PCB Tech - Carbon dioxide (CO2) laser equipment processing technology of PCB board

Carbon dioxide (CO2) laser equipment processing technology of PCB board

With the high-density interconnection design of PCB boards and the advancement of electronic technology, carbon dioxide (CO2) laser processing equipment has become an important tool for circuit board (circuit board) manufacturers to process PCB micro-holes, carbon dioxide (CO2) lasers and UV fiber lasers It is a laser processing equipment commonly used by PCB manufacturers. The development of laser processing PCB micro-hole technology is also rapid.

At present, in some large-scale printed circuit board manufacturers in China, multilayer PCB multilayer boards with higher density interconnections are gradually processed by carbon dioxide (CO2) laser and UV laser hole forming technology. With the development of copper carving crafts technology With continuous progress, the carbon dioxide (CO2) laser processing method of forming holes has been rapidly popularized and widely used in PCB multilayer circuit boards. And further promote the multilayer multilayer board to the field of flip chip packaging, so as to promote the multilayer multilayer board to continue to develop to higher density. As a result, the number of blind hole processing holes in multi-layer PCB multi-layer boards is increasing, and its single side is generally about 20,000 to 70,000 holes, and even as high as 100,000 holes or more. : For such a large number of blind holes, in addition to using the photo-induced method and plasma method to make the blind holes, especially as the blind via hole diameter becomes smaller and smaller, the use of carbon dioxide (CO2) laser and UV Laser processing to make blind vias is one of the low-cost, high-speed processing methods that circuit board manufacturers can achieve.

In the late 1980s, AT&T's circuit board research and development department had developed carbon dioxide laser processing equipment to process micro-holes on FR-4 PCB boards made of epoxy glass. Due to the infrared wavelength of 10.60um, the copper skin on the surface of the circuit board cannot be ablated (because the metal copper has a low infrared absorption rate), and the inner copper (bottom copper) surface will leave organic carbides, and the dielectric The glass fiber cloth (filament) in the layer is not easy to burn or leave a molten state (glass has a very low infrared absorption rate), so it must be carefully treated before plating the hole, otherwise it will cause difficulty in hole plating or cause hole wall The roughness is large, so it has not been promoted and applied in the PCB industry. Then IBM and Simens developed gaseous lasers, such as excimer lasers such as argon lasers, krypton lasers, xenon lasers, etc., with laser wavelengths between 193nm and 308nm (nanomicrons). Although it can effectively avoid the carbonization phenomenon of rabbit organic matter and the problem of glass protruding melt head, it is not in the PCB industry due to the special inert gas, the slow processing speed, the instability, and the low output (energy). Has been widely promoted and applied. However, it can be used to effectively remove the carbonized residue caused by the carbon dioxide laser, so the carbon dioxide laser can be used to form a hole, and then the excimer laser can be used to remove the residue to ensure the quality of the laser hole.

The method of laser processing PCB boards has been applied to circuit board manufacturers so far. Due to the sharp increase in the micro-hole requirements of multilayer PCBs, coupled with the continuous improvement and perfection of carbon dioxide laser equipment and processing technology, carbon dioxide lasers have been rapidly promoted and applied. . At the same time, more stable solid-state (bulk) laser equipment has been developed. After multiple harmonics, it can reach ultraviolet light level lasers. Because the peak value can reach 12kw and the repetitive power can be at 50, it is also suitable for various types of lasers. PCB circuit board materials (including copper foil and glass fiber cloth, etc.), therefore, for the processing of micro-holes less than 0.1 microns, it is undoubtedly the most effective way for circuit board manufacturers to produce high-density interconnection multi-layer PCB multi-layer boards. Future processing methods.

The laser processing equipment that is actually applied to PCB manufacturers to produce PCB boards are mainly carbon dioxide lasers and UV lasers. The functions of the laser sources of these two lasers are different. One is for burning copper and the other is for burning. The substrate is used, so CO2 lasers and UV lasers are used in the laser processing of PCB boards.