Patent Publication Number: US-2007115012-A1

Title: Reinforced guide panel for vertical probe card

Description:
BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a guide panel for a vertical probe card and more specifically, to a guide panel having a reinforced structure.  
      2. Description of the Related Art  
      A vertical probe card uses a plurality of vertical probe pins to contact test points of the electronic component under test for enabling the test of the electric characteristics of the electronic component. In order to prohibit the vertical probe pins of the vertical probe card from sideway displacement and anisotropic curving, guide panels having feed through vias are used to guide movement of the vertical probe pins in the axial direction of the feed through vias during test, so that probing of the test points of electronic component can be smoothly achieved.  
      However, following fast development of modern technology, the test area on each test procedure is relatively larger, and a single electronic component to be tested has relatively a bigger count of test points. Further, it is not economic to test one single electronic component in one test step (it is the market trend to test multiple electronic components under test in one single test step). Therefore, the guide panels for vertical probe card must be made having a relatively large area. Further, following the development of electronic components having a relatively smaller pitch among test points, it is required to have smaller vertical probe pins to fit the pitch. Therefore, under the limitation of space constraint, it is the market trend to provide guide panels having the characteristic of thin wall thickness.  
      However, when increasing the area of a guide panel and reducing its wall thickness, the structural strength of the guide panel becomes weak, and the guide panel may be deformed easily. This problem may occur in the conventional guide panel design such as U.S. Pat. No. 6,297,657 B1.  
      U.S. Pat. No. 5,977,787 discloses a multiple-chip probe assembly suitable for wafer testing over a wide temperature range, which uses a support structure to support buckling beam probe elements. The support structure includes a principal support material having a thermal coefficient of expansion matched with the wafer under test and a second material other than the principal support material, wherein a contact positioning of the plurality of buckling beam probe elements upon the wafer under test during a testing operation is maintained. The second material prevents an individual probe element from electrically contacting the principal support material. However, because the second material is made out of polyimide (PI), it wears quickly with use, doing little help to mechanical structural strength of the support structure. U.S. Pat. No. 6,163,162 discloses a temperature compensated vertical pin probing device, which is constructed with a housing spaced upper and lower dies of Invar®, which substantially matches the coefficient of thermal expansion of the silicon wafer being probed. Spaced slots in the top and bottom dies of the housing contain inserts of Vespel®. The inserts are provided with matching patterns of holes supporting probe pins and insulating the probe pins from the housing. This design has a limitation to the pitch of probe pins. Further, spaced upper and lower dies of Invar® are not used to reinforce the structural strength of the probing device. Therefore, this design cannot prevent deformation, and the pitch precision is not easy to maintain. Further, the installation procedure of this design is complicated.  
     SUMMARY OF THE INVENTION  
      The present invention has been accomplished under the circumstances in view. It is the main object of the present invention to provide a guide panel for a vertical probe car, which has the mechanical structural strength well reinforced against deformation.  
      To achieve this object of the present invention, the guide panel comprises a via area and a reinforcing area bonded to the via area. The via area has a plurality of feed through vias for insertion of the probe pins of the vertical probe card. The reinforcing area has at least one through hole in communication with the feed through vias and at least one reinforcing rib formed around the at least one through hole and bonded to the via area.  
      In a preferred embodiment of the present invention, the guide panel includes a substrate defining the via area and a reinforcing board defining the reinforcing area and having a plurality of through holes. The reinforcing board is bonded with its top side to the bottom side of the substrate so that the through holes are respectively axially aligned with the feed through vias one by one.  
      In another preferred embodiment of the present invention, the guide panel is formed by a single substrate having a top portion defining the via area and a bottom portion defining the reinforcing area.  
      In still another preferred embodiment of the present invention, the reinforcing area has a plurality of through holes, each of which is in communication with a plurality of the feed through vias.  
      In still another preferred embodiment of the present invention, the reinforcing area has only one through hole in communication with all of the feed through vias of the via area. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIGS. 1A-1D  are schematic drawings illustrating steps of making a guide panel according to a first preferred embodiment of the present invention.  
       FIGS. 2A-2D  are schematic drawings illustrating steps of making a guide panel according to a second preferred embodiment of the present invention.  
       FIGS. 3A-3C  are schematic drawings illustrating steps of making a guide panel according to a third preferred embodiment of the present invention.  
       FIG. 4  is a schematic sectional view showing the structure of a guide panel according to a fourth preferred embodiment of the present invention.  
       FIG. 5  is a schematic bottom view in an enlarged scale of the guide panel shown in  FIG. 4 .  
       FIG. 6  is a schematic sectional view showing the structure of a guide panel according to a fifth preferred embodiment of the present invention.  
       FIG. 7  is a schematic bottom view in an enlarged scale of the guide panel shown in  FIG. 6 . 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIGS. 1A-1D  are schematic drawings illustrating the steps of a method for making a guide panel  10  according to a first preferred embodiment of the present invention. According to this embodiment, the method includes the following steps.  
      (A) As shown in  FIG. 1A , prepare a thin substrate  11  made of a silicon material and then form feed through vias  111  on the substrate  11  by an anisotropic etching. In this embodiment, the substrate  11  has a thickness smaller than 1 mm. In practice, the thickness of the substrate  11  can be thinner subject to the pin diameter of the probe pins of the vertical probe card. As shown in  FIG. 1A , the substrate  11  defines a via area including the feed through vias  111 , and the feed through vias  111  are formed through the top and bottom sides of the via area.  
      (B) As shown in  FIG. 2B , prepare a reinforcing board  12  made of silicon material and then form through holes  121  of greater diameter than the feed through vias  111  on the reinforcing board  12  by an anisotropic etching. In this embodiment, the reinforcing board  12  has a thickness smaller than 1 mm. In practice, the thickness of the reinforcing board  12  can be thinner subject to the pin diameter of the probe pins of the vertical probe card. The reinforcing board  12  defines a reinforcing area including the through holes  121  and a plurality of reinforcing ribs  122 , i.e. the unetched portion of the reinforcing board  12 , around the through holes  121 .  
      (C) As shown in  FIGS. 1C and 1D , the top side of the reinforcing board  12  is bonded to the bottom side of the substrate  11  by any of a variety of fastening or bonding technique or means, keeping the through holes  121  of the reinforcing board  12  in axial alignment with the feed through vias  111  of the substrate  11  in a coaxial manner such that the reinforcing ribs  112  support the via area of the substrate  11  between each two adjacent feed through vias  111 .  
      As indicated above, the guide panel  10  provided by the present invention has a via area with feed through vias  111  and a reinforcing area bonded to the via area. Because the through holes  121  of the reinforcing area are respectively aligned with the feed through vias  111  of the via area, the reinforcing area does not interfere with the insertion of the respective probe pins. Further, because the through holes  121  in the reinforcing area have a diameter greater than the feed through vias  111 , the sideway biasing of the inserted probe pins can be effectively limited by the feed through vias  111  as the conventional guide panel did. Further, the reinforcing ribs  121  greatly enhance the structural strength of the whole assembly, preventing deformation of the guide panel  10 . Because of the structural reinforcing effect of the reinforcing area, the guide panel  10  can be made having a large area to fit modern probing requirements. Further, the via area and the reinforcing area can be made of same or different materials/methods subject to different requirements. Therefore, the manufacturer can select the most cost-saving material/method to make the guide panel for saving the manufacturing cost.  
      Further, except the anisotropic etching, conventional mechanical drilling or laser processing techniques may be employed to make feed through vias on the substrate.  
      Furthermore, the bonding between the via area (substrate) and reinforcing area (reinforcing board) can be done with or without a bonding medium. The bonding technique without a bonding medium can be anodic bonding or fusion bonding. The bonding technique with a bonding medium can be adhesive bonding, eutectic bonding, or glass frit bonding.  
       FIGS. 2A-2D  illustrate the steps of a method for making a guide panel  20  according to a second preferred embodiment of the present invention. According to this embodiment, the method includes the following steps.  
      (A) As shown in  FIG. 2A , bond a thin substrate  21  and a reinforcing board  22  together. The substrate  21  and the reinforcing board  22  are made of silicon material and have a thickness smaller than 1 mm respectively. In practice, the thickness of the substrate  21  and the thickness of the thick reinforcing board  22  can be determined subject to the pin diameter of the probe pins of the vertical probe card. The bottom side of the substrate  21  is bonded to the top side of the reinforcing board by any of a variety of fastening or bonding technique or means for enabling the substrate  21  to define a via area and the reinforcing board  22  to define a reinforcing area.  
      (B) As shown in  FIG. 2B , a plurality of feed through vias  211  are formed by an anisotropic etching on the substrate  21  within the via area through the top and bottom sides of the feed through hole area.  
      (C) As shown in  FIGS. 2C and 2D , through holes  221  of greater diameter than the feed through vias  211  are formed on the reinforcing board  22  by an anisotropic etching within the reinforcing area through the top and bottom sides of the reinforcing area in axial alignment with the feed through vias  211  on the substrate  21  in a coaxial manner so that a plurality of reinforcing ribs  112 , i.e. the unetched portion of the reinforcing board  22 , are defined in the reinforcing area around the through holes  221  to support the via area of the substrate  21  between each two adjacent feed through vias  211 .  
       FIGS. 3A-3C  illustrate the steps of a method for making a guide panel  30  according to a third preferred embodiment of the present invention. According to this embodiment, the method includes the following steps.  
      (A) As shown in  FIG. 3A , a thin substrate made of silicon material is provided. The substrate has an upper portion defining an upper via area  31  having a thickness smaller than 1 mm and a bottom portion defining a lower reinforcing area  32  having a thickness smaller than 1 mm.  
      (B) As shown in  FIG. 3B , a plurality of feed through vias  311  are formed by an anisotropic etching on the upper via area  31  subject to a predetermined diameter and depth.  
      (C) As shown in  FIG. 3C , a plurality of through holes  321  of greater diameter than the feed through vias  311  are formed by an anisotropic etching on the lower reinforcing area  32  in communication with the feed through vias  311  respectively so as to form a plurality of reinforcing ribs  322 , i.e. the unetched portion of the reinforcing area, in the lower reinforcing area  32  around the through holes  321  to support the upper via area  31  between each two adjacent feed through vias  311 .  
       FIGS. 4 and 5  illustrate a guide panel  40  according to a fourth preferred embodiment of the present invention. According to this embodiment, the guide panel  40  comprises a thin substrate defining an upper via area  41  and a lower reinforcing area  42 . The upper via area  41  has a plurality of feed through vias  411  formed through the top and bottom sides thereof by an anisotropic etching. The lower reinforcing area  42  has a plurality of rectangular through holes  421  formed through the top and bottom sides thereof by an anisotropic etching at locations respectively corresponding to some of the feed through vias  411  on the upper via area  41 , and a plurality of reinforcing ribs  422  formed around the rectangular through holes  421  and supported at the bottom side of the upper via area  41  to reinforce the structural strength of the guide panel  40 . This design of guide panel  40  makes the guide panel can be made with a large area size, and the fabricated guide panel  40  is durable in use against deformation. Further, a polymer coating, for example, polyimide (not shown) may be coated on the guide panel  40  to enhance the toughness of the structure or the lubricity of the feed through vias  411 . Furthermore, the guide panel  40  may be further processed to provide a fastening structure (not shown) for fastening to the probe head of a probe card or other device.  
       FIGS. 6 and 7  illustrate a guide panel  50  having a via area  51  and a reinforcing area  52  according to a fifth preferred embodiment of the present invention. The via area  51  has a plurality of feed through vias  511  through the top and bottom sides thereof. The reinforcing area  52  has a circular through holes  521  through the top and bottom sides thereof in communication with the feed through vias  511 , i.e. the area of the circular through hole  521  covers the area of the feed through vias  511 , and a reinforcing rib  522  formed around the circular through hole  521  and supported at the bottom side of the via area  51  around the feed through vias  511  to reinforce the structural strength of the guide panel  50 .  
      Further, an insulative material such as SiO 2 , Al 2 O 3 , TiO 2 , or any of a variety of suitable dielectric materials may be coated on the guide panel  50  to enhance the electric insulative characteristic of the guide panel  50 .  
      In conclusion, the reinforcing rib of the present invention is adapted to reinforce the structural strength of the guide panel. Therefore, the reinforcing rib can be made in a latticed, circular, polygonal, or any of a variety of shape that can support the via area.