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I do board layout; the engineers use a “formula” to calculate board space required for components.
When they do the calculations, they don’t take into consideration for things like high voltage spacing; for lighting the IPC indicates ~.061” clearance between components and trace width and we require .075” spacing on test points for all nets for the flying probe.
Then when all the components won’t fit because of the DRC rules, I hear, well there just guidelines anyway.
Dave
I wonder if they used a formula or a desired form factor (board area). Certainly the engineer(s) gave you overview information on the project?
I'm sure you're using an auto router electrical board layout software. Do the best you can to meet that requirements knowing that reality may be that the board is smaller or maybe bigger.
There should be design guidelines in your organization and the software typically has settable parameters for spacing to industry standards.
[QUOTE=dperuso;17852]I do board layout; the engineers use a “formula” to calculate board space required for components.
When they do the calculations, they don’t take into consideration for things like high voltage spacing; for lighting the IPC indicates ~.061” clearance between components and trace width and we require .075” spacing on test points for all nets for the flying probe.
Then when all the components won’t fit because of the DRC rules, I hear, well there just guidelines anyway.
Dave[/QUOTE]
They use a formula but it doesn’t take into account the space needed for: lightning, the requirement for this is a .061” clarence between pads they only use the body dimension and they don’t include the trace width for high current traces; The test department requires a test point for every node with a .075 spacing requirement, this also isn’t taken into account.
The engineer is also required to fill out a PCB layout requirements document that tells the board designer what the DRC should be set for, these requirements come for the IPC rules.
In the end when I tell the product manager who sold the form factor based on their formula that all the parts won’t fit on the PCB, I’m told and I quote “ the IPC rules are a guideline”
When you deal with aircraft electronics there is no room for error.
So, I ask are the IPC rules only a guideline?
"So, I ask are the IPC rules only a guideline?"
Unless otherwise specified - yes