Application of ultraviolet laser processing in PCB industry

- Aug 28, 2018-

For laser cutting or drilling in the circuit board industry, only a few or more watts of UV laser can be needed, and no kilowatt laser power is needed. In consumer electronic products, automobile industry or robot manufacturing technology, the use of flexible circuit board becomes increasingly important.Due to the flexible processing mode, high-precision processing effect and flexible and controllable processing, UV laser processing system has become the first choice of flexible circuit board and thin PCB laser drilling and cutting. 

Today, the long life laser source equipped with the laser system is almost maintenance-free. In the production process, the laser level is 1, and there is no need for other protection devices.The LPKF laser system is equipped with a dust absorber that does not cause hazardous material emissions.Coupled with its intuitive and easy to operate software control, laser technology is replacing traditional mechanical process, saving the cost of special tools. 

CO2 laser or UV laser? 

For example, when PCB divider or cutting, the selected wavelength can be about 10.6. CO2 laser system in m.Its processing costs are relatively low and the laser power provided can reach several kilowatts.But it produces a lot of heat during the cutting process, resulting in severe carbonization of the edges. 

The wavelength of the UV laser is 355 nm.This wavelength of laser beam is very easy for optical focusing.A UV laser with less than 20 watts of power has a spot diameter of only 20 m - and produces an energy density comparable to that of the sun's surface. 

Advantages of UV laser processing

UV laser is especially suitable for cutting and marking of hard board, soft and hard board, soft board and auxiliary materials.So what are the advantages of this laser process? 

The UV laser cutting system shows great technical advantages in the areas such as the board divider of SMT industry and the micro-drill of PCB industry.Depending on the thickness of the circuit board, the laser is cut once or more along the desired outline.The thinner the material, the faster the cutting.If the accumulated laser pulse is lower than the laser pulse required to penetrate the material, only scratches will appear on the material surface;Therefore, the qr code or barcode can be marked on the materials to track the information of the subsequent process. 

The pulse energy of UV laser only affects the microsecond time on the material, and there is no obvious thermal effect on a few micrometers beside the incision, so it is not necessary to consider the damage caused by the heat generated on the element.Lines and solder joints near the edges are intact and free of burrs. 

In addition, LPKF UV laser system integrated CAM software can directly import the data derived from CAD, edit the laser cutting path, form the laser cutting contour, and select the processing parameter library applicable to different materials, then direct laser processing.The laser system is suitable for mass production and sample production. 

Drilling applications

The through-hole in the circuit board is used to connect the front and back circuits of the double panel or any interlayer circuits in the multi-layer board.In order to conduct electricity, the hole wall needs to be plated with metal after drilling.Nowadays, traditional mechanical methods are unable to meet the requirement of smaller and smaller bore diameter: although the spindle speed is increased, the radial speed of precision drill cutter will be reduced due to the small diameter, or even the required machining effect can not be completed.In addition, in terms of the economy, easy to wear tool consumables are also a limiting factor. 

LPKF has developed a new laser drilling system for drilling flexible circuit boards.The LPKFMicroLine 5000 laser device is equipped with a 533mm x 610mm work table, which can be rolled up to roll automatically.When drilling, the laser can cut the microhole profile from the center of the hole, which is more accurate than the ordinary method.The system can drill microholes with a minimum diameter of 20 plus m on organic or non-organic substrate at a high aspect to depth ratio.Such precision is needed on flexible circuit boards, IC substrates, or HDI boards. 

Semi-cured sheet cutting

In the manufacture of electronic components, what conditions require cutting of semi-solidified sheet material?In the early days, the semi - solidified sheet material has been used in the multilayer circuit board.Each circuit layer in the multilayer circuit board is pressed together by the action of semi-solidified sheet.According to the circuit design, the semi-solidified sheet in some areas needs to be cut into the window before being pressed. 

A similar process applies to the FPC coating.The coating is usually made of a polyimide with a thickness of 25 plus m or 12.The rubber layer of m is formed and is easily deformed.A single area (such as solder pad) does not need to be covered with film for later assembly, connection and other work. 

This thin material is very sensitive to mechanical stresses - easily done by non-contact laser machining.At the same time, the vacuum adsorption table can fix its position and keep its flatness. 

Hard and soft board processing

In the soft and hard board, the rigid PCB and flexible PCB are pressed together to form a multi-layer board.During the pressing and sealing process, the flexible PCB is not pressed and glued together with the rigid PCB. The rigid cover covering the flexible PCB is cut and separated by laser depth setting cutting, leaving the flexible part and forming the soft and hard bond plate. 

Such depth machining is also applicable to the blind groove machining of surface embedded integrated elements in multi-layer plates.UV laser precisely cuts the blind groove 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. 

High efficiency board for PCB and FPC

The SMT rear divider is the circuit board that cuts a variety of electronic components that have been assembled, and the process is already at the end of the production chain.For the divider, different techniques are available: for the commonly used PCB, traditional cutting, stamping and contour milling processes are preferred.For more complex electronic circuits and thin substrate especially sensitive to mechanical stress, dust and dimensional deviation, UV laser cutting is more advantageous.The following three charts evaluate these three approaches from different factors. 

For the cutting of complete contour, LPKF of Germany will recommend cutting material thickness not exceeding 1 according to different laser sources used.6 mm.For some thicker materials and expensive assembly components, safety and quality are prioritized, while cutting time is secondary. 

Cutting the breakpoint plate, the laser system will cut the connection point through a process described above.This cutting process can be done close to the edge of the components, is also very economical for thicker circuit boards. 

Other application areas

Because of the short wavelength of UV laser, it can be used in most materials processing.For example, it can be used in the electronic industry:

Processing TCO/ITO glass and base no damage

Hole holes in flexible or thin materials

Wall soldering layer or covering film to open window

Rigid/flexible circuit board divider

Low slot

Repair of assembled or unassembled circuit boards

Cutting sintered ceramics

Precision cutting LTCC

It is not limited to the processing of circuit boards, UV laser system can also complete the cutting, direct writing and drilling of LTCC components in a processing operation.