106 glass has quite a history as a low-priced, dual-ply alternative adjacent to power planes, in part as a means of managing dielectric-breakdown risks (e.g., electrochemical migration
, arcing, etc.) At higher speeds, where glass-weave skew (GWS) is a concern, dual-ply 1067 is in vogue.
Other analytical test methods include electrochemical migration
resistance and surface organic contamination testing, each performed in accordance with IPC standards.
Contamination "favors" moisture absorption, and with it comes electrochemical migration
and corrosion-induced leakage currents.
Abstract: This paper focuses on understanding the synergistic effect of contamination, humidity, PCB surface finish, pitch, and potential bias on leakage current under different humidity levels, and electrochemical migration
probability under condensing conditions.
Three common failure mechanisms that tray come into play on RF high-frequency circuits are electrochemical migration
(ECM), electromigration (EM), and parasitic capacitance.
This means that the cleaning agent might not be able to clean at its full strength, possibly resulting in board failure due to contamination-induced electrochemical migration
. But there is no way of knowing, unless the operator sends the contaminated sample to the cleaning agent manufacturer and has more elaborate analytical tests performed, such as GC (gas chromatograph) measurements.
ECM, or electrochemical migration
(FIGURE 1), can wreak havoc on a circuit assembly, causing everything from harmless signal glitches to complete failures.
Conductive anode filament (CAF) is a conductive copper-containing salt created by electrochemical migration
. It is a significant and potentially dangerous source of electrical failure in the PCB.
To err on the side of safety, I would suggest subjecting the product to SIR or electrochemical migration
tests when processed under the coolest anticipated SnPb profile--with an adequate safety margin--before it is introduced into production.
Group B Bromide findings of contamination levels of bromide below 7.0 [micro]g/[in.sup.2] or less have good high SIR values and no signs of electromigration for 6, 10 and 50 mil spacing, while levels of 5 [micro]g/[in.sup.2] and 10[micro]g/[in.sup.2] show low SIR and the presence of dendrite shorting, which is considered failing per the IPC criteria, with values less than 1.0e8 ohms of resistivity or signs of electrochemical migration
debris (FIGURE 13).
The coating can crack and temperature fluctuations and moisture can lead to electrochemical migration
and leakage currents.