|Yesterday, 07:49 AM||#53|
Join Date: Apr 2012
Location: Bern, Switzerland
Because is has influence on the Circuit
I have to redesign a PCB for a Class A the third time because of Capacitive Problems where the layout of two lines do falsify the output of the input Signal, creating Noise and generating not recoverable Errors like Hum, Noise, Oscillation, all stuff no one wants.
Make short, and where ever it's possible thin lines except when there is a lot of power passing through. If you need to draw long lines - over 10 cm in lengt to make them at least 2mm wide, and if these are Signal lines, stay away from lines which powers up the Board. because of inductive and capacitive noise generation which will occur on the board.
Make if possible a double Layer, if you can't do by yourself then let some shop do it for you. Use a top ground Plane if possible.
I make my double layer by myself. If you need help on that I have wrote some documentation on this some years ago. Can be uploaded here..
The most important thing is, work exactly and clean. If you use Positive Photo reactive PCB from Bangard or any manufacturer, be sure to read their instruction. DO NOT USE TRANSPARENT FILM when you print the LAYOUT with a LASER PRINTER.. I assure you, there will be a lot of Testing and wasted PCB's.
Use Transparent Drawing Paper this will work very well. Make sure that you put the PRINTED SIDE FACE DOWN on the PCB to Avoid Ghost images. After you printed the Layout, check the print if its really DARK BLACK . If you find parts of the print where you think that it needs to be better either print a second sheet and put it over the first one - or manually correct it using Black No Water soluble drawing Pen. Make sure that the PCB side is correct before you print Negative Positive..it's not the same if you look a the PCB "through the PCB" at the lines or if you Flip it.. and look it from Bottom.
May there is need of inverted Printing for double sided PCB. Otherwise when the PCB is finished you will not be able to place the parts as you wish if layout on the PCB is the wrong way around..
Check development Times of the developer you will use.
Check Water temp and amount of developer used with a Scale, which is accurate to at least 1Gramm/Kilo or better.
If you use ACID to Edge the lines, like Ferro3 or similar, make sure that you stand by there while its etching. Use Warm Water of about 50Degrees Celsius, this will speed up the edging and also give better results..From time to time shake the container with the acid that some Air gets into it, this will sure help to reduce etching time.
Documentation you can find on the internet if you want to know more than this or have any other question., all you need to do is to ask.
Hope this helps
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