CURING PROCESS OF PHOTOPOLYMER RESIN BOND DIAMOND TOOLS

CHINESE JOURNAL OF MECHANICAL ENGINEERING.6.Vol. 20, No. 3, 2007CURING PROCESS OF PHOTOPOLYMERGAO TaoRESIN BOND DIAMOND TOOL .S*PENG WeiAbstract: Analytical simulation and corresponding proof test are adopted to study the principle of thecuring process of photopolymer resin diamond tools. The influence of the diamond as abrasives inYAO Chunyanphotopolymer resin owing to the absorptivity of the diamond for the UV light on the photopolymerMinistry of Education Key Laboratoryresin curing process is discussed. Based on the above, a kind of diamond tool- dicing blade isof Mechanical Manufactureselected to analyze the curing process of photopolymer bond diamond tools. An analytical model ofand Automation,curing process is developed and a correlation curve between the depth of polymerization of theZhejiang University of Technology,photopolymer resin diamond tools and the exposure time to represent the curing process ofHangzhou 310014, Chinaphotopolymer bond dicing blade. A test is done to proof-test the validity of the analytical model andthe correlation curve. The simulated data fit the experimental results, which demonstrates theanalytical models and numerical algorithm are of high reliability. The analytical simulation methodcould possibly be used to optimize the curing cycle and improve the quality of the photopolymersresin bond diamond tools.Key words: Pbotopolymer Curing process Simulation Diamond toolsphotopolymer resin.0 INTRODUCTIONIn IT industry, diamond tools are used widely in precision口processing to different kinds of semiconductor materials such assilicon, crystal, etc. The bonding materials of these tools areCH2=CH+CH2- CH单CH2-CH- CH2-CHprimarily resin or metal. Resin bond tools are usually used ofthermosetting resin. This kind of tools is fabricated by as high as100 MPa pressure and 220-250 C temperature sintering'". InFig. I Bond process of photopolymersaddition, those courses of manufacture often last several hours. Asa result, this technique consumes. much energy and lasts long1.2 Influence of the diamond abrasivesmanufacturing period, furthermore causes much environmentalThe diamond abrasives are normal in grinding or cuttingpollution by reason of volatilization of harmful gas, and finallytools. According to the National Standard of the PRC (GB), thebrings high manufacturing costindustry diamonds are divided into eight kinds of levels, in whichOn the other hand, photopolymer resins are used in industry the standard level (label: TB) is mostly popularity with themore and more widespread for various purposes for example rapid characteristics of having the proportion of the octahedron regularprototyping, solid printing, etc due to their superiorities such as shapes as 90%~95%". So the octahedron diamonds israpid through cure, low energy requirements, non-polluting andinvestigated in this study.low costs. In the middle of 1990's, it was applied to makeIn optics, when the surface of the diamonds is iradiated bygrindingtols. Recently the application of diamond dicing bladethe light, three kinds of phenomena will happen: absorbability,bonded with photopolymer resin has been developed in China闲]reflection and transmission. Fig. 2 shows the octahedron diamonds.They have designed a kind of new die and fabricated super thinApparently for a light unit with intensity E, there isdicing blade used in dicing saw machine with photopolymer resinas bonded material. It has been proved its practicability by cuttingE,=E。+E,+E.(1)different materials (51With the development of the photopolymer bond diamondwhere E-Part of absorbabilityEp一Part of reflectiontools, the cure process and the change of the light inside the-Part of transmissionphotopolymer haven't been studied. The aim of this paper is tostudy the curing process of photopolymer bond diamond tools. Ananalytical model of curing process is established to represent theEIcuring process of photopolymer bond dicing blade.1 ANALYSIS OF CURING PROCESSErEp1.1 Curing principle of photopolymersThe photopolymers at least include three kinds of composites:monomer, photopolymerizer, and prepolymer 0. For photop-olymer diamond tools, the liquid photopolymers are mixed intodiamond abrasives and cured by UV irradiation. The curingof the diamond abrasivesprocess is particularly important in the manufacture of diamondtools that can influence the properties of final products.Therefore. the relation, amnno, the absorptivity, reflectivityConsequently, knowledge of the degree of curing process is and trans中国煤化工important and useful for predicting the curing process. Fig. 1(2)shows the cure process of a kind of photopolymers, epoxyTYHCNMHG-Reflectivity， This project is supported by National Natural Science Foundation of Chinaτ-- Transmitivity(No. 50075084) and Advanced Manufacturing Technology & EquipmentThe absorptivity of the diamonds can be determined withZhejiang Provincial Key Disciplines, China. Received September 27, 2006;received in revised form March 19, 2007; accepted March 21, 200710%，The transmittivity to the UV of the diamonds is 70%, andCHINESE JOURNAL OF MECHANICAL ENGINEERINGthe reflectivity of the diamonds can be calculated by Eq. (2): 20%.It was found fom Fig. 3 that the proportion of the light lossIt will occur total intemal reflection while the light iradiated decreased as the rflection times of the light inside the diamondsinto the diamonds. The critical angle is defined asincreased. On the other hand, the available proportion of the lightincreased. When the reflection times were up to 16, the availablesinθ=凸(3) proportion achieved a steady result: 78.48%.n1.3 Analysis of the curing processwhere θ一Critical angleWe choose; photopolymer bond dicing blade and the-Refractive index of the photopolymerepoxy photopolymer resin to discuss. The manufacturing process-Refractive index of the diamondsof the dicing blade can be described as following steps. The liguidThe rfactive index of the diamonds and the photpolymers photopolymers are mixed with diamond abrsives and othercan be determined respectively as 2.443 6 and 1.5586, the criticaladditives are injected into a mould then put on the conveyer beltangle can be calculated by Eq. (3): 0-39.37". For all of the of the UV-light cure machine, cured with the movement of thediamonds abrasives in the tools, the probability of total internal conveyer belt. Fig. 4 shows the curing process of the photopo-reflection can be estimated by Eq. (3) according to statistical lymer bond dicing blade.principleP()= (90 -39.37/90 -56.25%(4)uv lampMould Conveyer beltIn this study the concentration of the diamond tools and themesh of the diamonds were selected respectively by 100% andW10. Assumed the principles of the absorbability, reflection andtransmission for light inside the diamonds each time are the same,the part of absorbability, reflection and transmission are defined asa4, Pi and G The following function can be characterized as(a) Schematic model of UV-light cure machine( 90-39.37. 39.37(5)9090-x0.2[5=gxox( 90(39.37，-x0.8 )Fig. 4 Curing process of photopolymer bond dicing blade(b) Position of curing process of bladewhere So一- -Minimal distance between the mould and the UV-Distance between the mould and the UV lamp in(90-39.37. 39.37.Pm=-xρ,X9x0.2| i=0,2,.. (6)L-discretional positionLength of the conveyer belt( 39.37- Speed of the conveyer belt叫=gxp.x-x0.8Light intensity in any position can be defined aswhere ao= 0.1,ρo= 0.2,的= 0.7(7)a一- Part of absorbability after every time of reflectionand transmissionPart of reflection after every time of reflection thSince the exposure values of the mould are proportional to .the result of integration between light intensity and exposure time,the total exposure values within a period T of exposure can be一Part of transmission after every time of reflection witen asPS。It could be assumed that En is the sum of the available partE=PT=τj°-=dtof the light after absorbability, reflection and transmission, andEar is the sum of the part of the light absorbed by diamonds.(--n'+s:From Eq. (6), we found that the light inside the diamondsdecreased.0