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Laser Micro-machining

We have two laser machining systems, UV and IR

LPKF Microline 5120 Laser Milling Machine (UV)

The LPKF Microline 5120 laser milling machine (10 watts ultra violet, UV) is a universal tool. It drills and cuts panels up to 533 mm × 610 mm. Width of cut is only 20µm, and it cuts demanding contours at high speeds. An integrated vision system ensures fast fiducial recognition and precise alignment. The camera uses almost any PCB feature as a fiducial mark. An integrated power measurement device determines the laser power at the cutting face giving reliable and repeatable control. The sweet spot for the machine is drilling small holes (c. 100um) in organic materials (FR4 resin) and thin copper (<35um) and contouring to depths of up to 0.3 mm. It is not suitable for cutting metal > 35um. UV lasers ablate organic materials. UV energy tears organic molecules apart. This ablative effect has no impact on metals, and the cutting action required is reliant on heat from the laser which is only sufficient to cut thin metal layers. UV laser systems with this wavelength of 355 nm are especially suitable for micro-processing of metals, plastics, ceramic materials and material composites.

LPKF G6060 Laser Solder Paste Stencil Cutting Machine (IR)

The LPKF G6060 laser solder paste stencil cutting machine (infrared, IR) is mostly used for cutting stainless steel stencils on material up to 0.5mm thick, but typically in the 0.1mm range. It is equally effective for general purpose machining of small parts in all manner of sheet metals with high accuracy. Holes as small as 25um can be drilled, and sheets as large as 600mm x 450mm can be contoured with unlimited complexity. The infra laser heats the metal to the point where a fine jet of air compressed makes a clean cut by oxidising the metal in its path. This laser is most effective cutting metal. IR laser systems with this wavelength of 1064 -1090 nm are also suitable for direct copper structuring of HF and microwave circuits.

 

 

Data

Data should be presented in Gerber combined with notes as to what the features represent. Lasers will remove material, so the documents must be clear as to which features represent the path of the laser. For example, pads might indicate a contour cut to create a pad size aperture, or they might indicate a pad sized shape to be ablated down to a copper base.

Process Development

Newbury Electronics has many years of experience in laser micro-processing. We are happy to provide proof of concept test samples. Our range of services includes assistance with selection of suitable materials and prototype production. Our application engineers will assist with optimising the production process.

 

Applications

1 – Drilling Microvias

Under production conditions, laser processing is an efficient technology for producing microvia holes with diameters less than 200 µm. However, high density interconnect (HDI) technology in particular requires connecting bores with diameters of at least 50 µm. Microvias may be drilled in materials such as RCC, FR4, FR5, TeflonTM and ThermountTM. When drilling with the UV laser, both the copper top layer as well as the substrates made of epoxy resin and glass fibers are pierced in one operation. The laser energy is controlled so precisely here that the lower target strip conductor layer is just lightly roughened and
simultaneously cleaned. In contrast to CO2 and hybrid laser systems, a UV laser system requires neither an upstream etching process nor a second laser.
UV laser processing offers short pulse lengths in the nanosecond range, which leads to high pulse peak outputs. This guarantees very good hole quality and high throughput.

Advantages of UV laser drilling:

  • Holes in various materials, e.g., RCC, FR4, FR5, Teflon® and Thermount®
  • No delamination and reduced “red ring effect”
  • Automatic correction of position and deformations by recording the corner marks and
    online scaling
  • High level of precision and positional accuracy of the holes
    Ideal hole geometry



2- Laser Cutting

A UV laser provides a universal tool for material processing. The focused laser beam creates ultra-fine, clean contours in a variety of materials and types of printed board (e.g: Multilayer, Flexible printed boards, Flex-rigid printed boards, Thin rigid substrates, De-panelling of webs or tabs, Ceramics, LTCC (low temperature co-fired ceramics), HF materials and Composite materials)

The focused laser beam reliably cuts through all layers in one or several passes and can be set to defined depths. It is suitable for cutting rigid and flexible printed board components with Multilayers or for cutting films with thin and sensitive materials, for example, the UV laser can structure, engrave and cut even the sensitive Low Temperature Cofired Ceramic (LTCC) components in one operation. A vacuum table holds the materials to be processed
gently and without a tensioning tool. Due to contactless material processing, no deformation comes about even with thin materials, as can happen when milling or stamping, for example.

The target material is vaporised by the UV laser, so that no burr forms minimally affected by heat preventing delamination of the material composites.
Using the vision option for touching corner marks and online rectification, deformations from previous processing steps can be compensated for and the cut contours in the layout can be exactly positioned.

The results of laser cutting are precise, nearly radius-free contours. The cut edges are smooth and vertical. The process ensures a maximum of dimensional stability, edge quality and throughput. The laser also cuts complex contours without masks or special tools.

Advantages of UV laser cutting:

  • Clean cut edges without burr or dust formation
  • Cutting of extremely fine contours and practically radius-free inner edges
  • Low thermal influence, i.e., no delamination
  • Cutting of various material thicknesses and combinations in one operation
  • Separation of fitted printed boards
  • No material deformation due to contactless material processing
  • No tensioning device or protective cover necessary
  • High level of precision and positional accuracy of the cut edges due to automatic
    recording
  • Maximum utilization of circuit boards because no space has to be kept free for cutting
    channels



3 – Opening of Solder-Resists and Foils

UV laser processing allows milling of solder resist openings in the HDI area <50 µm features. The laser ablates the solder resist in the area of the openings and cleans the underlying metal layer. A residue-free copper surface remains. Minimum openings are 30 µm in diameter. By means of vision systems, the laser positional errors are corrected during processing guaranteeing the best positional accuracy and production throughput. Opening of cover-lay on copper-clad base material The UV laser ablates the cover-lay material laminated upon the PCB laminate in the area of the desired openings. The precision of the laser beam creates ultra-fine openings with high positional accuracy.

Advantages of UV laser processing:

  • Ultra-fine openings in the HDI area of <50 µm in the solder resist are possible
  • Ultra-fine openings in cover sheeting, e.g. polyimide
  • Residue-free copper surface
  • No film or screen tooling required, direct CAD data conversion
  • Automatic registration via fiducials
  • Automatic correction of stretch and shrinkage possible through scaling
  • High level of precision and positional accuracy for the openings


4 – Micro-machining of Ceramics

The possibilities for UV laser processing of ceramics include cutting, drilling and engraving of green ceramics as well as cutting, drilling, scribing, engraving and marking of sintered ceramics.
Improved production of complex geometries and guarantee of maximum of dimensional stability, edge quality and throughput are benefits.
The following ceramic materials can be processed: Silicon nitride (Si3N4), Aluminium oxide (Al2O3), Aluminium nitride (AlN), Zirconium oxide (ZrO2), LTCC (low temperature co-fired ceramic), Composite ceramic materials.

Laser cutting and drilling of ceramics

In laser cutting, a continuous kerf (width of cut) is created, e.g., as an opening, contour cut or hole. Laser drilling allows production of the smallest hole diameters (for example, <75 µm in LTCC with high aspect ratios). Essential features of the processing are ultra-fine structures with high-quality edge structures.

Laser scribing

In laser scribing, a kerf that is 20 µm to 50 µm deep is initially cut in the ceramic material. The depth of the scribing can be controlled by precisely adjusting the laser focus. Then the material is broken along this kerf. Laser scribing allows clean cutting of segments with high quality and accuracy. In contrast to mechanical processing, no micro-cracks are caused in the material. Since little material is vaporised, the laser works with very high
scribing speeds of up to 100 mm/sec without damaging the material.

Fuel cell technology

UV laser processing of a membrane electrode assembly (MEA) allows graphite ablation on both sides in only one work step without damaging the MEA Nafion core membrane. In addition, the entire MEA can be cleanly cut to the desired shape and size. MEA are the basic elements in the assembly of a polymer membrane fuel cell PEM.

Advantages of UV laser micro-machining:

  • High degree of edge steepness
  • Low degree of edge roughness
  • No formation of micro-cracks
  • Holes <75 µm in high aspect ratios possible
  • Low thermal influence due to optimized UV processing
  • Contactless material processing, thus no material deformation
  • High level of precision and positional accuracy of the cut edges

5 – Micro-machining of components

With modern IR lasers, highly precise cut parts can be cut with a thickness of up to 0.5mm from commercially available sheet metal. Newbury Electronics processes stainless steel, nickel, molybdenum and titanium with a repeat accuracy of ±2 µm and radii of 10µm. Production of hard tooling unnecessary and small runs become economical.

Advantages of laser technology:

  • Flexibility, contour cutting directly from the CAD layout data
  • Precision with high degree of edge steepness without reworking
  • Neither thermal nor mechanical influencing of cut parts
  • Cost-effective even with small quantities
  • High level of repeat accuracy
  • No tool costs
  • Any contour and opening

6 – Repair & Rework of PCBs

Defective PCBs which otherwise would have been scrapped due to design, process errors or modification can be quickly and inexpensively repaired by UV laser. Possible repairs include ablation of solder resist or cover-lay, opening of existing pads, creation of new pads to allow fitment of new components, opening of larger copper surfaces, cleaning of plated through holes, separation of circuits from handling frames, the UV laser is characterised by high peak pulse outputs due to the short pulse lengths. They vaporise the dielectrics without damaging the copper base. The result is a clean surface suitable for reworking.

Advantages of laser repair:

  • Clean copper surfaces and cut edges
  • Selective material processing, the copper base is not damaged
  • Processing of assembled PCBs possible
  • Contactless material processing, thus no risk of collateral damage
  • No tensioning device or protective cover necessary
  • High level of precision and positional accuracy of the cut edges due to automatic fiducial alignment
  • High level of flexibility
  • Quick and inexpensive printed board repair

7 – TCO / ITO Laser Processing

The UV laser creates ultra-fine insulation spaces in the invisible Transparent Conductive Oxide (TCO) layer. Invisible conductive structures < 50 µm and insulation gaps can be created. For example, Indium Tin Oxide (ITO) is used for TCO coatings. It can be applied as a very thin conductive and light-transmissive coating on glass or plastics. ITO glass is used, for example, in high-quality display and touch screen technology. The ITO coating is produced using sputter technology. The electrical and transparent characteristics depend on precise control of the oxygen content during the coating process and the indium/tin ratio, among other things. The TCO layer can be applied to the most varied substrate materials such as PET (polyethylene terephthalate), cellulose triacetate, PEN (polyethylene naphthenate), glass, etc.

Advantages of ITO laser structuring:

  • Absolutely invisible structuring of transparent ITO coatings
  • Flexibility: the layout can be changed at any time
  • Reduction of technological steps (no resist application, no etching)
  • Ultra-fine structures with <50 µm lines/spaces possible
  • High level of positioning accuracy through recording of corner marks or other visible marks
  • Structuring directly from CAD data

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