The x hatching thing was very popular on two sided boards way long ago as
the liquid, non-photoimageable sm was over tin lead plating that was fused
(still the most solderable surface on earth to me but I'm old and imfermed
and how do you spell that on a midget laptop keyboard). The problem was,
molten metals, as tin lead fused metals reflowed during assembly thus
rendering the solder mask a bit unstable. This meant using x hatching was
needed to ensure better solder mask adhesion. Really, the solder mask had to
be used as a boat anchor to hold the solder down and for it to do its job -
the solder mask that is.
This also was a problem with the advent of direct IR reflow, instead of
peanut oil or hydrosqueegee methods used in fab shops at the time. Damned IR
would have worked too if only it had been convection. Should have seen those
boards explode or popcorn at the very least.
Multilayer x hatching on inners reached great popularity in the early '80's,
partly thankfully to me of course, in the ECL days when impedance was just
getting started.
I could post an example but why bother. Simply, my thesis (am I using that
word?) was we needed to satisfy both electrical/impedance requirements and
innerlaminar integrity along with dimensional stability. On the ground
plane's 100 mil centers were "traces," forming a grid, however but usually
40 mils leaving an open square area of 60 mils. This area allowed using a 40
mil square pad with 10 mils all around, or whatever depending on the ground
plane trace width. This left everyting on a 100 mil grid.
Now, the next layer down were the signal traces. You could run two 10 mil,
or so, traces directly under the 40 mil, or so, wide plane "traces" on the
layer above or below.
Hel, I'm getting tired of writing this. I can say it did work at that time
for the right reasons of the time and innerlaminar bond was great as was
registration and dimensional stability.
As for thieving, just don't let those R/F buys find you using it in your
designs.
Whew,
MoonMan
And I do know that was much more information than you needed.
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