What is New in IPC-7351C.pdf - 第26页

PC B L ibr ar i es Pr e s ents : Wh at is N ew i n IPC- 7351C Sna p G ri d & F e atur e R ou nd-of f 0.01 mm Footp r int F e atures in 0.0 1 mm inc reme nts *Jap anese 80% r ule 0.0 1 0.0 1 0 .0 1 0.0 05 f o r 0.65 p…

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PCB Libraries Presents:
What is New in IPC-7351C
• The land pattern origin is typically located at the center of gravity of the
component, but sometimes this is difficult to calculate with irregular
shaped components, so Pin 1 is used in these cases. Also Pin 1 in most
through-hole connectors.
• The centroid origin marking in the picture below is an unfilled 0.50 mm
diameter circle with a 0.05 line width with a 0.70 crosshair for cursor
alignment.
Land Pattern Origin Guidelines
PCB Libraries Presents:
What is New in IPC-7351C
Snap Grid & Feature Round-off 0.01 mm
Footprint Features in 0.01 mm increments
*Japanese 80% rule
0.01
0.01
0.01
0.005 for 0.65 pitch
0.01
0.01
0.01
0.01
0.01
0.01
0.01
Line Widths
0.01
Corner Radius
0.01
PCB Libraries Presents:
What is New in IPC-7351C
• Local Fiducials have been used only on fine pitch QFP and BGA
Land Patterns
• Fine pitch QFP = Less than 25 mil (0.635 mm) pitch
• Fine pitch BGA = Less than 32 mil (0.8 mm) pitch
• Future Local Fiducial sizes will be:
• Level A (Most) = 40 mil (1.0 mm) with 80 mil (2.0 mm) solder mask & keep-out
• Level B (Nominal) = 30 mil (0.75 mm) with 60 (1.5 mm) solder mask & keep-out
• Level C (Least) = 20 mil (0.5 mm) with 40 mil (1.0 mm) solder mask & keep-out
3-Tier Local Fiducials