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Failure is not an option for a PCB

More than 30% of the Gerbers NCAB Group Benelux B.V. reviews, have problems. However, the PCB are integrated in key end-user product with more and more High Tech PCB. We are here to support you on the new technologies growth to maintain a high reliability and quality. Contact us to review it together.
High-tech PCBs – Make the right choice for a reliable design By NCAB Group Benelux B.V. Electronic products offer more advanced functions, while the products themselves are becoming smaller. This puts greater constraints on the PCB (printed circuit board) design and the manufacturing process. The PCB reliability becomes a critical factor right from the start of the PCB production process. If a PCB has a reliability issue, the end-product itself is at risk. Designing reliable PCBs is an outcome of considering all aspects that can affect reliability as early as possible in the design process. As a custom component, the PCB’s purpose is critical. A good board design improves the reliability of the end product and reduces the risk of failure. GET THE RIGHT DESIGN THE FIRST TIME A key aspect to prioritise with advanced/high-tech boards is the design itself. The margins are tiny with regard to such factors as conductor widths, impedance requirements (could reach >20% price impact), isolation distances between copper features… All these pose a considerable challenge at the layout stage. Bengt Bostrom, PCB Engineer at NCAB mentioned “be careful when choosing components for a new design. For example, to select a 0,4mm pitch BGA that requires µvias to be able to rout out the tracks can be very costly if it is one single component in a whole design. To add a process have a significant cost, when decision is made you can use it frequently on the board for the same initial cost”. It is key to zoom in some key features for designing and producing a reliable PCB as seen by NCAB Group Benelux B.V. Note that some of these features are not mentioned in IPC standards, but NCAB finds these ones critical. For high-reliability PCB, here some guidelines we recommend in general and for HDI: 1. No track welding or open circuit repair 2. 25-micron nominal hole plating per IPC Class 3 3. Tolerance for copper-clad laminate is IPC-4101 Class B/L 4. Defined solder mask, ensuring accordance to IPC-SM-840 class T 5. Tighter requirements of resin filling (TYPE VI & VII) ZOOM IN THE HDI DESIGN With the miniaturization of components (in The Netherlands free seminar on November 13th), a key growth is on the HDI (High Density Interconnect) technology. We need to face higher layers’ number, more connections in and out the PCB, utilising finer conductor widths and narrower spaces between them, special via, since normal through hole vias simply wouldn’t fit into the space available. All of which increases the number of interconnections within the board and frees up valuable space on the outer layer for more components to be placed. Nikolina Strezovska, PCB Engineer highlighted that “the first consideration in generating micro vias is that of advanced laser drills that can drill blind holes, down to 50µm, although most micro vias normally have a diameter of around 100µm. The latest generations of these machines are capable of drilling up to 500 holes a secondPositioning the solder mask correctly against the pattern poses a significant challenge, since extreme components have to provide registration down to 37µm (and in extreme cases, 25µm). NCAB Group sees some incorrect or missing information on this high-tech technology that are not properly mentioned in the customer design. We found: • Too small microvia size required • Dielectric too thick for some laser via • Too tight demands on permitted dimple on copper filled microvias • Too small capture and target lands for the microvia • Too tight demands on the thickness of overplating of plugged via For the HDI, it is not only a challenge for the PCB manufacturer but also for the component manufacturer who got the challenge level increased. For example, if you can avoid BGA escape routes that use six or seven different layers of blind or buried vias and reduce it to a standard multilayer board, it is a good idea to do so. Avoid making a PCB design that is limited to a single factory’s unique processes. GET A RIGHT SET OF DATA In many situations, the supplier is involved too late in the design and cannot support a good product specification. It is key to have a dialogue with the customer before the quotation phase and until the production begins. Our experience at NCAB shows that about 30% of all of the new articles provided to us arrive with missing data or contain ambiguous or conflicting information in describing the build. This causes many engineering questions to be raised, which take time to clarify and can easily affect delivery dates. It can be unspecified features (soldermask, material, drill files…), contradictory PCB dimensions between drawing and Gerber, specific impedance… We could recommend: • To provide the original data and not just a specification • Include the stackup • Create a specification of fabrication datasheet referring to the different IPC (if you are interested in a seminar for your company as so many IPC, let me know). DO NOT OVERSPECIFY We receive some requests, which are too detailed. Being too specific when telling your supplier what the design requires can potentially cause unintentional costs. For example, it may seem like a good idea to specify an exact material from a precise brand to ensure adequate control. It may seem contradictory at first, but unless the design absolutely requires one specific material only, it might be safer to specify an IPC standard and benefit from a number of approved brands. If demanding impedance of 5%, IPC class 3 full requirements or gold fingers when not necessary have a big impact on costs. (if you are interested in a PCB cost driver presentation, contact me). In conclusion, there are many factors to consider when first designing and then transferring a board to a supplier in order to build a reliable PCB It is important to choose a supplier who values quality, takes full responsibility for production, and works with you as a partner to help produce a reliable PCB. You can check on our website to get our Free design guidelines on all the high-tech technologies https://www.ncabgroup.com/pcb-design-guidelines/ Don't forget to join our free seminar, click this link for more information: NCAB Group seminar Ingrid De Leeuw Benelux MD - Ncab Group Benelux B.V.
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December 12 2019 10:59 am V14.8.5-1