Papers by Keyword: Polyurethane Pad

Abstract: Rotary punching is a sheet metal blanking process which utilizes shearing tools fixed to a pair of rollers. The polyurethane pad is adopted as the die instead of rigid mold because it has the advantages of wide hardness range and high load-bear capacity. Due to the application of polyurethane pad, the surrounding region adjacent to the pierced hole will occur to plastically deform and deflect, which greatly differs from that in the conventional blanking. In this paper, the effects of blank material and thickness, polyurethane hardness, punch penetration depth on deformation behavior were mathematically analyzed and modeled, and then a series of experiments through varying process parameters were conducted to validate the relationship between process parameters and product quality. The degree of sample deflection was exactly measured by scanning electron microscope (SEM). The results show that the deformed area varies with different blank elongations and increases with increasing blank thickness for a given material. When polyurethane pad with low hardness level is employed, it results in large area deformation and quality degradation. Moreover, the deflection degree around the hole edge becomes more severe along with punch penetration, but the penetration depth along blank thickness is not in proportion to the amount of punch advancement.

Abstract: A diamond conditioner or dresser is needed to regenerate the asperity structure of the pad and recover its designed ability in chemical mechanical polishing (CMP) process. In this paper a new design of diamond conditioner is made by shaping a sintered matrix of polycrystalline diamond (PCD) to form teethed blades. These blades are arranged and embedded in epoxy resin to make a designed penetration angle, called the blade diamond disk. The dressing characteristics of pad surface textures are studied by comparison with conventional diamond conditioner. It is found that the height variation of the diamond tip of blade diamond disk is significantly smaller than the conventional diamond disk. The dressing rate of blade diamond disk is lower than that of the conventional diamond disk, and hence the pad life is prolonged. As a result, reduction of the cost CMP is expected. In addition the pad surface roughness Ra of about 3.79μm is less than Ra of about 4.15μm obtained after dressing using a conventional diamond disk.

Abstract: The fundamental characteristics of dressing action on the polyurethane pad are investigated via dressing by single diamond of different orientations, dressing parameters and dressing path in this study. Experimental results show that a groove with pile-up on both side walls forms as the diamond moves over the pad with a specific dressing depth. The resulting asperities on the pad are strongly affected by the diamond orientation. Plowing is found to be the major mechanism responsible for this surface topology if dressing is conducted by the face of a diamond. On the contrary, cutting action dominates when the point of a diamond is responsible for dressing. It is also found that dressing velocity has an insignificant effect on the groove and ridges created on the pad. The depth of the groove is smaller than the dressing depth due to the spring back of the pad. When the groove created is repeatedly dressed over the same track, the ridge height and groove depth increases for each additional dressing. When two grooves cross each other, the ridges at the four corners of the intersection grow while the depth of the overlapped area decreases. These ridges will become the pressure enhancer of the abrasives to polish the wafer.