The process of coating super-fine particles of multi-element thin film

Abstract

This invention provides a process for coating super fine ion particles of multiple elements on the surface of a micro router substrate, characteristics of which is that the coating step is operated under low temperatures and vacuums. First, raw micro routers are cleaned by electron beams under atmospheric pressures and room temperatures, then the raw micro routers are transferred into a vacuum environment, and increase the temperature of the environment. Next, the surface of the micro router is cleaned by ions, then proceed with the coating process. An arc source is used to bombard cations from a target, while a filtration net is used to get filtrate of small cation particles. Then, an ion assistant device is operated to further fine the filtrated particles, therefore only super fine ion particles are coated on the surface of the micro router substrates. The coated substance is super fine particle and has good adhesion to the micro router substrate, therefore cutting speed and wear-resistance of the coated micro router has increased, the cutting precision, and the life has also improved. This invention has short process time and successfully coats a thin film with good adhesion to a micro router substrate which can not be easily achieved by conventional technologies.

Description

FIELD OF THE INVENTION

[0001] This invention relates to the application principles of low temperature physical vapor deposition (PVD), ion cleaning, and ion coating to coat super fine ion particles of multiple elements on the surface of a micro router substrate forming a thin film, especially relates to coat zirconium (Zr), hafnium (Hf), carbon (C), nitrogen (N) multiple elements on the surface of a micro router substrate.

BACKGROUND OF THE INVENTION

[0002] The small router is usually installed on the computer numerical control (CNC) routing machine to route the material of printing circuit board (PCB) via automatic operation. In modern CNC routing machine operation plant, it is desired to increase productivity, besides, it is also desired by the vendor to increase mass production without increasing the machine, since the purchase cost of the machine is usually the highest percentage among manufacturing costs. Therefore, it is urgently desired by the vendor to get the router with higher cutting performance, better hardness, better wear-resistance, as well as longer life. So it is desired to have better adhesive thin film, to get better quality of a coated micro router, which could bear higher rotation speed, further to increase the speed of feed and thus to increase the capacity of cutting. However, it is not easy for the vendor to develop a process of coating a thin film with high adhesion to the substrate of a micro router. This invention is aimed to solve this problem by developing a process of coating a multiple-element thin film of ultra-fine ion particle on the substrate of a micro router.

[0003] Theoretically, it is possible to coat titanium nitride (TiN), titanium carbon nitride (TiCN) thin film on large cutting micro router via physical vapor deposition (PVD), since it can enhance the hardness of micro routers, raise cutting performance as well as enhance micro router's life, however, it is still impossible for the vendors to coat a thin film with better adhesion to the substrate of a micro router. In the prior art the processing of coating film is to clean the raw micro router in the presence of air first, then proceed with coating under vacuums. In the coating process, ions bombarded from a target is not fined further by an ion assistant device or any other method.

[0004] When a coated micro router cools in the presence of air, oxides contaminations are easily formed on the surface of the coated micro router substrate. The coated materials are large particles having low adhesion to the micro router substrate when the coating process is an application of conventional physical vapor deposition (PVD). The coated micro router thereof does not have substantially higher hardness, enough tough internals, higher wear-resistance, and the life of the coated micro router does not increase much. More importantly, it is difficult to coat a thin film on the surface of a raw micro router substrate so that the film has good adhesion to the substrate. Conventional chemical vapor deposition (CVD) is carried out at 950° C. which easily results in decreased toughness and decreased hardness of the coated micro router. Therefore, CVD will not do a good job for coating thin films on a micro router.

SUMMARY OF THE INVENTION

[0005] The object of this invention, therefore, is to provide a process to coat ZrxHfxCxNx multi-element thin film onto the surface of a micro router substrate. The materials coated are fine particles, and have good adhesion to the substrate; the coated materials remain on the surface even when the life of the coated micro router is over. The process time of this invention is also short. The coated micro router has hard surface, tough internals, good wear-resistance, good dissipation of heat, and longer life, and the size and appearance of the coated micro router as compared with raw micro routers, still remain the same.

[0006] Thus the further object of this invention is to provide a physical vapor deposition (PVD) process operated under low temperatures, i.e., a raw micro router is cleaned by electron beams in the presence of air, then put the raw micro router in a vacuum condition, warm it up. Next, the surface of the raw micro router is cleaned by ions, and finally the coating process is operated under low temperatures. This invention uses arc sources to bombard cations, using a filtration net to get filtrates of small cation particles, and at the same time uses an ion assistant device such as an ion gun to make the filtrated cations become smaller, which makes the coated materials to be fine particles and have good adhesion to the surface of the micro router substrate whereof the coated micro router has hard surface, tough internals, good wear-resistance, and the cutting speed and cutting precision thereof increases. The coated micro router has longer life and the process time is short. Conventional PVD, CVD can not coat films with good adhesion to the substrate of the micro router, so this invention solves the problems that can not be solved by conventional PVD, CVD.

[0007] The other objects and characteristics of this invention are farther described in accordance with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING

[0008] FIG. 1 is a simplified drawing of a PVD low temperature deposition system of this invention.

[0009] FIG. 2 shows the working principal of this invention (a drawing shows operations of a target).

[0010] The meanings of the reference numerals of FIG. 1 and FIG. 2 are shown in the following:

[0011] 1 arc source

[0012] 2 arc power supplier

[0013] 3 touch off device

[0014] 4 target

[0015] 5 gas (nitrogen gas or reaction gas)

[0016] 6 pump (diffusion pump and mechanical pump)

[0017] 7 conical jig

[0018] 8 spinning direction of conical jig 7

[0019] 9 revolution direction of the working holder for conical jig 7

[0020] 10 anodes

[0021] 11 metal ion

[0022] 12 evaporated metal atom

[0023] 13 filtration net

[0024] 14 plasma region

[0025] 15 ion gun

[0026] 16 micro droplet

[0027] 17 vacuum chamber

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0028] This invention discloses a process of coating multiple-element ZrxHfxCxNx on the surface of a raw micro router substrate using principles of low temperature PVD, ion cleaning, ion coating. The diameter of the router is 0.2 mm-3.175 mm, and the substrate of the router is tungsten carbide (WC) or cermet. According to this invention, the multiple-element ZrHfCN could be coated onto the surface of the router substrate forming 3-4 &mgr;m thickness thin film, so that the coated micro routers have advantages of high hardness.

[0029] The process of this invention is illustrated as follows in accordance with FIG. 1:

[0030] a. Load raw micro routers onto a jig, proceed to wash them using electron beams and dry them under room temperatures and atmospheric pressures;

[0031] b. Transfer the jig into a vacuum chamber, proceed to vacuum the chamber, and warm the chamber up to 120° C. -380° C.;

[0032] c. Use an ion cleaning device bombarding ions to clean the surface of the raw micro router substrate, and this ion cleaning device may be an ion gun;

[0033] d. Proceed with coating process:

[0034] (i) Operate arc sources to bombard ions from targets, and then use an ion assistant device such as an ion gun to further fine the bombarded ions more delicately;

[0035] (ii) There is one metal filtration net between a target and raw micro routers to filtrate bombarded ions, so that small ions pass the net and large ions are blocked by the net. This filtration net is insulated by ceramics to avoid forming a electrode such that it is advantageous for small ions to pass the net. Further, the passed small ions are refined to super fine particles by an ion gun then only the super fine particles are coated on the surface of the micro router substrate;

[0036] e. Input C2H2 gas into the chamber;

[0037] f. Cool the coated routers using nitrogen (N2) gas;

[0038] In the beginning of the process, loading raw micro routers onto a conical jig 7 (see FIG. 1). This invention overcomes the influence of gravitational force on substances in a vacuum chamber 17 using conical jig 7. Before coating step, clean the surface of the routers by use of physical electron beams under room temperatures and atmospheric pressures, which makes the micro router substrate to be cleaned thoroughly. After the cleaning and drying steps, transfer the routers as well as conical jig 7 into the vacuum chamber. After vacuuming the vacuum chamber, warm up the vacuum chamber. When the temperature of the vacuum chamber reaches a pre-determined value, bombard the surface of the raw router substrate using an ion cleaning device such as an ion gun to bombard the ions in order to purge rid of dirts and oxidized substances, which are produced by the contact of the raw routers with air after the cleaning step.

[0039] After ion cleaning, start a coating process, which is operated under vacuums, low temperatures. Arc devices (see FIG. 1) comprising an arc source 1 and an arc power supplier 2 are employed to bombard metal ions from a target 4. Since it is possible that ions bombarded by arc source 1 are large particles, this invention fines the bombarded metal ions by use of an ion assistant device such as an ion gun to make the bombarded particles smaller. The metal ions bombarded by arc source 1 are assisted by an ion assistant device, an ion gun 15, which fines the bombarded ions, thus the dimension of the fined ion particles is {fraction (1/20)} of that of the unfined ion particles. Since the particle size is super fine, the particles adhere to the router substrate more easily, and the particles can be more compatible with other required element ions to form a multiple-element thin film. The surface of the film layer is smooth, the thin film has high hardness, has good adhesion to a router's substrate, high density of the coated particles. Therefore, an ion assistant device is required in this invention.

[0040] In addition, between a target (exit of cations) and a raw micro router (see FIG. 2), one filtration net 13 designed according to the dimension of the raw micro router to filtrate ions is installed to decrease the speed of metal ions (cations) 11, so that it has more abundant time for the an assistant device to separate metal ions 11 which makes small ions pass through filtration net 13, while the larger ions are blocked by filtration net 13. Only super fine particles are coated on the substrate of the micro routers. It can be sure that the coated micro routers have smooth surfaces as well as excellent cutting performance. Usually filtration net 13 is made up of metal, while the outersphere of the filtration net is made up of insulated materials such as ceramics, the filtration net does not form a electrode thereof, so that the small ions can easily pass through the filtration net. The operation temperature of the coating step is 120° C.-380° C., which belongs to relative low temperatures since this invention has the procedure of ion cleaning as well as ion assistant. Thus the toughness of the coated micro router will not be reduced, and the coated micro router has above two-fold hardness than before, and the coated film has good adhesion and good wear-resistance.

[0041] Conical jig 7 must make micro routers revolute in revolution direction 9 as well as spin in spin direction 8, and more important, the revolution direction and spin direction can be clockwise as well as counterclockwise. Therefore, the film thickness of blade as well as that of back of cuttery can be controled.

[0042] In the late stage of the coating step, nitrogen is used to fast cool micro routers, achieving the aim of hard surfaces and tough insides without affecting the adhesion of the coated materials and short the process time. According to the process of this invention, the process time of the invention is 2-2.5 hours, which is shorter than the conventional coating process time. Besides, this invention is advantageous in that the particles coated onto the substrate of micro routers are super fine, the coated micro routers have smooth surfaces and the coated film has good adhesion. Usually the thickness of the thin film formed on the coated micro routers is between 3-4 &mgr;m, which will not influence the apparent dimensions of the cutting micro routers.

[0043] Right now the most widely used substrate of the micro router is super-hard metal alloy comprising tungsten carbide (WC), tantalum carbide (TaC),cobalt (Co), and titanium carbide (TiC). The cermet containing titanium carbide (TiC) as a major component, comprises tungsten carbide (WC), titanium nitride (TiN), tantalium carbide (TaC) and Colbalt (Co), and is better than superalloy in respect of temperature-resistance as well as wear-resistance. The micro router of this invention uses tungsten carbide (WC) super-hard alloy or cermet as the substrate. Since the thickness of a coated film is only 3 &mgr;m-4 &mgr;m, a micro router could not only depends on a coating layer to maintain its cutting capability. So cermet substrate has great influence upon characteristics of micro routers. Understanding the nature and characteristics of the coated substances, we decide target elements of this invention based on characteristics of materials to be cut, thus we produce the best micro routers. This invention uses tungsten carbide super-hard alloy or cermet as the substrate of micro routers, so the target elements contain an alloy of zirconium (Zr) and hafnium (Hf), which are in the same family with titantium (Ti).

[0044] The process of low temperature physical vapor deposition of this invention has the following advantages:

[0045] 1. Coating at low temperatures: The process of physical vapor deposition operates at relative low temperatures, 120° C.-380° C., which can avoid the decrease of toughness of coated material due to high temperatures; besides, the coated micro routers have more than two fold hardness, the adhesion and wear-resistance of the coated film also increase. Under such conditions, when other elements are coated, the elements have better adhesion. The coated film remains on the micro router under atmospheric pressures and room temperatures for a long time.

[0046] 2. Using an ion assistant device: The ions bombarded from a target by an arc source are further fined to {fraction (1/20)} of the dimension of the ions bombarded directly by the arc by use of an ion assistant device such as an ion gun. Since the fined ion is smaller, more easily adheres to the micro router substrate, and more easily compatible with other required element ions to be coated and a stable multiple-elements thin film is formed, and the degree of surface smoothness is high, the hardness and the adhesion as well as the density of the film is high.

[0047] 3. Directing dissipation of heat: This invention will direct the heat produced to the bottom of the article (the micro router), i.e., the heat dissipates over the region of the micro router which does not have cutting functions. This invention can avoid the phenomena of “thermal stress” focus caused by the substrates of the micro routers, and can avoid the top of the micro routers to become the heat dissipating point. Without this invention, the heat dissipating point will cause poor adhesion of the coated material to be shown on the top of the coated micro routers and leading to the film to get off thereof.

[0048] 4. Cleaning the surface of raw micro routers by electron beams: Before coating, clean the surface of raw micro routers using physical electron beams under atmospheric pressures and room temperatures as well as clean smears inside the raw micro router so that the raw micro router can be cleaned thoroughly.

[0049] 5. Scopes of the application: It must be careful in practicing this invention since the coated material is different and different shapes of raw micro routers have different requirements. Different coated elements have different properties, this invention has a variety of operation methods under different operation temperatures, and different materials to be cut have different characteristics; thus, there are many process variables for this invention. This invention has run lots of experiments and built a data base in accordance with different elements to be coated and different micro routers, and has a broad scope of applications.

[0050] The coating process provided by this invention is suitable for coating multiple elements on the substrate of micro routers. Having generally described in this invention, a further understanding can be obtained by reference to certain specific examples, which are provided herein for purposes of illustrations only and are not intended to be limiting unless otherwise specified.

EXAMPLE 1

[0051] The article to be coated is a micro router, the substrate of the micro router is cermet, and the router's diameter is 1.5 mm. The router's effective knife length is 8 mm, which is called raw Cosmos micro router hereinafter. According to the process of this invention, the target is zirconium(Zr), hafnium (Hf) alloy, the operation temperature of the coating step is 120° C.-380° C.

[0052] After completing the process of this invention, it is found that the coated material contains 65 wt % zirconium(Zr), 8 wt % carbon (C), and 12 wt % nitrogen (N) through element analysis, and the router is called coated Cosmos micro router hereinafter. The thickness of coated thin film is 3-4 &mgr;m. The hardness of the coated Cosmos micro router after coating is larger than two fold of the original substrate. The coated Cosmos micro router has increased wear-resistance, better heat-dissemination, unchanged dimensions, longer cutting life, thus increase the productivity of routing machines and decreases the cost of the micro routers consumed.

[0053] Router's test report:

[0054] Generally there are three key parameters for the micro routers used in routing machines.

[0055] 1. Rotation speed: the speed of a micro router's rotation, representing a cutting rate of a micro router.

[0056] 2. Feed speed: the speed of a micro router's movement, representing a cutting quantity of a micro router.

[0057] 3. Micro router life: the highest usage quantity for a micro router, usually it is represented by a cutting length of the micro router, i.e., life for a micro router to be broken.

[0058] Now the test samples are raw Union micro router, coated Union micro router according to this invention, raw Cosmos micro router, and coated Cosmos micro router according to this invention. The diameters of the above-mentioned micro routers are all 1.5 mm, which have the same knife length, i.e., 8 mm. The test machine is LS-3B and LS-4B of Li-Son (using the axis of Hitachi ), FR (glass fiber rubber)-4 chipping board (the thickness is 1.6 mm, the dimension is 16″×18″, the manufacturer is Formosa Plastic) is used to test the optimum operating condition of all the micro routers in comparing with their working efficiency as well as their life. The test results are as follows:

[0059] 1. raw Union micro router:

[0060] When rotation speed is 28-30 KRPM and feed speed is 14-16 mm/s, the raw Union micro router life is 20-40 m.

[0061] 2. coated Union micro router:

[0062] When rotation speed is 28-32 KRPM and feed speed is 18-22 mm/s, the coated Union micro router life is 60-80 m.

[0063] 3. raw Cosmos micro router:

[0064] When rotation speed is 28-32 KRPM and feed speed is 16-20 mm/s, the raw Cosmos micro router life is 40-60 m.

[0065] 4. coated Cosmos micro router:

[0066] When rotation speed is 30-34 KRPM and feed speed is 24-32 mm/s, the coated Cosmos micro router life is 80-100 m.

[0067] Although the present invention has been disclosed as above, obviously, numerous modifications and variations of the present invention are possible in light of the above teachings to those who were skilled in the art. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.

Claims

1. A process of coating super-fine particles of multi-element thin film comprising the steps of:

a. loading a raw micro router onto a jig, washing said micro router using electron beams and drying said micro router under room temperatures and atmospheric pressures;

b. transferring said jig into a vacuum chamber, vacuuming said chamber, and warming said chamber up to 120-380° C.;

c. using ions to clean the surface of said micro router;

d. proceeding with coating process: coating target elements on surface of said micro router substrate via applying PVD low-temperature deposition, an ion assistant device and a filtration net are used to fine ions bombarded from said target;

e. passing C2H2 gas into said vacuum chamber;

f. using nitrogen gas to cool said coated micro router.

2. The process of

claim 1, wherein said substrate is tungsten carbide (WC), said target is an alloy of zirconium (Zr) and hafnium (Hf).

3. The process of

claim 1, wherein said substrate is cermet, said target is an alloy of zirconium (Zr) and hafnium (Hf).