Necking traces - Page 1
Forum section: electronics / general

author: Simon
author_rank: Unknown
timestamp: November 29, 2019, 11:23:16 am
content: I need to pass traces between some closely spaced header pins (2 row). Ideally i want 0.25mm tracks but this is impossible on 1.27mm pitched pins (https://www.eevblog.com/forum/eda/smallest-header-pin-pads/new/#new)But I could accept necking of tracks as they pass the pins. But I can't find any such option in KiCad. Is this currently not a feature?

author: langwadt
author_rank: Super Contributor
timestamp: November 29, 2019, 11:55:13 am
content: when routing just click to finalize the segment, change the track width (w/shift-w to step up/down the defined widths) and keep routing,

author: mark03
author_rank: Frequent Contributor
timestamp: November 29, 2019, 09:22:44 pm
content: It's not currently a feature AFAIK, but I think it's on the roadmap, maybe even in v6. Definitely one of my top issues with Kicad at the moment---although for me it's usually the starting and ending of a trace, rather than squeezing a trace through a tight gap. It's a huge pain when you can't use a trace any wider than the pin pitch, e.g. when laying out switching power supplies. You can always "paint" your way to an acceptable geometry, but it is ugly and time-consuming.

author: Simon
author_rank: Unknown
timestamp: November 30, 2019, 08:44:11 am
content: Ah well I will just have to route in the smaller trace and then increase the segments. I wonder if I can prep one trace set and then copy and paste it over the top.

author: pierreraymondrondelle
author_rank: Contributor
timestamp: November 30, 2019, 04:16:35 pm
content: Why not creating adequate SMD pads, put them on the bottom face and connect the tracks to ?

author: Simon
author_rank: Unknown
timestamp: November 30, 2019, 04:31:03 pm
content: Quote from: pierreraymondrondelle on November 30, 2019, 04:16:35 pmWhat? TH was prefered for mechanical strength. I could use SMD and put vias through the PCB and run everything underneath if the SMD pads will hold the module boards without breaking joints.

author: pierreraymondrondelle
author_rank: Contributor
timestamp: November 30, 2019, 09:00:38 pm
content: Sorry, maybe, I wasn't clear.In the past, when typons were handmade with decadry or Mecanorma pads and ribbon, there were dedicated footprints for DIL with "bones" in between the pads where the ribbon was glued on.When I proposed to use SMD pads, I was intending to design them narrower than the usual tracks, keeping the compliance to the insulation rules and to put them on the same side as the nominal tracks, between the pads. So no need to put vias. In fact it was an upgrade of the old fashioned bones !Specific footprints might even be designed. It is however important to insert the "bones" into the schematics, to give them a ref and a value in order that net names are allocated. I didn't do that yet but I think that multi-part symbols would do the trickI already used for months a similar method for creating jumpers on single side PCBs. They're also defined within eeschema, keeping the netnames they're connected to.The footprint has 3 pads connected together, on the library symbol they are stacked, the pin 1 name only is visible.I don't know if this fully acceptable regarding kicad's policy but I didn't get any warning from the error checker.PS. Sorry if the 4 pictures are not showing on the forum, this is the first time I'm trying to include an attachment.Thanks for the help to do it.

author: PlainName
author_rank: Super Contributor
timestamp: December 01, 2019, 02:14:09 pm
content: QuoteDo you do that because the jumpers are actual parts you specify on a BOM?

author: pierreraymondrondelle
author_rank: Contributor
timestamp: December 01, 2019, 11:02:29 pm
content: exactly

author: PlainName
author_rank: Super Contributor
timestamp: December 01, 2019, 11:13:26 pm
content: OK, thanks