Patent Publication Number: US-2022217834-A1

Title: Wiring board, electronic component package, and electronic apparatus

Description:
FIELD 
     The present invention relates to a wiring board, an electronic component package, and an electronic apparatus. 
     BACKGROUND 
     As electronic devices including mobile phones are widespread, these devices use electric signals with higher frequencies to transmit larger volumes of information at higher speeds. For better frequency response at high frequencies, packages containing semiconductor devices may include lead terminals with tapered ends, or ends gradually thinner toward their tips, for connection to wiring (refer to, for example, Patent Literature 1). 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: Japanese Unexamined Patent Application Publication No. 2004-134614 
       
    
     BRIEF SUMMARY 
     A wiring board according to an aspect of the present disclosure includes a dielectric substrate, a first lead terminal, and a second lead terminal. The dielectric substrate has a first surface, a second surface opposite to the first surface, and a first side surface continuous with the first surface and the second surface. The first surface includes a first terminal joint and a second terminal joint arranged along the first side surface. The first lead terminal includes a first base bonded to the first terminal joint and a first lead extending from the first base. The second lead terminal includes a second base bonded to the second terminal joint and a second lead extending from the second base. The first base has a larger thickness than the first lead. 
     An electronic component package according to another aspect of the present disclosure includes a substrate, and the wiring board according to the above aspect bonded to the substrate. 
     An electronic apparatus according to still another aspect of the present disclosure includes the electronic component package according to the above aspect, and an electronic component mounted on the substrate and electrically connected to the wiring board. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The objects, features, and advantages of the present disclosure will become more apparent from the following detailed description and the drawings. 
         FIG. 1  is a perspective view of a wiring board according to a first embodiment. 
         FIG. 2  is an enlarged plan view of the wiring board according to the first embodiment. 
         FIG. 3  is an enlarged cross-sectional view of the wiring board according to the first embodiment. 
         FIG. 4  is an enlarged perspective view of the wiring board according to the first embodiment. 
         FIG. 5  is an enlarged cross-sectional view of a wiring board according to a second embodiment. 
         FIG. 6  is an enlarged perspective view of the wiring board according to the second embodiment. 
         FIG. 7  is an enlarged cross-sectional view of a wiring board according to a third embodiment. 
         FIG. 8  is an enlarged perspective view of the wiring board according to the third embodiment. 
         FIG. 9  is a perspective view of an electronic component package and an electronic apparatus according to another embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     A wiring board, an electronic component package, and an electronic apparatus according to one or more embodiments of the present disclosure will now be described with reference to the drawings.  FIG. 1  is a perspective view of a wiring board according to a first embodiment.  FIG. 2  is a plan view of the wiring board according to the first embodiment.  FIG. 3  is an enlarged cross-sectional view of the wiring board according to the first embodiment.  FIG. 4  is an enlarged perspective view of the wiring board according to the first embodiment. 
     The first embodiment of the present disclosure will now be described with reference to  FIGS. 1 to 4 . A wiring board  1  includes a dielectric substrate  10 , first lead terminals  31 , and second lead terminals  32 . The dielectric substrate  10  has a first surface  10   a , a second surface  10   b  opposite to the first surface  10   a , and a first side surface  10   c  continuous with the first surface  10   a  and the second surface  10   b.    
     The dielectric substrate  10  may be a stack of multiple insulating layers formed from a dielectric material. The dielectric substrate  10  may be, for example, rectangular, U-shaped, or in any other shape as viewed from above. Examples of the dielectric material include ceramic materials such as sintered aluminum oxide, sintered mullite, sintered silicon carbide, sintered aluminum nitride, and sintered silicon nitride, or glass ceramic materials. 
     The first surface  10   a  includes one or more first terminal joints  12  and one or more second terminal joints  13  arranged along the first side surface  10   c . Each first terminal joint  12  is bonded to the corresponding first lead terminal  31  for electrical connection between them. Each second terminal joint  13  is bonded to the corresponding second lead terminal  32  for electrical connection between them. In the present embodiment, for example, the first lead terminals  31  are ground terminals, and the second lead terminals  32  are signal terminals. 
     The first surface  10   a  may include multiple first terminal joints  12  and multiple second terminal joints  13  arranged along the first side surface  10   c . One or more third terminal joints (described later) may also be multiple third terminal joints. In the present embodiment, for example, each set of a second terminal joint  13 , a first terminal joint  12 , and a third terminal joint  14  is arranged repeatedly along the first side surface  10   c . In the present embodiment, two first terminal joints  12  may extend away from the first side surface  10   c  and be connected to each other. This stabilizes the ground potential. The stabilized ground potential improves the frequency response for high-frequency signals. 
     Each first terminal joint  12  may include, for example, a metal layer (hereafter, a first metal layer)  12   a  for electrical connection to the corresponding first lead terminal. Each second terminal joint  13  may include, for example, a second metal layer  13   a  for electrical connection to the corresponding second lead terminal. The first metal layers  12   a  and the second metal layers  13   a  may be metallization layers formed on the first surface  10   a  of the dielectric substrate  10 . The metallization layers are formed from, for example, a metal material such as tungsten, molybdenum, or manganese, and may be plated with nickel or gold. 
     The dielectric substrate  10  may include, for example, wiring conductors and conductor layers between the insulating layers. For example, the dielectric substrate  10  may include, as viewed from above, multiple wiring conductors and multiple conductor layers overlapping the first metal layers  12   a  and the second metal layers  13   a , which may be electrically connected with feedthrough conductors. The wiring conductors and the conductor layers include multiple ground wiring conductors and multiple ground conductor layers that are electrically connected to one another and to the first metal layers  12   a . The wiring conductors and the conductor layers include multiple signal wiring conductors that are electrically connected to the second metal layers  13   a.    
     Each first lead terminal  31  is bonded to the corresponding first terminal joint  12  with a bond. Each second lead terminal  32  is bonded to the corresponding second terminal joint  13  with a bond. The first lead terminals  31  and the second lead terminals  32  are also connected to, for example, an external mounting board. The first lead terminals  31  and the second lead terminals  32  may be formed from, for example, a metal material. Examples of the metal material include iron, copper, nickel, chromium, cobalt, molybdenum or tungsten, or an alloy of these metals, such as a copper-tungsten alloy, a copper-molybdenum alloy, or an iron-nickel-cobalt alloy. 
     The bond for bonding the first lead terminals  31  to the first terminal joints  12  and the second lead terminals  32  to the second terminal joints  13  may be, for example, a silver-copper brazing material containing silver and copper as its main components, or a bond with a low melting point (solder) containing silver and copper, and additionally containing tin. Each first lead terminal  31  may be bonded to the corresponding first terminal joint  12  by melting the bond on the first terminal joint  12 , placing the first lead terminal  31  on the molten bond, and then cooling and solidifying the molten bond. Each second lead terminal  32  is connected to the corresponding second terminal joint  13  in the same manner. 
     Each first lead terminal  31  includes a first base  31   a  bonded to the corresponding first terminal joint  12  and a first lead  31   b  extending from the first base  31   a . Each second lead terminal  32  includes a second base  32   a  bonded to the corresponding second terminal joint  13  and a second lead  32   b  extending from the second base  32   a . The first lead  31   b  extends from the first base  31   a  outwardly from the dielectric substrate  10 . The second lead  32   b  extends from the second base  32   a  outwardly from the dielectric substrate  10 . Each first lead terminal  31  includes the first base  31   a  having a larger thickness than the first lead  31   b . The thickness herein is the dimension perpendicular to the first surface  10   a  of the dielectric substrate  10 . 
     The lead terminals in the wiring board are bonded to the mounting board and can be under an external force. The lead terminals being narrow and thin may undergo plastic deformation under an external force and can deviate from being horizontal after mounted. The lead terminals being wide and thick can be rigid and may have portions connected with the wiring damaged under an external force and come off together with the wiring. In known wiring boards, such lead terminals can have varying electrical characteristics and thus have deteriorating high-frequency response. 
     In the present embodiment, each first lead terminal  31  includes two portions with different thicknesses, of which the first base  31   a  bonded to the first terminal joint  12  is thicker. The first base  31   a  that is thicker allows the entire lead terminal to be sufficiently rigid, whereas the first lead  31   b  that is thinner is flexible and can deform elastically. This structure reduces the likelihood of the wiring board  1  being inclined during mounting and allows the wiring board  1  to be closer to being horizontal. This structure thus reduces the likelihood of the wiring board  1  being damaged. The lead terminals are less likely to have varying electrical characteristics and improve the high-frequency response of the wiring board  1 . 
     Each second lead terminal  32  includes the second base  32   a  and the second lead  32   b  with the same thickness and the same width. Each second lead terminal  32  is thus entirely band-shaped. The second base  32   a  is a linear portion extending parallel to the first surface  10   a  and bonded to the second terminal joint  13 . The second lead  32   b  includes a bent portion  32   b   1  that is continuous with the second base  32   a  and extends away from the dielectric substrate  10  outwardly, and a straight portion  32   b   2  that is continuous with the bent portion  32   b   1  and extends parallel to the second base  32   a . The first base  31   a  in each first lead terminal  31  may have a larger thickness than the second base  32   a  in each second lead terminal  32 . 
     The first base  31   a  and the first lead  31   b  may have the same width or may have different widths. In the present embodiment, the first base  31   a  may have a larger width than the first lead  31   b . The width herein is the dimension perpendicular to the thickness and to the direction in which the lead extends. The first lead  31   b  is directly bonded to the mounting board. As the width of the first lead  31   b  is smaller, the wiring on the mounting board can have a smaller width and can be denser. The first base  31   a  contributes to the rigidity of the first lead terminal  31 . The first base  31   a  having a smaller width similarly to the first lead  31   b  can lower the rigidity of the first lead terminal  31 . The first base  31   a  thus has a larger width than the first lead  31   b  to appropriately increase the rigidity of the entire lead terminal. For example, the first lead terminals  31  are ground terminals, and the second lead terminals  32  are signal terminals. The ground wiring and the signal wiring may both have the same wiring width on the mounting board. In this case, the first lead  31   b  and the second lead  32   b  may have the same width. Each second lead terminal  32  includes the second base  32   a  and the second lead  32   b  with the same width. The first base  31   a  may have a larger width than the second base  32   b.    
     The dielectric substrate  10  may have cutouts  11  that are open at the first surface  10   a  and at the first side surface  10   c . Each cutout  11  is located between the first terminal joint  12  and the second terminal joint  13  and defines a space to improve electrical insulation between the first terminal joint  12  and the second terminal joint  13 . Also, cutouts similar to the cutouts  11  may be formed between second terminal joints  13 . 
     The cutouts  11  may have any shape but are rectangular and each have two facing inner surfaces parallel to each other in the present embodiment. The cutouts  11  may be, for example, tapered or flared and may each have two facing inner surfaces that are not parallel to each other. 
     The dielectric substrate  10  may further include ground conductor layers  11   a  covering the inner surfaces of the cutouts  11 . The ground conductor layers  11   a  may be, for example, metallization layers formed on the inner surfaces of the cutouts  11 . The metallization layer is formed from, for example, a metal material such as tungsten, molybdenum, or manganese, and may be plated with nickel or gold. The ground conductor layers  11   a  are electrically connected to, for example, the ground wiring conductors, the ground conductor layers, or the first terminal joints  12  (first metal layers  12   a ) in the dielectric substrate  10  to further stabilize the ground potential. 
     In the present embodiment, each first terminal joint  12  may include a step  20  defined in a portion adjacent to the first side surface  10   c  and recessed toward the second surface  10   b . For example, the first terminal joint  12  includes a rectangular portion  20   a  continuous with the first side surface  10   c  and located one step (equivalent to, for example, a single insulating layer) closer to the second surface  10   b  than the other portion. The first metal layer  12   a  is located on the step  20 . The step  20  includes the rectangular portion  20   a  and a wall surface  20   b  between the rectangular portion  20   a  and the other portion. The first metal layer  12   a  is also located on the wall surface  20   b . The wall surface  20   b  increases the area of the first terminal joint  12 , or more specifically the first metal layer  12   a , in the structure including the step  20  more than in the structure without the step  20 . The step  20  thus stabilizes the ground potential further. 
     The step  20  is rectangular in the present embodiment, but may be in another polygonal shape or may be semicircular. The step  20  with such a shape also has the wall surface that increases the area of the first terminal joint  12 , thus stabilizing the ground potential further. 
     In the present embodiment, for example, the first base  31   a  is either rectangular or prismatic, and the first lead  31   b  continuous with the end of the first base  31   a  has a smaller thickness than the first base  31   a , is band-shaped, and extends outwardly. As described above, the first base  31   a  is bonded to the first terminal joint  12  with a bond. The first base  31   a  overlaps the step  20  as viewed from above. The first base  31   a  may partially overlap the rectangular portion  20   a  as viewed from above. The portion of the first base  31   a  overlapping the rectangular portion  20   a  is spaced from the rectangular portion  20   a . When each first lead terminal  31  is connected to the corresponding first terminal joint  12 , the molten bond enters the space and solidifies to form a fillet of the bond. This improves the bonding strength between the first lead terminal  31  and the first terminal joint  12 . 
     The first base  31   a  may overlap the step  20  as viewed from above, and may have an end adjacent to the first lead  31   b  located outwardly from the first side surface  10   c . The end of the first base  31   a  opposite to the first lead  31   b  is bonded to the other portion of the first terminal joint  12  excluding the step  20 . The first base  31   a  extends across the rectangular portion  20   a  as viewed from above, and is firmly bonded to the first terminal joint  12  with the bond entering the entire portion overlapping the rectangular portion  20   a.    
     For the connection between the first base  31   a  and the first lead  31   b , the first lead  31   b  may be connected to the end of the first base  31   a  at any position in the thickness direction. In the present embodiment, the first lead  31   b  is connected to the end of the first base  31   a  at a position most distant from the first terminal joint  12  in the thickness direction. More specifically, the first base  31   a  has a base first surface  31   a   1  adjacent to the first terminal joint  12  and a base second surface  31   a   2  opposite to and parallel to the base first surface  31   a   1 . The first lead  31   b  has a lead first surface  31   b   1  flush with the base second surface  31   a   2 . The first lead  31   b  has a lead second surface  31   b   2  parallel to the lead first surface  31   b   1 . The lead second surface  31   b   2  is orthogonal to an end face  31   a   3  of the first base  31   a . In the present embodiment, as shown in  FIG. 3 , the end (end face  31   a   3 ) of the first base  31   a  adjacent to the first lead  31   b  is located outwardly from the first side surface  10   c.    
     In the present embodiment, the wiring board  1  may further include third lead terminals  33 . The first surface  10   a  of the dielectric substrate  10  includes, opposite to the second terminal joint  13  across each first terminal joint  12 , a third terminal joint  14  that is bonded to the third lead terminals  33  with a bond. Similarly to the second lead terminals  32 , the third lead terminals  33  are signal terminals. The first lead terminal  31  as a ground terminal is located between each second lead terminal  32  and the corresponding third lead terminal  33 . Each third lead terminal  33  includes a third base  33   a  bonded to the third terminal joint  14  and a third lead  33   b  extending from the third base  33   a . The first base  31   a  has a larger thickness than the third base  33   a , similarly to the second base  32   a.    
     The second lead terminals  32  and the third lead terminals  33  are both signal terminals. When these terminals are electromagnetically coupled to each other, an electrical signal transmitted through one terminal affects an electrical signal transmitted through the other terminal. This noise phenomenon is called crosstalk. The second lead  32   b  and the third lead  33   b  are weakly coupled to each other electromagnetically with air as the dielectric being between the leads. In contrast, the second base  32   a  and the third base  33   a  can be strongly coupled to each other electromagnetically with the dielectric substrate  10  between the bases. Noise from crosstalk is thus more likely to occur between the second base  32   a  and the third base  33   a . The first lead terminals  31  are ground terminals. The first base  31   a  of each first lead terminal  31  between the corresponding second base  32   a  and third base  33   a  has a larger thickness than the second base  32   a  and the third base  33   a . The third base  33   a  electromagnetically insulates between the second base  32   a  and the third base  33   a , causing the bases to be weakly coupled to each other electromagnetically and thus reducing crosstalk. 
     The third lead terminal  33  may have the same shape as or a different shape from the second lead terminal  32 . The third lead terminals  33  may be formed from the same metal material as or a different material from the second lead terminals  32 . In the present embodiment, the third lead terminals  33  and the second lead terminals  32  are formed from the same material and have the same shape. 
     A second embodiment will now be described.  FIG. 5  is an enlarged cross-sectional view of a wiring board according to the second embodiment.  FIG. 6  is an enlarged perspective view of the wiring board according to the second embodiment. The present embodiment is the same as the first embodiment except the structure of the first lead terminals  31 . The same components as in the first embodiment are given the same reference numerals and will not be described in detail. 
     Each first lead terminal  31  includes, between a first base  31   a  and a first lead  31   b , a joint  31   c  connecting the first base  31   a  and the first lead  31   b . The joint  31   c  has either an inclined surface or a curved surface continuous with one surface of the first base  31   a  and one surface of the first lead  31   b . In the present embodiment, for example, the joint  31   c  has a curved surface. The joint  31   c  has a joint first surface  31   c   1  flush with a base second surface  31   a   2  and a lead first surface  31   b   1 . The joint  31   c  has a joint second surface  31   c   2  continuous with the base first surface  31   a   1  of the first base  31   a  and the lead second surface  31   b   2  of the first lead  31   b . The joint second surface  31   c   2  is a curved surface. Although each first lead terminal  31  may be under an external force applied to the lead first surface  31   b   1  during bonding to the mounting board, the stress is distributed, thus reducing damage between the first base  31   a  and the first lead  31   b . The joint second surface  31   c   2  may be inclined to produce the same advantageous effects as the curved surface. 
     A third embodiment will now be described.  FIG. 7  is an enlarged cross-sectional view of a wiring board according to the third embodiment.  FIG. 8  is an enlarged perspective view of the wiring board according to the third embodiment. The present embodiment is the same as the second embodiment except the structure of the first lead terminals  31 . The same components as in the second embodiment are given the same reference numerals and will not be described in detail. 
     Each first lead terminal  31  in the present embodiment has a recess  310  on a base second surface  31   a   2  of a first base  31   a . The recess  310  is a portion of the base second surface  31   a   2  that is recessed toward the base first surface  31   a   1 . The recess  310  may be a portion of the base second surface  31   a   2  that is cut out from the base first surface  31   a   1 . The recess  310  on the base second surface  31   a   2  lowers the effective relative dielectric constant and improves the high-frequency response. 
     The recess  310  in the present embodiment has one end adjacent to the joint  31   c  located at the boundary between the first base  31   a  and the joint  31   c . This structure reduces a load from the stress applied at the boundary between the first base  31   a  and the joint  31   c . The recess  310  in the present embodiment includes an inner wall  310   a  extending from the boundary between the first base  31   a  and the joint  31   c  to its bottom surface. The inner wall  310   a  is inclined with respect to the base first surface  31   a   1  and with respect to a bottom surface  310   b  of the recess  310 . The inner wall  310   a  may be inclined with respect to the base second surface  31   a   2 . This structure allows the lead terminals to maintain rigidity and reduce a load from the stress applied. This structure thus improves the high-frequency response of the wiring board  1 . 
     An example method for manufacturing the wiring board  1  will now be described. The dielectric substrate  10  including multiple insulating layers formed from, for example, sintered aluminum oxide may be prepared in the manner described below. An aluminum oxide-containing powdery raw material and a silicon oxide-containing powdery raw material are mixed with, for example, an appropriate organic binder and an appropriate solvent to form slurry. The slurry is then shaped into sheets using, for example, the doctor blade method, to yield multiple ceramic green sheets. 
     The ceramic green sheets are then stacked on one another and pressure-bonded. The stacked ceramic green sheets are then fired in a reducing atmosphere, and cut or punched into an appropriate shape to complete the dielectric substrate  10  with an intended shape. 
     The first metal layers  12   a , the second metal layers  13   a , the ground conductors, and the signal conductors are formed from, for example, metallization layers that may be formed from a metal having a high melting point, such as tungsten, molybdenum, or manganese, prepared in the manner described below. A metal powder with a high melting point is kneaded with an organic solvent and a binder fully into a metal paste. The metal paste is then printed at predetermined positions on the ceramic green sheets to be the upper and lower surfaces of the insulating layers by, for example, screen printing. These ceramic green sheets with a printed metal paste are stacked on one another, pressure-bonded, and then co-fired. Through the above process, the metallization layer is deposited on the upper surface and the inner layer of the dielectric substrate  10  as the first metal layers  12   a , the second metal layers  13   a , the ground conductors, and the signal conductors. The first metal layer  12   a , the second metal layer  13   a , and the conductor layers may be plated with nickel or gold. 
     The feedthrough conductors are prepared by, for example, forming through-holes in multiple ceramic green sheets to be the insulating layers, and filling the through-holes with a metal paste similar to the metal paste used to form the conductor layers. The ceramic green sheets are then stacked on one another, pressure-bonded, and then co-fired to form the feedthrough conductors. The through-holes can be formed by, for example, die machining using a metal pin, or punching, for example, with laser. The filling of the through-holes with the metal paste may be facilitated with, for example, vacuum suction. 
     The first lead terminals  31 , the second lead terminals  32 , and the third lead terminals  33  may then be prepared by processing (e.g., rolling or punching) an ingot formed from such a metal material. The first lead terminals  31 , the second lead terminals  32 , and the third lead terminals  33  are then bonded to the first terminal joints  12 , the second terminal joints  13 , and the third terminal joints  14  in the dielectric substrate  10  with a bond to complete the wiring board  1 . 
       FIG. 9  is a perspective view of an electronic component package and an electronic apparatus according to another embodiment of the present disclosure. An electronic component package  50  includes a substrate  2  and the wiring board  1  bonded to the substrate  2 . In the present embodiment, the wiring board  1  is U-shaped and is attached to a sidewall  4  to form a frame, which is then bonded to the surface of the substrate  2 . The substrate  2  and the sidewall  4  may be formed from, for example, a metal such as iron, copper, nickel, chromium, cobalt, molybdenum or tungsten, or an alloy of these metals, such as a copper-tungsten alloy, a copper-molybdenum alloy, or an iron-nickel-cobalt alloy. The metal member for the substrate  2  and the sidewall  4  may be prepared by processing (e.g., rolling or punching) an ingot formed from such a metal material. 
     An electronic apparatus  100  includes the electronic component package  50 , an electronic component  3  mounted on the substrate  2  and electrically connected to the wiring board  1 , and a lid  5 . 
     The electronic component  3  may be, for example, an optical semiconductor device such as a laser diode (LD) or a photodiode (PD). For an LD, the sidewall  4  may have a through-hole  40  to receive an optical fiber. The lid  5  is bonded to the upper edges of the wiring board  1 , which is a frame, and the sidewall  4  to cover the electronic component package  50 . The lid  5  may be formed from, for example, a metal such as iron, copper, nickel, chromium, cobalt, molybdenum or tungsten, or an alloy of these metals, such as a copper-tungsten alloy, a copper-molybdenum alloy, or an iron-nickel-cobalt alloy. The metal member for the lid  5  may be prepared by processing (e.g., rolling or punching) an ingot formed from such a metal material. 
     The electronic component  3  is mounted inside the electronic component package  50 , and is electrically connected to the wiring board  1  with, for example, bonding wires. The electronic component  3  is then sealed with the lid  5 . 
     The present invention is not limited to the above embodiments, and the embodiments may be combined and changed variously without departing from the spirit and scope of the present invention. For example, the electronic component package  50  and the electronic apparatus  100  may include the wiring board  1  according to any of the above embodiments or combining any features in the embodiments. Modifications contained in the claims can fall within the scope of the present invention. 
     REFERENCE SIGNS LIST 
     
         
           1  wiring board 
           2  substrate 
           3  electronic component 
           4  sidewall 
           5  lid 
           10  dielectric substrate 
           10   a  first surface 
           10   b  second surface 
           10   c  first side surface 
           11  cutout 
           12  first terminal joint 
           12   a  first metal layer 
           13  second terminal joint 
           13   a  second metal layer 
           14  third terminal joint 
           20  step 
           20   a  rectangular portion 
           20   b  wall surface 
           31  first lead terminal 
           31   a  first base 
           31   a   1  base first surface 
           31   a   2  base second surface 
           31   a   3  end face 
           31   b  first lead 
           31   b   1  lead first surface 
           31   b   2  lead second surface 
           31   c  joint 
           31   c   1  joint first surface 
           31   c   2  joint second surface 
           32  second lead terminal 
           32   a  second base 
           32   b  second lead 
           32   b   1  bent portion 
           32   b   2  straight portion 
           33  third lead terminal 
           33   a  third base 
           33   b  third lead 
           40  through-hole 
           50  electronic component package 
           100  electronic apparatus 
           310  recess 
           310   a  inner wall 
           310   b  bottom surface