The annular nail has a high initial peak; however, the load generally decays quickly due to the annular rings
"coring" the wood.
It should be noted that although the wider traces offer some protection against copper erosion of the exposed portion of the trace, the "knee"--the area where the annular ring
meets the barrel--is typically a bit thinner than the barrel or the ring, and can be very vulnerable to erosion.
Classes 1 and 2 permit some missing annular ring
on internal layers, expressed as "breakout angle.
Tenders are invited for Annular Ring
I've seen some that just use the via's annular ring
Shrinkage grooves appeared minimal, with the groove propagation only slightly deeper than the annular ring
for both alloys.
In the past, breakout and annular ring
requirements were for holewall reliability concerns.
Install mechanical anchorage or annular ring
Drill diameters were compared to copper pad sizes to ensure sufficient annular ring
for minimum acceptability.
An established dissolution hierarchy confirmed that the knee location has the highest dissolution rate, followed (in order) by the annular ring
(or pad) geometries and the inner barrel wall (Figure 1).
The arrow indicates a tangency feature, called zero annular ring
Knees, the area where the barrel of the PTH meets the annular ring
, are particularly susceptible to erosion problems.