Circuit Mechanix Sept 2016

Issue 3 September 2016 Circuit Mechanix The magazine for the PCB industry in the UKDesigning smaller PCB’s –The ChallengesFabrication pitfalls inmaking smaller PCB’sReview:Smaller PCB’s and theAssembly & Reworkchallenges.News & more...

Circuit Mechanix Circuit MechanixSeptember 2016 –Issue 1 Contents:The PCB magazine forthe UK printed circuitindustry.ContentsArticle:The challenges of shrinking PCB Designs P. 3Review: P.5SnapEDAIndustry News P. 9Article:The pitfalls in fabricating smaller PCB’s P.7Article:Smaller PCBs and overcoming the assemblyand re-work challenges they present P. 10Page 1 Circuit Mechanix – September 2016

Circuit MechanixMechanix MusingsWe’re now a the dizzying heights of issue three of Circuit Mechanix and this issuefocusses on miniaturization. Electronics is shrinking and continues to shrink. We needsqueeze more functions into a smaller space and maintain the reliability of function in thecircuit as well. This drive to shrink designs down impacts component packaging, design,thermal, noise considerations and everything else to do with it. This issue hopes theengineer around designing and making smaller and smaller electronics and how adesigner can limit the risk to the design failure.I would like to hear from you, the issues you have, the problems you can or can’t solve asthis will give me the feedback I need on the real problems you as engineers face so I candirect the content at these areas and who knows – maybe we can all learn something? Ifyou’re interested use the email to get in contact.Circuit Mechanix is aimed at being a useful, practical source of information for engineersand technicians working in the PCB industry. If you want more information, feel like youcan contribute in some way or if you’re a company that wants to see your name in CircuitMechanix then send an email to: [email protected], make sure to have a look at the new look Circuit Mechanix website. As more issuesare published there are more articles to view, building up a useful resource for and PCBor Electronics professional. Page 2 Circuit Mechanix – September 2016

The Challenges of Designing Smaller PCB’sThe PCB designer is our hero in this Once the circuit has been agreed andstory and hero’s never get an easy ride. all the necessary working out of whatThis story involves the evil manager of the circuit needs to do has been workedthe PCB designer walking up to him out there’s the next step.one day, possibly with the even moreevil mechanical engineer in tow. The Components:PCB engineer’s next task is to re- Most components come in more thandesign a board that they’ve put blood, one package type these days –sweat and tears into and make it even selecting the one that’s going to be thesmaller, based on the mechanical right fit is easy. Making sure it’sengineer’s drawings. available and still meets cost restrictions can be harder.Happy that this task has been offloadedthe evil manager and mechanicalengineer disappear, leaving our hero towork out how to do this.Sounds familiar?But what does our PCB engineer do PCB Strategy:next? The chances are that this isn’t Before starting any design work havingsmall reduction, they’ve not messed a design strategy is going to saveabout and want it half the size. Because messing about later in the process.the mechanics have already been made Every detail that can give or take spacethere’s no chance of negotiation. needs considering.The first thing is to go back to the Layers: Estimating how many moreengineer – what can be cut out of the layers will be needed ensures thedesign. Every component counts and design can be completed, too many willspare connectors can free up lots of add unnecessary cost.room. Continued on page 4…Page 3 Circuit Mechanix – September 2016

The Challenges of Designing Smaller PCB’s… The Challenges of Designing Silk Markings: So after all of this there still isSmaller PCB’s Continued. nowhere near enough room to squeeze everything in. Component references on theTrack and gap: Reducing the track silk screen are very useful, but they do take upand gap can have a big impact on a lot of space. A component reference for ansaving space in a board design. If 0402 component would need to be about twicethe components are being reduced as big as the component to be readable.in size then it makes sense toreduce the track and gap in line If the naming strategy hasn’t been created wellwith this. Check to see what the the component reference can dwarf thefabricator can achieve before component. So getting rid of them on the boardcommitting and see what the cost / will save a lot of space. Make sure there’s ayield implications might be. well checked and marked assembly drawing for the PCB – fault finding will be pain as it is,Via’s: Via’s can suddenly seem don’t make it harder!huge when using smallercomponents. See what the Now our hero the PCB designer has workedfabricator can make as a out how to work the impossible there are stillminimum, making sure the aspect issues that can foul things up. EMC, thermalratio is achievable. considerations and creepage and clearance are just some of them. Assembly issues canAnnular ring: If there are any arise from shrinking a design too and that’splated through holes in the PCB before testability and service and reworkdesign, reducing the annular ring problems.can help add some much neededspace. 2 x the drill hole diameter is When shrinking the size of electronics thereaccepted as the standard, are always compromises and they’re usuallyhowever 1.5 x the drill diameter is sent down the process chain. This is almosttypically the minimum that should unavoidable.be used. © Circuit Mechanix 2016Page 4 Circuit Mechanix – September 2016

Review: Snap EDAA few years ago I found out about aproject being undertaken calledSnapEDA, which aims to bring accurateand detailed library components to PCBdesign tools. The idea is to save timefor the PCB / electronics engineermaking library components and bringthem the parts they need across arange of different design tools.The idea came from Natasha Baker data downloaded straight to the(pictured right) who started Snap EDA engineer when they need it for free.to address the market of delivering PCB Snap EDA’s components are availablelibrary components to engineers quickly in formats that can be used by all of theand cost effectively. The website gives main PCB EDA providers. And area library of parts in it’s database, a constantly looking to expand the rangedesign hub from semiconductor of components they offer and the rangemanufacturer’s, a diagnostics tool for of tools that can be provided for.checking library parts and a communityto share key topics with other Labelling itself as the universal partsengineers. library their features and rate of progress means that this title is wellEach part in the SnapEDA library has deserved.it’s own symbol, PCB footprint andparts. Continued on page 6Page 5 Circuit Mechanix – September 2016

Review: Snap EDASnapEDA review – continued… When considering the time it takes to create complex components like IC’sBy interacting and addressing the $75 for a full part in 24 hours savesneeds of electronics and PCB time and a lot of money. The engineerengineers there may soon be a time is concentrating on design aspects aswhen spending hours making library they should be rather than takingparts could be a thing of the past. precious time in creating the part for their library.Into this mix SnapEDA just justlaunched a new feature into it‘s cluster Have a look at the website –of useful and innovative services – www.snapeda.com have a look and seeInstapart. The engineer can request a if they can transform library creation forpart for $29 or the part and it’s 3D you.model for $79 and is delivered fordownload within 24 hours. © Circuit Mechanix 2016Page 6 Circuit Mechanix – September 2016

Featured Article: Fabrication pitfalls in makingsmaller PCB’sThe thing with making PCB’s smaller – These issues are enough to give evenis that everything gets smaller. It the experienced PCB engineer asounds obvious but this is the cause of headache. In order to get the designthe issues with getting smaller PCB’s or right for fabrication the whole deignmore densely packed PCB fabricated. from the stackup upwards needs considering.The issue is that every detail is smallerand more prone to error in the In every PCB design there are tinymanufacturing process. Resistor pads details that exist, some my flag up asfor 0402, 0201, or the tiny pads of a design rules and some might not.BGA are smaller than what would be Slivers of solder mask that have beenpossible from mainstream fabricators processed in the design could causetwenty years ago. In those days such havoc with solder pads if they weredetails would have been the kind of made and came adrift. There has to bedetail that would have been fabricated that decision about who’s going toout and yet now engineers want it remove them in the processing – themade, with a solder resist aperture and fabricator or the PCB designer. Theplating with gold. With this is the other fabricator should be able to processissue with making the circuit tiny. The these small features out - but if they0.3 / 0.4mm hole used for via’s is now get missed it could mean trouble.far too big. Nowadays a 0.2mm hole orsmaller is frequently used, enabling The same can be true of coppercomponents with 0.5mm pitch pins to features caused when creating copperbe routed out without much difficulty. pours and plane layers. Tiny features can come adrift in processing andSmaller holes are required if designs cause connections to short, making aare to pack in all the connections they circuit useless. Getting rid of them atneed. The plating and aspect ratio of either end will save a huge amount ofthese holes needs to be taken into strife.account – this affects the entire designof the PCB. Continued on Page 8…Page 7 Circuit Mechanix – September 2016

Fabrication pitfalls in making smallerPCB’s - Continued…While testing and inspection at the Knowing and understanding thefabricator can pick up shorts in a circuit mechanics involved in PCB fabricationthe best approach is to give the process and how these will be applied toevery chance of being able to make a designs that are created is essential togood PCB without errors occurring. knowing the right questions to ask anyTesting and inspection is not 100% one involved in the fabricationaccurate, especially with the human processes. It’s hopeful to think thatfactor involved. When faults are found questions will be raised when issuesafter the board has been assembled are encountered, but this isn’t reliable.more time and money has been wastedon something potentially very simple It’s better to make sure there are as fewthat could have been avoided. questions as possible to be asked before the design is released – or doThe key is making sure the design and you trust your fabricator(s) that much?review process for a design is robustenough to pick up issues and to make Circuit Mechanix © 2016good decisions on what to do aboutthem. Sending PCB design’s out andkeeping your fingers crossed usuallyresults in a cross boss that wants toknow why good money has beenwasted.Page 8 Circuit Mechanix – September 2016

Circuit MechanixIndustry News: Options are now availablPage 9 Circuit Mechanix – September 2016

Overcoming the assembly and re-work challenges smaller PCB’s presentAssembling PCB’s with smaller proper, quality soldering iron and hot aircomponents has it’s own challenges. pencil as a minimum. But what aboutThe rework and inspection challenges techniques?are far greater however! Wen it comes to cut and hack’s they’re nearly impossible – but with a sharpRework / Repair: scalpel and a steady hand they can still be done. Circuit MedicThe hero PCB engineer had a tough (http://www.circuitmedic.com/) offers atime designing the PCB as small as range of kits which help with the cut andwas needed. With the best will in the hack process. With everything fromworld the electronics engineer made tracks in common widths to FR4some mistakes which now means that delamination repair kits they’re verythe PCB needs to be reworked or useful.repaired. Now the hero hat goes to theperson reworking the PCB. Having passives or discrete components inline on the track can helpBack in the nineties and early noughty’s if breaks need to be make –PCB’s were hard enough to repair, cut unsoldering them and standing them onand hack tracks could be done and legs end does this perfectly.of IC’s cut and hacked as necessary.Roll forward to today and with track and Links can be made with some of thegaps of 0.15mm or smaller, cut and small components that are on PCB’s.hacks are much harder. Our poor PCB Where the wire could be butted andrepair person is desperately trying to soldered onto the joint, today’s smallfind some component pins with not pads break very easily. Insteadmuch success. unsolder the component, solder the wire down and replace the part. ThisWhat can be done? follows for IC’s too – getting that part off is the only way to get to the pad. MakeThe key to any chance of success here sure that wires are secured downis equipment. A proper rework viewer though – any force WILL break them.like a Mantis isn’t optional, neither is a Continued on Page 11…Page 10 Circuit Mechanix – September 2016

Overcoming the assembly and re-work challenges smaller PCB’s presentAssembly and Rework of Multilayer While I can understand the businessPCB’s continued… case for such an approach, from an engineering point of view this makes noThe other problem that is obvious with sense, make sure that it’s understoodthese components with no legs is what’s required of them.inspecting them. Using an eye glassjust doesn’t cut it – what’s the point of Smaller boards also always mean moreinspecting the soldering of a part like layers, more copper and more heatthis when the pads are underneath. needed to unsolder parts during re- work. I dare to put into print thatCEM’s are increasingly using X-Ray sometimes the hot air gun that’sequipment to inspect boards after needed far exceeds the Jedec specs,assembly, but are they using this in the but this is the case. Getting all theinspection process? component to heat up so it can be removed and replaced again is often aIncredibly not all of them are, using x- necessary evil the re-work hero willray is an optional extra or has to be have to prepare for. So if there’sasked for especially. someone in the workplace with a hunch , squinting with sore fingers – you found you repair and rework tech. Give them a break and get them better kit! Circuit Mechanix © 2016Interested in seeing your company name in here, or doing something you want to tell everyone about? Email [email protected] for more information.Page 11 Circuit Mechanix – September 2016

Circuit Mechanix Next Issue: Next issue out in September 2016 - What’s going to be in it? Articles: Designing in reliability Enhancing the reliability of PCB’s Soldering and reliability. Review: Web based PCB resources. And more…Page 12 Circuit Mechanix – September 2016