Gold has been a popular material in the electronics industry for many years due to the corrosion protection that it offers. In the early days, gold was applied as a thick layer however, this led to problems with the solder joint formation; the gold layer created an inter-metallic condition that could lead to fractures in the joints.
Military, aerospace, harsh environment applications and even some industrial standards specify that gold plating needs to be removed from devices prior to being soldered to the PCB. Such measures inhibit the formation of gold inter-metallic issues, escaping the risk of fractures forming in the solder joint as a result.
With the almost total market domination of Electroless Nickel Immersion Gold (ENIG) finish on PCB’s, the risk of soldering a gold component to a pad is great. This in itself can make even the smallest of contributions to the gold percentage running a real risk of brittleness caused by gold dendrite growth. Historically, research into gold embrittlement has referenced the specific thickness of the gold plating. However, it is now proven that gold that dendrites inside solder joints can form no matter the thickness of gold.
Many factors play a part in the risk of Gold Embrittlement including gold thickness, solder type, solder quantity, ramp rate, dwell times and gold layer condition.
The Retronix solution is to remove the gold from the termination, using our in house alloy conversion process:
This trend has expanded through to customers in other sectors who are also now using our de-golding service when they would not have previously required the complete removal of the gold layer before assembly onto PCBs.
FURTHER INFORMATION IS AVAILABLE
Our Full BOM tinning brochure provides further details on our specialised service which can mitigate tin whiskers, convert from RoHS to Non-RoHS and vice versa.
The change was reflected in the J-STD-001 from rev E to rev F.
J-STD-001 Revision “E” stated :
4.5.1 Gold Removal
Gold shall be removed:
A double tinning process or dynamic solder wave may be used for gold removal prior to mounting the component on the assembly.
J STD-001 Revision “F” (For all classes) now states:
(the changes are underlined)
4.5.1 Gold Removal
Gold removal is performed to reduce the risk of failure associated with embrittled solder. Gold embrittlement is not a visually inspectable anomaly. In cases where analysis has determined there is a gold embrittlement condition, the gold embrittlement shall be considered a defect, see IPC-HDBK-001 or IPC-AJ-820 handbook for guidance. Except as noted above, gold shall be removed:
A double tinning process or dynamic solder wave may be used for gold removal prior to mounting the component on the assembly.
Note: Gold embrittled solder connections can occur regardless of gold thickness when solder volume is low or the soldering process dwell time is not sufficient to allow the gold to dissolve throughout the entire solder joint.
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