The future high-density line width/pitch will be from 0.20mm-O.13mm-0.08mm-0.005mm to meet SMT and Multichip Package (MCP) requirements. Therefore, the following technology is required.
The functional holes of the printed circuit board for surface mounting are mainly used for electrical interconnection, thus making the application of microporous technology more important. The use of conventional drill materials and CNC drilling machines to produce micro-holes has many failures and high costs. Therefore, the high density of printed boards is mostly done in the thinning of wires and pads. Although great achievements have been made, their potential is limited. To further improve the densification (such as wires less than 0.08 mm), the cost is urgent. Lit, thus turning to micropores to improve the densification.
In recent years, breakthroughs have been made in the development of CNC drilling machines and micro drill bits, and the micro-hole technology has developed rapidly. This is the main outstanding feature in the current production of printed boards. In the future, the micro-pore forming technology mainly relies on advanced CNC drilling machines and excellent micro-heads, and the small holes formed by laser technology are still inferior to the small holes formed by the CNC drilling machine from the viewpoints of cost and hole quality.
At present, the technology of CNC drilling machines have made new breakthroughs and progress. And formed a new generation of CNC drilling machines featuring drilling micro holes. Micro-hole drilling machine drilling hole (less than 0.50mm) is 1 times more efficient than conventional CNC drilling machine, less failure, speed is 11-15r/min; can drill O.1-0.2mm micro-hole, with high cobalt content The high-quality small drill can be drilled by stacking three plates (1.6mm/block). When the drill bit is broken, it can automatically stop and report the position, automatically change the drill bit and check the diameter (the tool magazine can accommodate hundreds of pieces), can automatically control the constant distance between the drill tip and the cover plate and the drilling depth, so the blind hole can be drilled. It will not break the countertop. The numerical control drilling machine table adopts air cushion and magnetic-floating type, which is faster, lighter, and more precise, and will not scratch the table. Such drilling machines are currently very tight, such as the Italian Pyruette Mega 4600, the American ExcelIon 2000 series, and a new generation of products such as Switzerland and Germany.
There are many problems with drill bits to drill tiny holes. It has hindered the progress of micro-hole technology, so laser etches holes have been valued, researched, and applied. However, there is a fatal disadvantage in that the horn holes are formed and become severe as the thickness of the plate increases. In addition to the high-temperature ablation pollution (especially multi-layer board), the life and maintenance of the light source, the repeatability of the hole and the cost, the promotion and application of the production of micro-holes in printed boards are limited. However, laser etches holes are still used in thin high-density microplates, especially in MCM-L high-density interconnect (HDI) technology, such as polyester film etch holes and metal deposition (sputtering) in MCMs. Technology) is used in a combination of high-density interconnects. Buried hole formation in high-density interconnected multilayer boards with buried, blind via structures can also be applied. However, due to the development and technological breakthrough of CNC drilling machines and micro drill bits, it has been rapidly promoted and applied. Therefore, the application of laser drilling in surface-mounted printed boards cannot be dominant. But still have a place in a certain field.
buried, blind, through-hole bonding technology is also an important way to improve the high density of printed circuits. Generally, buried and blind holes are micro holes. In addition to increasing the number of wires on the board surface, the buried and blind holes are interconnected by "nearest" inner layers, which greatly reduces the number of through-holes formed. The reduction increases the number of effective wiring and interlayer interconnections in the board and increases the density of the interconnection. Therefore, the buried, blind, and through-hole combined multi-layer board has a higher interconnect density of at least 3 times in the same size and number of layers than the conventional all-through-hole structure. If under the same technical specifications, buried, blind, The printed board combined with the through-holes will be greatly reduced in size, or the number of layers will be significantly reduced. Therefore, in high-density, surface-mounted printed boards, buried and blind-hole technologies are increasingly used, not only in surface-mounted printed boards in large computers, communication equipment, etc. but also in civil and industrial applications. The field has also been widely used, and even in some thin plates, such as various PCMCIA, Smart, IC card, and other thin six-layer boards.
The printed circuit board with buried and blind hole structure is generally completed by the “sub-board” production method, which means that it can be completed after multiple presses, drilling, and hole plating, so precise positioning is very important.