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Consistency errors

maciv4

Well, its happened again. I have consistency errors. How do I resolve them. I have tried to delete the offending part from the schematic, both with the board open and closed. I have tried replacing the offending part with a new part from a brand new library. I have tried to delete the part from the schematic, close the schematic reopen the schematic and the board. I have airwires on the board but can't place or select the part. What do I try next?

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  • First, I have downloaded a DRC file from a board house, and that is what I'm using to check the parts. Second, how would I know if this file is changing the pads? I tried measuring the pad diameter by first changing the grid to a smaller increment and then recording the start diameter and the end diameter using the cursor.

    Thirdly, I have no idea if the errors can be ignored. They are between the pins of the component so I assume that they are important. I was getting overlap errors on the pins, those I felt I could ignore.

  • in reply to maciv4

    Jim McAuley wrote:

     

    First, I have downloaded a DRC file from a board house, and that is what I'm using to check the parts.

    Okay, that's one potential issue out of the way, that's fine.

    Jim McAuley wrote:

     

    Second, how would I know if this file is changing the pads? I tried measuring the pad diameter by first changing the grid to a smaller increment and then recording the start diameter and the end diameter using the cursor.

    I'd have the board and library part open side by side and zoomed in so the part fills the window. Then I would see if there was any obvious difference or start doing what you did with grids to try and determine any differences.

    Jim McAuley wrote:

     

    Thirdly, I have no idea if the errors can be ignored. They are between the pins of the component so I assume that they are important. I was getting overlap errors on the pins, those I felt I could ignore.

    Looking at the part, it's a 1.7mm pitch and the recommended pad diameter is 1.47mm nominal. That only leaves 0.23mm or 9 mil clearance before you even factor in tolerances so with a standard DRC file for a lot of online board houses that will probably give an error. That doesn't mean they can't do it though, these days most can easily, it might just add a little to the cost, but probably not if it's just one small part. Lots of components, especially fine pitch QFP / QFN parts will give DRC errors on a lot of standard DRC profiles and trying to increase clearances by reducing pad sizes to compensate may lead to solderability issues so you often have to make some compromises and either just approve these errors or start adjusting the DRC rules in order to be able to get a successful DRC pass.

     

    Is this a personal project or a commercial project? If its personal and you are hand soldering then you should be able to get it to work fine. If it's a commercial project and you need to think about long term manufacturing reliability then speak to your board house and get their opinion on it if you are concerned. Personally, if I were putting that on one of my boards I would probably just approve the DRC and make a note to investigate the soldering on my prototype boards to make sure there were no issues with shorts or incorrectly soldered joints.

     

    Best Regards,

     

    Rachael

  • in reply to rachaelp

    This is a commercial product, and the components will probably be hand soldered to start.

    I did check the library and the board component side by side as suggested, and found they are different. How do I get them to be the same? If I can do that on one board I can do that on any board. I am currently testing this out on a board that just has the two libraries alone, nothing else. Once I get that worked out I will try this on the finished product.

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  • in reply to rachaelp

    This is a commercial product, and the components will probably be hand soldered to start.

    I did check the library and the board component side by side as suggested, and found they are different. How do I get them to be the same? If I can do that on one board I can do that on any board. I am currently testing this out on a board that just has the two libraries alone, nothing else. Once I get that worked out I will try this on the finished product.

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