Patent Publication Number: US-2022214380-A1

Title: Heat dissipatable die unit and probe seat using the same

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to die units of probe seats of probe cards and more particularly, to a heat dissipatable die unit, and a probe seat using the die unit. 
     2. Description of the Related Art 
     Referring to  FIG. 1 , a conventional probe card primarily includes a probe head  10 , a main circuit board  16 , and a space transformer  19  disposed between the main circuit board  16  and the probe head  10 . The probe head  10  primarily includes a probe seat  11  and a plurality of probes  12 . In practice the probe head includes hundreds or even thousands of probes, but only three probes are shown in  FIG. 1  for concise illustrative purpose. The probe seat  11  usually includes a die such as a middle die  13 , and upper and lower die units  14  and  15  disposed on top and bottom surfaces of the middle die  13  respectively. Each of the upper and lower die units  14  and  15  usually includes an inner die  142  or  152  connected with the middle die  13 , and an outer die  144  or  154  connected with the inner die  142  or  152 , to avoid the problem that a single die is too thick and thereby difficult to be drilled. For each of the die units  14 ,  15 , the inner and outer dies are usually adhered to each other, and then fastened to each other and fastened to the middle die  13  by bolts  17 . Besides, the inner and outer dies  142 ,  152 ,  144  and  154  of the upper and lower die units  14  and  15  are each provided with a plurality of probe holes  18  with tiny size for the probes  12  to be inserted therethrough. The bottom end (i.e. probe tip) of each probe  12  protrudes below the lower die unit  15  for probing an electrically conductive contact of a device under test (not shown). The top end of each probe  12  protrudes above the upper die unit  14  to be abutted against an electrically conductive contact (not shown) provided on a bottom surface of the space transformer  19 . Alternatively, there may be no such space transformer  19 , and the top end of each probe  12  is directly abutted against an electrically conductive contact provided on a bottom surface of the main circuit board  16 . 
     SUMMARY OF THE INVENTION 
     However, when the above-described conventional probe head  10  performs a test under high temperature, the device under test is heated to a specific temperature, such as 100° C. or higher. The heat is transmitted to the probe head  10  by conduction or radiation. Especially, where relatively closer to the device under test, such as the lower die unit  15 , is heated even more obviously. Besides, the electrical signal transmission between the probes  12  and the device under test also generates some heat, which also heats the dies. Taking the lower die unit  15  as an example, the outer die  154  is located relatively closer to the device under test, so it is heated more than the inner die  152  is heated. In other words, the heated inner and outer dies  152  and  154  have a temperature difference therebetween, so that the inner and outer dies  152  and  154  will deform with different degrees. Because the inner and outer dies  152  and  154  are adhered to each other in a surface contact manner, the aforementioned different degree of deformation will make the inner and outer dies  152  and  154  bend, resulting in that the probes  12  will slightly slant and thereby making the tips of the probes  12  inaccurate in position. 
     Therefore, it is an objective of the present invention to provide a die unit for the usage in a probe seat, which has a heat dissipating function, especially lowering the influence of heat on deformation of dies, thereby ensuring positions of tips of probes. 
     To attain the above objective, the present invention arranges a metal heat dissipating layer between an outer die and an inner die and makes them piled in order from a surface of a die, such as middle die. 
     In this way, when a probe head having the die unit performs a test under high temperature, the metal heat dissipating layer can transmit heat from where close to the center of the probe head, i.e., the inside of the probe head, to the outer periphery of the probe head so as to dissipate the heat to the external environment, thereby attaining the effect of improving heat dissipation. 
     However, the arrangement of the metal heat dissipating layer between the inner die and the outer die for improving the heat dissipating effect of the probe head will increase the thickness of the die unit, such as the die unit disposed on the side of the middle die close to the device under test. At this circumstance, for ensuring the length of the part of the probe downwardly protruding out of the lower die unit, the length of the probe should be increased. But the length increase of the probe will affect its electrical property such as high frequency property, and performance of mechanical geometry. In other words, exceeding length of the probe will break the design of the original electrical and mechanical specifications of the probe. Besides, a vertical size of the probe seat protruding out of a bottom surface of a substrate (the main circuit board of the probe card) is defined as the overall depth of the probe seat, which is restricted by hardware specifications of a test machine and thereby has an upper limit. Therefore, the arrangement of the metal heat dissipating layer should not result in increase of the overall depth of the probe seat and the required length of the probe. 
     Therefore, the present invention is the result of a further review. For ensuring the length of the part of the probe protruding downwardly from the bottom surface of the probe seat, the length of the probe should be provided according to the depth of the probe seat, i.e., the distance between the bottom surface of the main circuit board of the probe card and the bottom surface of the probe seat. Further, the length of the probe will affect its high frequency property, and the depth of the probe seat is restricted by the test machine. Therefore, the depth of the probe seat should be prevented from increased resulted from the arrangement of the metal heat dissipating layer. As a result, a solution capable of solving the above-mentioned problems has been found, and the present invention given hereinbelow is conceived. 
     The present invention provides a die unit for being disposed on a surface of a die, such as a middle die. The die unit includes an outer die, an inner die, and a metal heat dissipating layer. The inner die, the metal heat dissipating layer and the outer die are piled in order from the surface of the die (e.g., the middle die). The inner die includes a probe installation section for a plurality of probes to be inserted therethrough, and a peripheral portion surrounding the probe installation section. The peripheral portion is provided on opposite sides thereof with an outer connecting surface, and an inner connecting surface for being connected to the die (e.g., the middle die). The probe installation section has a recessed portion recessed from the inner connecting surface, and a protruding portion protruding from the outer connecting surface, so that the probe installation section is formed with a level difference portion bordering the peripheral portion. The outer die includes an installation recess for the probes to be inserted therethrough, and a supporting portion surrounding the installation recess. The supporting portion has an inner surface. The installation recess is recessed from the inner surface. The installation recess is larger than the protruding portion of the inner die. The protruding portion is accommodated in the installation recess. The metal heat dissipating layer is disposed between the peripheral portion of the inner die and the supporting portion of the outer die. 
     As a result, the die unit is appliable in a probe seat. The probe seat is adapted for being inserted with probes therethrough, thereby forming a probe head. When the probe head performs a test under high temperature and the probe head is heated by the heat resulted from the electrical signal transmission by the probes or the heated device under test, the metal heat dissipating layer can transmit the heat inside the probe head to the outer periphery of the probe head, thereby attaining heat dissipating effect. 
     Besides, by the structural configuration that the outer die has the installation recess and the inner die has the level difference portion, the present invention can be ensured in thickness after the inner and outer dies are combined. In this way, it can avoid increase of the required length of the probes and the resulting affection on high frequency property thereof, and prevent the arrangement of the metal heat dissipating layer from causing the probe seat too large depth to meet the specification requirements of the machines of various manufacturers. 
     In addition, after the arrangement of the metal heat dissipating layer, when a metal heat dissipating sheet is installed, a probe damage problem may be caused by improper installation of the metal heat dissipating sheet, such as inserting to the probe installation section too much. Therefore, the probe installation section of the inner die has the protruding portion to make the metal heat dissipating layer only located around the outer periphery of the probe installation section or abutted against lateral sides of the protruding portion so as to disable the metal heat dissipating layer from entering the probe installation section, so that the metal heat dissipating layer (metal heat dissipating sheet) is prevented from contacting the probes when being detached or installed by the user. 
     Thus, the heat dissipatable die unit provided by the present invention can not only reduce affection of heat on deformation of dies, but also make the probe seat maintained with the required depth to meet the requirement of test machines and prevent the probes from increase of the required length thereof to ensure the high frequency property thereof. 
     The metal heat dissipating layer in the present invention may include a plurality of metal heat dissipating sheets separatable from each other. The metal heat dissipating sheets may be arranged surrounding the protruding portion collectively, so that the protruding portion of the probe installation section of the inner die is located in the space surrounded by the metal heat dissipating sheets collectively. Such metal heat dissipating layer has great heat dissipating effect, and the metal heat dissipating layer is annularly arranged around the outer periphery of the protruding portion of the inner die, thereby providing great support between the inner and outer dies and preventing the probe seat from uneven thickness. 
     The metal heat dissipating layer in the present invention may be composed of a plurality of metal heat dissipating sheets which are originally separatable from each other directly, so that the user can directly take out the metal heat dissipating sheets of the metal heat dissipating layer after removing fastening members of the probe seat, and then install another metal heat dissipating layer with different heat dissipating efficiency. However, the metal heat dissipating layer in the present invention may be monolithically and annularly made and provided with a plurality of tearing lines which divide the metal heat dissipating layer into a plurality of metal heat dissipating sheets. In other words, the metal heat dissipating sheets are originally connected monolithically. The user can tear the metal heat dissipating layer along the tearing lines to separate the metal heat dissipating sheets from each other. Alternatively, the metal heat dissipating layer in the present invention may be not composed of a plurality of metal heat dissipating sheets, but monolithically and annularly made to define a hollow portion, in which the protruding portion of the probe installation section of the inner die is located. Besides, the metal heat dissipating layer has an inner periphery defining the hollow portion, an outer periphery, and a tearing line extending from the inner periphery to the outer periphery, so that the user can tear the metal heat dissipating layer along the tearing line to take out the metal heat dissipating layer. 
     The present invention further provides a probe seat which comprises a middle die, and upper and lower die units. The middle die has a top surface, a bottom surface opposite to the top surface, and an accommodating hole penetrating through the top surface and the bottom surface. The upper and lower die units are disposed on the top surface and the bottom surface of the middle die respectively. At least one of the upper and lower die units is the aforementioned heat dissipatable die unit, the recessed portion of the inner die of which and the accommodating hole of the middle die collectively form a probe accommodating space. 
     The detailed structure, features, assembly or usage of the heat dissipatable die unit and the probe seat using the die unit provided by the present invention will be described in the following detailed description of embodiments. However, those skilled in the field of the present invention should understand that the detailed descriptions and specific embodiments instanced for implementing the present invention are given by way of illustration only, not intended to limit the scope of the claims of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematical sectional view of a conventional probe card. 
         FIG. 2  and  FIG. 3  are an assembled perspective view and an exploded perspective view of a probe seat according to a first preferred embodiment of the present invention respectively. 
         FIG. 4  and  FIG. 5  are sectional views taken along the line  4 - 4  and the line  5 - 5  in  FIG. 2  respectively. 
         FIG. 6  is a top view of a metal heat dissipating layer of the probe seat. 
         FIG. 7  to  FIG. 13  are top views of various types of metal heat dissipating layers. 
         FIG. 14  is a schematic bottom view of a middle die, an inner die and a metal heat dissipating layer, which is similar to that shown in  FIG. 6 , of the probe seat, but showing a configuration different in positions of disassembly positioning holes. 
         FIG. 15  is a bottom view of a middle die, an inner die and a metal heat dissipating layer of a probe seat according to a second preferred embodiment of the present invention. 
         FIG. 16  to  FIG. 20  are similar to  FIG. 15 , but showing various types of metal heat dissipating layers. 
         FIG. 21  and  FIG. 22  are similar to  FIG. 14  and  FIG. 16  respectively, but showing configurations different in positions of disassembly positioning holes. 
         FIG. 23A  and  FIG. 23B  are similar to  FIG. 6 , but showing different types of metal heat dissipating layers. 
         FIG. 24  is a chart showing a simulated result of the present invention. 
         FIG. 25  is a top view of another type of metal heat dissipating layer. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     First of all, it is to be mentioned that same reference numerals used in the following embodiments and the appendix drawings designate same or similar elements or the structural features thereof. It should be noticed that for the convenience of illustration, the components and the structure shown in the figures are not drawn according to the real scale and amount, and the features mentioned in each embodiment can be applied in the other embodiments if the application is possible in practice. Besides, when it is mentioned that an element is disposed on another element, it means that the former element is directly disposed on the latter element, or the former element is indirectly disposed on the latter element through one or more other elements between aforesaid former and latter elements. When it is mentioned that an element is directly disposed on another element, it means that no other element is disposed between aforesaid former and latter elements. 
     Referring to  FIG. 2  to  FIG. 5 , a probe seat  20  according to a first preferred embodiment of the present invention primarily includes a die such as a middle die  30 , and two die units, i.e., an upper die unit  40 A and a lower die unit  40 B. 
     In this embodiment, the middle die  30  is rectangle-shaped and has two opposite surfaces, i.e., a top surface  31  and a bottom surface  32 , a rectangular accommodating hole  33  located at the center of the middle die  30  and penetrating through the top and bottom surfaces  31  and  32 , and a plurality of threaded holes  34  and  35  and through holes  36  and  37  surrounding the accommodating hole  33 . The middle die  30  is adapted to carry the upper die unit  40 A and lower die unit  40 B and provide the upper die unit  40 A and lower die unit  40 B great supportive rigidity. 
     Each of the upper and lower die units  40 A and  40 B in this embodiment includes an inner die  41 , an outer die  42 , and four fastening members  60 . Each of the inner and outer dies  41  and  42  is rectangle-shaped and sized smaller than the middle die  30 . The fastening members  60  are bolts. Each of the inner dies  41  includes a probe installation section  413 , and a peripheral portion  417  surrounding the probe installation section  413 . The peripheral portion  417  has an outer connecting surface  411 , and an inner connecting surface  412  opposite to the outer connecting surface  411 . The probe installation section  413  has a rectangular protruding portion  414  protruding from the outer connecting surface  411 , and a rectangular recessed portion  415  recessed from the inner connecting surface  412 . The recessed portion  415  is located correspondingly to the protruding portion  414  and sized smaller than the protruding portion  414 , so that the probe installation section  413  is formed with a level difference portion  413   a  bordering the peripheral portion  417 . Each of the inner dies  41  further has a plurality of fastening holes  416  and through holes  418  and  419  surrounding the probe installation section  413 . Each of the outer dies  42  includes an inner surface  421 , an outer surface  422 , an installation recess  423 , and a supporting portion  425  surrounding the installation recess  423 . The inner surface  421  and the outer surface  422  face opposite directions. Specifically speaking, the inner surface  421  faces toward the outer connecting surface  411  of the inner die  41 . The installation recess  423  is recessed from the inner surface  421  and rectangle-shaped. The installation recess  423  is larger than the protruding portion  414  of the inner die  41  for accommodating the protruding portion  414 . Each of the outer dies  42  further has a plurality of fastening holes (counter bores)  424  and through holes  426  and  427  surrounding the installation recess  423 . 
     The upper die unit  40 A is disposed in a way that the inner connecting surface  412  of the inner die  41  is connected to the top surface  31  of the middle die  30 , the inner surface  421  of the outer die  42  is connected to the outer connecting surface  411  of the inner die  41 , and the protruding portion  414  of the inner die  41  is located in the installation recess  423  of the outer die  42 . The fastening members  60  are inserted through the fastening holes  424  of the outer die  42  and the fastening holes  416  of the inner die  41 , and screwed into the threaded holes  34  of the middle die  30 . In this way, the inner and outer dies  41  and  42  of the upper die unit  40 A are detachably fastened to each other and detachably fastened to the top surface  31  of the middle die  30 . 
     The lower die unit  40 B is disposed on the bottom surface  32  of the middle die  30  in a similar way of the upper die unit  40 A being disposed. The bottom surface  32  refers to the surface on the side close to the device under test. In other words, the bottom surface  32  faces toward the device under test (not shown). However, the lower die unit  40 B further includes a metal heat dissipating layer  70  disposed between the inner and outer dies  41  and  42 . The metal heat dissipating layer  70  is disposed between the peripheral portion  417  of the inner die  41  and the supporting portion  425  of the outer die  42 . In other words, for the lower die unit  40 B, the inner die  41  is connected to the bottom surface  32  of the middle die  30  by the inner connecting surface  412  and connected to the metal heat dissipating layer  70  by the outer connecting surface  411 , the outer die  42  is connected to the metal heat dissipating layer  70  by the inner surface  421 , and the protruding portion  414  of the inner die  41  is located in the installation recess  423  of the outer die  42 . As shown in  FIG. 4  and  FIG. 5 , there is a gap between the protruding portion  414  of the inner die  41  and the installation recess  423  of the outer die  42 . The height H 1  of the gap is larger than the thickness T 1  of the metal heat dissipating layer  70 , but unlimited thereto. For example, the height H 1  of the gap may be smaller than the thickness T 1  of the metal heat dissipating layer  70 . The probe installation section  413  of the inner die  41  includes an insertion portion  413   b , through which the probes are adapted to be inserted. The level difference portion  413   a  is located between the insertion portion  413   b  and the peripheral portion  417 . The thickness T 2  of the insertion portion  413   b  is preferably smaller than the thickness T 3  of the peripheral portion  417 . In this way, it can ensure the thickness T 3  to maintain the supportive strength of the peripheral portion  417  and also prevent the insertion portion  413   b  of the probe installation section  413  from being too thick and thereby difficult to be drilled. As a result, in the condition that the depth of the probe seat is not changed, it can ensure increase of the space (thickness) for the installation of metal heat dissipating sheets, and also ensure supportive strength and easiness of being drilled. The height H 2  of the level difference portion  413   a  of the inner die  41  is preferably larger than the height H 3  of the protruding portion  414  of the inner die  41 , i.e., the height of the side  414   a  of the protruding portion. In this way, it can ensure to obtain a relatively larger probe accommodating space  22 , also ensure the increase of the space (thickness) for the installation of the metal heat dissipating sheets in the condition that the depth of the probe seat is not changed, and also coordinate with larger thickness T 3  of the peripheral portion  417  and smaller thickness T 2  of the insertion portion  413   b  of the probe installation section  413  to ensure satisfying both the supportive strength of the peripheral portion  417  and the easiness of drilling the insertion portion  413   b  of the probe installation section  413 . For the probe installation section  413  of the inner die  41 , the thickness T 2  of the insertion portion  413   b  is preferably smaller than the height H 2  of the level difference portion  413   a , and the height H 2  of the level difference portion  413   a  is preferably larger than the thickness T 3  of the peripheral portion  417 . The thickness T 3  of the peripheral portion  417  of the inner die  41  is preferably smaller than the thickness T 4  of the supporting portion  425  of the outer die  42 . In this way, in the condition that the depth of the probe seat is not changed, it can ensure the increase of the space (thickness) for the installation of the metal heat dissipating sheets. The thickness T 1  of the metal heat dissipating layer  70  is preferably smaller than the height H 2  of the level difference portion  413   a . In this way, in the condition that the depth of the probe seat is not changed, it can ensure the increase of the space (thickness) for the installation of the metal heat dissipating sheets. The thickness T 1  of the metal heat dissipating layer  70  is preferably smaller than the thickness of the inner die  41 , which equals to the thickness T 2  of the probe installation section  413 , and preferably smaller than the thickness of the outer die  42 , which equals to the thickness T 4  of the supporting portion  425 , thereby ensuring the depth of the probe seat. The sum of the thickness T 1  of the metal heat dissipating layer  70  and the thickness T 3  of the peripheral portion  417  of the inner die  41  is smaller than the height H 2  of the level difference portion or the height H 3  of the protruding portion  414 . Specifically speaking, the sum of the thickness T 1  of the metal heat dissipating layer  70  and the thickness T 3  of the peripheral portion  417  of the inner die  41  is smaller than the height H 3  of the protruding portion  414  of the inner die  41 , i.e., the height of the side  414   a  of the protruding portion  414 . In this way, in the condition that the depth of the probe seat is not changed, it can ensure the increase of the space (thickness) for the installation of the metal heat dissipating sheets. 
     The metal heat dissipating layer  70  in this embodiment includes two metal heat dissipating sheets  71  separatable from each other. The two metal heat dissipating sheets  71  are the same in shape and collectively define a space  75 , which is also called hollow portion  75  hereinafter. As shown in  FIG. 6 , each of the metal heat dissipating sheets  71  includes a first section  711  shaped as a rectangle larger in width, a second section  712  shaped as a rectangle smaller in width and connected with the first section  711  perpendicularly, and exposed portions  713  protruding in the same direction from two ends of the second section  712  respectively, so that each metal heat dissipating sheet  71  is approximately L-shaped. Each of the first and second sections  711  and  712  is provided with a fastening hole  72  and a through hole  73 . Each of the exposed portions  713  is provided with a through hole  74 . When the metal heat dissipating layer  70  is disposed between the inner and outer dies  41  and  42 , the protruding portion  414  of the probe installation section  413  of the inner die  41  is located in the hollow portion  75  of the metal heat dissipating layer  70 , so that the first and second sections  711  and  712  are located by four sides  414   a - 414   d  of the protruding portion  414  of the inner die  41  respectively, as shown in  FIG. 4  and  FIG. 5 . The fastening members  60  of the lower die unit  40 B are inserted through the fastening holes  424  of the outer die  42 , the fastening holes  72  of the metal heat dissipating layer  70  and the fastening holes  416  of the inner die  41 , and screwed into the threaded holes  35  of the middle die  30 . In this way, the inner and outer dies  41  and  42  and metal heat dissipating layer  70  of the lower die unit  40 B are detachably fastened to each other and detachably fastened to the bottom surface  32  of the middle die  30 . 
     It is to be mentioned that the ‘a plurality of metal heat dissipating sheets separatable from each other’ mentioned in the present invention includes the structural configurations as shown in  FIG. 6  to  FIG. 8  and  FIG. 14  to  FIG. 23B , wherein the metal heat dissipating sheets  71  and  71 A-I are directly arranged separately from each other, which means the adjacent metal heat dissipating sheets  71  and  71 A-I are provided with gaps G therebetween. The configurations, which are not shown in the drawings, that the metal heat dissipating sheets  71  and  71 A-I are abutted against each other without any gap therebetween but still separatable directly are also included. Besides, the configurations shown in  FIG. 9  to  FIG. 11  are also included, wherein the metal heat dissipating layer  70  has tearing lines  76  and thereby can be torn by the user into a plurality of metal heat dissipating sheets  77 A,  77 B and  77 C, which will be specified hereinbelow. However, the metal heat dissipating layer in the present invention is unlimited to include a plurality of metal heat dissipating sheets. For example, the metal heat dissipating layer  70  as shown in  FIG. 25  includes only one metal heat dissipating sheet. The metal heat dissipating sheet is monolithically made with an annular shape and arranged surrounding the protruding portion  414 , so that the protruding portion  414  of the probe installation section  413  of the inner die  41  is located in the space  75  surrounded by the metal heat dissipating sheet. Such metal heat dissipating layer  70  can be removed and installed when the fastening members  60  and the outer die  42  are not installed. 
     After the assembly of the probe seat  20  is accomplished in the above-described manner, the through holes  426  of the outer dies  42  and the through holes  418  of the inner dies  41  of the upper and lower die units  40 A and  40 B, the through holes  36  of the middle die  30 , and the through holes  73  of the metal heat dissipating layer  70  collectively form four disassembly positioning holes  21 , as shown in  FIG. 2 . Besides, the through holes  427  of the outer die  42  of the upper die unit  40 A, the through holes  419  of the inner dies  41  of the upper and lower die units  40 A and  40 B, the through holes  37  of the middle die  30 , and the through holes  74  of the metal heat dissipating layer  70  collectively form four installation positioning holes  23 , as shown in  FIG. 2 . The outer die  42  of the lower die unit  40 B is provided on four corners thereof with chamfers  428  located correspondingly to the installation positioning holes  23 , so the part of each exposed portion  713  of the metal heat dissipating layer  70  provided with the installation positioning hole  23  is not connected with the outer die  42  but exposed outside. 
     As shown in  FIG. 4  and  FIG. 5 , the recessed portions  415  of the inner dies  41  of the upper and lower die units  40 A and  40 B and the accommodating hole  33  of the middle die  30  collectively form a probe accommodating space  22 . Besides, the inner dies  41  of the upper and lower die units  40 A and  40 B further have a plurality of inner probe holes (not shown) located in the recessed portions  415  and penetrating through the protruding portions  414 . The installation recesses  423  of the outer dies  42  have a plurality of outer probe holes (not shown) communicating with the inner probe holes respectively for a plurality of probes (not shown) to be installed in the probe seat  20  by being inserted through the inner and outer probe holes of the upper and lower die units  40 A and  40 B and partially accommodated in the probe accommodating space  22 . This part is relatively less related to the technical features of the present invention. For the simplification of the figures and the convenience of illustration, the inner and outer probe holes of the upper and lower die units  40 A and  40 B and the probes are not shown in the figures. 
     It can be known from the above description that the upper and lower die units  40 A and  40 B are structurally similar to each other, but in this embodiment the lower die unit  40 B has the additional metal heat dissipating layer  70  when compared with the upper die unit  40 A. Such structural feature makes the lower die unit  40 B a heat dissipatable die unit. The dies are usually made of ceramic material, thereby having relatively lower heat conductivity. However, metal material has relatively higher heat conductivity, so the metal heat dissipating layer  70  can attain heat dissipating effect. When the probe head heated by a heat resulted from the electrical signal transmission by the probes or the heated device under test, the metal heat dissipating layer  70  can transmit the heat inside the probe head to the outer periphery of the probe head, thereby attaining the heat dissipating effect. However, the probe seat  20  of the present invention may be configured in a way that the upper die unit  40 A is the aforementioned heat dissipatable die unit, or the upper and lower die units  40 A and  40 B are both the aforementioned heat dissipatable die units. But, the lower die unit  40 B is located relatively closer to the device under test and thus heated relatively more obviously. Therefore, it can bring relatively better heat dissipating effect to make the lower die unit  40 B the aforementioned heat dissipatable die unit. Besides, the probe seat  20  of the present invention is unlimited to include the middle die  30 , and the one of the upper and lower die units  40 A and  40 B, which is not the heat dissipatable die unit, may include at least one die. From this it is knowable that the dies of the probe seat  20  of the present invention may include only the inner and outer dies  41  and  42 , between which the metal heat dissipating layer  70  is disposed, and another die connected with the inner die  41 , which is the middle die  30  in this embodiment. In other words, the probe seat  20  of the present invention may include at least three dies. 
     Taking the configuration of this embodiment that the lower die unit  40 B is the heat dissipatable die unit as an example, when it is required to replace the metal heat dissipating layer  70 , the user can firstly dispose the probe seat  20  on a jig (not shown), and insert four positioning pins (not shown) in the four disassembly positioning holes  21  respectively to disable the dies  41 ,  42  and  30  from moving relative to each other in the following detaching and installing process. Then, the user can remove the fastening members  60  of the lower die unit  40 B to unfasten the inner and outer dies  41  and  42  and the metal heat dissipating layer  70  of the lower die unit  40 B from each other. Then, the user can insert a tool (not shown) in the through hole  74  of the exposed portion  713  of the metal heat dissipating sheet  71  through the chamfer  428  of the outer die  42  of the lower die unit  40 B, so as to draw out the metal heat dissipating sheet  71  between the inner and outer dies  41  and  42 . It should be mentioned here that the metal heat dissipating layer  70  in this embodiment includes two metal heat dissipating sheets  71 , and the two metal heat dissipating sheets  71  can be positioned by the respective positioning pins. Therefore, before taking out one of the metal heat dissipating sheets  71 , the user can remove the positioning pin inserted in the metal heat dissipating sheet  71  to enable the metal heat dissipating sheet  71  to be separated from the inner and outer dies  41  and  42  and thereby taken out. Meanwhile, the positioning pin inserted in the other metal heat dissipating sheet  71  can still prevent the dies from displacement. Alternatively, the metal heat dissipating layer  70  may be configured in a way that the metal heat dissipating sheets  71  give way to the positions the positioning pins are inserted. Thus, the metal heat dissipating sheets  71  may be not completely close, but have gaps therebetween. In other words, the disassembly positioning holes  21  are aimed at the metal heat dissipating sheets  71 , such as the configuration as shown in  FIG. 14 , wherein the metal heat dissipating sheets  71  have no such through hole  73  as described above. The positions of the through holes  36 ,  418  and  426  of the dies  30 ,  41  and  42  for pass of the positioning pins therethrough, i.e., the positions of the disassembly positioning holes  21 , aim at the gaps G between the two metal heat dissipating sheets  71 , such as the positions of the two through holes  418  shown in  FIG. 14 , which may be located anywhere in the gaps G between the metal heat dissipating sheets  71  and unlimited in amount. In this way, it has no need to remove some positioning pins during taking out the metal heat dissipating sheets  71 . 
     After taking out all the metal heat dissipating sheets  71 , the user can directly fasten the inner and outer dies  41  and  42  to each other again by the fastening members  60  of the lower die unit  40 B, such that the thickness of the probe seat  20  is reduced by the thickness of the metal heat dissipating layer  70 . Alternatively, the user can install another metal heat dissipating layer  70  structurally similar to the former metal heat dissipating layer  70  between the inner and outer dies  41  and  42 , then insert four other positioning pins (not shown) in the four installation positioning holes  23  respectively to accurately position the metal heat dissipating sheets  71  of the latter metal heat dissipating layer  70 , and then fasten the inner and outer dies  41  and  42  and the latter metal heat dissipating layer  70  to each other by the fastening members  60  of the lower die unit  40 B. By replacing different metal heat dissipating layers  70 , the heat dissipating efficiency of the probe seat  20  can be modified according to requirements. It is to be mentioned that in the condition that the metal heat dissipating sheets  71  have the aforementioned through holes  73 , i.e., the condition that the disassembly positioning holes  21  penetrate through the metal heat dissipating sheets  71 , the disassembly positioning holes  21  can serve as the aforementioned installation positioning holes and no additional installation positioning hole is provided. However, in the configuration with the aforementioned installation positioning holes  23 , the through holes  74  of the metal heat dissipating sheets  71  are not covered by the outer die  42  but visible to the user directly, such that the user can install and position the metal heat dissipating sheets  71  more easily and it is convenient to take out the metal heat dissipating sheets  71  by using the through holes  74  as described above. 
     Because the probe installation section  413  of the inner die  41  has the protruding portion  414 , the metal heat dissipating layer  70  may be configured in a way that at least a part of each of the metal heat dissipating sheets  71  is abutted against the protruding portion  414  of the inner die  41 . In this way, as long as the first section  711  of the metal heat dissipating sheet  71  is abutted against the protruding portion  414 , the user is aware that the metal heat dissipating sheet  71  is approximately installed at the right position. But the present invention is unlimited to the aforementioned configuration. For preventing the processing tolerance from causing interference between the metal heat dissipating sheets  71  and the protruding portion  414  of the inner die  41 , each of the metal heat dissipating sheets  71  may be at least partially non-abutted against the protruding portion  414  of the inner die  41 . For example, as shown in  FIG. 4 , in this embodiment the second sections  712  of the two metal heat dissipating sheets  71  are respectively distanced from the sides  414   a  and  414   b  of the protruding portion  414  of the inner die  41  by an interval d. Besides, as shown in  FIG. 5 , in this embodiment there are tiny intervals provided between the first sections  711  of the two metal heat dissipating sheets  71  and the sides  414   c  and  414   d  of the protruding portion  414  of the inner die  41  respectively. The first sections  711  of the metal heat dissipating sheets  71  may be configured to be stair-shaped as shown in  FIG. 7  to reduce material cost and still have certain structural strength. The protruding portion  414  of the inner die  41  not only has the above-described effect of positioning the metal heat dissipating sheets  71 , but the sides  414   a - 414   d  of the protruding portion  414  are like protective walls surrounding the probes to restrict the metal heat dissipating sheets  71  to be located around the outer periphery of the probe installation section  413  or abutted against the sides  414   a - 414   d  of the protruding portion  414  but unable to enter the probe installation section  413 , such that the metal heat dissipating sheets  71  are prevented from contacting the probes when being detached or installed by the user. 
     Besides, for ensuring the length of the parts of the probes protruding downwardly from the bottom surface of the probe seat, the length of the probes should be provided according to the depth of the probe seat, i.e., the distance between the bottom surface of the main circuit board of the probe card and the bottom surface of the probe seat. The length of the probes will affect the high frequency property of the probes. The depth of the probe seat is restricted by the test machine. Therefore, the depth of the probe seat should be prevented from the increase resulted from the arrangement of the metal heat dissipating layer. By the configuration that the outer die  42  has the installation recess  423  and the inner die  41  has the level difference portion  413   a , the inner and outer dies  41  and  42  in the present invention can be relatively smaller in thickness than the conventional ones, thereby preventing the arrangement of the metal heat dissipating layer  70  from causing the probe seat  20  too large depth to meet the requirement. In other words, the heat dissipatable die unit of the present invention can not only lower the affection of heat on the deformation of the dies, but also enable the probe seat to be maintained with the required depth to meet the requirement of the test machine and avoid the change of the required length of the probes. 
     The above-described way to take out or replace the metal heat dissipating layer  70  is fast, simple and convenient for the user to modify the heat dissipating effect of the probe seat  20 . The dies or probes need not to be detached in the above-described modifying process, so the process has high efficiency and the operating range of the probes is prevented from change and thereby ensures identical probing performance. The metal heat dissipating sheets  71  can be made in a high accuracy processing manner, so that the depth of the probe seat  20  can be maintained accurately, and the metal heat dissipating sheets  71  can be provided with great structural strength to improve the structural strength of the whole probe seat  20 . 
     It can be known from the above description that the present invention attains the heat dissipating effect by the arrangement of the metal heat dissipating layer  70  between the inner and outer dies  41  and  42  of at least one of the upper and lower die units  40 A and  40 B. The metal heat dissipating layer  70  in the present invention is arranged surrounding the protruding portion  414  of the inner die  41 , not U-shaped or other configurations with one or a plurality of open sides. Therefore, the metal heat dissipating layer  70  in the present invention can bring great support between the inner and outer dies  41  and  42  and prevent the probe seat  20  from uneven thickness. In the configurations shown in  FIG. 6  and  FIG. 7 , the metal heat dissipating layers  70  are each approximately shaped as a square ring and composed of two metal heat dissipating sheets  71  for the user to take out or replace the metal heat dissipating sheets  71  without detaching the dies of the probe seat  20 . The amount and positional distribution of the metal heat dissipating sheets  71  of the metal heat dissipating layer  70  are unlimited and adjustable according to requirements. For example, the metal heat dissipating layer  70  as shown in  FIG. 8  includes four metal heat dissipating sheets  71 A and  71 B, the shapes of which are configured like dividing the first and second sections  711  and  712  of the metal heat dissipating sheet  71  shown in  FIG. 6  into different metal heat dissipating sheets  71 A and  71 B. When the metal heat dissipating layer  70  as shown in  FIG. 8  is disposed between the inner and outer dies  41  and  42 , the four metal heat dissipating sheets  71 A and  71 B are located by four sides  414   a - 414   d  of the protruding portion  414  of the inner die  41  respectively. 
     The metal heat dissipating layers  70  as shown in  FIG. 6  to  FIG. 8  and  FIG. 14  to  FIG. 23B  are each composed of a plurality of metal heat dissipating sheets originally separatable from each other directly, so that after removing the fastening members  60 , the user can directly take out the metal heat dissipating sheets and can install a different metal heat dissipating layer  70 . However, in the condition that it requires to take out the metal heat dissipating layer  70  only but install no more metal heat dissipating layer  70 , the metal heat dissipating layer  70  in the present invention may be made monolithically and shaped annularly. For example, the metal heat dissipating layers  70  as shown in  FIG. 9  to  FIG. 11  are each shaped as a monolithic square ring and provided with a plurality of tearing lines  76  made by preformed perforations. The tearing lines  76  divide the metal heat dissipating layer  70  into a plurality of metal heat dissipating sheets. The amount and positional distribution of the tearing lines  76  and the metal heat dissipating sheets are unlimited and adjustable according to requirements. For example, the metal heat dissipating layers  70  as shown in  FIG. 9  and  FIG. 10  both include four tearing lines  76 , and four metal heat dissipating sheets  77 A and  77 B defined by the tearing lines  76 . However, the metal heat dissipating layers  70  as shown in  FIG. 9  and  FIG. 10  are different in the positional distribution of the tearing lines  76  and the metal heat dissipating sheets  77 A and  77 B. The metal heat dissipating layer  70  as shown in  FIG. 11  includes only two tearing lines  76 , and two metal heat dissipating sheets  77 C defined by the two tearing lines  76 . When it is required in application to remove the metal heat dissipating layer  70 , after removing the fastening members  60 , the user can tear the metal heat dissipating layer  70  along the tearing lines  76  to separate the originally monolithically connected metal heat dissipating sheets from each other, and then take out the metal heat dissipating sheets. 
     The probe seat  20  of the present invention may include a plurality of metal heat dissipating layers  70  disposed between the inner and outer dies  41  and  42  at the same time, so that the user can draw out the metal heat dissipating layer  70  for multiple times. For example, two metal heat dissipating layers  70  for being disposed between the inner and outer dies  41  and  42  at the same time are shown in  FIG. 11 , wherein each of the metal heat dissipating layers  70  is provided on the outer periphery  78  thereof with an indentation  782  adjoining one of the tearing lines  76 . The indentations  782  of the adjacent metal heat dissipating layers  70  are not aimed at each other. Such configuration is convenient for the user to tear one metal heat dissipating layer  70  and take it out. 
     Referring to  FIG. 12  and  FIG. 13 , the metal heat dissipating layers  70  shown therein are similar to the metal heat dissipating layers  70  as shown in  FIG. 9  to  FIG. 11 , which are each made monolithically and shaped annularly to define a hollow portion  75 , but the metal heat dissipating layers  70  as shown in  FIG. 12  and  FIG. 13  each include only one tearing line  76 . The tearing line  76  extends from an inner periphery  79  of the metal heat dissipating layer  70 , which defines the hollow portion  75 , to the outer periphery  78 . In  FIG. 12 , the tearing line  76  of the metal heat dissipating layer  70  is provided at the position where no fastening hole  72  or through hole  73  is provided. In  FIG. 13 , the tearing line  76  of the metal heat dissipating layer  70  passes through the fastening holes  72  of the metal heat dissipating layer  70  for insertion of the fastening members  60  therethrough and the through holes  73  for insertion of the positioning pins therethrough, which means it passes through the aforementioned disassembly positioning holes  21 . In this way, the user can tear the metal heat dissipating layer  70  along the tearing line  76  to take out the metal heat dissipating layer  70  between the inner and outer dies  41  and  42 . 
     The above-described various types of metal heat dissipating layers  70  provided by the present invention may be modified in a manner described below, thereby applicable to the probe head of a multi-DUT probe card for testing a plurality of devices under test at the same time. For example, in a second preferred embodiment of the present invention as shown in  FIG. 15 , the metal heat dissipating layer  70  is similar to the metal heat dissipating layer  70  as shown in  FIG. 8 . They are primarily different in that each of the metal heat dissipating sheets  71 A and  71 B shown in  FIG. 15  includes not only a main section  714  similar to the metal heat dissipating sheet shown in  FIG. 8 , but also a strengthening rib  715  connected with the main section  714  monolithically. The main sections  714  form a peripheral unit  80  defining the hollow portion  75 , which means the metal heat dissipating sheets of a same metal heat dissipating layer  70  shown in  FIG. 6  to  FIG. 14  form a peripheral unit. The strengthening ribs  715  extend from the peripheral unit  80  toward the hollow portion  75  to divide the hollow portion  75  into four regions  752 . Such metal heat dissipating layer  70  is adapted for the probe card for testing four devices under test at the same time. In such condition, the inner die  41  is provided with four protruding portions  414 , which means the probe head has four probe installation sections for the installation of the probes for probing the four devices under test respectively. The metal heat dissipating layer  70  shown in  FIG. 15  is adapted for receiving the four protruding portions  414  in the four regions  752  respectively, thereby attaining great supporting effect and still enabling the user to remove or replace the metal heat dissipating layer  70 . It is to be mentioned that in the practical application, the aforementioned features such as the strengthening ribs  715 , the regions  752  and the protruding portions  414  are unnecessary to be sized according to the scale proportion as shown in  FIG. 15 . The probes disposed on the adjacent protruding portions  414  may be used to probe the adjacent devices under test. Alternatively, there may be one or a plurality of other devices under test located between the devices under test probed by the probes disposed on the adjacent protruding portions  414 , which is the test method commonly known as skipping DUT. 
     The above-described metal heat dissipating layer  70  shown in  FIG. 15  is composed of T-shaped metal heat dissipating sheets  71 A and  71 B. However, the above-described metal heat dissipating layer  70  including the strengthening rib  715  may be composed of metal heat dissipating sheets of other shapes, e.g., L-shape, I-shape, and so on, such as the configurations as shown in  FIG. 16  to  FIG. 20 . The metal heat dissipating layer  70  shown in  FIG. 16  includes two metal heat dissipating sheets  71 C and two metal heat dissipating sheets  71 D. Each of the metal heat dissipating sheets  71 C includes a first section  716  and a second section  717 , which are monolithically connected with each other into an L-shape. Each of the metal heat dissipating sheets  71 D includes a third section  718  and a strengthening rib  715 , which are monolithically connected with each other into an L-shape. The first sections  716  of the two metal heat dissipating sheets  71 C are located adjacent to the third sections  718  of the two metal heat dissipating sheets  71 D respectively, and the second sections  717  of the two metal heat dissipating sheets  71 C are located adjacent to the strengthening ribs  715  of the two metal heat dissipating sheets  71 D respectively, so that the first, second and third sections  716 ,  717  and  718  form a peripheral unit  80  defining a hollow portion  75 , and the strengthening ribs  715  of the two metal heat dissipating sheets  71 D extend from the peripheral unit  80  toward the hollow portion  75  to divide the hollow portion  75  into two regions  752 . Each of the regions  752  may be provided therein with one or a plurality of protruding portions  414 . For example, in  FIG. 16 , each of the regions  752  is provided therein with three protruding portions  414 , which means the inner die  41  has six protruding portions  414 , and so do the inner dies  41  shown in  FIG. 17  to  FIG. 20 . Such configuration is applicable to the probe card for testing six devices under test at the same time. 
     The metal heat dissipating layer  70  shown in  FIG. 17  is similar to the metal heat dissipating layer  70  shown in  FIG. 16 , but the metal heat dissipating layer  70  shown in  FIG. 17  is configured in a way that the metal heat dissipating sheets  71 C shown in  FIG. 16  are each replaced by metal heat dissipating sheets  71 E,  71 F and  71 G, which are T-shaped, L-shaped and I-shaped respectively. In other words, the metal heat dissipating layer  70  shown in  FIG. 17  includes eight metal heat dissipating sheets  71 D,  71 E,  71 F and  71 G, wherein not only the metal heat dissipating sheet  71 D includes the strengthening rib  715 , but the metal heat dissipating sheets  71 E and  71 F also include the strengthening rib  715 . Therefore, the metal heat dissipating layer  70  includes six strengthening ribs  715  extending from the peripheral unit  80  toward the hollow portion  75  to divide the hollow portion  75  into six regions  752 . The six protruding portions  414  of the inner die  41  are located in the six regions  752  respectively. 
     The metal heat dissipating layer  70  shown in  FIG. 18  is similar to the metal heat dissipating layer  70  shown in  FIG. 8 , but the primary difference therebetween is that each of the metal heat dissipating sheets  71 A shown in  FIG. 18  includes not only a main section  714  similar to the metal heat dissipating sheet  71 A shown in  FIG. 8 , but also a strengthening rib  715  monolithically connected with the main section  714 . That means each of the metal heat dissipating sheets  71 A is approximately T-shaped, but the strengthening rib  715  is deviated to a side of the main section  714 , not located at the center of the main section  714 . Each of the metal heat dissipating sheets  71 B includes no strengthening rib  715  and thereby I-shaped, so the metal heat dissipating layer  70  includes only two strengthening ribs  715  extending from the peripheral unit  80  toward the hollow portion  75  to divide the hollow portion  75  into three regions  752 . Each of the regions  752  is provided therein with two protruding portions  414 . 
     The metal heat dissipating layer  70  shown in  FIG. 19  is similar to the metal heat dissipating layer  70  shown in  FIG. 18 , but in  FIG. 19  the main section  714  of the metal heat dissipating sheet  71 A has relatively smaller area and the metal heat dissipating sheet  71 B has an additional section extending toward the metal heat dissipating sheet  71 A, so that the metal heat dissipating sheet  71 B is L-shaped. 
     The metal heat dissipating layer  70  shown in  FIG. 20  is also similar to the metal heat dissipating layer  70  shown in  FIG. 18 , but the metal heat dissipating layer  70  shown in  FIG. 20  is configured in a way that the T-shaped metal heat dissipating sheets  71 A shown in  FIG. 18  are each replaced by metal heat dissipating sheets  71 H and  711 , which are L-shaped and I-shaped respectively. In other words, the metal heat dissipating layer  70  shown in  FIG. 20  includes two L-shaped metal heat dissipating sheets  71 H and four I-shaped metal heat dissipating sheets  71 B and  711 . 
     The above-described various types of metal heat dissipating layers  70  can attain great supporting effect by the strengthening ribs  715  extending from the peripheral unit  80  toward the hollow portion  75 , and the user can still remove or replace the metal heat dissipating layer  70 . Besides, the strengthening ribs  715  located in the hollow portion  75  can directly transmit the heat inside the probe head outwardly, which can further improve the heat dissipating effect. In addition, the strengthening ribs  715  are also effective in enhancing the structural strength. Especially, in the aforementioned test method commonly known as skipping DUT, the adjacent protruding portions  414  are distanced from each other relatively farther and thereby more possible to cause the problem of insufficient strength. The strengthening ribs  715  of the metal heat dissipating layer  70  can extend between the adjacent protruding portions  414  to strengthen the support. Besides, under the tendency to large dies, the die with large area is liable to have bent deformation at the center thereof. In such condition, the strengthening ribs  715  of the metal heat dissipating layer  70  can be further provided with fastening holes for pass of screws therethrough, such as the fastening holes  715   a  as shown in  FIG. 20 , so that the strengthening ribs  715  can be fastened to the inner and outer dies  41  and  42  by screws to prevent the center of the dies from bent deformation. 
     As described above, by means of the arrangement of the disassembly positioning holes  21  at the positions not aimed at the metal heat dissipating sheets  71 , it is unnecessary to remove some positioning pins during taking out the metal heat dissipating sheets  71 , thereby achieving the convenience of removing the metal heat dissipating sheets  71 . The aforementioned positions that are not aimed at the metal heat dissipating sheets  71  are unlimited to the positions corresponding to the gaps G between the metal heat dissipating sheets  71  as shown in  FIG. 14 , as long as interference with the path of removing the metal heat dissipating sheets can be avoided. 
     Taking the configuration similar to the metal heat dissipating layer shown in  FIG. 14  for example, as shown in  FIG. 21 , the disassembly positioning holes  21  may be located correspondingly to the positions between the metal heat dissipating sheets  71  and the protruding portion  414 , i.e., aimed at the space  75 , such as the positions of the two through holes  418  shown in  FIG. 21 . That is, the disassembly positioning holes  21  can be anywhere between the metal heat dissipating sheets  71  and the protruding portion  414  and unlimited in amount. Alternatively, as shown in  FIG. 21 , the metal heat dissipating sheet  71  may have a notch  719  opened toward another metal heat dissipating sheet  71 . The disassembly positioning hole  21  may be located correspondingly to the notch  719 , i.e., located at the positions of the two through holes  418 ′ shown in  FIG. 21 . The position of the notch  719  and the position of the through hole  418 ′, i.e., the position of the disassembly positioning hole  21 , are unlimited to be located at the center of the terminal end of the metal heat dissipating sheet  71 . For example, they may be located at the terminal end of the metal heat dissipating sheet  71  and also located at the outer side of the metal heat dissipating sheet  71 , or may be located at the terminal end of the metal heat dissipating sheet  71  and also located at the inner side of the metal heat dissipating sheet  71 . Alternatively, the notch  719  and the through hole  418 ′ may be not located at the terminal end of the metal heat dissipating sheet  71 , but located at the inner side of the metal heat dissipating sheet  71 , which means the notch  719  of the metal heat dissipating sheet  71  is opened toward another metal heat dissipating sheet  71  with the space  75  located therebetween. 
     Taking the configuration similar to the metal heat dissipating layer shown in  FIG. 16  as another example, as shown in  FIG. 22 , the metal heat dissipating sheets  71 C may be each provided at the terminal end thereof with a notch  719  opened at the outer side of the metal heat dissipating layer  70 . The disassembly positioning holes  21  may be located correspondingly to the notches  719 , i.e., located at the positions of the two through holes  418  shown in  FIG. 22 . 
     Likewise, the monolithically made metal heat dissipating layers  70  as shown in  FIG. 9  to  FIG. 13  may be provided without such through hole  73  for pass of the positioning pin therethrough, and optionally provided with the notch opened toward the hollow portion  75  or toward the outside of the metal heat dissipating layer  70 . The disassembly positioning hole  21  may be located correspondingly to the hollow portion  75  or the aforementioned notch. 
     As described above, the metal heat dissipating layers  70  in the present invention may be configured as being various types. The metal heat dissipating layers  70  provided with tearing lines  76  as shown in  FIG. 9  to  FIG. 13  enable the user to conveniently tear and remove the metal heat dissipating layer  70  without removing the fastening members  60 . The configurations with the metal heat dissipating sheets directly separated from each other as shown in  FIG. 6  to  FIG. 8  and  FIG. 14  to  FIG. 23B  enable the user to remove the metal heat dissipating layer  70  and then install different metal heat dissipating layers  70 . The aforementioned metal heat dissipating sheets directly separated from each other may be configured abutted against each other without any gap therebetween (not shown), thereby convenient for assembly. Alternatively, the aforementioned metal heat dissipating sheets directly separated from each other may be configured as shown in  FIG. 6  to  FIG. 8  and  FIG. 14  to  FIG. 23B , wherein there are gaps G between the adjacent metal heat dissipating sheets, such that the gaps G can serve as heat dissipating passages for the heat inside the probe head to be discharged outwardly through the gaps G, thereby improving the heat dissipating effect. 
     The result of a simulation of the present invention is shown in  FIG. 24 . The simulation is performed in the situation that the metal heat dissipating layer  70  has gaps G, the situation without such gap and the situation without such metal heat dissipating layer. The simulation is set with a condition that the temperature in the central region for the installation of the probes is 125° C., so as to simulate the temperature distribution of the outer die  42 , the metal heat dissipating layer  70  and the inner die  41  of the lower die unit  40 B when the temperature of 125° C. is attained. The aforementioned three situations all have the result that the outer die  42  obviously has high temperature in the central region thereof, and the closer to the outer periphery, the lower the temperature is. The metal heat dissipating layer  70  and the inner die  41  also approximately have the distribution that the inside thereof is higher in temperature and the outer periphery is lower in temperature. The highest temperatures and lowest temperatures of the outer die  42 , the metal heat dissipating layer  70  and the inner die  41  are as shown in  FIG. 24 . Although the aforementioned three situations are not quite different in the highest temperatures and lowest temperatures in the simulated results, they have obvious difference in distributive areas of high and low temperatures. Especially, the low temperature (about 114° C.) area of the inner die  41  in the situation that the metal heat dissipating layer  70  has the gaps G is obviously larger than that in the situation that the metal heat dissipating layer has no such gap. As shown in  FIG. 24 , the aforementioned three situations are obviously different in the percentage of the area with temperature higher than 116° C. of the inner die  41 . The percentage of the area with temperature higher than 116° C. in the situation with the metal heat dissipating layer  70  is much lower than that in the situation without the metal heat dissipating layer. The percentage of the area with temperature higher than 116° C. in the situation that the metal heat dissipating layer  70  has the gaps G is also much lower than that in the situation that the metal heat dissipating layer  70  has no such gap. From this it is knowable that the gaps G of the metal heat dissipating layer  70  can improve the heat dissipating effect. 
     As shown in  FIG. 23A  and  FIG. 23B , the metal heat dissipating layer  70  may be provided on the outer periphery thereof with one or a plurality of indentations  82  (unlimited in amount). The indentations  82  penetrate through the top surface  84  and bottom surface of the metal heat dissipating layer  70  for increasing the surface area of the outer periphery of the metal heat dissipating layer  70  to increase the heat dissipating area, so that the metal heat dissipating layer  70  has the structure similar to heat dissipating fins, thereby further improving the heat dissipating effect. The indentations  82  may penetrate through the metal heat dissipating layer  70  and thereby shaped as through grooves, as shown in  FIG. 23A . Alternatively, the indentations  82  may not penetrate through the top and bottom surfaces of the metal heat dissipating layer  70  and thereby shaped as recessed grooves, as shown in  FIG. 23B . The indentations  82  are recessed from a surface (e.g., top surface  84 ) of the metal heat dissipating layer  70  and not penetrate through the other surface (e.g., bottom surface). 
     Likewise, in the configuration shown in  FIG. 22 , there is a gap G between the adjacent metal heat dissipating sheets  71 C and  71 D, which can attain great heat dissipating effect. The metal heat dissipating layer  70  shown in  FIG. 22  is also like those shown in  FIG. 23A  and  FIG. 23B  in that the metal heat dissipating layer  70  is provided on the outer periphery thereof with indentations  82 . The indentations  82  penetrate through the top and bottom surfaces of the metal heat dissipating layer  70  and thereby shaped as through grooves for increasing the surface area of the outer periphery of the metal heat dissipating layer  70  to improve the heat dissipating effect. Specifically speaking, the indentations  82  penetrate through the top and bottom surfaces of the metal heat dissipating sheets  71 C. In another embodiment of the present invention, the indentations are recessed from a surface of the metal heat dissipating layer  70 . Specifically speaking, the indentations are recessed from a surface of the metal heat dissipating layer  70 , thereby forming recesses on the surface of the metal heat dissipating layer  70 . The aforementioned indentations shaped as through grooves may extend from the inner periphery to the outer periphery of the metal heat dissipating layer  70 , thereby increasing the surface area of the metal heat dissipating layer  70  in contact with the ambient atmosphere and also communicating the space  75 , in which the probe installation section  413  is located, with the external environment by the indentations shaped as through grooves, so that the heat in the probe installation section  413  can be discharged to the external environment through the indentations shaped as through grooves. 
     It is to be mentioned that the present invention takes only the configurations as shown in  FIG. 23A ,  FIG. 23B  and  FIG. 22  as examples to illustrate that the metal heat dissipating layer  70  may be provided with the indentation  82  to improve the heat dissipating effect. In  FIG. 23A  and  FIG. 23B , each metal heat dissipating sheet  71  of the metal heat dissipating layer  70  is provided on the outer periphery thereof with the indentation  82 , but such structural feature is not to limit that every metal heat dissipating sheet must be provided with the indentation  82 . The amount and position of the indentation  82  can be arranged according to requirements, and such structural feature is also applicable to other embodiments. The aforementioned indentation  82  not only has the heat dissipating effect, but also enables identification of the metal heat dissipating layer  70  or metal heat dissipating sheet. Specifically speaking, the metal heat dissipating layers  70  or metal heat dissipating sheets of different shapes or heat dissipating efficiency can be provided with the indentation  82  of different shape (through groove or recessed groove), width or amount. After the assembly of the probe head is accomplished, the user can still see the indentation  82  from the lateral sides of the probe head, and can identify the type of the metal heat dissipating layer  70  or metal heat dissipating sheet by the indentation  82 . The above-described metal heat dissipating layer  70  provided with the gaps G between the metal heat dissipating sheets can also attain similar effect. From the lateral sides of the probe head, the user can see the indentations formed by the gaps G on the outer periphery of the metal heat dissipating layer  70 , thereby identifying the type of the metal heat dissipating layer  70  or metal heat dissipating sheet. 
     At last, it should be mentioned again that the constituent elements disclosed in the above embodiments of the present invention are only taken as examples for illustration, not intended to limit the scope of the present invention. The substitution or variation of other equivalent elements should be included within the scope of the following claims of the present invention. 
     For example, in the embodiments, it takes one layer and two layers of metal heat dissipating layers for illustration. However, it is unlimited thereto, but may be a multi-layer configuration such as the configuration with three layers.