At the heart of virtually every electronic assembly is a printed circuit board (PCB) onto which semiconductors and other components are electrically and mechanically connected.
PCBs are designed using computer-aided design (CAD), so when the time comes to hand over from designer to manufacturer, the CAD information needs to be transferred to a computer-aided manufacturing (CAM) system.
In this blog post, Steve Shipway, Technical Manager at NCAB Group UK, provides us with his insight into the features, the advantages and the potential draw-backs of the two key data formats used in the world of PCB manufacturing.
The format and type of data file that you choose to transfer this essential information can make all the difference - both in terms of the speed and accuracy of the response to your request for quotation (RFQ) and in ensuring the quality and consistency of your finished board.
For the past thirty plus years, there have been two data formats that between them have succeeded in dominating the PCB manufacturing marketplace - RS-274X (Gerber) & ODB++.
Approximately 90% of all PCB designs worldwide are transferred from designer to fabricator using Gerber RS-274X, and, therefore, regarded by many as the de facto industry standard.
In contrast, the ODB++ file format is estimated to account for around 10% of the total PCB market. However, its simplicity and user friendliness are making it an increasingly compelling option.
So what are the differences between the two? And how do you decide which format is best suited to your needs?
Gerber RS-274X
The vast majority of all PCB designs produced worldwide are transferred as Gerber files using RS-274X. But what makes it so popular?
Well firstly, it's a simple concept that's been created specifically with PCB design in mind. It's clear and unambiguous - and easily person-readable should any questions arise.
It offers customers the reassurance of rendering accurate and precise designs - and each file is complete, meaning designers can draw any pad-shape or copper area that they want.
On most CAD systems the Gerber files are also output automatically which means designers rarely have to concern themselves with how their data is represented.
Despite its prevalence, however, RS-274X has some practical limitations. It's only able to provide a graphical representation of the design, the layer stack up isn't defined (which can result in boards where the copper layers are out of order) and it doesn't include drill information which increases the risk of drill holes being mis-registered or missed out completely.
ODB++
The ODB++ format was originally introduced to eliminate the need for a collection of CAM files in multiple formats by providing an intelligent, single-data structure for transferring PCB designs.
A key feature of ODB++ is its hierarchical structure which removes the necessity to work with multiple low-level files and which allows designers to transfer much more than just the standard conductor layer artwork and drill data.
Using ODB++ huge amounts of additional data can be contained within a single file - including material stack up, component bill of materials (BoM), component placement and dimension/fabrication data.
Its comprehensive file structure means there's less chance of machine or human error during production. The import and export diagnostics of ODB++ are also significantly reduced, so any errors can be identified, and eliminated, much earlier in the process.
On the downside though, the file size of ODB++ is always considerably larger, which can create some issues when trying to send data via email.
Deciding on the most most appropriate format with which to organise and hand over your complex PCB design information is a crucial decision that can directly impact the quality of your finished board.
The debate over which is best has been going on for decades - and it's one which is only likely to continue. The good news though is that with both options being commonly supported by electronics manufacturers, either could well be sufficient for your needs.
If in doubt, be sure to consult with your PCB supplier as early as possible. This way you can ensure you receive the speediest and most accurate response to your RFQ and you'll avoid the risk of any delays or misunderstandings during the design-to-manufacturing exchange process.
