Prototyping PCB's Part III - Bootnotes
ThIs article will take the form of a log of tips and tricks, and issues and opportunities as we gain more experience routing PCBs. Our successes to date have encouraged more complex boards, and more consistent results, but also some interesting observations...(click any photo to get a full size view)
CNC routing is not entirely without it's foibles though, and below we will get the ball rolling with one we found recently .. Exhibit 1 is a control board and will be the subject of our first notes
Exhibit 2 - incorrectly routed track
Exhibit 3 (click to see image full size)
Exhibit 4 (click to see image full size)
Routing Residual Artifacts
CNC routing is not entirely without it's foibles though, and below we will get the ball rolling with one we found recently .. Exhibit 1 is a control board and will be the subject of our first notes
Exhibit 1 Controller Board
This is the control board for a project we will review in these pages in the near future. From a process execution standpoint the making of the PCB had no issues. But in review we noticed a couple of errors. Looking closely (Exhibit 2) at the bottom right hand side of the copper is an anomoly. The track has been routed out completely as if there was to be a pad there
Exhibit 2 - incorrectly routed track
There is no pad in PCBNew (Exhibit 3), note the image is flipped because we are now looking at the top view (see the highlighted track).
Exhibit 3 (click to see image full size)
But if we delete a vertical and a horizontal segment of the track, in this area what is revealed is segment artifact that must have been left over from the initial layout editing. (see Ehibit 4).
Exhibit 4 (click to see image full size)
The artifact is easily deleted and quick to replace the segments in PCBNew, you'd have to make your own decision about re-routing another board, in this case it is a trivial task to solder over the 'pad' and extend the tracks. It would be interesting to know how a production house would handle such an issue.
Finishing your PCB
Elsewhere in these notes, you will find a comment about removing swarf and rough edges using 240 grit emery (sanding) paper. In particular this relates to edges caused a a result of blunted or broken tool bits.
Under normal circumstances it is not necessary to sand the copper side of your board. Aside from filing the tabs left as a part of the Edge Cuts function, usually all that is required is to wash the copper side in Isopropyl Alcholol (or similar), then spray the board with a light coat of solder flux, a quick wipe over and let dry for 30 minutes. The flux prevents the copper from oxidising, and assists the soldering process. When complete your board will be bright shining copper with no finger marks.
In the event there are some scratches, or a hard to remove substance (residual masking tape perhaps), a light rub over with green Scotchbrite will be more than enough abrasive to give that wonderful copper lustre...
Hope this is of some help, comments and questions are always welcome, thanks for dropping by ....
We have two other articles on related topics, they can be found here :
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