Study on UV Curing Inks for Laminated Panels (I)

A Printed Circuit Board (PCB) is a substrate for mounting and connecting components of modern electrical appliances and is an important basic component in the electronic industry. Its production technology clearly reflects the comprehensive characteristics of the disciplines, here: microelectronics technology, radio technology, automation technology, coating technology, materials chemistry, radiation chemistry, surface mounting, high precision machining, computer aided design, electroplating, chemistry Plating and environmental chemistry are all useful.

With the small size and light weight of portable electronic products, especially the high integration of semiconductor chips, the rapid progress in high-density mounting technology has brought new issues to the PCB industry. PCBs using high-density interconnect (HDI) technology are one of the most competitive products on the market today. The laminate method (BUM) process enables products to meet stringent requirements with the latest, smallest, fastest speed equipment and is consistent with the goal of continuous cost reduction.

Japan's well-known PCB manufacturing and research expert Gao Muqing defines the multilayered multilayer technology as follows: it is a general multilayer core, and its surface is composed of insulating layers, conductor layers, and through-holes connected between layers. One-layer circuit board, multilayer board technology made by layer stacking.

The inter-layer interconnections and component insertions of early multi-layer boards all rely on full-scale plated-through holes (PTH) to perform. At that time, the assembly was not dense and the wiring was not large, so the problem was not great. With the advancement of electronic products and the increase in the number of parts, the use of earlier through-hole insertions has led to the development of surface-mount surface mounting. Since 1980, SMT has begun mass production, making PCBs an important issue in the fine holes. However, this double-sided mounting method using solder paste and wave soldering still has certain limitations. Under the pressure of multi-layers subjected to increasingly complicated parts and continuously increasing pin counts and extremely thin and light “chip-level package” (CSP), the active PCB industry has launched “non-mechanical drilling” since 1990. Blind vias and even through vias, as well as successive buildup layers (BuildUpProcess) outside the board. As a result, revolutionary progress has once again occurred in the aspect of meagreization.

Using a photosensitive insulating material as a permanent photosensitive medium layer (Photo-ImageableDielectric abbreviation PID), a PID layer is first coated on a completed double-sided core board, and development is performed for a specific hole position to expose the bowl. The copper pad reserved at the bottom forms a bowl-shaped bare blind hole. A full addition of chemical copper and electroplated copper, followed by selective etching, results in an outer circuit and blind vias. It is also possible to complete the conduction without changing the copper paste or copper paste filling the hole. After the double-sided core board is firstly “laminated” on both sides, PID and additive copper plating and etching can be further applied to make a high-density and thin Buildup multilayer board.

1 BuildUpProcess

Based on the concept of "Sequential Lamination" on the basis of double-sided or four-layer boards, the circuit layer is added on the outside of the board one by one, and blind holes of "non-drilled type" are used as the mutual layers. Even, it has become the "Layup Process" (BuildUpProcess), which is now the most watched by the global industry. These new types of non-drilling ultra-thin multilayer boards are extremely versatile. There are a variety of tricks that can be divided into three categories:

1.1 Laser Ablation

This method utilizes CO2 and other gases such as N2, He and CO to generate pulsed infrared lasers with practical wavelengths between 9300 nm and 10600 nm under increased power and sustained discharge times. The PCB industry uses borehole lasers excited by RF Excited CO2 and TEACO2 in two ways. It can be used to fabricate blind-hole plates with a special coated copper Foil (RCC) without glass fiber cloth. The ordinary copper foil and traditional Film laminated blind holes can also be done. However, the selective copper etching process is required to remove the partial copper foil “lid” to expose the substrate at the hole position, and then to burn the non-metal CO2 laser without damaging the copper foil, and to burn out one by one according to the drilling procedure. Blind hole. These lasers can be absorbed in large quantities by the tree fingers, so they can be burned and gasified to complete drilling. As for the glass fiber part, the burn-out effect is poor due to insufficient absorption.

1.2 Plasma Etching This is a method of laminating on the core (Core), which is similar to the above-mentioned laser method except that the non-metallic plate in the blind hole is replaced by a plasma etching to expose the bottom of the bowl. However, the plasma can only eat the resin without biting the glass. After the line is made, the interconnects between the layers can be completed.

This method was first introduced in 1989 by Dyconex, which was founded by Dr. Walter Schmidt in Zurich. The commercialized name is DYCOstrate.

1.3 Photo-Via

UV-curing ink is used as a permanent photo-imageable dielectric layer (Photo-ImageableDielectric referred to as PID), and a PID layer is coated on a completed double-faced core board, and a specific hole position is visualized to expose the bottom of the bowl. The reserved copper pad forms a bowl-shaped bare blind hole. The full addition of chemical copper and electroplated copper results in selective etching of the outer layer to the circuit and blind vias. It is also possible to complete the conduction without changing the copper paste or copper paste filling the hole. After the double-sided core board is firstly “laminated” on both sides, it can be further coated with PID and additive copper plating and etching to make a high-density and thin-layer laminated multi-layer board.

(to be continued)