Lapping Plate Research Articles

Mechanical Characterization of Lapping Plate Materials in Diamond Charging Process

In the lapping of magnetic heads and other electronic components composed of multiple materials, differences in the processing characteristics of the composite materials result in “residual steps” forming on the surface at composite interfaces. Residual step heights have been reduced to as little as a few nanometers. We investigated using fine abrasives in fixed abrasive lapping for this purpose, which requires highly secure, high-density embedding of the abrasives on the lapping plate. To this end, we modeled the abrasive embedding process and investigated the relationship between the mechanical properties of the lapping plate and the retention of the abrasive, to determine the direction of further research and development. The results of this investigation revealed a correlation between the work hardening in the plate and the resulting abrasive density and cutting edge height. The investigation also showed that it is possible to suppress the reduction in lapping rate that occurs during use by increasing the work hardening coefficient of the plate.

Damage mechanisms during lapping and mechanical polishing CdZnTe wafers

CdZnTe wafers were machined by lapping and mechanical polishing processes, and their surface and subsurface damages were investigated. The surface damages are mainly induced by three-body abrasive wear and embedded abrasive wear during lapping process. A new damage type, which is induced by the indentation of embedded abrasives, is found in the subsurface. When a floss pad is used to replace the lapping plate during machining, the surface damage is mainly induced by two-body abrasive and three-body abrasive wear, and the effect of embedded abrasives on the surface is greatly weakened. Moreover, this new damage type nearly disappears on the subsurface.

Theoretical Analysis and Uniformity of Trajectories in Lapping Process

A new trajectory and uniformity was studied for single lapping process, kinematic theory analysis trajectories of the workpiece under the mode driven by swing motion. According to the theoretical analysis on lapping trajectory and simulated results, uniformity during swing driven lapping process is better than tranditional lapping process, angle rotation ratio between lapping plate and swing plate has great effect on lapping uniformity, when rotation speed of lapping plate is three times to that of swing plate, best uniformity could be gotten during lapping process.

Statistical Analysis on Lapping Parameters for Sapphire Wafer

Effect of lapping speed, plate material and crystal orientation on material removal rate and surface roughness were investigated by experiments and Taguchi Methods. Experimental results show both materials remove rate and surface roughness could be finished by using sythetic copper lapping plate with w3.5 cubic boron nitride abrasive than that for thin plate. Materials removal rate and surface roughness have no much difference for different crystal orientation as A-plane, C-plane and M-plane with experimental parameter conditions, lapping speed would be recommonded to not over 40rpm.

Optimisation of D2 steel lapping with a polymer plate

Experimental research on surface roughness and material removal rate of D2 steel lapping is carried out using a polymer plate. The tribological mechanism of lapping for ductile materials is presented and the polymer-based lap plate is described in this study. Thus, an investigation is conducted using ANOVA method to determine the effects of lapping time, lap rotation speed, applied load and abrasive particle size on the lapping process for D2 steel discs with the polymer-coated plate. Regression models are put forward and verified for predicting surface roughness and material removal rate (MRR) as a result of the control variables. An optimal combination of process parameters is given for optimising the lapping process.

Investigation to Semi-Fixed Abrasives Plate Lapping SUS440 Stainless Steel

To obtain high surface quality and high finishing efficiency in machining SUS440 stainless steel, a novel machining technology employing a semi-fixed abrasive plate (SFAP) is adopted. The SFAP is developed for preventing lapped surface from damage caused by larger particles (from grain size dispersion or from outside of processing area, larger particles could bring uneven load distribution on processing region). The effects of different parameters on the surface quality and the material removal rate (MRR) of SUS440 stainless steel which is lapped by SFAP are investigated in this paper. The control parameters of the lapping process include the lapping time, the load, the rotating speed of the lapping plate, and etc. SFAP of 800# SiC abrasive used, Experimental results indicate that SFAP can avoid the large scratch effectively and the surface roughness (Ra) of the workpiece could be improved from 250 nm to 50 nm in 12 Min. A nearly mirror-like surface can be obtained.

Heat phenomena on grinding of thin plates by wheels of cubic boron nitride

The R18 plate-attachment finite element model is constructed with the MSC.Marc/Mentat computer programs. The model takes into account the physical nonlinearity of the process of lapping plates by the face of a cup wheel of cubic boron nitride. The thermal physics of the process with variable cross-feeds is analyzed. Simulation data made it possible to study little-investigated heat phenomena at periods of nonstationary cutting (penetration and withdrawal of the plate from the contact with the wheel) in the case of operating and sparking-out motions.

Laser direct joining of metal and plastic

We have developed an innovative rapid laser direct joining process of metal and plastic lap plates without adhesives or glues. The joints made between a Type 304 stainless steel plate and a polyethylene terephthalate (PET) plastic sheet of 30 mm width possessed tensile shear loads of about 3000 N. Transmission electron microscope photographs of the joint demonstrated that Type 304 and the PET were bonded on the atomic, molecular or nanostructural level through a Cr oxide film.

Statistical characterization of the lapping plate surface morphology evolution in a diamond charging process

The topographical evolution of a lapping plate surface during a diamond charging process was followed by analysis of atomic force microscopy (AFM) images. AFM measurements were performed in the tapping mode on several Sn–Sb alloy lapping plates containing different amounts of encrusted diamond particles on their surface. Such plates were processed under different charging times at the Lapping Plate Area of Hitachi Global Storage Technologies in Guadalajara, Mexico. Statistical functions were applied to the AFM data to determine the height and spatial characteristics of the plate's surface roughness. The resulting probability density function of heights, height–height correlation function (HCF) and power spectral density (PSD) showed characteristic patterns of evolution related to the amount and distribution of diamond particles incorporated on the plates. The HCF evolution proved how the locally non-flat initial plate surface evolves into a self-affine fractal after the plate is uniformly charged. Surface roughness parameters were found to increase during diamond charging up to a saturation value. The statistical analysis of surface slopes allowed determining the average angle of diamond edge protrusion. According to our results, the RMS roughness along with the HCF morphology analysis could be used to establish quality control measures for diamond charged lapping plates.

D21 枚葉ラップ盤を用いた大口径工作物のラッピング加工(OS-10 研磨技術)

The lapping process is a processing method to improve waviness or bow of the sliced wafers using slurry. The silicon wafer for LSI or IC to improve the productivity has been required larger size diameter every each year. Therefore, the lapping machine size becomes large in proportion to the enlargement of the wafer size. As the results, the upsized lapping machine brings some problems about deflection of the lapping plate by self-weight, and so on. This study aims to develop the single wafer lapping machine to process the large sized silicon wafer by the small sized machine. This report describes the basic lapping characteristics at the single wafer lapping machine.

Research and Simulation on the Wear Uniformity of Lapping Plate

Lapping plate wear is of great influence on shape precision of workpiece. Investigation on the wear uniformity of uncertain eccentricity plane lapping was carried out in this research. The relative velocity function of the plate to the workpiece is obtained through kinematic analyses in the mode of uncertain eccentricity plane lapping, and material removal rate (MRR) function and wear uniformity function were deduced based on Preston equation. Effects of the ratio and eccentricities on the wear uniformity are discussed in detail through MATLAB simulation. Theoretical analysis and simulation results show that the ratio k1 of workpiece revolution speed to lapping plate is the key to decide whether the lapping plate is lapped uniformly. Theoretically, when k1<0, the greater |k1| is, the better the lapped uniformly of lapping plate can be. The ratio k2 of workpiece rotation speed to lapping plate has great influence on the lapped uniformly when k1 approximate 1, and k2 has little influence on the lapped uniformly when k1<0 or k1>1, Besides, a bit bigger eccentricity e1 is propitious to the lapping uniformly of the lapping plate, and bigger eccentricity e2 are also helpful to lapping uniformly of the lapping plate. And the conclusion could be extended to single-side plane lapping and double-side plane lapping process.

Observations in the flat lapping of stainless steel and bronze

Lapping is a finishing process, in which material removal takes place due to relative motion between the workpiece, loose abrasive grains, and the lapping plate. This process is used in achieving finer surfaces and closer fits, correction of minor imperfections, and maintaining close tolerances. Although a significant underlying science-base exists with regards to the physics, mechanics, dynamics, and thermal effects, lapping has been considered an art, rather than a science. Exploring lapping at a fundamental level will help improve its application. This study discusses the effects of using various abrasive materials on surface topography via flat lapping. Stainless steel and bronze specimens were lapped using a set of different abrasives. Topography of the surfaces generated by lapping is investigated using a scanning electron microscope. The surface generated as a result of abrasive particles has been characterized based on concepts in tribology. The goal of this research was to quantify the influence of abrasives material properties in flat lapping with an application in reconditioning valve seats. The lapping process using different abrasives as applied in this study showed no significant material removal rates. However, the surface roughness and the surface topography are seen to be readily affected by the use of different abrasives. The results on MRR obtained by lapping stainless steel and bronze with garnet, alundum, and crystolon indicate that, even though crystolon is harder than alundum, alundum abrasive was more efficient in removing material than crystolon. In general, the surface finish and flatness was observed to improve with the hardness of the abrasive grit.

Research on the properties of ultraviolet-curing resin lapping plate

This paper reports a new method using ultraviolet-curing resin as a bonding agent to develop a new fixed-abrasive lapping plate. The results of lapping experiments have shown that it increases the machining efficiency compared with the conventional loose abrasive lapping plate and makes the machined surface roughness to reach nanometre level. Moreover, this technique of the lapping plate makes it not only easier to manufacture but also more convenient to dress with low cost, high speed and clean technology.

Study on Lapping Characteristics of Silver using Brittle Material (1st Report)

The authors have recently researched interesting phenomena on lapping tests for a glass on a silver lapping plate using different quaternary ammonium chloride solutions. The silver lapping plates were not worn during the lapping process even under the condition of large stock removal of the glasses. In this research, glasses, silicon wafers and ceramics were used as lapping plates for lapping test in the various quaternary ammonium chloride compound solutions as suspensions with aluminium oxide abrasive grains. It inquired into relations between the phenomena and concentration of NaCl, KCl, NH4Cl and ZnCl2 solutions, too. The surfaces of silvers were observed by SEM and EDX after lapping test. In the case when NaCl, KCl, NH4Cl and ZnCl2 lapping solutions were used on glass lap plate, also stock removals of silvers become zero. Any differences of structures on the silver surfaces were not observed after lapping by SEM and EDX even if this phenomenon occurred or not.

Experimental Study on New Bonding Materials for Developing Nano-Grinding Plates

This paper describes a method for experimental development of a novel fixed abrasive nano-grinding plate (FAG-plate) which is proposed for lapping some rigid brittle materials, such as quartz crystal and silicon. The FAG plate is developed with ultraviolet-cured resin by rapid prototyping technology. The analysis shows that such FAG-plate can keep its grinding ability constant and continuous and it can make the roughness of machined surface reach to nanometer level. Based on experimental comparisons with conventional free abrasive slurry lapping plates, the lapping process using FAG-plate has several distinct advantages. One is that the machining efficiency is significantly improved. The second is that it improves the surface roughness of machined work-pieces, although it decreases the flatness tolerance of materials. Furthermore, the fixed abrasive nano-grinding plate is made by the new bonding materials- ultraviolet curing resin and thus the fabrication of FAG-plate is convenient and economical.

Temperature Rise and Welding Characteristics of Various-Frequency Ultrasonic Plastic Welding Systems

Welding characteristics and temperature increases of ultrasonic plastic welding parts over a frequency range from 27 to 94 kHz are studied. Using 27, 40, 67, and 94 kHz ultrasonic plastic welding systems, temperature increases at welding surfaces of lapped 1.0-, 2.0-, and 3.0-mm-thick polypropylene plates and polymethyl methacrylate plates are measured using 0.1- and 0.2-mm-diameter thermocouples inserted between plates, and temperature distributions at cross sections of lapped plate specimens are measured using a thermotracer. The 94 kHz vibration system used for ultrasonic plastic welding consists of a bolt-clamped Langevin-type longitudinal vibration source using four 30-mm-diameter piezoelectric ceramic (PZT) rings, a stepped horn (vibration velocity transform ratio N=3.0) and a catenoidal horn (N=3.13) with an 8-mm-diameter welding tip. The other vibration systems have similar configurations. In the case of using a higher-frequency system, increases in temperature measured at the welding parts are larger. Temperature rises are larger for lapped plate specimens than that for a one-piece specimen owing to the vibration loss of welding surfaces.

An investigation of acoustic emission to monitoring flat lapping with non-replenished slurry

Lapping is a precision manufacturing process. However, the material removal rate and surface roughness show significant variation between trials for repeated experiments and, thus, the repeatability of the results depends on the machine operator’s skill. Acoustic emission (AE) seems to be capable of monitoring the process. Therefore, an understanding of AE generation during lapping is important to predict the performance of the grains and hence the lapping results. Based on a theoretical analysis and experimental results collected during flat lapping, the AE signal was investigated for the situation when slurry is supplied without replenishment. The experiments were carried out with a wireless rotating AE sensor mounted in the middle of the lapping plate. Three parameters related to the AE curve are proposed to monitor the process. The influence of process parameters (lapping pressure, velocity, average grain size, concentration of grains in lapping compound and the number of conditioning rings) on the characteristics of the AE curve was investigated.

Modeling and Simulation of Lapping Processes Based on Grain Size Sensitivity Model

It is of high importance to avoid scratches in lapping process. A Grain Size Sensitivity (GSS) model is put forward in this paper. The GSS is a relative parameter which defines the relative change of the depth of cutting, influenced by the change of the size of grain powders, by which it is possible to evaluate quantificationally the capability of lapping machines in avoiding scratches. It is useful for designing and using lapping machines. The simulating of lapping processes based on GSS model is carried out. The transferring of error is also discussed and a new structure of lapping plate with spring cells developed by the authors is introduced.

Frequency Characteristics of Ultrasonic Plastic Welding: (27 kHz to 180 kHz Ultrasonic Plastic Welding Systems)

Welding characteristics and temperature rises at plastic welding part over frequency range from 27kHz to 180kHz were studied. Ultrasonic plastic welding systems of 27, 40, 67, 94, 150 and 180kHz were developed and direct welding characteristic of lapped plastic sheets were measured. The temperature rises at welding surfaces of lapped 1.0-mm-thick polypropylene and polymethyl methacrylate plates were measured using thermocouples inserted between plate specimens. And also, temperature rise distributions in cross sections of the lapped plate specimens were measured using a thermotracer. The longitudinal vibration systems used for ultrasonic plastic welding consisted of a bolt-clamped Langevin type longitudinal vibration source using two or four piezoelectric ceramic (PZT) rings, a stepped horn and a catenoidal horn with a 4-mm- or 8-mm-diameter welding tip. Using higher frequency system, temperature rise measured at the welding part were higher. Maximum temperature rise measured using thermocouples and a thermotracer was over 350°C under excessive condition.

Studies on Oscillation Controlled Lapping using Small Diameter Lap Tool

INTRODUCTIONS With development of the recent semiconductor industry, the demands for the higher precision and productivity of silicon wafers used as the electronic element materials have grown up. Currently, silicon wafers with diameter as 300mm are generally used. Generally, the lapping of these wafers is performed using a “4 way lapping” system. In the 4 way system, the several wafers can be lapped simultaneously by rotating and revolving the several wafers and rotating the lapping plate. However, various problems are pointed out when the large diameter wafers are lapped in the 4 way system. Therefore, the single wafer lapping/polishing techniques which use the small diameter lap/polish tool have been discussed, recently. This paper describes the basic characteristics of the Oscillation Controlled Lapping (OCL) method as the single wafer lapping technique. Figure 1 shows the schematic drawing of the OCL method. Especially, the OCL method discussed this paper has two parameters such as staying time and position. Furthermore, both Preston’s equation expressed traction and genetic algorithm are used to the theoretical simulation for deciding the OCL parameters. In this paper, the provided results are described by the theoretical simulation and experiments.