Palladium coatings are useful for many different purposes. From ASTM B679 – 98(2004)e1, “Palladium is the lightest and least noble of the platinum group metals. It has a specific gravity of 12.0, which is substantially less than gold (19.3) and platinum (21.5). This yields a greater volume or thickness of coating and, consequently, some saving of metal weight accompanied by a small sacrifice in corrosion resistance and reflectivity. The hardness range of electrodeposited palladium compares favorably with the other electroplated noble metals and their alloys.” As we see from the ASTM specification, palladium coatings offer corrosion resistance and reflectivity at a lower weight than gold or platinum. Palladium coatings are harder than “hard gold” or cobalt hardened gold coatings in general. Palladium’s non-oxidizing properties make it useful for electrical and electronic connectors. Palladium coatings can be applied to most types of materials including metals and non-conductive plastics, ceramics and other materials. Palladium coatings are more ductile and less porous than hard gold. Some customers prefer a flash of gold below the palladium topcoat to improve solderability.
Palladium coatings typically have a minimum thickness of 50u” or 1.3 microns on functional surfaces. Palladium coatings are harder, more
corrosion resistant and less porous compared to hard gold. Palladium is a precious metal and it costs
more than many other metals such as copper, nickel, tin or silver. Palladium coatings appear white or gray in
color. Palladium coatings are softer
and less wear resistant compared to rhodium.
Silver and copper are more electrically conductive, and silver is also better
for soldering and thermocompression bonding compared to palladium.
The maximum temperature relies on other information such as atmosphere, undercoats, CTE mismatch and substrate material. Palladium melts at 1555 deg C, so we would need to keep below that temperature but you could see diffusion and coating changes at much lower temperatures depending on the other materials and situation outlined previously. For precise advice regarding your project contact Dr. Francis Honey at fhoney@intatech.com.
Palladium along with rhodium, ruthenium, osium, iridium and platinum are all part of the platinum group of metals (PGM). Palladium is a face-centered cubic crystal and at low to medium temperatures (in air) is resistant to corrosion and low temperature acids. Palladium coatings are less porous and more corrosion resistant compared to hard gold coatings. For testing, INTA recommends ASTM B117 (salt spray). Palladium is attacked by hot acids and dissolves in aqua regia.
A good coating will not peel under normal
circumstances. Tests are performed on
the coatings before items are shipped to ensure good adhesion. INTA also inspects parts at 20-30x visually
to confirm quality. According to the
Mil specification (Mil-P-45209B 3.6.2) “The formation of cracks in the basis
metal or plate which do not result in flaking, peeling, or blistering of the
plate shall not be considered as non-conformance to this requirement.” INTA inspects all material before and after plating. We look for peeling, blistering and
discoloration. We also perform several
tests such as a tape test on most components and assemblies. We also use XRF equipment from Oxford
Instruments to test for coating thickness.
Yes, the material makes a difference when it comes to plating. Palladium plating works well with most materials but some materials are difficult to plate such as glass and quartz. The substrate needs to be dense and non-porous for palladium plating. The material should be able to withstand temperatures of 150 deg C.
INTA is RoHS compliant and practices green environmentally friendly processes therefore we recommend looking into alternatives for materials containing the following:
Lead
Cadmium
Mercury
Arsenic
Hexavalent chrome
Certain items such as PZT and brass can be processed by INTA.
Lead time depends on project scope but in general delivery is one week after receipt of material.
The cost varies according to project specifications. Pricing can range from pennies per part for millions of small items or thousands of dollars each for very large or complex parts. Contact INTA 408-748-9955 to request a quote. Be sure to include the following:
Drawing or SOW (statement of work)
Target price or project budget
Anticipated delivery schedule
Other pertinent information is also helpful
Palladium is more affordable than gold.
Palladium coatings are more costly than silver coatings.
MIL-P-45209B recommends 50u” minimum. The thickness required really depends on a number of factor including:
Application
Use environment including temperature
Test conditions
Subsequent processes
Intended use
Undercoats
Substrate material
For a detailed recommendation tailored to fit your project please contact Dr. Francis Honey, fhoney@intatech.com
Palladium can absorb up to 900 times its own volume of hydrogen which can reek havoc in a pumped down vacuum chamber. For more information regarding palladium coatings for use in vacuum please contact Dr. Francis Honey, fhoney@intatech.com
Palladium is useful due to many material properties including high reflectivity (useful for solar). Palladium coatings are also useful in emission control applications and during catalytic processes performed at oil refineries.
INTA has acid bright palladium in stock and ready (lead time about 1 week ARM). Other special types of palladium are only available via special order and have longer lead times.
A very small portion of revenues are derived from palladium plating but we can increase capacity if necessary.
Yes, it is a common ingredient although many alloys do not contain it. Many of the alloys containing palladium are intended for relatively high temperature thermal sets.
Yes, palladium coatings are resistant to salt spray testing per ASTM B117 but it is always a good idea to perform the testing on new items. Salt spray testing is not a stand function offered by INTA.
We do not have a maximum thickness requirement. Let us know how thick your desired coating is and we will try to accommodate or offer feedback. Anything over a few hundred micro-inches may be considered experimental. For more details contact Dr. Francis Honey, fhoney@intatech.com
INTA may require an undercoat or primer layer between the substrate and palladium. The primer layer helps aid adhesion. Check your quote carefully for notes such as “Nickel undercoat allowed”. To request a quote please contact INTA.
Undercoats are used for many purposes but the main reason is to provide a good adhesion layer. INTA does not use levelers or fillers therefore undercoats cannot be expected to fill large gaps, scratches or other surface defects. Undercoats will sometimes affect the item’s appearance (luster, shine). Without a good undercoat, the top coat may peel off.
It is possible depending on the substrate material. Contact Dr. Francis Honey, fhoney@intatech.com, to discuss. INTA may require a no return, no exchange clause in the contract if we deem the project as unlikely to succeed. We do not mind trying new processes (research and development) but must get paid regardless of project success/failure.
Visual (20-30X), tape test, bake test and other tests occasionally. In general, visual and tape test are practiced but exceptions exist for certain projects (size, fragility, etc.). Bake test and other tests are typically only performed if specified.
Yes, palladium is considered a noble metal. Noble metals are metals which are resistant to corrosion or oxidation. Here is a list of other noble metals:
Copper
Ruthenium
Rhodium
Silver
Rhenium
Osmium
Iridium
Platinum
Gold
Mercury
To
a physicist, palladium is not considered noble because not all the d-bands in
the electronic structure are filled. In
which case the only noble metals are copper, silver and gold. Try this experiment: Prepare a clean palladium plated surface in
high vacuum and then compare the results using the same process with a gold
plated surface.
Please see the previous answer. For more information please contact Dr. Francis Honey 408-748-9955 x103.
Palladium coatings are more expensive than other coatings such as nickel, copper, silver, tin and more. Palladium can also absorb up to 900 times its volume of hydrogen at room temperature with normal atmospheric pressure. Palladium is attacked by hot acids.
There are many coatings available but each is unique. Not one coating is better than another, each has benefits and challenges.
Here is an example:
Note |8|: 50-150u” palladium plating per Mil-P-45209B. Undercoat choice of plating vendor. Critical surfaces are marked with |8|. Non-critical surfaces are marked |9|. Voids < dia .020” allowed. Slight discoloration allowed.
Note |9|: Plating optional on surfaces marked |9|.
Here is another example:
Note 2: 50u” min palladium electroplating per Mil-P-45209B. Nickel undercoat allowed. Plate all. No wire marks.
The key items to include in the document are type of plating, specification, undercoat allowance, thickness, critical surfaces.
Applicable to steel springs and parts subject to flexure or repeated impact and hardness greater than Rockwell C40. Embrittlement relief, when necessary, involves a 3 hr heat treat post-plating prior to flexure/impact. Subsequently, the samples are subjected to a 200 hour tensile test with an appropriate load tailored for the intended application.
Keep in mind that palladium can absorb up to 900 times its volume of hydrogen which could outgas into the chamber during pump down. For more information please contact Dr. Francis Honey x103.
Last revised: 6 JAN 2009
