{"id":499,"date":"2010-01-22T11:46:32","date_gmt":"2010-01-22T10:46:32","guid":{"rendered":"http:\/\/www.ibexuk.com\/resource\/?p=499"},"modified":"2022-02-18T15:05:18","modified_gmt":"2022-02-18T15:05:18","slug":"a-good-pcb-design-checklist","status":"publish","type":"post","link":"https:\/\/ibex.tech\/resources\/geek-area\/electronics\/pcb-design\/general-pcb-design\/a-good-pcb-design-checklist","title":{"rendered":"Good PCB Design Checklist"},"content":{"rendered":"<p>A good list of checks to make before committing the design of a new printed circuit board:<\/p>\n<ul>\n<li>EMI &amp; Signal Integrity checks:<\/li>\n<\/ul>\n<p style=\"padding-left: 60px;\">Are there decoupling capacitors in all areas where there are connectors or via&#8217;s, to  minimise EMI loop sizes of signals and their return ground path?  If not do you need to add some?  A power plane will act like the ground plane to high speed signals as long as the return signal can jump to the real ground plane through a nearby decoupling capacitor.<\/p>\n<p style=\"padding-left: 60px;\">Ensure all high speed signal traces run over their own ground \/ power planes.  Do not allow say a digital signal to travel over the analog plane unless it is going to a device in that area and in which case follow the devices digital ground trace to minimise the loop and therefore noise.<\/p>\n<p style=\"padding-left: 60px;\">If there are any slots or gaps in the Gnd \/ Power planes ensure no high speed signals run over them (to avoid the return path having to loop round, creating EMI problems).<\/p>\n<p style=\"padding-left: 60px;\">For high speed signals minimise track stubs (to below the critical length &#8211; ideally &lt; 6.5mm, no more than 12mm for a 1ns rise time signal).<\/p>\n<p style=\"padding-left: 60px;\">Ideally high speed connectors should have the ground plane getting through between pins to avoid signal return paths having to go round the connector to a ground pin on it.<\/p>\n<p style=\"padding-left: 60px;\">Differential pair tracks are as close together as possible, or spaced based on impedance calculation?<\/p>\n<p style=\"padding-left: 60px;\">Do any high speed signals need termination?  This can be to VCC or Gnd and ideally should be at end of bus after the last receiving device.  A good value is typically 50ohm, but anywhere from 30 &#8211; 100ohms is often fine.  Should ideally match the impedance of the track.<\/p>\n<ul>\n<li>Add test points for important buses and connections to tight SMD chips so its easy to attach a wire or scope probe.<\/li>\n<\/ul>\n<ul>\n<li>Are power tracks big enough and do they have big enough via&#8217;s?<\/li>\n<\/ul>\n<ul>\n<li>Are there any very big through hole components such as elect capacitors?\u00a0 If so don&#8217;t connect to internal layers on multilayer designs in case they get knocked and the internal connection is damaged.<\/li>\n<\/ul>\n<ul>\n<li>Check connections into power planes on &gt;2 layer boards are big enough (enough via&#8217;s and big enough tracks).<\/li>\n<\/ul>\n<ul>\n<li>Check all important IC power pins have good decoupling capacitor connections<\/li>\n<\/ul>\n<ul>\n<li>Check crystal connections are short<\/li>\n<\/ul>\n<ul>\n<li>Do you need to add manufacturer test points (pads) for voltage rails etc?<\/li>\n<\/ul>\n<ul>\n<li>Are there components that need copper plane heatsinking (voltage regulators, mosfets etc)?<\/li>\n<\/ul>\n<ul>\n<li>Do you need to separate earth tracks from other tracks to avoid static problems?<\/li>\n<\/ul>\n<ul>\n<li>Are all jumpers, connectors etc labelled on the silkscreen?<\/li>\n<\/ul>\n<ul>\n<li>Check all surface mount pads have tracks that come out of the end, not the side (i.e. no links between adjacent IC pads that will look like a short during inspection).<\/li>\n<\/ul>\n<ul>\n<li>Do you need to add fiducial marks for the pick and place machine?<\/li>\n<\/ul>\n<ul>\n<li>Are there nets that need their length equalised (e.g. fast differential connections such as Ethernet)?<\/li>\n<\/ul>\n<ul>\n<li>Add a hatch fill done on both sides connected to GND to improve EMC?\u00a0 These are a good general setting for the fill:- Track width:\t\t0.3mm, Grid size:\t\t\t0.6mm<\/li>\n<\/ul>\n<ul>\n<li>Create board outline on a mechanical layer<\/li>\n<\/ul>\n<ul>\n<li>Do a final design rule check<\/li>\n<\/ul>\n<ul>\n<li>Double check mounting positions will be OK in the equipment the PCB is fitted in.<\/li>\n<\/ul>\n","protected":false},"excerpt":{"rendered":"<p>A good list of checks to make before committing the design of a new printed circuit board: EMI &amp; Signal Integrity checks: Are there decoupling capacitors in all areas where there are connectors or via&#8217;s, to minimise EMI loop sizes of signals and their return ground path? If not do you need to add some? [&hellip;]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[31],"tags":[],"class_list":["post-499","post","type-post","status-publish","format-standard","hentry","category-general-pcb-design"],"_links":{"self":[{"href":"https:\/\/ibex.tech\/resources\/wp-json\/wp\/v2\/posts\/499","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/ibex.tech\/resources\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/ibex.tech\/resources\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/ibex.tech\/resources\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/ibex.tech\/resources\/wp-json\/wp\/v2\/comments?post=499"}],"version-history":[{"count":1,"href":"https:\/\/ibex.tech\/resources\/wp-json\/wp\/v2\/posts\/499\/revisions"}],"predecessor-version":[{"id":1606,"href":"https:\/\/ibex.tech\/resources\/wp-json\/wp\/v2\/posts\/499\/revisions\/1606"}],"wp:attachment":[{"href":"https:\/\/ibex.tech\/resources\/wp-json\/wp\/v2\/media?parent=499"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/ibex.tech\/resources\/wp-json\/wp\/v2\/categories?post=499"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/ibex.tech\/resources\/wp-json\/wp\/v2\/tags?post=499"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}