Posted on 25 Jun, 2015 by Russell Poppe
One of the most common requests an Electronics Manufacturing Services (EMS) provider will make before starting on a new assembly project will be for Computer Aided Design (CAD) data. And one of the most common responses to this request is "why"?
As an Original Equipment Manufacturer (OEM) this is confidential information - the essence of your product design - so why should you hand this over to your EMS partner, particularly in the early stages of a new relationship?
Let’s think about Printed Circuit Board Assemblies (PCBAs) first. Things have moved on considerably during the last few years. Gone are the days when PCBs were laid out with masking tape. Gone too are the days when surface mount (SMT) machines had to be manually programmed or test fixtures drilled by "digitising" the PCB, or from an x-y placement file cross referenced to a parts list. Sure, it can still be done – but why would you when modern tools make it so much easier and more accurate?
Modern manufacturing software systems take CAD input in a variety of formats, extract the relevant data for the target machine(s) and very quickly produce accurate outputs for surface mount machine programming, build documents and test programmes. Getting to the bottom line, if a manual process takes longer it’s going to cost more to do, and the EMS partner you are working with will be passing that onto you in one way or another.
But it’s not all about the obvious costs. Consider quality too. Any manual process is prone to human error, and if the information supplied is in any way ambiguous – or simply if there is a lot of it - then there is the possibility that something could go wrong.
Consider, for example, the silkscreen on a densely packed surface mount assembly, with the component references wedged in at various angles between the components. How sure can you be that you’ve matched the right designator to the right component? Do you really want your EMS provider to be programming their production lines or making expensive test fixtures with that information?
Programming from CAD takes the original design data and converts it directly into the production machine format, with no unreliable human intervention. Such software has been around for some years now, and is remarkably stable and accurate; after all, it is essentially just converting one format into another, which is hardly challenging by modern standards, for a computer anyway.
A common argument against the release of CAD data is protection of Intellectual Property. Certainly a fair concern of course, though the CAD required is usually only an output (e.g. the ASCII file), and not in the actual native CAD format itself. You will already be providing a CAD output called Gerber to get your bare PCBs made, plus the BoMs for component purchasing, and probably the circuit diagrams if test is involved, plus any device programmes; so in terms of handing over valuable information it’s already done.
For electrical and mechanical assemblies, provision of CAD files that can be transferred between systems is equally useful. For example, these files can be used to produce assembly guides. It also makes it possible for your EMS partner to update drawings where errors need to be corrected or changes incorporated, or where additional details (fixings and the like) need to be added.
Producing more detailed drawings or assembly instructions can help ensure a more consistent manufacturing standard and, where applicable, aid transition to lower cost manufacturing centres. Electrical schematics can be converted into "cutting lists" to help reduce manufacturing time. Naturally anything the EMS provider updates must be agreed and fed back to you so the drawings and revisions are consistent.
So, if you’ve had a PCB or mechanical product designed any time in the past 20 years then CAD data most probably exists – so why not get hold of it, pass it onto your EMS provider to avoid the potential for additional costs or human error during the manufacturing process?
If you already have the data but are concerned about trusting your EMS provider with it then it makes sense to go and audit their document control process and procedures if you haven’t already. Good EMS providers will be used to managing large amounts of complex data and should be happy to walk you through all the steps they take in keeping their clients' manufacturing data systemised and secure.
Image by: Siemens PLM Software
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