There are several plating processes available for electronic components today. Do you know the ins and outs of each? In this blog, we will review loose piece plating techniques, (as opposed to reel-to-reel methods that we’ve covered in the past). Loose piece methods include barrel plating, vibratory plating, spouted bed electrode plating and rack plating. The optimal process for your part depends on several factors, including: component size, geometry, volume, material strength and more as explained below.
Barrel Plating is the veteran of the group, with roots reaching way back to the post Civil War era. It’s a fairly straight-forward process which is performed in polypropylene barrels. They are equipped with cable danglers or a straight rod acting as the cathode that conducts electricity to the parts being plated. The barrel is then submerged in a plating solution, which contains ions of the metal to be deposited. The barrel rotates causing the parts to tumble and be exposed to the plating solution.
Not all components are candidates for barrel plating. Larger, heavier parts can get dented or dinged due to the tumbling motion. Flat parts have a tendency to stick together, preventing the metal from depositing over the whole part. Due to the dimensions of some parts, “nesting” or clumping together can occur in a rotating barrel. Other parts may be too delicate to be plated in a barrel and end up being bent or deformed.
Barrel Plating Advantages:
· Versatile, able to plate a variety of shapes and different size parts.
· Efficient, can plate a large number of parts.
· Able to plate many different finishes
Vibratory Plating also utilizes a cathode to make electrical contact with the parts to be plated. Instead of danglers, “buttons” on the bottom of the vibratory basket do the job. Vibration is used to rotate the parts in the basket while making contact with the buttons. Unfortunately, some parts are too heavy to be moved by vibration. Other parts are too light and can’t be plated by this method either. Certain part geometries allow them to line up perfectly and nest together, making them unfit for the process.
Vibratory Plating Advantages:
· Improves thickness distribution
· Reduces precious metal consumption because of improved thickness distribution
· Decreases part damage
· Minimizes solution drag-out, which also aids rinse cycles
Spouted Bed Electrode (SBE)
Spouted Bed Electrode (SBE) is the new kid on the block, relatively speaking. It’s been developed over the last 20 years in response to the electronics miniaturization movement. SBE plating uses an electrolyte jet to move parts in the plating chamber. This unit allows for very uniform plating at increased speeds compared to barrel plating. However, load sizes are limited to 50 to 400 mls, so other methods should be considered for larger parts.
Spouted Bed Electrode Plating (SBE) Advantages:
· Excellent for plating small parts
· Reduced damage
· Minimal part to part plating variation
· Plate small volumes with no media
Rack Plating is used when large or delicate components need processing. Parts must be placed on a rack using compression contacts or other means such as wiring. Designing, building and loading racks can be labor intensive and expensive when compared to barrel plating. Further, it is difficult to control thickness distribution with rack plating. Staining can be an issue when rinsing and drying.
Rack Plating Advantages:
· Allows for plating of large parts
· Good for delicate parts that can’t be tumbled
· Good when a cosmetic finish is necessary.