Laser Direct Structuring (LDS) versus 5-axis Laser Sintered Printing (LSP-5)

If you have picked up on this Blog then chances are you already know about Laser Direct Structuring (LDS), it has been around for a while, and was commercialised by LKPF some 20 years ago. But I am guessing 5-axis Laser Sintered Printing is probably a mystery to you. The laser sintering process was pioneered by M-Solv, where they call it One-Step Metallisation (OSM) and use it for adding conductive tracks to glass and sheet polymers for applications like capacitive touch sensors. Q5D Technology has taken this process and adapted it for their 5-axis platform so that it can be used to create three-dimensional structures, very similar to those made with LDS. Since there are never enough TLAs in the world (Three Letter Abbreviations) Q5D have coined the phrase LSP-5, 5-axis Laser Sintered Printing.

Both techniques are a way of creating high quality conductive tracks on a polymer substrate that has a complicated three-dimensional shape. LDS has found a market making moulded interconnect devices (MIDs), embedded antennas, compact LED lighting, medical devices, or electromechanical products such as keys or electrical terminations.

Both processes have significant benefits over more conventional PCB manufacture:

  • They give engineers huge design freedom.
  • They can make smaller, lighter components.
  • They have low set-up costs.
  • They give a faster time to market.
  • And both reduces the cost of manufacture.

Enough of the sales pater how do they work?

Laser Direct Structuring (LDS)

Injection Moulding

The parts are produced using injection moulding using polymers loaded with special additives.

Laser Activation

A laser is used to activate the polymer by creating and exposing microscopic metallic particles.

Cleaning

The part is cleaned prior to metallisation.

Metallisation

The part is immersed in an electrodeless bath where copper is deposited onto the areas activated by the laser. Other coatings can be added to the copper, such as nickel, gold or tin.

Assembly

Many of the plastics are sufficiently heat resistant so that components can be soldered and standard SMT processes used.

5-axis Laser Sintered Printing (5-LSP)

Start with existing component

Almost any structure can be used as a starting point: an injection moulded part, a composite panel, a ceramic or a piece of sheet metal.

Add Polymer

Polymer can be added to create structural features, dielectrics or electrical insulation.

Printing

Conductive metal paste is printed onto the surface of the piece. Typically, silver or copper. An Infra-red lamp is used to rapidly dry the paste as it is deposited.

Laser Sintering

A laser then follows the paste tracks and sinters it into a solid.

Assembly

The assembly is then the same as for LDS, where standard SMT processes can be used.

Given that the two techniques can both deposit tracks on 3D polymer structures, what are the differences? And what are the benefits of one process over the other?

There is a more detailed comparison in the table, but in short:

  • LDS can create tracks with about twice the conductivity, but the part size it is possible to work on is much larger with LPS-5.
  • LPS-5 is a very flexible process, it is possible to switch between the laser sintering and the polymer deposition almost any number of times to create complex 3D structures. Whereas LDS is good at creating high quality single layer conductive tracks on a 3D surface.
  • Although both techniques can work with the same wide range of polymers, LPS-5 does not require polymers with expensive additives.
  • Although it looks like both processes have the same step, the LPS-5 is all done on the same machine automatically, not need to swap from the laser to a chemical bath. It feels like a one-step process.

Compared to flex-circuits, both techniques do not have a minimum bend radius, it is possible to print over sharp corners and the parts are robust and don’t require any special handling.

LDS LPS-5
3D Capability Single layer 3D Multi-layer 3D
Feature Size 150 µm track / 200 µm gap 100 µm track / 200 µm gap
Track Thickness 3 – 8 µm 3 – 10 µm
Substrate Loaded thermoplastic for injection moulding Most insulating surfaces: paint, polymers, anodized metal, ceramics etc.
Conductivity 2/3rd of the metal (typically Cu, Ni, Ag) 1/3rd of the metal (typically Cu, Ni, Ag)
Component size and geometry Typically centimetres in size, with compound curved surfaces No restriction in lateral size

~0.5m height

Process time Depends on track thickness. Needs a laser machine and a separate chemical bath. Depends on track length and complexity. But all done on same machine.
Adhesion Good Good

You are now in a position to impress your friends and colleagues with your newfound expertise in 5-axis Laser Sintered Printing, your boss will be highly impressed that you have your finger painfully pressed against the cutting edge of technology.  If you want to know more then don’t hesitate to get in touch.

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