阅读说明：本技术 一种功能梯度金刚石/铝复合材料封装壳体的制备方法 (Preparation method of functionally gradient diamond/aluminum composite material packaging shell ) 是由 周洪宇 刘俊友 郑文跃 王慧敏 李亚强 于 2021-06-09 设计创作，主要内容包括：本发明公开了一种功能梯度金刚石/铝复合材料封装壳体的制备方法,涉及金刚石/铝复合材料及其近净成形制备方法。具体步骤为：1、金刚石颗粒和铝粉按一定比例机械混合后压制成冷压坯料；2、将冷压坯料在液固分离模具系统中加热至液固混熔态；3、在压力的作用下液固混熔浆料完成充型过程,其中部分金属液相通过液固分离通道完成定向分离处理以调节腔体顶部金刚石所占体积比；4、剩余浆料在底端冷却系统作用下逐层凝固,在此过程中持续保压,最终制备金刚石/铝复合材料梯度封装壳体。壳体底部承载芯片部位金刚石含量高,热膨胀系数与芯片相匹配的同时具有高的热导率；墙体顶部金刚石含量低,保证与盖板材料的焊接相容性。(The invention discloses a preparation method of a functionally graded diamond/aluminum composite material packaging shell, and relates to a diamond/aluminum composite material and a near net shape preparation method thereof. The method comprises the following specific steps: 1. mechanically mixing the diamond particles and the aluminum powder according to a certain proportion and pressing into a cold-pressed blank; 2. heating the cold-pressed blank in a liquid-solid separation die system to a liquid-solid mixed molten state; 3. the liquid-solid mixed melting slurry completes the mold filling process under the action of pressure, wherein part of the metal liquid phase completes the directional separation treatment through a liquid-solid separation channel so as to adjust the volume ratio of diamond at the top of the cavity; 4. and solidifying the residual slurry layer by layer under the action of a bottom end cooling system, and continuously maintaining the pressure in the process to finally prepare the diamond/aluminum composite material gradient packaging shell. The diamond content of the chip bearing part at the bottom of the shell is high, and the thermal expansion coefficient is matched with that of the chip and simultaneously has high thermal conductivity; the diamond content of the top of the wall body is low, and the welding compatibility with the cover plate material is ensured.)

1. A preparation method of a functional gradient diamond/aluminum composite material packaging shell is characterized by comprising the following steps:

(1) cold pressed billet preparation

Mechanically mixing diamond particles and Al powder according to a certain proportion to prepare mixed powder; then putting the mixed powder into a cold pressing die to prepare a blocky cold pressing blank;

(2) preparation of liquid-solid mixed melting slurry

Putting the cold-pressed blank into a liquid-solid separation die system, and heating to prepare liquid-solid mixed molten slurry with coexisting diamond particles and liquid metal aluminum; or putting the cold-pressed blank into an electric furnace, heating to prepare liquid-solid mixed molten slurry, and putting the slurry into a liquid-solid separation die system;

(3) mixed molten slurry shell preparation

Under the action of the special-shaped pressure head, the fluidity of molten metal is ahead of that of diamond particles, and the metal is reversely extruded from the bottom, the diamond content at the bottom of the shell is high, the diamond content at the top of the wall is low, and a mixed-melting slurry shell with the diamond particles distributed in a gradient manner is formed; the diamond content of the center of the bottom of the shell is calculated by the thickness of the bottom of the shell, and the volume ratio of diamond particles at the top of the wall is adjusted by changing the volume of the cavity of the liquid phase cavity.

(4) Preparation of gradient composite material

And starting the forced cooling system when the pressure head is close to the closed position of the liquid-solid separation cavity, solidifying the liquid-solid mixed molten slurry layer by layer, wherein the pressure head continuously provides pressure, and finally manufacturing the diamond/aluminum composite material packaging shell with the structure and the performance of which are in gradient change.

2. The method for preparing the functionally graded diamond/aluminum composite material packaging shell according to claim 1, wherein in the step (1), diamond particles and Al powder are mechanically mixed according to a ratio of 1: 9-1: 1, and the mixture is prepared into mixed powder after 1-48 hours; then placing the mixed powder into a cold pressing die, and maintaining the pressure for 0.5-5 min under the pressure of 20-400 MPa to prepare a blocky cold pressing blank; and (2) completely retaining the diamond particles at the central part of the cold-pressed blank in the step (1) at the bottom of the shell, so that the volume fraction of the diamond particles at the bottom of the final diamond/aluminum composite shell can be adjusted through the thickness of a final product.

3. The method for preparing the functionally graded diamond/aluminum composite material packaging shell according to claim 2, wherein the steps of raw material blending, mechanical mixing and loading into a cold-pressing mold are all completed in a vacuum glove box in order to prevent aluminum powder from being oxidized; the mechanical mixing process is done in a planetary ball mill or a 3D blender.

4. The method for preparing a functionally graded diamond/aluminum composite encapsulating shell according to claim 1, wherein in the step (1), the diamond particles are subjected to metal plating treatment or carbide plating treatment, and the film layer comprises one or more layers; the metal comprises Cr, Cu, Ti, W, Mo, Ni, Al and Zr; the carbide includes B₄C、Mo₂C、TiC、WC。

5. The preparation method of the functionally graded diamond/aluminum composite material packaging shell according to claim 1, wherein in the step (2), the cold-pressed blank is placed into a liquid-solid separation die system, and is subjected to heat preservation at 630-730 ℃ for 10-60 min to prepare liquid-solid mixed molten slurry with coexisting diamond particles and liquid metal aluminum; or putting the cold-pressed blank into an electric furnace, preserving heat for 10-60 min at 630-730 ℃ to prepare liquid-solid mixed melting slurry, and putting the slurry into a liquid-solid separation mould system; in order to ensure the preparation purity of the liquid-solid mixed melting slurry, a reducing atmosphere or an inert gas atmosphere is adopted for protection.

6. The preparation method of the functionally graded diamond/aluminum composite material packaging shell according to claim 1, wherein in the step (3), a pressure acting force of 5-100 MPa is applied to a special-shaped pressure head to prepare the mixed melting slurry shell with the diamond particles distributed in a gradient manner; the liquid-solid separation channel in the mold system allows only the aluminum melt to pass through.

7. The method for preparing the functionally graded diamond/aluminum composite material packaging shell according to claim 6, wherein the liquid-solid separation channel is a filtering and blocking gap with the width of 0.5-5 mm or a filtering and blocking circular hole with the diameter of 0.5-5 mm, and diamond particles are blocked to be completely retained in the liquid-solid separation cavity and only aluminum liquid is allowed to pass through.

8. The method for preparing a functionally graded diamond/aluminum composite material package housing according to claim 1, wherein in the step (3), the diamond content at the center of the bottom of the housing is calculated by the thickness of the bottom of the housing, and the volume ratio of the diamond particles at the top of the wall is adjusted by changing the volume of the cavity of the liquid phase cavity.

9. The method for preparing the functionally graded diamond/aluminum composite material packaging shell according to claim 1, wherein in the step (4), the bottom end of the mold system is forcibly cooled by circulating water or air cooling or external chilling blocks; the liquid-solid mixed slurry is solidified layer by layer from bottom to top under the action of forced cooling, meanwhile, a liquid-solid separation channel is not closed, molten metal in the liquid-phase cavity enters the liquid-solid separation cavity under the action of gravity and cavity pressure, and solidification shrinkage is filled.

10. The method for preparing the functionally graded diamond/aluminum composite material packaging shell according to claim 1, wherein diamond particles of the prepared diamond/aluminum composite material are in gradient change, the diamond content of a chip-bearing part at the bottom of the shell is high, and the thermal expansion coefficient is matched with that of a chip and has high thermal conductivity; the diamond content at the top of the wall body of the shell is low, so that the welding compatibility with the cover plate material is ensured; meanwhile, the structure and the performance are in gradient change, so that the thermal stress concentration is reduced, and the stability of the packaging shell is improved.

Technical Field

The invention designs a preparation method of a functional gradient diamond/aluminum composite material packaging shell.

Background

Different from the heat dissipation substrate, different functional regions of the package casing have different requirements on performance. The chip bearing part at the bottom of the shell is matched with the chip, and requires low thermal expansion coefficient and high thermal conductivity; the top of the shell wall requires low content of reinforcing phase in order to ensure weldability with the encapsulation cover plate. At present, the packaging shell is manufactured by machining uniform block-shaped samples, so that not only is the raw material greatly wasted, but also the problem of performance difference requirements cannot be solved.

The functional gradient composite material with high diamond content at the bottom of the shell and low diamond content at the top of the wall perfectly solves the problems and improves the stability of the packaging assembly to the maximum extent. The functional gradient composite material has the advantages of ensuring the structural integrity, bearing larger temperature gradient, eliminating/reducing the problem of interface, reducing the concentration of thermal stress, reducing the residual stress and the like.

However, conventional methods for preparing diamond/aluminum composites mainly include pressureless infiltration, air pressure infiltration, squeeze casting, vacuum hot pressing, powder metallurgy, spark plasma sintering, and the like. None of these methods is capable of producing gradient composites in near net shape. Diamond, the hardest material in nature, has high processing cost as a main barrier limiting the application of diamond in the field of electronic packaging. Therefore, the near-net forming technology of the diamond/aluminum composite material packaging shell is developed, the mechanical processing on the shell is reduced, and the method has important significance for promoting the application of a new-generation thermal management material.

Disclosure of Invention

The invention provides a novel method for preparing a diamond/aluminum gradient composite material by near-net-shape forming. The diamond/aluminum composite material with the structure and the performance changing in a gradient manner perfectly meets the special requirements of different functional areas of the packaging shell on the performance, and reduces the mechanical processing to the maximum extent.

A preparation method of a functional gradient diamond/aluminum composite material packaging shell is characterized by comprising the following steps:

(1) cold pressed billet preparation

Mechanically mixing diamond particles and Al powder according to a certain proportion to prepare mixed powder; then putting the mixed powder into a cold pressing die to prepare a blocky cold pressing blank;

(2) preparation of liquid-solid mixed melting slurry

Putting the cold-pressed blank into a liquid-solid separation die system, and heating to prepare liquid-solid mixed molten slurry with coexisting diamond particles and liquid metal aluminum; or putting the cold-pressed blank into an electric furnace, heating to prepare liquid-solid mixed molten slurry, and putting the slurry into a liquid-solid separation die system;

(3) mixed molten slurry shell preparation

Under the action of the special-shaped pressure head, the fluidity of molten metal is ahead of that of diamond particles, and the metal is reversely extruded from the bottom, the diamond content at the bottom of the shell is high, the diamond content at the top of the wall is low, and a mixed-melting slurry shell with the diamond particles distributed in a gradient manner is formed; the diamond content of the center of the bottom of the shell is calculated by the thickness of the bottom of the shell, and the volume ratio of diamond particles at the top of the wall is adjusted by changing the volume of the cavity of the liquid phase cavity.

(4) Preparation of gradient composite material

And starting the forced cooling system when the pressure head is close to the closed position of the liquid-solid separation cavity, solidifying the liquid-solid mixed molten slurry layer by layer, wherein the pressure head continuously provides pressure, and finally manufacturing the diamond/aluminum composite material packaging shell with the structure and the performance of which are in gradient change.

Further, in the step (1), mechanically mixing the diamond particles and Al powder according to the ratio of 1: 9-1: 1 for 1-48 h to prepare mixed powder; and then placing the mixed powder into a cold pressing die, and maintaining the pressure for 0.5-5 min under the pressure of 20-400 MPa to prepare a blocky cold pressing blank. And (2) completely retaining the diamond particles at the central part of the cold-pressed blank in the step (1) at the bottom of the shell, so that the volume fraction of the diamond particles at the bottom of the final diamond/aluminum composite shell can be adjusted through the thickness of a final product.

Further, in order to avoid the oxidation of the aluminum powder, the processes of proportioning raw materials, mechanically mixing and loading the raw materials into a cold-pressing die are all finished in a vacuum glove box; the mechanical mixing process is done in a planetary ball mill or a 3D blender.

Further, in the step (1), the diamond particles may be subjected to metal plating treatment or carbide plating treatment, and the film layer may be composed of one or more layers; the metal comprises Cr, Cu, Ti, W, Mo, Ni, Al, Zr and the like; the carbide includes B₄C、Mo₂C. TiC, WC, and the like.

Further, in the step (2), the cold-pressed blank is placed into a liquid-solid separation die system, and heat preservation is carried out for 10-60 min at the temperature of 630-730 ℃ to prepare liquid-solid mixed molten slurry with coexisting diamond particles and liquid metal aluminum; or putting the cold-pressed blank into an electric furnace, preserving heat for 10-60 min at 630-730 ℃ to prepare liquid-solid mixed melting slurry, and putting the slurry into a liquid-solid separation mould system; in order to ensure the preparation purity of the liquid-solid mixed melting slurry, a reducing atmosphere or an inert gas atmosphere is adopted for protection.

Further, in the step (3), applying a pressure acting force of 5-100 MPa to the special-shaped pressure head to prepare a mixed melting slurry shell with diamond particles distributed in a gradient manner; the liquid-solid separation channel in the mold system allows only the aluminum melt to pass through.

And (3) the liquid-solid separation channel is a filtering separation gap with the width of 0.5-5 mm or a filtering separation round hole with the diameter of 0.5-5 mm. A certain amount of molten aluminum is extruded into the liquid phase cavity through the liquid-solid separation channel, and the diamond particles are completely retained in the liquid-solid separation cavity.

Further, the volume ratio of the diamond particles at the top of the wall body in the step (3) is adjusted by changing the volume of the liquid phase cavity.

Further, the step (4) provides a temperature gradient at the bottom end of the mold system by means of circulating water or air cooling or external chilling blocks and the like.

Further, the liquid-solid mixed molten slurry in the step (4) is solidified layer by layer from bottom to top under the action of forced cooling, meanwhile, the liquid-solid separation channel is not closed, and molten metal in the liquid-phase cavity enters the liquid-solid separation cavity under the action of gravity and pressure to fill up solidification shrinkage.

Furthermore, the diamond particles of the prepared diamond/aluminum composite material are in gradient change, the diamond content of the chip bearing part at the bottom of the shell is high, and the thermal expansion coefficient is matched with that of the chip and simultaneously has high thermal conductivity; the diamond content at the top of the wall body of the shell is low, so that the welding compatibility with the cover plate material is ensured; meanwhile, the structure and the performance are in gradient change, so that the thermal stress concentration is reduced, and the stability of the packaging shell is improved.

The principle of the invention is as follows:

a step-shaped pressure head is researched and designed, and by utilizing the characteristic that the fluidity of molten metal is superior to that of diamond particles, molten aluminum is preferentially extruded reversely from the bottom to form a composite material shell with the diamond particles in gradient distribution (the diamond content at the bottom of the shell is high, and the diamond content at the top of a wall body is low). The diamond content of the chip bearing part at the bottom of the shell is high, and the thermal expansion coefficient is matched with that of the chip and simultaneously has high thermal conductivity; the diamond content of the top of the wall body of the shell is low, and the welding compatibility with the cover plate material is ensured.

The preparation process of the diamond/aluminum composite material packaging shell sequentially comprises the following steps: preparing cold-pressed blank, preparing mixed liquid-solid mixed molten slurry, preparing mixed molten slurry shell, preparing gradient composite material and the like.

Firstly, mechanically mixing diamond particles and aluminum powder according to a certain ratio (1: 9-1: 1), and pressing the mixture into a cold-pressed blank in a press machine; secondly, placing the cold-pressed blank in a liquid-solid separation die system and heating to a liquid-solid mixed molten state; thirdly, completing the shell mold filling process by the mixed molten slurry under the action of pressure, wherein the high fluidity of the aluminum melt ensures that the top of the wall has high aluminum content and the bottom of the shell has high diamond content; and fourthly, solidifying the liquid-solid mixed molten slurry layer by layer under the action of a forced cooling system to prepare the diamond/aluminum composite material packaging shell with the structure and the performance changing in a gradient manner.

Wherein, the quality of the raw materials is determined: according to the mass conservation law, the mass of the diamond particles at the central part of the bottom of the shell before and after liquid-solid separation is kept unchanged, and an equation is established for calculation:

h_shell×V_Shell＝h_Blank×V_Blank

In the formula h_Blank-cold pressing the blank thickness;

h_shell-the thickness of the bottom of the shell;

V_blank-the diamond particles account for volume fraction,%, in the cold-pressed blank;

V_shell-volume fraction% of diamond particles in the bottom of the shell.

The invention has the following advantages:

(1) the invention discloses a short-flow low-cost liquid-solid separation technology, which is a novel method for preparing a functionally gradient packaging shell. The functional gradient diamond/aluminum composite material packaging shell prepared by the technology is suitable for components requiring air tightness packaging, such as IGBT (insulated gate bipolar translator) and phased array radar packaging shells, and paves a way for large-scale use of the diamond/aluminum composite material shell;

(2) the diamond particles of the prepared diamond/aluminum composite material are in gradient change, the diamond content of the chip bearing part at the bottom of the shell is high, and the thermal expansion coefficient is matched with that of the chip and simultaneously has high thermal conductivity; the diamond content at the top of the wall body of the shell is low, so that the welding compatibility with the cover plate material is ensured;

(3) the near-net-shape preparation structure and the performance are in gradient change, the functionally gradient packaging shell is obtained, the stress concentration and the thermal stress concentration effect in the composite material are reduced to the maximum extent, and the stability of the packaging shell is improved. Meanwhile, the machining workload is reduced, and the machining cost is greatly reduced.

Drawings

FIG. 1 is a schematic diagram of a liquid-solid separation technique;

FIG. 2 is a fracture morphology of the functionally graded diamond/aluminum composite material encapsulating shell prepared in embodiment 1 at different sampling positions;

fig. 3 shows different performance results of the functionally graded diamond/aluminum composite packaging case prepared in embodiment 2.

Detailed Description

Embodiments of the present invention include not only the following embodiments, but also any reasonable combination of the embodiments, without limiting the detailed embodiments listed below.

The first specific embodiment is as follows:

a functionally graded diamond/aluminum composite packaging shell is prepared by using a liquid-solid separation system shown in FIG. 1.

The diamond particles and the aluminum powder are weighed according to the proportion (1: 9-1: 1) and then placed in a 3D mixer for mechanical mixing, and the powder mixing time is 1-48 h.

And (3) placing the mixed powder into a cold pressing die, and maintaining the pressure for 0.5-5 min at the pressure of 20-400 MPa to prepare a blocky cold pressing blank.

And (3) putting the cold-pressed blank into a liquid-solid separation die system, and preserving the heat for 10-60 min at the temperature of 630-730 ℃ to prepare liquid-solid mixed molten slurry with the coexistence of diamond particles and liquid metal aluminum.

Under the action of the special-shaped pressure head, the fluidity of the molten metal is ahead of that of diamond particles, and the molten metal is reversely extruded from the bottom, so that the diamond content at the bottom of the shell is high, the diamond content at the top of the wall is low, and the mixed and melted slurry shell with the diamond particles distributed in a gradient manner is formed.

Under the action of pressure intensity of 5-100 MPa, molten aluminum enters a liquid phase cavity through a liquid-solid separation channel with a gap of 0.5-5 mm, and diamond particles are completely blocked in the liquid-solid separation cavity. And the mass percentage of the molten metal on the top of the wall body is adjusted by changing the volume of the liquid phase cavity.

And starting the circulating water cooling system when the pressure head is close to the closed position of the liquid-solid separation cavity, solidifying the liquid-solid mixed molten slurry layer by layer from bottom to top, wherein the pressure head at the upper part continuously provides pressure, and finally manufacturing the diamond/aluminum composite material packaging shell with the structure and the performance in gradient change.

The second specific embodiment:

the difference between this embodiment and the specific embodiment lies in:

the diamond particles and aluminum powder were mechanically mixed in a planetary ball mill.

And heating the cold-pressed blank under the inert gas protective atmosphere condition to prepare liquid-solid mixed molten slurry.

The liquid-solid separation channel is a circular hole with the diameter of 0.5-5 mm.

The composite material is solidified layer by layer through forced cooling by additional chilling blocks.

The third concrete implementation scheme is as follows:

the difference between this embodiment and the specific embodiment lies in:

placing the cold-pressed blank in a container with H₂And heating the mixture in a heating furnace protected by atmosphere until the mixture is in a liquid-solid mixed molten state, and transferring the mixture to a special die system with a liquid-solid separation channel.

The layer-by-layer solidification of the composite material is realized by forced air cooling.

The fourth specific embodiment:

the third difference between this embodiment and the specific embodiment is that:

the diamond particles and the metal aluminum powder are mechanically mixed in a 3D blender.

Placing the cold-pressed blank in a heating furnace with inert atmosphere protection, and heating to a liquid-solid mixed molten state

The liquid-solid separation channel is a circular hole with the diameter of 0.5-5 mm.

The composite material is solidified layer by layer through a circulating water cooling system.

The fifth concrete embodiment:

the difference between this embodiment and the specific embodiment lies in:

the diamond particles and the metal aluminum powder are mechanically mixed in a 3D blender.

The liquid-solid separation channel is a gap with the width of 0.5-5 mm reserved between the upper die and the lower die.

The present invention will be described in detail with reference to examples.

Example 1:

industrial aluminum powder with the average particle size of 37 mu m and the purity of 99.81 wt.% and diamond particles with the average particle size of 106 mu m and the grade of HFD-B are selected as raw materials.

The diamond particles and the aluminum powder are placed into a 3D mixer according to the volume ratio of 1: 4, and mechanically mixed for 12 hours.

Keeping the pressure of the mixed powder material at 300MPa for 1min to prepare a cold-pressed blank. The billet size was 48X 38X 7.5 mm.

And (3) putting the cold-pressed blank into a liquid-solid separation die system, heating to 683 ℃ under the protection of reducing gas, and preserving heat for 50min to prepare liquid-solid mixed molten slurry.

Molten aluminum enters the liquid phase cavity through the filtering and blocking gap with the width of 2mm, and diamond particles are completely blocked in the liquid-solid separation cavity. And the mass percentage of the molten metal on the top of the wall body is adjusted by changing the volume of the liquid phase cavity.

And applying 60MPa pressure to the liquid-solid mixed slurry, and performing backward extrusion on the molten metal from the bottom in advance of the diamond particles under the action of a step-shaped pressure head to finally form a mixed slurry shell with the diamond particles in gradient distribution (the diamond content at the bottom of the shell is high, and the diamond content at the top of the wall is low).

And starting the circulating water cooling system when the pressure head is close to the closed position of the liquid-solid separation cavity, solidifying the liquid-solid mixed molten slurry layer by layer from bottom to top, wherein the pressure head at the upper part continuously provides pressure, molten metal in the liquid-phase cavity enters the liquid-solid separation cavity through a filtering and blocking gap with the width of 2mm under the action of gravity and pressure, filling solidification shrinkage is realized, and finally the diamond/aluminum composite material packaging shell with the structure and the performance in gradient change is manufactured.

The final housing has dimensions of 40X 50X 8mm in external dimensions and 20X 30X 5mm in central cavity dimensions. The sampling position is shown in fig. 2a, wherein point O is located at the center of the bottom of the shell, and point a is located at the top of the wall. The diamond content and the mechanical and thermophysical properties at different sampling positions are shown in table 1.

TABLE 1

Example 2:

industrial aluminum powder with the average particle size of 37 mu m and the purity of 99.81 wt.% and diamond particles with the average particle size of 124 mu m and the grade of HFD-B are selected as raw materials. The diamond is subjected to surface chromium plating treatment, and the thickness of a plating layer is 100 nm.

The diamond particles and the aluminum powder are placed into a 3D mixer according to the volume ratio of 1: 9, and mechanically mixed for 24 hours.

And putting the mixed powder into a cold pressing die, pressing a cold pressing blank at the pressure of 200MPa, and keeping the pressure for 2 min. The blank size was 48X 38X 15 mm.

And (3) putting the cold-pressed blank into a liquid-solid separation die system, heating to 670 ℃ under the condition of He gas protective atmosphere, and preserving heat for 40min to prepare liquid-solid mixed molten slurry.

And applying 40MPa pressure to the liquid-solid mixed slurry, and performing backward extrusion on the molten metal from the bottom in advance of the diamond particles under the action of a step-shaped pressure head to finally form a mixed slurry shell with the diamond particles in gradient distribution (the diamond content at the bottom of the shell is high, and the diamond content at the top of the wall is low).

And placing an additional chilling block at the bottom of the die system when the pressure head is close to the closed position of the liquid-solid separation cavity, solidifying the liquid-solid mixed molten slurry layer by layer from bottom to top, wherein the pressure head at the upper part continuously provides pressure, the molten metal in the liquid-phase cavity enters the liquid-solid separation cavity through a filtering and blocking hole with the diameter of 2mm under the action of gravity and pressure, filling solidification shrinkage is filled, and finally the diamond/aluminum composite material packaging shell with the structure and the performance in gradient change is manufactured.

The final housing has dimensions of 40X 50X 18mm in external dimensions and 20X 30X 10mm in central cavity dimensions. The sampling position is comparable to that of fig. 2 a. The diamond content and the mechanical and thermophysical properties at different sampling positions are shown in table 2.

TABLE 2