Ultraviolet laser processing and application in PCB industry

- Jul 26, 2018-

For laser cutting or drilling in the circuit board industry, the use of flexible circuit boards is becoming increasingly important in consumer electronics, automobile industry or robot manufacturing technology.

Because the UV laser processing system has flexible processing mode, high precision processing effect and flexible and controllable processing process, it has become the first choice for flexible circuit board and thin PCB laser drilling and cutting.

FIG. 1: CO2 laser (left) compared with UV laser (right).

The thermal effect of UV laser is small and its cutting edge is clean and tidy.

Nowadays, the laser system is equipped with a long life laser source that is almost maintenance-free. In the production process, the laser grade is 1, and there is no need for other protective devices.

The LPKF laser system is equipped with a dust suction device, which will not cause the emission of harmful substances.

Combined with its intuitive and easy to operate software control, laser technology is replacing traditional machinery technology, saving the cost of special tools.

The UV laser cutting system has shown great technical advantages in the field of PCB subboard and micro-drilling in the SMT industry.

Depending on the thickness of the PCB material, the laser is cut once or more along the desired contour.

The thinner the material, the faster the cutting speed.

If the accumulated laser pulse is lower than the laser pulse required to penetrate the material, only scratches will appear on the surface of the material.

Therefore, you can mark the qr code or barcode on the materials for follow-up information tracking.

Figure 2: a substrate with multiple components can be safely split even if it is attached to the line.

The pulse energy of UV laser only ACTS on the material for a microsecond time, and there is no obvious thermal effect at a few meters by the incision. Therefore, it is unnecessary to consider the damage caused by the heat generated by UV laser to the elements.

The lines and solder joints near the edges are intact and free of burrs.

In addition, the integrated CAM software of LPKF UV laser system can directly import the data derived from CAD, edit the laser cutting path, and form the laser cutting profile. By selecting the processing parameter library suitable for different materials, direct laser processing can be carried out.

The laser system is suitable for both mass production and sample production.

Drilling applications

The through-hole in the circuit board is used to connect the front and back lines of the double panel, or to connect any interlayer lines in the multilayer board.

To conduct electricity, the hole wall needs to be plated with metal after drilling.

Nowadays, the traditional mechanical method cannot meet the requirement of smaller and smaller drilling diameter: although the spindle speed is increased, the radial speed of precision drilling tool will be reduced because the diameter is too small, and even the required machining effect cannot be completed.

In addition, from the economic perspective, easy to wear tool consumption is also a restrictive factor.

LPKF has developed a new laser drilling system for flexible circuit board drilling.

The LPKFMicroLine 5000 laser device is equipped with a 533mm x 610mm working table, which can be rolled automatically.

When drilling a hole, the laser can cut out the outline of the microhole from the center of the hole, which is more accurate than the usual method.

The system can drill microholes with a minimum diameter of 20 millimetres on an organic or non-organic substrate under the condition of high diameter to depth ratio.

Flexible circuit boards, IC baseboards, or HDI circuit boards all require such precision.

Semi-cured wafer cutting

In the manufacture of electronic components, what conditions require the cutting of semi-cured sheet materials?

As early as the beginning, semi - cured sheet material has been used in multi - layer circuit boards.

Each circuit layer in a multilayer circuit board is pressed together by the action of a semi-cured sheet.

According to the circuit design, some areas of the semi - cured pieces need to be pre-cut Windows and then compressed.

Figure 3: precise contours can be formed on sensitive cladding by laser technology.

A similar process is applied to FPC coatings.

The covering film is usually polyimide with a thickness of 25.

5. The colloidal layer with a temperature of 5 is formed with a temperature of m, and it is easy to deform.

A single area (such as a solder plate) does not need to be covered by the film for later assembly, connection and other work.

This thin material is very sensitive to mechanical stress - it can be done easily by non-contact laser processing.

At the same time, the vacuum adsorber can fix its position and keep its flatness.

Soft and hard combined plate processing

The rigid PCB and the flexible PCB are pressed together to form a multi-layer board in the soft and hard bonding board.

During the compaction process, the upper part of the flexible PCB is not bonded to the rigid PCB, and the rigid cover over the flexible PCB is cut and separated by laser fixed depth cutting, leaving the flexible part and forming the soft and hard binding plate.

This kind of fixed depth machining is also suitable for blind slot machining of integrated elements embedded on the surface of multilayer plates.

The UV laser precisely cuts the blind slot of the target layer separated from the multilayer circuit board.

In this area, the target layer is not connected to the material covered above it.

FIG. 4: comparison of panel splitting methods: other methods cannot achieve the panel quality of UV laser.

For complete contour cutting, LPKF of Germany will recommend cutting material thickness not exceeding 1 according to the different laser sources used.

6 mm.

For some thicker materials and expensive assembly components, safety and quality are preferred, while cutting time is secondary.

Figure 5: in tab-cut, the laser cuts the breakpoint splitter.

Cutting a breakpoint splitter, the laser system will cut off the joint through a process described above.

This cutting process can be performed close to the edge of the components, and is also very economical for thicker circuit boards.

Other applications

Because of the short wavelength of UV laser, it is suitable for most materials processing.

For example, it can be used in the electronic industry:

Ending processing TCO/ITO glass with no damage to base

Boring on flexible or thin material

The solder baffle layer or cover film window opening

Ending/flexible circuit board parting

Low slot

Turn off the assembled or unassembled circuit board

Sintering ceramic with ending cutting

Ending precision LTCC cutting

UV laser processing and application in PCB industry

In addition to the processing of circuit boards, the UV laser system can simultaneously cut, write and drill LTCC components in a processing operation