By Mark Thompson | Published on: January 13, 2014
This series topic of CAD/CAM is very near and dear to my heart having done the "front end" of PCB fabrication for over 30 years.
CAM vs. Capability
Many new customers have some misconceptions about what a typical Fab shop can and cannot do. There are levels of manufacturing that need to be well understood by the Buyer. The PCB Buyer needs to know where a board will be a good fit based on the parts complexity. How does this happen? How does the PCB Buyer or a contract manufacturer know who is and who is not a good fit based on a myriad of different designs from simple 2 to 4 layer RF parts to high layer count HDI, blind and buried via parts? If the part is of medium complexity, (meaning it can be built by virtually any mid to higher level PCB fabricator) Many times it boils down to things like quote response time. More diligent Buyers may use a tool such as the PCB List through this site where they can compare technology levels side by side and make good decisions about where a part should go. Not all PCB Buyers need a shop that can do 2 mil lines and spaces or laser stacked vias. Sometimes the product dictates a shop of this type must be used, other times, when a given design does not “push” the fabricators limits more fabricators obviously then have an opportunity to show what they can do.
What is CAM?
Not all Board fabricators have the ability to have both CAD and CAM. You may say to yourself, “But a CAM tool should be able to do some if not all CAD functions” and that is true but if you are really getting to the Design level you need to have a design team. Many PCB fabricators do NOT have Design capabilities but DO have the ability to understand the customers’ needs and recognize design attributes.
Let me give you some examples of this from simple CAM assumptions to more complex ones.. Let’s say a design has copper poured right to the edge of the part but is NOT a Z axis or edge plated part, A good CAM department may do a very minimal clip of the metal around the periphery like .003-.004. This is imperceptible to the end user as it appears metal is right to the edge and if the metal would have been left alone there may be burring at final rout. (Functional, but not cosmetically the best ... )Again, this is where a Good CAM person comes into play, when would they NOT do something like a minimal clip for rout? RF launches on an Obvious RF part, Here, we know the intention is to literally have metal right to the edge and that any burring at final rout is acceptable with the customer. This is where their understanding of electrical function comes in as well, that and YEARS of practical experience.
And when I say “CAM” department I mean both PEOPLE and TOOLS as the TOOLS are only as good as the People behind it. I have said many times a good CAM operator is worth their weight in gold.
Likewise there are MANY levels of designers and layout folks. Some with years of knowledge and good common sense layout practices. These are the guys and gals that ask the important questions at the right time, which is to say at the design/layout stage and not after the part gets to the board fabricator.
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