Materials for laser welding Laser welding

Summary

  • Engineering plastics are materials that combine the advantages of typical plastics—they are lightweight, electrically insulating, and rust-proof—with excellent performance, including heat resistance, strength, and flame-retardant behavior. Thanks to these unique properties, engineering plastics are widely used in the manufacture of products such as automobiles—for which durability is crucial—and electrical/electronic devices and office-automation equipment, which demand high-precision and superior electrical properties.
  • Common applications of engineering plastics include chassis bodies to protect sensors, actuators and other sensitive instruments from moisture, dust, and damage, as well as casings for high-energy-density lithium-ion batteries. The fabrication of plastic chassis bodies and casings of this sort often requires  junctions between two pieces of plastic, which may be realized in a variety of ways: screws or bolts, snap fit, rivets, and various types of welding.
  • Among the various techniques for realizing plastic junctions,  laser welding excels in handling miniature components while avoiding contamination and offering extensive flexibility regarding the appearance and shape of processed products.
  • Laser welding offers many advantages and has a growing track record of practical successes. Asahi Kasei recommends our engineering plastics specialized for use in laser welding.

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What is laser welding?

Laser welding is a technique that exploits the transparency of plastics to laser light. In this technique, laser light irradiating a target body (made of resin or plastic) generates heat at the interface between the body and a separate absorber layer to create welded junctions.

 

The advantages of laser welding include vibration-free operation, improved appearance of welded junctions (elimination of burrs), avoidance of contamination, protection of interior content, space-saving (compact) and lightweight. The transmission/absorption approach to resin welding involves a combination of two resin materials: one light-transmitting resin (the transmitter) and one light-absorbing resin (the absorber).

Typical setup for laser welding

  • The transmitter is placed atop the absorber and laser light irradiates this two-layer stack from above (laser irradiation).
  • The laser passes through the transmitter and is absorbed in the absorber, generating heat (absorption/photothermal conversion).
  • This heat generation causes the absorber to expand, transmitting heat to the absorber/transmitter interface (heat transfer).
  • This heat induces melting in the transmitter, resulting in formation of a welding pool and welded junction (solidification).
Typical setup for laser welding

Typical setup for laser welding

Advantages and disadvantages of various techniques for junction formation and welding

Laser welding is one of many available techniques for junction formation and welding of resins and plastics; other approaches include hot-plate welding, vibration welding, ultrasonic welding, adhesive junctions, snap-to-fit junctions, and screws or bolts.

 

The following table compares key features of several common techniques.

Laser-weldable materials

In principle, laser welding is applicable to any thermoplastic resin. The key point is the transmissivity of the transmitter resin to laser light of the relevant wavelength.

 

In general, laser welding requires the transmitter resin to exhibit a transmissivity of around 20% or greater; below this threshold, the transmitter resin absorbs too much of the laser light and begins to melt. Most of  natural resin materials are white or transparent and can generally exhibit sufficient transmissivity to allow laser welding, although this is depends on the thickness of the material.

 

Laser welding typically uses diode lasers or YAG lasers as sources, producing light at wavelengths in the 800-1200 nm range, slightly longer than visible light wavelengths. Welding is possible as long as the materials involved exhibit adequate transmissivity and absorptivity in this wavelength regime; thus, appropriate selection of pigments and laser absorbers allows even colored resin products to be welded. The following table lists a few common combinations.

Laser-weldable materials and combinations

Laser-weldable materials and combinations

Asahi Kasei’s Recommended Solutions

Asahi Kasei’s laser-weldable engineering plastics

Asahi Kasei offers a variety of laser-weldable engineering plastics, including general-purpose GF grades, hydrolysis-resistant grades, and flame-retardant grades.

Suitable materials and grades

For detailed information on suitable materials and grades, please contact Asahi Kasei via inquiries below. Also, please feel free to contact us regarding any concerns or difficulties you may encounter in designing products to be handled via various forms of laser welding.

Development case

Flame-retardant grade for electrical components

The conventional flame-retardant grade was difficult to process via laser welding techniques because of its low transmissivity. We increased the transmissivity of the material, thereby allowing welding at lower energies; as a bonus, welding at lower output levels reduced scorching at welded interfaces.

Using the flame-retardant grade

Applications


We would like to talk to you about Asahi Kasei’s laser-weldable engineering plastics. Please contact us to ask any questions, discuss any concerns, and request samples.

Inquiries