process of how to create a PCB design using the best software, this can be built by any circuit board manufacturer. We've created a basic guide of how to create a PCB design.  Click here to read this first. Potential problems, issues and challenges will be addressed. We will also provide cutting edge solutions to prevent complications whilst designing the PCB layout. One of the best tools to use e.g, Cadance, Allegro will be used to show the design cycle. There are some useful online videos available to explain this further. Schematic Drawing the PCB schematic is fundamental as designing the PCB itself. The schematic is used to place all of the parts and add the connections. Once completed, the schematic will create the PCB layout, adding the components and signals. To start working on the schematic, click on page 1. Right-click on New Page to add additional pages.   Adding all of the parts together before you begin is the best way to avoid missing any components whilst adding the connections. Schematic symbols can be obtained from the libraries provided by Orcad. For the schematic to load the component to the design, the correct footprint has to be assigned. It is essential to follow an IPC naming convention such as IPC-7351. Click on the link to learn more about this. At this point, further part information such as part numbers, values and packages must be provided. The more information that can be added, the more detailed parts lists and other reports can be generated. Once all of the symbols have been added to the schematic and the correct footprint names have been assigned, the connections can be added. Drawing the wires accurately is essential to creating the PCB design. Before the PCB layout can be created, the schematic needs to be assured to help identify any errors are not carried on the design. Adding the connections is very straight forward. Power and ground symbols can be added to simplify the schematic. It's easy to run out of room whilst building the schematic. Keep groups of components close together but away from other groups, whilst…

12 Layer PCB with Xilinx Artix®-7 35T and Semtech GS2961A

50, 75 ohms & 100 ohm diff pairs used. DDR3 signal lengths are routed within 5PS. Xilinx XC7A35T-L1CSG324I 256 MB DDR3 SDRAM 16 MB of QSPI Flash 10/100 Ethernet Interface 4 Digilent compatible Pmod™ interfaces enabling 32 user I/O pins Applications Embedded controllers, General-purpose prototyping, Networking and communications I/O expansion, Sensor fusion, Arduino expansion Semtech GS2961A 3G-SDI, HD-SDI, SD-SDI and DVB-ASI Receiver with SMPTE Video Processing and Integrated Adaptive Cable Equalizer Integrated adaptive cable equalizer Integrated Reclocker with low phase noise, integrated VCO Typical equalized length of Belden 1694A cable: 150m at 2.97Gbps 230m at 1.485Gbps 440m at 270Mbps Operation at 2.97Gbps, 2.97/1.001Gbps, 1.485Gbps, 1.485/1.001Gbps and 270Mbps Supports SMPTE 425M (Level A and Level B), SMPTE 424M, SMPTE 292M, SMPTE 259M-C and DVB-ASI Applications Monitors, Camera control units, Multiviewers, Production switchers Master control switchers, VTRs, Video servers, Encoders/decoders Up/down/cross converters, Audio de-embedders, Format detectors Test and measurement equipment

100 GBE DDR4

16 layer PCB with 90 & 100 OHM diff pairs. Xilinx Ultrascale FBGA & DDR4 memory DDR4 tracking DDR4 signals to Dimm Socket 100 Ohm 25 Ghz


4 layer PCB with 50 OHMs SARA-G450 2.5G GSM/GPRS cellular module

Case Study – Cloud based telecoms system

Case Study - Cloud based telecoms system Background We were approached by a company specialising in cloud-based telecoms to develop a revolutionary comms device for virtual call centres. The PCB would need to interface with other bespoke and off-the-shelf devices. All with their own functions and requirements. Our PCB would have to be the “brain” to control all of these devices.  Requirements All of these peripherals have their own high speed signal requirements: PCI-E connector, Ethernet connector, USB connector, QSFP+ connector, DDR4 SODIMM connectors, DDR4 RAM 8Gbit. If any one of the interactions between PCBs does not perform correctly, costly reworks would be required. Time would also be lost to identify the problem, this could also lead to our customer losing ground to competition. The PCB would also be the power supply for most of these interfacing PCBs. 60 A is required, flowing through various SMPS (switch mode power supply) to provide power to each connector. The high speed requirements for this PCB are extremely complicated, adding SMPS as well can cause problems with the high frequency electrical noise. For the high speed signals, we would need to route the signals at 50 ohms (DDR), 90 ohms (USB), 100 ohms (PCI-E, DDR diff pairs, Ethernet connector). The QSFP connector would need to use 100 ohm tracks at 25 Ghz. Most complex microprocessors have rules to follow. Chip manufacturers supply these rules as well as guidelines and reference designs to follow Using the numerous tools at our disposal, we were able to adjust the PCB stack up, the gap and track thickness to obtain the required impedance for each peripheral to operate correctly. Rules Nets are assigned to differential pairs, buses and classes to for complex rules to be assigned. These rules control the track thickness, track length and clearances to other nets and classes. Assigning the rules accurately allows the PCB to be routed without reworking and unnecessary mistakes. As the majority of these signals need to run at 50 ohms, we decided to organise the PCB stack for all of the signals to run at 50 ohms.  PCB Layout QSFP connector - TE Connectivity 2299940-5 16 diff pairs 100 ohm 25 GHZ, tracks with no 45 corners. The diff pairs are connected using 100 ohm diff pair coplaner signals. As the tracks are running at 25 GHz, there can be no 45 degree bends in the tracks. Track lengths…

CPU Card

26 layer PCB with 75, 90, 100 & 120 OHM diff pairs Zynq Ultrascale+ FBGA & DDR4 memory

PCB Design Apprentice

What was it like to start working as a PCB design engineer? I Started working for DL Designs as an apprentice after I completed my A-Levels. I came to DL Designs with qualifications in physics, electronics and maths. University wasn't the best option for me and learning on the job whilst gaining working experience was the best for me. Therefore, I found the apprenticeship with DL Designs. I found it challenging at first. For instance, learning a new set of skill whilst working in a new environment. How did you find the job initially. What did you struggle with? It was surprising how complicated PCB software was. Different PCB layout software work and function differently. For instance, Cadence Allegro is the main tool at DL Designs. I started learning the basics with Allegro, particularly creating footprints and tidying references. DL Designs works to a high standard to a satisfy it's customers. However, my colleagues were helpful and encouraging to enhance my skills as a PCB designer. What was your role within the business at the beginning? Once I had learned the operation of DL Designs, my main role was to generate the footprints using an IPC generator. This creates the part as well as supplying the optimal pad size, solder mask and paste sizes may differ depending on the part. Above all, creating footprints is one of the most important parts of PCB design. After that, I moved into the routing the PCBs. I started with Allegro at first and then onto Altium and PADS. What do you enjoy most from designing PCBs? What give you the most satisfaction? I find routing PCB layouts the most satisfying part of my job. Cadence Allegro is the main tool at DL Designs. I started learning the basics with Allegro, creating footprints and tidying references. Most of our designs are very complex. For instance I have to adopt various routing strategies to complete my objectives. Thinking 2, 3 or even 10 steps ahead is key to routing complicated areas such as BGAs or Ethernet signals. I also enjoy knowing working products will be developed from my designs. Meeting my customer's needs around the world, even in Outer Space! What do you hope to learn in the future to better yourself as a PCB designer? I am currently learning how to work with PCB layouts using DDR technology. Allegro is the best tool for…

How to design a good PCB Layout

Information It's important to have everything necessary to make the perfect PCB Layout. A good engineer would foresee any complications that may crop up; problems with sourcing datasheets, lack of available space on the design to avoid manufacturing headaches. Three types of information are crucial for a successful PCB design. DXF or mechanical drawing, BOM (parts list) and a schematic. A layout guide provided by the design engineer and necessary reference designs is also useful for a successful PCB layout. Mechanics Today's PCB designs are very complicated with limited space. Some projects may involve multiple layouts fitted together in a box. The best way to ensure the PCBs fitted together correctly without complications is with a CAD package such as solid works. The PCB design import the CAD drawings. This saves a lot of time, we place the parts on the imported locations. This is the most accurate and cost-effective way of placing components in specified areas.   Design Rules This is a crucial stage and makes up the backbone of any PCB layout. Accurate placement is essential, there could be major flaws with the functionality of the circuit board. The rules basically control any clearance and track thickness on the design. For more complicated layouts; rules for impedance controlled signals, extra clearances for noisy tracks, implementation for relative propagation delays and constraint regions are necessary.   Component stage It is crucial to start and maintain a parts library during the PCB layout stage. Most of the PCB design errors come from incorrect footprints. Using a standard footprint name such as IPC can help design engineers and colleagues select the correct part without recreating the same footprint over again. Part generators are useful tools to create parts. Entering part sizes into the generator,  the software calculates the optimum size for pads, including the paste (reducing this by 30% to prevent excessive solder shorting pads together). Other useful information such as component and placement outlines, component heights and keepouts simplify and aid the PCB layout. All components must be double checked before added to the library and updating the PCB design. Time and money's saved when using a library with reliable components. Placement stage Each PCB layout is unique, there are many questions that are asked to make sure the design meets the customer or engineer's needs. Failing to resolve these queries, could end up with the placement reworked multiple times. Is there…

Switch Mode Power Supplies

When using components such as switch mode power supplies (SMPS), the PCB layout is critical. Faults in the PCB layout cause a number of problems including switching jitter.  Poor output voltage regulation and possible failure with the PCB design. Issues like this can be avoided, saving money and time on scrapped circuit boards and PCB modifications.   Datasheets When putting together a PCB layout the best approach is to review datasheets for devices such as SMPS. A respectable manufacturer such as Texas Instruments will offer guidelines and reference designs to follow for your PCB layout. Usually a layout guide will show a PCB design with all of the parts, copper tracks and vias arranged for an optimum performance. It will show lots of space with no other components interfering. This does not happen in the real world, most of the time there is not enough room to keep parts and tracks away from critical areas. The best way is to follow the guide and bend the rules only when it's absolutely necessary to do so. Below is a part of the schematic that show the SMPS and the related components. The second diagram is the recommended PCB layout from the manufacturer.   Layout Guide The decoupling caps (input and output) must be close to the regulator. The most important aspect of SMPS is to reduce high current loops. The recommended layout shows a GND plane under the component, flooding over other components connecting to GND. There is also a skinny blue line representing a track on the bottom side of the board.  This is the feedback signal, the track is on the bottom side to reduce interference and must not be in the high current path. The PCB layout must follow this guide for it to function correctly. Here is the schematic and PCB layout to highlight the key areas, orange for input, purple for output and burgundy is feedback.   Comparison The PCB layout shows the input signal running from a plane (using vias) through the decoupling caps through the inductor and into the module (REG1 highlighted in yellow) via more caps. The output signal runs through decoupling caps and away through the inductor. The GND signals connect to the GND plane through vias at the module and at the decoupling caps. The burgundy feedback signal is routed from pin 4 of the module, through the resistor and capacitor…

How you can reduce your PCB manufacturing costs

  1. Smarter design Planning the PCB layout and assembly process is one of the most smart and cost effective ways of saving money. The strategical engineering of these boards can result in using fewer and more cost effective parts which will significantly lower the cost of each PCB. In the long run, this will enable your company to reduce costs and deliver high quality PCB layouts.   2. Use manufacturers reference designs Engineers designs can look good on paper but when it comes to design, costs could impact on overall cost and reduce profit. Costs can increase during the manufacturing stage. One of the cost effective ways is to refer to manufacturers notes. The information provided can save effort, time and money for the design to be produced. A decent chip manufacturer will provide a schematic, BOM, gerber and assembly drawings and reference designs. The reference designs are created by the manufacturer to show how the design is made to their specification.   3. Panelise Placing multiple PCBs on the same panel allows all of them to processed at the same time, instead of separately. Not only are boards manufactured like this, they are assembled and shipped on a single panel. The more PCBs on one panel, the more cost effective it becomes.   4. Get the Manufactures involved Providing the manufacturers with any information during the design process can pay dividends when it comes to releasing the production files. Board stack up, clearance issues, materials and special requirements - these could cause problems for the manufacturer and these could be costly if told in the last-minute. By communicating and agreeing with in advance this would give the manufacturer time to resolve any issues and even offer an alternative solution. You could have time to find an alternate manufacturer if your demands are not met.   5. Using the same assembly house for prototyping and mass production Once the boards have been designed and manufactured, the assembly process can begin. If there are no design changes between prototyping and productions it would be practical to use the same assembler for both and to start mass production as soon as possible. Material costs are fairly low, significantly lower when bought in bulk. The main costs are time spent assembling the PCB. It takes time to review the design and resolve any potential problems. It takes even more time to add…