> ...but your number of "sub-composites" grows exponentially. In > theory, whatever the lowest-level composite is, your sub-composite > set is the power set of that!
No, because fabs can't drill that way. You can't have a copper layer that's part of two separate sub-assemblies before those sub-assemblies are assembled to each other. Let's say we're doing the top half of an 8-layer board... copper ----- 1 top fr4 ===== 2 copper ----- 3 fr4 ===== 4 copper ----- 5 fr4 ===== 6 copper ----- 7 fr4 ===== 8 center Now, depending on how the fab makes it, determines what combinations of buried vias are possible. For example, if the fab makes two two-sided boards and glues them to a core, you get this: copper ----- 1 -- fr4 ===== 2 ][ copper ----- 3 -- fr4 ===== 4 copper ----- 5 -- fr4 ===== 6 ][ copper ----- 7 -- fr4 ===== 8 Thus, you can via from 1-3 or from 5-7, but not 3-5 because you never have 3/4/5 as a separate drillable unit. Thus, the composite is: ((123) 4 (567) 8 ...) Blind and micro vias are just special cases of this. You'd sub-composite the top copper/fr4 so you could list drills there: (((12) 3) 4 (567) 8 ...) _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
