Cu-Direct Laser Drilling of Blind Via-Hole in Multi-Layer PWBs: Influence of Surface Treatment on Drilled Hole Quality

2009 ◽  
Author(s):  
Toshiki Hirogaki ◽  
Eiichi Aoyama ◽  
Keiji Ogawa ◽  
Tsukasa Ayuzawa
Keyword(s):  
Surface Treatment ◽  
Co2 Laser ◽  
Copper Foil ◽  
Laser Energy ◽  
Copper Surface ◽  
Laser Drilling ◽  
Hole Quality ◽  
Direct Laser ◽  
Overhang Length ◽  
Direct Drilling

This report describes the quality assessment of Blind Via Holes (BVHs) of Printed Wiring Boards (PWBs) drilled by a CO2 laser using Cu-direct drilling. In the Cu-direct drilling method, the copper foil and the build-up layer are melted at the same time, and the surface is treated to increase the laser energy absorbed by the copper foil since an untreated copper surface reflects most of the 10.6-μm-wavelength CO2 laser beam. However, there are few reports dealing with Cu-direct laser drilling of PWBs. In addition, when copper and resin with different processing thresholds are drilled at the same time, occurrences of a defect called overhang have been observed. So, in this report, first we propose a new method using thermography to measure the absorptance of a PWB surface for a CO2 laser. Moreover, we investigate how surface treatment of the outer copper foil influences the quality of a laser-drilled hole. Then, we observe the circumference of a point irradiated with the CO2 laser and explain how melting processes are different from surface treatment. Finally, based on the research we establish a method in order to cut down the overhang length as a parameter of drilled-hole quality. We also show that a high absorptance improves BVH quality.

Influence of Cu Surface Treatment on the Cu-Direct Via Hole Drilling Efficiency of PWBs

2007 ◽  
Author(s):  
Toshiki Hirogaki ◽  
Eiichi Aoyama ◽  
Keiji Ogawa ◽  
Shogo Matsutani
Keyword(s):  
Laser Beam ◽  
Surface Treatment ◽  
Co2 Laser ◽  
Copper Foil ◽  
Copper Surface ◽  
Surface Shape ◽  
Hole Drilling ◽  
Black Oxide ◽  
Direct Drilling ◽  
The Relationship

This report describes the quality assessment of blind via holes (BVHs) of Printed Wiring Boards (PWBs) drilled by a CO2 laser using Cu-direct drilling. In the Cu-direct drilling method, the copper foil and the buildup layer are melted at the same time, and the surface is treated to increase the laser energy absorbed by the copper foil because an untreated copper surface reflects most of the 10.6-μm-wavelength CO2 laser beam. We used black-oxide and V-bond treatments as surface treatment. Previously, the only black-oxide treatment was paid attention to, but the new V-bond treatment is also investigated in this report. First, a straightforward method employing infrared thermography was proposed to determine the absorbance of the CO2 laser beam by the copper surface. Then, we used SEM to characterize the copper surfaces after surface treatment, and established the relationship between laser absorbance and surface shape. Subsequently, we observed the circumference of a point irradiated with the CO2 laser and explained melting processes were different from surface shape. Finally, we investigated the relationship between laser absorbance and BVH quality, and showed that a high absorbance improved BVH quality.

Microvia Formation for Multi-Layer PWB by Laser Direct Drilling: Improvement of Hole Quality by Silica Fillers in Build-Up Layer

2011 ◽  
Author(s):  
Keiji Ogawa ◽  
Toshiki Hirogaki ◽  
Eiichi Aoyama ◽  
Kuniyoshi Obata ◽  
Tsukasa Ayuzawa
Keyword(s):  
Copper Foil ◽  
Fem Analysis ◽  
Printed Wiring Boards ◽  
The Finite Element Method ◽  
Silica Filler ◽  
Silica Fillers ◽  
Via Holes ◽  
Overhang Length ◽  
Novel Method ◽  
Direct Drilling

Microvia formation technology using lasers has become the dominant method for drilling microvia called blind via-holes (BVHs) in printed wiring boards (PWBs). Laser direct drilling (LDD), drilling directly outer copper foil by laser, has attracted attention as a novel method. In particular, when copper and resin with different processing thresholds are drilled at the same time, an overhang defect occurs on the drilled hole. However, the overhang generation mechanism has not been clarified. Therefore, we investigated it by detailed observation of the drilled-hole section. Moreover, the overhang length was estimated using the finite element method (FEM). Influences of surface treatment of outer copper foil and thermal properties of the build-up layer were evaluated experimentally and analytically. Consequently, an experiment with a prototype PWB with silica filler added in the build-up layer was carried out. Using the prototype PWBs, the overhang was reduced as shown in FEM analysis results.

Microvia Formation for Multi-Layer PWB by Laser Direct Drilling: Improvement of Drilled Hole Quality of GFRP Plates

2012 ◽  
Author(s):  
Keiji Ogawa ◽  
Toshiki Hirogaki ◽  
Eiichi Aoyama ◽  
Tsukasa Ayuzawa
Keyword(s):  
High Speed ◽  
Fiber Reinforced ◽  
Hole Quality ◽  
Reinforced Plastics ◽  
Glass Fiber Reinforced ◽  
Via Holes ◽  
Overhang Length ◽  
Fiber Reinforced Plastics ◽  
Direct Drilling

Microvia formation technology using lasers has become the dominant method for drilling microvia that are called blind via-holes (BVHs) in printed wiring boards (PWBs). Laser direct drilling (LDD), which is direct drilling of the outer copper foil by laser, has attracted attention as a novel method. In particular, when copper and resin with different processing thresholds are simultaneously drilled, an overhang defect occurs on the drilled hole. On the other hand, aramid fiber reinforced plastics (AFRP) have been replaced by glass fiber reinforced plastics (GFRP) as the material used for the build-up layer because of its cost performance. Moreover, the PWB quality of the particle incrustations around the drilled holes has problems in the manufacturing process. However, the LDD process of such a composite has not been clarified. Therefore, we investigated it by detailed observation using a high-speed camera. We estimated the overhang length using the finite element method (FEM) and experimentally and analytically evaluated the effects of filler contented build-up layers. As a result, we improved drilled-hole quality by using prototype PWBs made of GFRP with filler in the build-up layer.

scholarly journals Evaluation of Blind Via Hole Quality on Multi-Layer Printed Wiring Boards by Cu Direct Laser Drilling

2006 ◽  
Vol 55 (3) ◽  
pp. 335-340 ◽  
Author(s):  
Toshiki HIROGAKI ◽  
Eiichi AOYAMA ◽  
Keiji OGAWA ◽  
Ryu MINAGI ◽  
Toshiki MURAKAMI ◽  
...  
Keyword(s):  
Laser Drilling ◽  
Printed Wiring Boards ◽  
Hole Quality ◽  
Direct Laser ◽  
Via Hole

Cu-Direct Laser Drilling of Blind Via-Hole in Multi-Layer PWBs: Process Visualization Using High-Speed Camera Images

2012 ◽  
Vol 516 ◽  
pp. 30-35 ◽  
Author(s):  
Kuniyoshi Obata ◽  
Toshiki Hirogaki ◽  
Eiichi Aoyama ◽  
Keiji Ogawa
Keyword(s):  
High Speed ◽  
Substrate Surface ◽  
Laser Drilling ◽  
Drilling Process ◽  
Positional Accuracy ◽  
Board Density ◽  
Process Visualization ◽  
Direct Laser ◽  
Via Holes ◽  
Direct Drilling

Electrical circuits of Printed Wiring Boards (PWBs) have become multi-layered. Therefore, the formation of micro-blind holes for interlayer electrical connections (blind via holes: BVH) is required. As a result, Cu-direct laser drilling is attracting attention. However, Cu-direct drilling is problematic in that it produces a copper overhang as a result of copper and resin, which have different decomposition points, being melted simultaneously. In addition, the state of PWB surface after the laser drilling is very important. However, this procedure restricts the board density that can be achieved as a result of the limited positional accuracy of the etching process. Consequently, using a Cu-direct drilling process, which does not require etching of the copper foil, to drill BVHs to connect copper foils using a CO2 laser beam has been receiving considerable attention for the next-generation high density PWB manufacturing. However, in the Cu process of generating a direct and overhang problem, there is the problem of accuracy on the substrate surface. In contrast, in-depth research on quality companies has not been performed. Thus, we observe the removal process. Furthermore, we demonstrated reduced overhang.

Cu-Direct Via-Hole Drilling of Aramid Fiber Reinforced Build-Up Layer by CO2 Laser Beam

2005 ◽  
Author(s):  
Eiichi Aoyama ◽  
Toshiki Hirogaki ◽  
Keiji Ogawa ◽  
Nobuyuki Doi ◽  
Ryu Minagi
Keyword(s):  
Co2 Laser ◽  
Copper Foil ◽  
Effective Means ◽  
Hole Diameter ◽  
Hole Drilling ◽  
Printed Wiring Boards ◽  
Laser Absorption ◽  
Direct Laser ◽  
Via Hole ◽  
The Difference

This report describes the features of Cu-direct laser drilled hole quality on multi-layer Printed Wiring Boards (PWBs). Cu-direct laser drilling drills the outer copper foil and build-up layer at the same time, which makes it difficult to form a blind via hole (BVH) with high quality because the copper foil has high reflection coefficient for a CO2 laser with wavelength 10.6 μm. Therefore, this study focused on improving drilled hole qualities such as diameter and overhang. First, the influence of laser irradiation conditions on forming BVH and the drilled hole diameter were investigated in detail. Second, a new method employing thermography was proposed in order to evaluate the absorption of copper foil after surface treatment. Third, the effect of mixing fillers into the build-up layer in order to reduce the amount of overhang was shown to be effective both experimentally and theoretically. As a result, it is clear that decreasing the difference in the laser absorption rate of the outer copper foil is an effective means to control the hole diameter and reducing the heat characteristic difference between the outer copper foil and the build-up layer can effectively decrease overhang.

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