Hiromichi Nobe

Investigation on cutting mechanism in small diameter drilling for GFRP (thrust force and surface roughness at drilled hole wall)

This study describes the relation between the cutting force and the surface roughness of a drilled hole wall in small-diameter drilling of GFRP for a printed wiring board. In order to investigate the characteristics of small diameter drilling for GFRP, the surface of the drilled hole wall is observed by SEM, and the surface roughness along the feed direction is measured at various edge position angles of the drilled hole. The cutting force during drilling is measured. Moreover, the thrust force is devided into two components (the static component and the dynamic component). It is shown that the dynamic components are related with the surface roughness of the drilled hole wall. In conclusion, it is found that the major cutting edge of the drill is more influential in the quality of the drilled hole wall than the chisel edge of the drill in small diameter drilling of PWB.

Study on small diameter drilling in GFRP

In small diameter drilling with the drilling machine, the drilled hole quality of the printed wiring board (PWB), made of GFRP, is evaluated by investigating the surface roughness and the internal damage to the hole. An investigation of the damage is conducted by changing the number of drilled holes. Additionally, in laser drilling using a CO2 source and a YAG source, the laser drilling process is clarified by observing the damage to the hole, and moreover the relation between the drilling conditions and the damage of the hole is obtained. In conclusion, it is shown that, in the case of the present drilling machine, the anisotropy of the hole surface roughness is able to be developed by the tool tip profile, and as the new process is of no contact drilling, the application of a laser beam machine using a CO2 laser source is effective in the smaller diameter drilling in PWBs.

Reproduction of Lustrous Object and Cutter Location Using the Normal Vector Generated by Photometric Stereo Method

In the present study, the shape of an object is first obtained from photographic images using the photometric stereo method, and then the target object is created using material that gives an artificial impression of wood. We found through experimentation that the output gradient on the surface of the target object is limited to 67°. Moreover, there is a fault that a lustrous object cannot be reproduced by a general photometric stereo method. Then, to overcome the fault, we propose using a Gaussian filter. The results showed that the maximum error margin of the shape of the reproduced object could be adjusted from 8.3 to 3.3%. At the end, the feature that the normal vector in respect is obtained by using the photometric stereo method is made the best use of, and we propose a new method to obtain cutting location (CL) data for ball-end milling using the normal vector of the object geometries generated by the photometric stereo method. As a result, the tool path was quickly and easily derived, without the use of CAD data.Copyright

Drilling of Small Diameter Holes for Circuit Connection of Printed Wiring Board (Hole Internal Damage and Geometoric Dimension of Fiber Bundle of GFRP)

プ リン ト基 板 の 回路 接 続 用 小径 穴 の ドリル 加 工 に関 す る研 究* (GFRPの 強化繊維束の幾何形状 と穴壁面の内部損傷) 青 山 栄 一*1, 廣 垣 俊 樹*1, 矢 村 剛 一*2 野 辺 弘 道*3, 生 田 忠 之*4, 片 山 傅 生*1 Drilling of Small Diameter Holes for Circuit Conection of Printed Wiring Board (Hole Internal Damage and Geometoric Dimension of Fiber Bundle of GFRP) Eiichi AOYAMA*5, Toshiki HIROGAKI, Koichi YAMURA, Hiromichi NOBE, Tadayuki IKUTA and Tsutao KATAYAMA *5 Faculty of Engineering, Doshisha University, 1-3 Miyakodani, Kyoutanabe-shi, Kyoto, 610-0394 Japan

Through-Hole Drilling Condition of FR-4 Printed Wiring Boards Based on Preventing Ion Migration

In the printed wiring board manufacturing sector, methods have been developed to improve the circuit packaging density. A problem has emerged in that the quality of drilled through hole is deteriorating in the smaller diameter drilling of printed wiring boards (PWBs) with high packaging density, because the insulation is insufficient among through-holes after plating in finer circuit pattern. Thus, we have attracted attention to occurrence of delamination in the glass cloth around the drilled hole of FR-4 type PWBs, because it is considered that the poor insulation among through holes is caused by ion migration along the delamination of glass cloth. In the drilling hole to GFRP, Damage occurs from the drilled hole wall to the inside of material by peeling off between layers, it is defined as delamination in this study. In the present report, we describe the influence of drilling conditions on the width of delamination of glass cloth around the drilled hole. First, we made the FR-4 type PWBs (thickness 0.2 mm) reinforced by five kinds of glass cloths. We carried out the drilling experiments (spindle speed 33000rpm and feed rate 0.01–0.06 mm/rev) for these PWBs with diameter 0.4 mm drill tools. Second, we researched the relationship between delamination width and relative hole position for the glass cloth thickness by image processing method. As a result, we demonstrate two important factors (the feed rate conditions in drilling and the thickness of glass cloth at drilled hole wall) to prevent the delamination of glass cloth. The practical formula is proposed to predict the delamination width around the drilled hole by a multivariate analysis method.Copyright

Study on Small Diameter Drilling in GFRP for Printed Wiring Board. Influence of Outer Corner of Drill Tool on Internal Damage.

Recently, it has been necessary to improve the packaging density of printed wiring board (PWB), because the demand for size reduction of the electric devices has begun to increase. Therefore, the pitches between through holes in electric circuits have become fine for the high package density. On the other hand, various forms of damage occur around the holes after drilling. Among them, internal damage has attracted attention in order to prevent the reduction of the insulation resistance between the holes after through-hole plating, and the blow holes after soldering. Therefore, this study researches the damage factors around the drilled hole wall in small diameter drilling of a printed wiring board in order to prevent the ion migration between the holes. First, the internal damage around a drilled hole is examined. Next, the dynamic force (thrust force) during drilling is measured in order to examine the factors causing the internal damage around the drilled hole. As a result, it is shown that the outer corner of drill is one of the most important part in the small diameter drilling for the damage around the drilled hole.

Study on Small Diameter Drilling for Printed Wiring Board. Comparison of Carbide Drill and Diamond Coated Drill.

It has been required that the packaging density of PWB(Printed Wiring Boad)is improved because high packaging density technology has allowed downsizing. Therefore, high-quality micromachinings are necessary for PWB. Especially, it is necessary that a great number of through-holes have to be drilled with high reliability to make a circuit. So it is required to improve the quality of the drilled hole. However, it is inevitabole that the quality of the drilled hole is varied owing to the wear of the cutting edge in a great number of drilling. In this paper, it is shown that the shape of the cutting edge is related to the damages around the drilled hole. And the internal damage, the surface roughness and the smear of the drilled hole are increased, as the number of drilled hole is increased. Additionally, it is cleared how the variation of edge shape due to diamond coating affects the drilled hole quality.

Damage Development in Small Diameter Drilling of GFRP for Printed Wiring Boards

This study deals with the internal damage around the drilled holes connecting the circuits in printed wiring boards made of GFRP (plain woven cloth, glass/epoxy-resin). The influencing factors were determined by measuring the thrust forces (the feed direction components of cutting force) and evaluating the relative position between the drill tool center and the yarn of the woven cloth. It is found that there are two important factors of the internal damage widths around the drilled hole; the relative angles between the cutting directions and the fiber directions, and the fiber bundle thickness of glass cloth on the drilled hole wall. As a result, it is indicated that the reduction of fiber bundle thickness of the glass cloth is effective to prevent the internal damage around the drilled hole.

Study on Small Diameter Drilling for Printed Wiring Board

It has been required that the packaging density of PWB (Printed Wiring Board) is improved because high packaging density technology has allowed downsizing. Therefore, high-quality micro-machining are necessary for PWB. Especially, it is necessary that a great number of through-holes have to be drilled with high reliability to make a circuit. So it is required to improve the quality of the drilled hole. However, it is inevitable that the quality of the drilled hole is varied due to the wear of the cutting edge in a great number of drilling. In this paper, it is shown that the shape of the cutting edge is related to the damages around the drilled hole. And the internal damage and the surface roughness of the drilled hole are increased as the number of drilled hole is increased. Additionally, it is cleared that deflection of the drilled hall is also affected by the drill wear.