Except liquid-phase sintering, infiltration and direct sintering, there are some new technologies of tungsten copper come out recently, which make the structure and micro-structure of tungsten copper electrode more stable.

3. FGM (Functional Gradient Material)

W-Cu composite material is kind of new material that tungsten copper composite layer is between Cu and W. It can apparently relax the heat stress by mismatch between tungsten and copper properties. There are two techniques for FGM, one is that discontinuous gradient layer, such as traditional powder piling, which has faults among each layer, the other is that continuous gradient layer, such as slip casting, settle casting, centrifugal casting, which takes advantage of natural transfer to forming continuous contents.

To some extent, FGM sintering is similar to traditional PM (Powder Metallurgy) process, which can be specifically divided into solid-phase sintering, liquid-phase sintering and dipping sintering. In addition, some processes adopt non-sintering method, such as plasma coating, laser-cladding, electrophoresis deposition and centrifugal casting.

More information about tungsten copper electrode technologies, click here:

http://news.chinatungsten.com/en/tungsten-information/80086-ti-10266 
http://news.chinatungsten.com/en/tungsten-information/80123-ti-10291

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In part 7 we know that the micro drilling by a tungsten carbide micro drill can also be applied to integrated circuits with finer quality compared to lithography and electroplating technology. Here we talk about the major disadvantage of the micro drills.

Micro drilling has one major disadvantage because of the tungsten carbide micro drill geometry. Because of the drill point, a flat-bottomed hole can not be produced. If one is attempting to produce cylindrical cavities in a micro mold, there must be a relatively thick plating base under the mold material, or the structural substrate of the mold could act as the plating base. To fully develop the diameter of the hole, projected onto a plane perpendicular to the drilling direction, requires the drill point to extend 30% of the drill diameter beyond the depth of the fully developed hole. For holes in the 100 micrometer region, requires a thick plating base to be deposited. One method for creating flat-bottomed blind holes is to use an end milling tool instead of a drill. The disadvantage to this procedure is that drills have a typical L/D ratio of 4 to 14 while end mills typicall have a ratio of only 1.5 to 3.

 (The end. This article is divided into several parts and this is part 8, for part 7 please refer to http://news.chinatungsten.com/en/tungsten-information/80115-ti-10285)

Tungsten Carbide Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-carbide.com.cn
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Except liquid-phase sintering, infiltration and direct sintering, there are some new technologies of tungsten copper come out recently, which make the structure and micro-structure of tungsten copper more stable.

2. In-situ reactions

Tungsten copper electrode always adopts passive pressure infiltration casting, but it has an unavoidable disadvantage that tungsten skeleton will be oxidized, which decreases the associativity of matrix and the properties of product. In the process of in-situ reactions, enhanced phase is forming in metal liquid and do not expose in the air so that it is isolated from outside and the properties will be improved. The process is that mix tungsten and copper powder (WO3 and CuO), and sinter in the air after forming (CuWO₄), then reduce in H₂. Finally, put the blank into copper solution. The relative density of tungsten copper composite material can reach 99% in such this way.

More information about tungsten copper electrode technologies, click here:

http://news.chinatungsten.com/en/tungsten-information/80086-ti-10266

Tungsten Copper Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-copper.com/
Tel.: 86 592 5129696; Fax: 86 592 5129797
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In part 6 we know that the micro drilling speeds and feeds are varied according to materials, but not in high speed in order to avoid the tungsten carbide micro drill staying in the hole bottom. Here we talk about the applicability of micro drilling in integrated circuit industry as a complementary process to lithography and electroplating.

The applicability of micro drilling as a complementary process with features produced by lithography and electroplating has been investigated. A cross section of a copper micro gear made by lithography is shown. The average roughness of the hub wall is 0.4 micrometers. A micro drilled hole in the same material gave a roughness of 0.15 micrometers over a much longer bore length. Micro drilling can also be used to augment lithography for mesoscopic (millimeter and larger) sized components. Often parallelism of deep holes is of concern. To determine typical values for parallelism of micro drilled holes, glass fibers were inserted into a number of holes drilled with a very slow starting sequence. This is necessary to ensure the tungsten carbide micro drill does not walk on the surface of the part and that the hole axis aligns with the un-deflected axis of rotation of the drill. Holes with a length-to-diameter ratio of 8 were drilled at 4000 rpm. The three-dimensional misalignment of the inserted fibers was measured to be 0.08 degrees (1.5 milliradians), which included skewing of the fiber in the hole due to oversize of the hole which was estimated to be 0.5 micrometers.

(To be continued. This article is divided into several parts and this is part 7, for part 6 please refer to http://news.chinatungsten.com/en/tungsten-information/80077-ti-10281; for part 8 please refer to  http://news.chinatungsten.com/en/tungsten-information/80116-ti-10290)

Tungsten Carbide Manufacturer & Supplier: Chinatungsten Online - http://www.tungsten-carbide.com.cn
Tel.: 86 592 5129696; Fax: 86 592 5129797
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