Re: Can only get a single isolation pass around tracks #eagle #pcbgcode #etch

Rick Obel
 

I do not use smd. 

 

From: Rick Obel
Sent: Monday, August 20, 2018 11:05 AM
To: pcbgcode@groups.io
Subject: RE: [pcbgcode] Can only get a single isolation pass around tracks

 

I tried autoleveler and concluded (maybe wrongly) that the PCB board high spots were the result of very minor warpage, not inconsistencies in the materials’ thickness.  As a result, I reasoned, when the autoleveler measures the height, it does so without the benefit of any pressure (mere electrical contact triggers height measurement), but when cutting, a little pressure will force the PCB’s high spots down, with the result that they are not fully cut in those areas.  To remedy that problem, I bought a thick piece of Plexiglas, a vacuum pump and other materials to make my own vacuum board, but then realized that I could get good results, cutting not more than 0.10 mm in two passes of 0.05mm each, by simply leveling my MDF in advance of a days’ cutting.  (I don’t know if it moisture or thermal expansion/contraction, or otherwise, but I find that more than after a few days, the MDF takes on a warp of up to 0.10mm. )

 

I would be very interested to see others’ vacuum boards.  I saw Peter’s earlier comment about success with his vacuum board (table) and his good results cutting 0.2mm  -- he must have meant 0.20 mm, right?  Because 0.2mm is 4 passes at 0.05, and I typically need only 1 pass, and rarely more than two.  Am I missing something here?  The boards I am cutting are usually 4”x6”, and are much more problematic than 2”x3”.

 

 

From: pcbgcode@groups.io [mailto:pcbgcode@groups.io] On Behalf Of Bernardc
Sent: Monday, August 20, 2018 10:41 AM
To: pcbgcode@groups.io
Subject: Re: [pcbgcode] Can only get a single isolation pass around tracks

 

Assume that you not use SMD on your PCB as etching with 0.9 mm….

Autoleveler is perfect to correct the copper default. I use 2 flutes V type 60° dia 0.127 mm with 0.05 mm depth and it is not necessary to make further pass.  Mini = 0.0254, Max = 0.762, Step = 0.0508, Feedrate = 400, Turn = 12000 T/mn. I can etch for SSOP. (The problem remains welding ;-)..)

 

Bernard  

 

De : pcbgcode@groups.io [mailto:pcbgcode@groups.io] De la part de Rick Obel
Envoyé : lundi 20 août 2018 17:32
À : pcbgcode@groups.io
Objet : Re: [pcbgcode] Can only get a single isolation pass around tracks

 

My approach is very similar to Sam’s, but three differences that I believe help:

1.       Immediately before cutting a PCB, I pre-level my sacrifice board, which is MDF.  I believe that the MDF warps over time, even though I rarely remove it, or even adjust it.

2.       I don’t use angled bits (sorry I don’t know the correct terminology).  Instead, I find that conventional end mills produce a cleaner, more consistent cut.  I am still experimenting with diameters, but find 0.6mm breaks easily, while 0.9 is unnecessarily wide.  Lately, I have been using 0.7mm but will focus on 0.8 next.

3.       If the incomplete etching (is that the right word?) is localized, I will re-run just those areas at a deeper depth.

Rarely do I need three passes, and a second pass is only required about half the time.

-Rick

 

From: pcbgcode@groups.io [mailto:pcbgcode@groups.io] On Behalf Of sdmonaco via Groups.Io
Sent: Monday, August 20, 2018 7:56 AM
To: pcbgcode@groups.io
Subject: Re: [pcbgcode] Can only get a single isolation pass around tracks

 

Hi Albert,

 

You might try my single pass etch approach, which I now use for all of my boards.  I setup pcb-gcode to do a singe pass etch for all traces and shapes.  After completion, I inspect the board without removing it from the fixture.  If I see any areas with incomplete etching, I lower my z-axis zero point by 2 mils and re-etch the board with the same gcode file.  I continue with this until I have a nicely etched PCB which usually only takes about 1 to 3 passes.  This approach also corrects most leveling issues as well.  I try to keep my trace widths over 12 mils because each pass will shrink your trace width by about 1 mill for a 30 degree spade bit.

 

Sam

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