60 PCB007 MAGAZINE I JUNE 2025
When we consider via reliability, the major
contributing factors are typically process-
ing deviations. ese can be subtle and not
always visible. One particularly insightful
column was by Mike Carano, "Causes of Plat-
ing Voids, Pre-electroless Copper," where he
outlined some of the possible causes of hole
defects for both plated through-hole (PTH)
and blind vias. Some of these causes are:
• Poor drilling resulting in rough hole walls
(many possible causes)
• Non-optimized laser drilling for microvias
(six different parameters to consider)
• Improper material curing
Other pre-metallization causes can be:
• e desmear operation that is not in con-
trol (the solvent conditioning, alkaline
permanganate, neutralizer, and glass etch)
• Inadequate textured Cu surface for
palladium coverage
ese can contribute to minimum or insuf-
ficient metal coverage in the conductor via,
resulting in partial voids that lead to prema-
ture hole failure.
For further discussion on this important
topic, I will reference the work of a dear friend
and colleague, Dr. Karl H. Dietz, a renowned
Happy's Tech Talk #40
Feature Column by Happy Holden, I-CONNECT007
Factors in PTH
Reliability: Hole Voids
