July 2017 Archives

#302 Electroforming of Precision Parts

| No Comments | No TrackBacks

Electroforming is an applied technique of electroplating by which an article is coated with a very thick plating. One of its characteristics is the capability of faithfully reproducing the shape of a master block (transferability). It is used in many fields, including multi-media, such as CDs and CD-ROMs, electric razor blades, and various molds.
Characteristics and applications of industrial electroforming are summarized in the Table.

[Table] Characteristics and applications of industrial electroforming
Applications Electroforming metals Characteristics
Multimedia
CDs, CD-ROMs, stampers, etc.
Nickel Transferability, dimensionality
Mechanical parts
Bellows, razor blades, etc.
Nickel Hardness, dimensionality, strength, corrosion resistance
Molds and electrodes
Various molds,
electric discharge machining electrodes, etc.
Nickel, copper Transferability, dimensionality
Electronic components and others
Masks, waveguides, meshes, micromachines, etc.
Nickel, copper Transferability, dimensionality, corrosion resistance

Electroforming has the following characteristics: 1. excellent transferability; 2. high dimensional accuracy; 3. freely-changeable electrodeposition thickness; 4. unaffected by the shape and dimensions of the workpiece; and 5. capable of manufacturing hollow articles; etc.
As a reference for transferability, accuracy is said to be 0.05 to 0.2 um, depending on the precision of the master block and plating conditions. It is widely known that stampers (molds) for manufacturing CDs and CD-ROMs leverage this accuracy.

CD, CD-ROM, manufactured with a precise nickel-electroformed stamper / Digital bits on a CD

#301 Dispersal (Composite) Plating of Precision Parts

| No Comments | No TrackBacks

Dispersal plating, which is also called composite plating, involves dispersion of chemically insoluble fine particles such as ceramic particles in electroplating or electroless plating baths to co-precipitate them with the plating metal. Nickel plating bath is generally used as the plating bath.

[Photo 1] shows a cross section of silicon carbide (SiC) -dispersed nickel plating film. It shows that silicon carbide is evenly dispersed in the nickel film and is also exposed on the film surface. The properties of the dispersed particles determine the characteristics of the plating film, such as enhanced wear resistance or self-lubricity.

[Table] shows the plating types and film characteristics of dispersal plating.

[Table] Plating types and film characteristics of dispersal plating
Types of plating bath Film characteristics Dispersed particles
1.
Nickel electroplating
Watts bath
Sulfamate bath

2.
Electroless nickel plating bath
Others such as cobalt
Wear resistance,
heat resistance
Oxides (silicon dioxide, alumina, zirconia, tungsten trioxide, titanium dioxide, etc.)
Carbides (silicon carbide, chromium carbide, tungsten carbide, boron carbide, etc.)
Self-lubricity Molybdenum disulfide, graphite, boron nitride, graphite fluoride, fluorinated polymer compounds, etc.
Nonadherence Graphite fluoride, fluoropolymer (Teflon, etc.)
[Photo 1]

Cross-sectional photo of silicon carbide-dispersed nickel plating film

Titanium carbide and tungsten carbide are co-precipitated in gold or palladium plating used for electrical contacts, or graphite is co-precipitated in palladium plating to improve wear resistance. A gear with PTFE (e.g. Teflon) -dispersed nickel-plating

*Self-lubricity means that the film itself has lubricity and is capable of preventing wear without use of a lubricant. It is an essential property for devices used in space and vacuum.
Non adherence means that an object does not stick to or repels other objects and contributes to dust-proofing, easy sliding, wear resistance, and contamination resistance.

Industrial plating that imparts functions such as corrosion resistance, wear resistance, and electrical characteristics is introduced here.
Applications of industrial nickel plating are classified as shown in the [Table].

[Table] Industrial uses of nickel plating
Types of plating bathsUsage
ElectroplatingWatts bathIn general, it is used as a base-coat plating to improve corrosion resistance of decorative plating, but it is also used for providing brazeability, weldability, and bondability to the stems and caps of semi-conductor components. Adhesion is crucial. 0.1 to 30 um
Sulfamate bathIt is used for cladding of recycled parts as a thick plating.As an electroforming bath, it is an essential plating for the production of CD stampers, resin molding dies, and metal bellows.
Electroless plating
Ni-P, Ni-B
Nickel-phosphorus and nickel-boron alloys, etc. can be obtained.Electroless plating can achieve a film with uniform thickness on complicated shapes and therefore is used for parts that require accuracy.It has superior hardness, corrosion resistance, and electrical characteristics.
Special platingDispersal platingIt is also known as composite plating.Dispersal plating can improve wear resistance and lubricity and add color by dispersing fine particles, such as ceramic particles, in the nickel film.
Ni-Cddiffusion platingFollowing the application of cadmium plating on top of nickel plating, heat treatment at 300°C is carried out to diffuse cadmium into nickel. This plating technique enhances heat resistance and seawater corrosion resistance.

Nickel plating for precision parts (Electroplating)

Semi-bright and bright plating deposited by the Watts bath are used as base-coat plating for various types of industrial plating.
Base-coat plating of gold, tin, and rhodium for connectors, switches, terminals and lead frames is an example of nickel plating usage that enhances corrosion resistance and adhesion and that contributes to preventing diffusion of such metals into the substrate.
Furthermore, application of about 0.1 to 0.3 um nickel strike plating as a base coat improves the adhesion, mechanical strength, and shock absorption of materials, such as stainless steel and kovar, for which normal plating techniques do not provide satisfactory adhesion.

#299 Tin-Lead Alloy/Lead Plating for Electronics

| No Comments | No TrackBacks

(1) Tin-lead alloy plating

Tin-lead alloy plating is widely used for electronics as solder plating.Solder plating has two types: molten soldering and electroplating. The former is used for printed circuit boards, whereas the latter is used for components that require dimensional accuracy and film uniformity and adhesion.
The alloy composition is controlled by the bath composition and working conditions. The alloy ratios shown in the table are used according to the intended purposes, including corrosion resistance, flexibility, lubricity, and solderability.
For mitigation of whisker growth on tin-plated electrical and/or electronic-related components, solder plating containing 5-10% lead is used.

Although the purpose of plating is to prevent corrosion, alloy plating containing 5-7% tin is used, instead of pure lead plating.Lead-antimony alloy plating is used for parts that require wear resistance.
  [Table] Applications and alloy ratios of solder plating
ApplicationsTin (%)Lead (%)
Anticorrosion of steel694
Lubrication of bearings, etc.793
Soldering6040
Whisker prevention90-955-10

(2) Lead plating

Although the purpose of lead plating is to prevent corrosion, alloy plating containing 5-7% tin is used, instead of pure lead plating. Lead-antimony alloy plating is used for parts that require wear resistance.

image

*Precautions for solder plating and lead plating
Plating metals used for solder plating and lead plating diffuse into the basis metal. In order to prevent this, a copper or nickel base-coat plating is necessary.
*As a measure for preventing environmental lead contamination caused by, for example, acid rain falling on discarded electronic equipment, a shift toward lead-free soldering and solder plating is accelerating.

月別 Archives

Pages

Powered by Movable Type 6.0.3

About this Archive

This page is an archive of entries from July 2017 listed from newest to oldest.

June 2017 is the previous archive.

August 2017 is the next archive.

Find recent content on the main index or look in the archives to find all content.