Research On HDI PCB Though Hole And Fine Line Production Technology

Print circuit board(PCB) for carrying electronic components and realizing the electrical interconnection should have high density and high reliability performance to meet the need of miniaturization, integration, more functional development of electronic information products. High density interconnection(HDI) PCB with the advantages of high density and high reliability has become a more and more important development direction of print circuit board. The main characteristics of high density interconnect PCB are intensive design of fine lines and miniaturization aperture of layer interconnection. Microvia manufacture, though-hole metallization with high aspect ratio and fine-line manufacture for HDI PCB was investigated in this paper. Research achievements are applied for the manufacture of industrialization. The research work and the results are shown as following.(1) The effects on the roundness and the length of overhang for through holes were analyzed using direct ablation and cutting grommet with ultra violet(UV) laser, respectively. The method of cutting grommet with UV laser was used to form through holes. The parameters of UV laser were evaluated to find the effects of laser power, laser frequency, processing speed and Z axis height on the length of overhang and aperture size. As a result, the aperture size and overhang length of through holes increases gradually with the increasing of laser power. The diameter of through holes exhibited no obvious change but overhang length decreased when increasing the processing speed of UV laser. The increment of laser frequency resulted in the decrease of overhang length but less influence on the diameter of through holes. Increasing Z axis height of UV laser leaded to the increment of the diameter of through holes but resulted in the decrease of overhang length. The optimal UV laser processing parameters were obtained to reach the minimum value of 6.3 μm of the overhang length after an orthogonal experiment as laser power of 6 W, processing speed of 120 mm/s, laser frequency of 40 k Hz and Z axis height of 0.3 mm.(2) Throwing power of high thickness to diameter ratio though hole was studied. The relationship between concentration of copper sulfate, sulfuric acid concentration, current density, aspect ratio of though hole and throwing power of though hole were analyzed. The results show that the throwing power of though hole declined with the increasing of concentration of cupric sulfate; the throwing power of though hole increased with increasing the concentration of sulfuric acid. The current density and the aspect ratio of though holes are negatively correlated with the throwing power of though hole. An orthogonal experiment was designed to get the optimum plating parameters of though hole plating. The optimum plating parameters included current density of 1.4 A/dm~2, sulfuric acid concentration of 180 g/L, the concentration of copper sulfate of 90 g/L. The throwing power reached to 85.2% for though holes with the aspect ratio of 7.5:1.(3) Improved semi-additive process was used to manufacture fine lines. Inverse copper foil was novelty employed as lamination copper foil. Inverse copper foil exhibited better binding force after the test of binding force. A new dry film for plating was used to find out its effects on adhesion, resolution and exposure energy. The problem of electroplating clip was solved by reducing the current density. Microetching solution was used to realize rapid etch for improved semi-additive process. Fine lines with line width / line spacing of 25μm / 25μm were obtained after the adjustment of etching rate and jet-flow pressure.