All recommended material in the case of CERN converter design can be found in the table below.

Material	Type		Treatment
Copper	C101/CW004A (ETP) Purity 99.9 %		Tin Plating - Matte (mandatory) Thickness > 12 µm
			Silver Plating Thickness > 12 µm
			Nickel plating Thickness > 12 µm
Aluminium	5xxx family : 5754-H111		Required on electrically conductive parts Surtec 650 Chromium(VI)-Free Passivation Surface Density > 110 mg/m2
	6xxx family: 6082-T6
Steel	Mild Steel (Low Carbon Steel)		Zinc Hot-dip galvanization Thickness > 50 µm
			Nickel plating Thickness > 10 µm
Stainless Steel	3xx Family:	316L	Not required
		304L

More information available here: "Material types and treatments for standard mechanical parts design", EDMS N° 1909061.

A specific treatment of all aluminium plates and pieces used in power module case conception is required to ensure a good electrical conductivity. This electrical conductivity is a key point for EMC purposes, since power module case is used for equipotential purpose.

SY-EPC-LPC recommended treatment	Process		Characteristic			Conformity
	Deposition	Thickness	Compatible Environment	Conductivity	Color	Standards
SURTEC 650	Immersion, spray, wipe (paint)	> 110mg/m²	90% humidity [-20°C..+85°C] no salt	< 5 mOhms/inch² < 0.77 mOhms/cm²	Detectable (blue) C or V-option	ROHS, MIL-DTL-81706B

SY-EPC-LPC recommended treatment	Process		Characteristic			Conformity
	Deposition	Thickness	Compatible Environment	Conductivity	Color	Standards
Metalast TC HF-EPA	Immersion, spray, dip, spin	60um (0.4-0.7mil)	90% humidity [-20°C..+85°C] no salt	< 5 mOhms/inch² < 0.77 mOhms/cm²	Detectable (blue to dark green) due to CC-600 additive	ROHS, MIL-DTL-81706B

Standard treatment like anodisation process is commonly used.

A specific treatment of all steel plates and pieces used in power module case conception is required to ensure a good electrical conductivity. This electrical conductivity is a key point for EMC purposes, since power module case is used for equipotential purpose. It could be noticed that time often reduces surface contact quality (passivation for inox, copper oxidation, or even dust for metal).

SY-EPC-LPC recommended treatment	Process		Characteristic			Conformity
	Deposition	Thickness	Compatible Environment	Conductivity	Color	Standards
Zinc galvanization	Electrolize	> 50 µm	90% humidity, [-20°C..+85°C], no salt	< 60 mOhms/inch² < 09  mOhms/cm²	Metal grey look	ASTM A123

Summary of treatment

Standard treatment like epoxy power paint process is commonly used.

The phenomenon of tin whiskers is a very important issue that designers must take very seriously during the mechanical design of the converter. They can easily cause short circuits and arrive also to important lengths like 1-2 cm.
This phenomenon occurs on tin-plated copper after an undefined period, and the factors that contribute to its appearance include the use of pure tin, humidity, temperature variation cycles, and mechanical stress. Please read this document on the subject: EDMS 1909061.

Mitigation Type	Effectiveness	Applicable parts size	EPC guideline
Tin plating thickness > 12µm	Mitigation	All	Mandatory
Tin plating matte finishing	Mitigation	All	Mandatory
Blocking material / Increased gap between polarities (> 12mm)	100%	All	Mandatory
Silver plating instead tin plating > 12µm	100%	Little parts	If possible
Pression reduction by fastening torque	Mitigation	All	Mandatory
Nickel underlayer of 2µm	Mitigation	All	Optional

Tin whiskers mitigation measures.