Welcome everyone to the PCB Fabrication blog.
I consider myself fortunate to have left my decision late to become an electrical engineer, having dabbled in a mechanical engineering career in my early working years.
That’s because when I started working in electrical/electronic design in the mid 1980’s, it was the advent of CAD tools for PCB layout and I made the decision right there and then that I would never want to spend endless hours cutting up strips of red tape and sticking them on pieces of paper large enough to carpet my living room, in order to provide the appropriate data needed to get a PCB fabricated.
I worked alongside those crusty old guys who had spent their entire careers in manual PCB design and even in my mid to late 20’s I was still considered a bit “flash” and an upstart just because I was the one using the new fangled computer software programs to design the PCB in a lot less time then they did.
So, I decided early on that the more data I sent to the fabricators the better and would generate every conceivable output that the CAD system was capable of at that time. Along with a Gerber file of every electrical layer, I provided drill and dimension drawings, Silkscreen, Solder Mask, Solder Paste layers and some component placement information, the list went on and the cool thing was that I generated it all on magnetic media (1/2 Inch tape reels at that time) no need for those living room sized pieces of paper.
However this was not a fool proof process, as more than once I wrote “all” my data to tape, then drove to the PCB fabricator to proudly deliver my PCB only to find that I forgotten something. Sometimes it was the tape recorders fault of course and certain Gerber files were not written to the tape, or maybe it just me rushing and I forgot to see the message regarding “please insert a 2nd tape” or something like that, or I failed to get a work order or pre approval from the buyers or other necessary documentation was missing.
So has anything really changed since then?
What are the typical data sets you provide to the PCB fabricators today?
It’s a fool proof process today right?
How many times do get a call from the fabricator to inform you that that cannot fabricate the board because of missing data or because critical design failures? Or that they can get the job done if you allow them to modify some of the supplied data!!!
Over the past few years I’ve worked quite closely with some customers and their fabricators to understand some of the issues regarding the critical design failures, after all there is nothing I can really do to help if you simply forget to provide a contract review or obtain financial approval.
The critical design failures appear to be fairly consistent and could be categorized as follows:
- Unable to add etch compensation (At the fabricator, due mainly to the ever decreasing feature sizes)
- Unbalanced build of the PCB design (The stackup simply does not jive)
- Annular ring failure (That smallest drill size will just not work with a board stackup this thick!)
- Unbalanced copper (On each of the PCB metal layers)
- Thermal annular ring failure (One 10 mil spoke will never be enough on a Ground pin on that negative plane layer)
- Plane layer clearances (Your minimum design clearance will just not suffice)
- Minimum track width failure (I know you had to neck down to squeeze those few traces in, but if they cannot be fabricated!)
Anyway, you may be familiar with some of the above problems or you may have others of your own? Why not share those and you resolve those issues with this audience?
My question is: has the advent of more sophisticated PCB CAD tools and fabrication/manufacturing formats made the process any more fool proof?
P.S. For those of you who already know me and noticed in my avatar that I was dressed in a suit and tie and wondered, “what’s up with that?”, well I recently became a US Citizen, (the photo was from the Naturalization Ceremony) so now I can do anything you can do, except become President of the United States of America. But watch out Bill Ritter, if it Arnold Schwarzenegger can become Governor of California, why can’t I become the Governor of Colorado.
A more advanced PCB CAD tool may allow you to place more constraints, or more complex DFM checking, but neither will do you any good if you source information is incorrect.
There is no substitue for knowing exactly what your fabricator can and cannot do, what will and wont add extra cost.
The second part of the equation is the diligence and abilities of you fabricator in checking the data your send them, some will accept what you send them as being "gospel" and will assume that you really did mean to drill a 3mm npth hole through the middle of that collection of pads. Other will question it.
Of course, after a period of time with a given fabricator, you build a raport, and they will know the nuances of you particualr designs, but this sort of thing can only be learned over time.
Of course, people should use DFM checks, checklisting and so on, but it os no good checking whether there are any traces under 0.1mm when your fabricator can only handle 0.2mmm