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BGA Chamfer

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AGONZ67 View Drop Down
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    Posted: 03 Dec 2012 at 3:05pm

When component dimensions are entered for a BGA package and the output created. The silkscreen chamfer will fall under the part as created if the physical part does not have a chamfer. All BGA packages do not physically have a corner chamfer so this silkscreen will sometimes be under the component and not visible after assembly. This violates the basic rule, "no silkscreen under the component" and "all silkscreen outlines visible after assembly". Maybe the chamfer can be eliminated and the remaining silkscreen without the chamfer would serve as the pin one indicator? I know there was discussion before on this, & there was a post showing the corner with a line extending from it on the silkscreen.

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Tom H View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Tom H Quote  Post ReplyReply Direct Link To This Post Posted: 03 Dec 2012 at 3:12pm
The BGA, CGA is an exception because the plastic package is lifted off the board surface by the Balls or Columns.
 
We didn't have to chamfer the BGA silkscreen and just left two lines. The absense of silkscreen is popular for all "Bottom Only" terminal packages.
 
But you can see the BGA silkscreen chamfer by tilting the PCB to look under the BGA.
 
When you look straight down on a BGA you cannot see the chamfer but you do immediately notice lines that do not form a crop mark (like the other 3 corners).
 
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