Abstract:
A package for electronic components that suppress the multipactor discharge is disclosed. The package comprises a metal base and the casing. The metal base provides a pocket in the side thereof. The casing, mounted on the metal base to surround electronic components therein, provides a lead terminal connecting the electronic components to the outside and a feedthrough to isolate the lead terminal from the metal base. The pocket in the metal base is positioned beneath the lead terminal with an insulator therebetween.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to a package for electronic components. 
         [0003]    2. Background Arts 
         [0004]    Electronic components such as semiconductor devices, capacitors, and so on are enclosed within a package of an electronic device. The electronic components are mounted on a metal base comprising the package and enclosed air-tightly by a casing and a lid surrounding and covering the electronic components. Lead terminals, which electrically connect the electronic components within the package to the outside, pass through the casing also mounted on the metal base as putting insulating feedthrough against the metal base to be electrically isolated from the base. 
         [0005]    In an application of the electronic device, namely, putting the electronic device in a high vacuum and inputting/outputting a high frequency signal having extremely large power to/from the electronic components through the lead terminals, a vacuum discharge called as the multipactor discharge possibly occurs between the lead terminal and the metal base. When the high frequency signal is constant in the frequency and the power thereof, the possibility to induce the multipactor discharge depends on a distance between the lead terminal and the metal base. One prior document has reported to take a distance from the lead terminal to the metal base longer than 1 mm. However, the feedthrough put between the lead terminal and the metal base usually determines the distance therebetween, and a thicker feedthrough possibly brings the failure of the air-tightness of the package. 
       SUMMARY OF THE INVENTION 
       [0006]    An aspect of the present invention relates to a package for enclosing electronic components of field effect transistors (FET), capacitors, inductors, and so on therein. The package comprises a base, a casing and feedthrough. The base may be made of metal and has a top surface for mounting the casing and the electronic components thereon. The casing surrounds the electronic components therein air-tightly. The feedthrough, which includes an insulator and a conductive pattern provided on the insulator, passes through the casing to input a signal into the electronic components and to output another signal from the electronic components. A lead terminal is fixed to the conductive pattern in an outside of the casing. A feature of the package of the present invention is that the base provides a pocket cut from an edge and positioned beneath the feedthrough. The cut preferably has a width perpendicular to the lead terminal greater than or equal to a width of the feedthrough perpendicular to the lead terminal. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    The foregoing and other purposes, aspects and advantages will be better understood from the following detailed description of a preferred embodiment of the invention with reference to the drawings, in which: 
           [0008]      FIG. 1  is a perspective view of a package according to an embodiment of the present invention; 
           [0009]      FIG. 2A  is a plan view of the package shown in  FIG. 1 , and  FIG. 2B  is a cross section of the package taken along the line IIb-IIb appearing in  FIG. 2A ; 
           [0010]      FIG. 3A  is a perspective view of a package comparable to that shown in  FIG. 1  of the present invention, and  FIG. 3B  is a cross section thereof taken along the line IIIb-IIIb indicated in  FIG. 3A ; 
           [0011]      FIG. 4A  is a cross section of a package modified from that shown in  FIG. 1 ; and  FIG. 4B  magnifies a portion of that shown in  FIG. 4A ; and 
           [0012]      FIG. 5  is a cross section of a package according to the second modification of the embodiment shown in  FIG. 1 . 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0013]    Next, some preferred embodiments of the present invention will be described as referring to accompanying drawings. In the description of the drawings, numerals or symbols same with or similar to each other will refer to elements same with or similar to each other without duplicating explanations. 
         [0014]      FIG. 1  is a perspective view of a package for electronic devices,  FIG. 2A  is a plan view of the package, and  FIG. 2B  shows a cross section taken along the line IIb-IIb appearing in  FIG. 2A . As shown in  FIGS. 1 to 2B , the package  1  primarily includes a base  2 , a casing  3 , a feedthrough, F 1  and F 2 , lead terminals,  9  and  10 , and a lid  4 . The base  2 , the casing  3 , and the lid  4  form a space into which electronic components  11  are air-tightly enclosed. The electronic components  11  include semiconductor devices, capacitors, and so on. The semiconductor devices may be a high electron mobility transistor (HEMI) made of nitride semiconductor materials capable of outputting the extremely high power of 100 to 200 W. The feedthrough, F 1  and F 2 , each includes an insulator,  5  and  6 , and a conductive pattern,  7  and  8 , provided on respective insulators,  5  and  6 . 
         [0015]    The base  2 , which is made of metal of a rectangular slab, is electrically grounded. Specifically, the base  2  may be made of copper (Cu), alloy or composite metal primarily containing copper (Cu) having a surface plated with multi-layered metal of titanium (Ti), nickel (Ni), and gold (Au). The explanation below assumes that the longitudinal direction is along to the direction where the lead terminals,  9  and  10 , are brought out from the casing  3 , and the lateral direction is perpendicular to the longitudinal direction. In the present embodiment, the base  2  has a primary surface  2   a  thereof with dimensions of 2 to 30 mm along the longitudinal direction and 5 to 40 mm along the lateral direction. Also, the base  2  has a thickness of 0.2 to 2 mm. The base  2  may have square planar dimensions or rectangle dimensions. 
         [0016]    The casing  3 , which is mounted on the base  2 , surrounds the electronic components  11 . The casing  3  also has a rectangular plane shape with sides extending in parallel to respective sides of the base  2 . The casing  3  may be made of metal or alloy, for instance, an alloy of iron (Fe), cobalt (Co), nickel (Ni), which is called as Kovar, or ceramic such as alumina (Al 2 O 3 ), zirconia (ZrO 2 ), titania (TiO 2 ), and so on. The casing  3  may have dimensions of 0.5 to 5 mm in height, 2 to 30 mm along the lateral and the longitudinal directions. The casing  3  includes insulating portions  31  in respective sides,  3   a  and  3   b . The insulating portions  31  electrically isolate respective conductive patterns,  7  and  8 , from the metallic sides,  3   a  and  3   b.    
         [0017]    The lid  4 , which is put on the casing  3  and has a rectangular plane shape, seam-seals the space surrounded by the casing  3  and the base  2  air-tightly. The lid  4  of the present embodiment is made of metal, but the lid  4  may be made of ceramic. 
         [0018]    The insulators,  5  and  6 , of respective feedthrough, F 1  and F 2 , each has a rectangular parallelepiped, pass through respective sides,  3   a  and  3   b , of the casing  3 . The insulators,  5  and  6 , of feedthrough, F 1  and F 2 , each has a height of 0.2 to 2 mm, and is made of ceramics. 
         [0019]    The conductive patterns,  7  and  8 , are provided on the top surfaces,  5   a  and  6   a , of respective insulators,  5  and  6 , and pass through the casing  3 . Specifically, the conductive patterns,  7  and  8 , electrically connect the electrical components  11  enclosed within the casing  3  to other electronic apparatuses outside of the casing  3 . The conductive patterns,  7  and  8 , may be made of stacked metals of titanium (Ti), nickel (Ni), and gold (Au), formed by the sputtering and/or the vacuum evaporation of those metals, where titanium (Ti) is in contact with the insulators,  5  and  6 . The conductive patterns,  7  and  8 , in an alternate may be an alloy containing those metals. 
         [0020]    The lead terminals,  9  and  10 , which are provided on the insulators,  5  and  6 , are electrically connected to the electronic components  11  enclosed in the casing  3  through the conductive patterns,  7  and  8 , the brazing metals,  12  and  13 , and the bonding wires, W 1  and W 2 , respectively. The brazing metals,  12  and  13 , between the lead terminals  9  and  10 , and the conductive patterns,  7  and  8 , not only electrically connect them but rigidly fix the lead terminals,  9  and  10 , on the conductive patterns,  7  and  8 , respectively. Thus, the lead terminals,  9  and  10 , are not peeled off from the conductive patterns,  7  and  8 . The lead terminals,  9  and  10 , may be made of copper (Cu), nickel (Ni), or titanium (Ti), or an alloy containing those metals plated with gold (Au). The brazing metals,  12  and  13 , are an alloy of silver (Ag), copper (Cu) and zinc (Zn), which is often called as a silver solder. In the electronic device of the present embodiment, the lead terminal  9  is the input terminal, and, the other lead terminal  10  is the output terminal. 
         [0021]    A feature of the base  2  of the present embodiment is that the base  2  provides pockets,  21  and  22 , in respective sides,  2   b  and  2   c , each extending along the lateral direction. The pocket  21  overlaps with the lead terminal  9  and the conductive pattern  7  as interposing the insulator  5 . The pocket  21  may have a width along the lateral direction wider than a width of the lead terminal  9 . In the present embodiment, the width of the pocket  21  is substantially equal to a width of the feedthrough F 1 . In the pocket  21 , a top end  21   a  thereof matches with the bottom surface  5   b  of the insulator  5 . On the other hand, the bottom end  21   b  thereof matches with the bottom  2   d  of the base  2 . That is, the pocket  21  extends from the bottom  2   d  to the primary surface  2   a  of the base  2 . The deep end  21   c  of the pocket  21  is positioned outside of the outer surface of the insulating portion  31 . That is, the pocket  21  is not overlapped with the whole of the lead terminal  9 , but overlapped only with a portion close the outer side  5   d  of the insulator  5 . 
         [0022]    The other lead terminal  10  has positional relations against the pocket  22  similar to the relation between the lead terminal  9  and the pocket  21 . That is, the pocket  22  is overlapped with the lead terminal  10  and the conductive pattern  8  as interposing the insulator  6  therebetween. The pocket  22  may have a width along the lateral direction greater than or equal to a width of the lead terminal  10 . The present embodiment has the pocket  22  whose width is substantially equal to the width of the feedthrough F 2 . The top end  22   a  matches with the top of the base  2  and the bottom surface  6   b  of the insulator  6 . The bottom end  22   b  matches with the bottom  2   d  of the base  2 . That is, the pocket  22  is formed in the side  2   c  as fully removing a portion of the base  2  from the bottom  2   d  to the primary surface  2   a . The deep end  22   c  of the pocket  22  is positioned outside of the outer surface of the insulating portion  31 . That is, the pocket  22  is not overlapped with the whole of the lead terminal  10  but a portion close to the outer side  6   d  of the insulator  6 . Thus, two pockets,  21  and  22 , have a shape same to each other. However, the pockets may have respective shape different from the other. 
         [0023]    An advantage of the package  1  according to the present invention will be described as comparing the package  1  with a comparable example.  FIG. 3A  is a perspective view showing a comparable example, and  FIG. 3B  is a cross section taken along the line IIIb-IIIb appearing in  FIG. 3A . The base  2  of the comparable example does not have any pockets in the side  2   b  thereof, which means that a distance from the lead terminal  9  to the side  2   b  of the base  2  along the surface of the insulator  5  becomes identical with the thickness of the feedthrough F 1 . In such a case, the lead terminal  9  possibly induces the multipactor discharge between the lead terminal  9  and the side  2   b  of the base  2 . 
         [0024]    On the other hand, the package  1  of the present embodiment, as shown in  FIGS. 1 to 2B , provides the pocket  21  in the side  2   b  and another pocket  22  in the side  2   c . Each of the pockets,  21  and  22 , forms a hollow along the longitudinal direction of the base  2  from respective sides,  2   b  and  2   c , thereof. This arrangement may expand a distance from the lead terminal  9  to the side  2   b  and another distance from the lead terminal  10  to the side  2   c , respectively along the surface of the insulators,  5  and  6 . Thus, the multipactor discharge may be effectively prevented. 
         [0025]      FIG. 4A  is a cross section of the package according to a modified example, and  FIG. 4B  magnifies a portion close to the outer side  5   d  of the insulator  5 . As shown in  FIGS. 4A and 4B , the brazing metal  12  in the outer edge  12   a  thereof is retreated from the edge of the outer side  5   d  and the conductive pattern  7  in the outer edge  7   a  thereof is also retreated from the edge of the outer side  5   d  of the insulator  5 . This arrangement of the lead terminal  9 , the brazing metal  12 , the conductive pattern  7 , and the insulator  5  form a gap S between the lead terminal  9  and the insulator  5  in an outside of the brazing metal  12  and the conductive pattern  7 . Thus, the conductive materials of the lead terminal  9 , namely, the brazing metal  12  and the conductive pattern  7 , become further apart from the side  2   b  of the base  2  along the surface of the insulator  5 , which effectively suppresses the multipactor discharge between the lead terminal  9  and the base  2 . 
         [0026]      FIG. 5  is a cross section of the package according to still another modification of the present invention. The lead terminal  9 A of the present modification has a portion  9 A 1  curved upward at the end of the outer side  5   d  of the insulator  5 . That is, the lead terminal  9 A in the portion  9 A 1  thereof has the reversed U-shape by bending the lead terminal  9 A upward at the outer edges,  7   a  and  12   a , of the conductive pattern  7  and the brazing metal  12 , forming the reversed U-shape, and bending again at a point whose horizontal level is substantially equal to the top of the insulator  5 . This arrangement of the lead terminal  9 A may expand the gap S in the forgoing modification shown in  FIGS. 4A and 4B , where the foregoing arrangement leaves possibility to induce the multipactor discharge between the lead terminal  9  and the base  2  because the gap S in a length thereof is merely equal to the overall thickness of the brazing metal  12  and the conductive pattern  7 . On the other hand, the lead terminal  9 A of the present modification is apart from the edge of the insulator  5 , which further effectively suppresses the multipactor discharge. Although the explanation above concentrates on the lead terminal  9 A for the signal input, the other lead terminal  10  for the signal output may have the arrangement same with those described above. 
         [0027]    The package according to the present invention may have arrangements not restricted to those described above, and the package may have an arrangement combining the embodiment and the modifications described above. For instance, the package has the arrangement of the first modification shown in  FIG. 4A  for the input lead terminal  9 , but the second modification shown in  FIG. 5  for the output lead terminal  10 . Also, the description above concentrates the base  2  made of metal, but the base  2  may be made of insulating material coated with metal. 
         [0028]    Moreover, the pockets,  21  and  22 , in the plane shape thereof is not restricted to be a rectangle; but a semi-circular plane shape with the root of the lead terminal  9  as the center thereof may be applicable. Also, the bottom end  21   b  of the pocket  21  is unnecessary to match with the bottom  2   d  thereof. The pocket  21  may be a hollow with the top end  21   a  coinciding with the top of the base  2  but the bottom end  21   b  is intermediate in the thickness of the base  2 . 
         [0029]    Thus, the present embodiments and the modifications of the invention should be considered in all respects as illustrative and not restrictive. Accordingly, the scope of the invention is determined by the appended claims and their equivalents.