Abstract:
A module includes a ceramic substrate, first and second electrodes provided on the ceramic substrate, a component having third and fourth electrodes connected to the first and second electrodes, respectively, and a resin filled in a space between the component and the ceramic substrate. The ceramic substrate has a surface thereof having a recess formed therein. The first and second electrodes are provided on the surface of the ceramic substrate so that the recess is located between the first and second electrodes. The component is located over the recess and spaced from the ceramic substrate with a space including the recess. The space including the recess is filled with the resin. The module allows each component to be surface mounted at higher bonding strength, thus preventing short-circuit between the electrodes on the substrate and improving the operation reliability.

Description:
CROSS REFERENCE TO RELATED DOCUMENT 
   This application claims priority to Japanese Patent Application No. 2003-337180, filed on Sep. 29, 2003. 
   FIELD OF THE INVENTION 
   The present invention relates to a module including a ceramic substrate having a wiring pattern thereon, and electronic components, such as ICs, SAW filters, resistors, capacitors, and coils, mounted on the ceramic substrate, and to a method of manufacturing the module. 
   BACKGROUND OF THE INVENTION 
   Ceramic modules including electronic components, such as ICs, SAW filters, resistors, capacitors, and coils, mounted on a ceramic substrate having a wiring pattern thereon is disclosed in Japanese Patent Laid-Open Publication Nos. 3-205857 and 4-252041. 
     FIG. 18  is a cross sectional view of a conventional ceramic module  50 . The ceramic module  50  includes a component  60 , such as a capacitor and an inductor, an active component  80 , such as an IC and a SAW filter, and a ceramic substrate  70 . The ceramic substrate  70  includes internal electrodes  51 , via electrodes  52  connecting between the internal electrodes  51 , land electrodes  55  connected with the active component  80  and the component  60  for surface-mounting them, and back electrodes  56  for mounting the ceramic module  50  on a mother board. The end electrodes  62  of the component  60  are connected to land electrodes  55  corresponding to them with a conductive adhesive  61 , such as solder, while the back electrodes  81  of the active component  80  are connected to land electrodes  55  corresponding to them with a conductive adhesive  61 . A gap between the active component  80  and the substrate  70  is filled with a resin  90  for increasing reliability of surface mounting of the active component  80 . 
   In the conventional module  50 , the component  60  and the active component  80  are mounted on the ceramic substrate  70  which has been baked, and may be molded with a resin  91  according to requirement. 
   When the component  60  has a small size, such as 1005 size or 0603 size, the conventional module  50  includes a small amount of the conductive adhesive  61  for avoiding short-circuit between the electrodes during the surface mounting. When being applied for molding the component  60  mounted, the resin  91  may fail to flow into beneath the component  60 , and may produce a gap  92 . When the ceramic module  50  is mounted on the mother board, the conductive adhesive  61 , such as solder, may melt and flow into the gap  92  between the component  60  and the ceramic substrate  70 , hence causing a short-circuit between the land electrodes  55  and disturbing the performance and the operational reliability of the ceramic module  50 . 
   The resin  90  is also applied to between the component  80  and the substrate  70  for mounting and securing the component  80  onto the substrate  70 . The resin  90 , upon not being applied sufficiently between the component  80  and the substrate  70 , may reduce the bonding strength and the operational reliability. 
   SUMMARY OF THE INVENTION 
   A module includes a ceramic substrate, first and second electrodes provided on the ceramic substrate, a component having third and fourth electrodes connected to the first and second electrodes, respectively, and a resin filled in a space between the component and the ceramic substrate. The ceramic substrate has a surface thereof having a recess formed therein. The first and second electrodes are provided on the surface of the ceramic substrate so that the recess is located between the first and second electrodes. The component is located over the recess and spaced from the ceramic substrate with a space including the recess. The space including the recess is filled with the resin. 
   Accordingly, the module allows each component to be surface mounted at higher bonding strength, thus preventing short-circuit between the electrodes on the substrate and improving the operation reliability. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a cross sectional view of a ceramic module according to an exemplary embodiment of the present invention. 
       FIG. 2  is an upper view of a ceramic substrate of the ceramic module according to the embodiment; 
       FIG. 3  is a cross sectional view of the module for illustrating a method of manufacturing the module according to the embodiment. 
       FIG. 4  is a cross sectional view of the module for illustrating the method of manufacturing the module according to the embodiment. 
       FIG. 5  is a cross sectional view of the module for illustrating the method of manufacturing the module according to the embodiment. 
       FIG. 6  is a cross sectional view of the module for illustrating the method of manufacturing the module according to the embodiment. 
       FIG. 7  is a cross sectional view of the module for illustrating the method of manufacturing the module according to the embodiment. 
       FIG. 8  is a cross sectional view of the module for illustrating the method of manufacturing the module according to the embodiment. 
       FIG. 9  is a cross sectional view of the module for illustrating the method of manufacturing the module according to the embodiment. 
       FIG. 10  is a cross sectional view of the module for illustrating the method of manufacturing the module according to the embodiment. 
       FIG. 11  is a cross sectional view of the module for illustrating the method of manufacturing the module according to the embodiment. 
       FIG. 12  is a cross sectional view of the module for illustrating the method of manufacturing the module according to the embodiment. 
       FIG. 13  is a cross sectional view of the module for illustrating the method of manufacturing the module according to the embodiment. 
       FIG. 14  is a cross sectional view of the module for illustrating another method of manufacturing the module according to the embodiment. 
       FIG. 15  is a cross sectional view of the module for illustrating the another method of manufacturing the module according to the embodiment. 
       FIG. 16  is a cross sectional view of the module for illustrating the another method of manufacturing the module according to the embodiment. 
       FIG. 17  is a cross sectional view of the module for illustrating a further method of manufacturing the module according to the embodiment. 
       FIG. 18  is a cross sectional view of a conventional ceramic module. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  is a cross sectional view of a ceramic module  1  according to an exemplary embodiment of the present invention.  FIG. 2  is an upper view of a ceramic substrate  13  of the module  1 . The ceramic module  1  includes the ceramic substrate  13 . The ceramic substrate  13  includes internal electrodes  2  provided as layers, via-electrodes  3  connecting between the internal electrodes  2 , and a ceramic base  14  made of electrically-insulating material. A component  6 , such as a chip resistor, a multi-layer ceramic capacitor, and a chip inductor, includes a main body  6 A and end electrodes  15 . An active component  8 , such as an IC and a SAW filter, includes a main body  8 A and bump electrodes  16 . The end electrode  15  and the bump electrodes  16  are connected by solders  7  to land electrodes  4 , and the components  6  and  8  are provided on the upper surface  13 A of the substrate  13 . Back electrodes  5  are provided on the lower surface  13 B of the ceramic substrate  13  for allowing the ceramic module  1  to be mounted on a mother board  40 . The ceramic substrate  13  has a recess  10 B in a portion of the surface of substrate  13  facing the component  6 , and has a recess  10 A in a portion of the surface of substrate  13  facing the component  8 . An insulating resin  11 , such as epoxy resin, filled between the component  6  and the substrate  13  while a resin  9  is filled between the active component  8  and the substrate  13 . The component  6  and the active component  8  are encapsulated with a resin molding  12  on the upper surface  13 A of the ceramic substrate  13  having the components  6  and  8  mounted thereon. 
   Since the internal electrodes  2  and the via-electrodes  3  in the ceramic substrate  13  are baked simultaneously together with the ceramic substrate  13  and are conductive, the electrodes are made of Ag paste having a large conductivity. The ceramic base  14  of the ceramic substrate  13  including the internal electrodes  2  of Ag is preferably baked substantially at 900° C. The ceramic base  14  may be made preferably of glass-ceramic mixture of Al 2 O 3  and glass. The materials of the internal electrodes  2  and the ceramic substrate  13  are not limited to the foregoing materials. 
   The resin molding  12  is made of electrically-insulating resin material, such as epoxy, phenol, or epoxy-silicone resin, and secures a bonding strength and a resistance against impact of the components  6  and  8  in the module  1 . The solders  7  may be replaced by electrically-conductive adhesives made of conductive resin. 
   The component  6  and the active component  8  are mounted and electrically connected on the ceramic substrate  13 . After the component  6  is placed on the ceramic substrate  13  and connected to the land electrodes  4 , the space  10 C including the recess  10 B between the component  6  and the ceramic substrate  13  is filled with the resin  11 . The recess  10 B enables the resin  11  to be easily filled between the component  6  and the ceramic substrate  13 . This arrangement produces no gap between the component  6  and the ceramic substrate  13 , and the solders  7  can be prevented from flowing when the solders are heated while the module  1  is mounted on the mother board  40 , thus preventing the electrodes  4  from short circuit. Particularly if the component  6  has such a small size that the electrodes  4  is spaced a little from each other, the recess  10 B is useful for receiving the resin  11 . 
   For improving a bonding strength and reliability of the component  8  for the surface mounting, the resin  9  of insulating resin material, such as epoxy resin, is often applied between the component  8  and the substrate  13 . The resin  9  may be made of material selected from various resins. The recess  10 A allows the resin  9  to be filled between the component  8  and the substrate  13  even if the distance between the component  8  and the substrate  13  is small. This arrangement produces no gap between the component  8  and the substrate  13 , hence providing the ceramic module  1  with large bonding strength and reliability for the surface mounting. 
   In order to fill spaces beneath the components  6  and  8  with the resins  11  and  9  at stably, a distance W 1  between the land electrodes  4  of the component  6  or  8  and a distance W 2  of the recess  10 B or  10 A satisfy W 1 ≧W 2  as shown in  FIG. 2 , and depths of the recess  10 B and  10 A are preferably not smaller than 10 μm. This arrangement prevents the solders or the conductive adhesive for mounting the component  6  or  8  on the substrate  13  from causing short-circuit between the electrodes  4  due to the flowing of the solder or adhesive, and prevents the resin  11  and  9  from being applied with insufficient amounts beneath the component  6  or  8 . Accordingly, the ceramic module  1  has large bonding strength and reliability for the surface mounting of the components  6  and  8 . 
     FIGS. 3 to 13  are cross sectional views of the ceramic substrate  13  for illustrating a procedure of manufacturing the substrate  13 . 
   The ceramic substrate  13  is formed by baking a green sheet of glass ceramic material, such as mixture of Al 2 O 3  and glass powder. The glass powder is preferably selected from SiO 2 , B 2 O 3 , Al 2 O 3 , CaCO 3 , SrCO 3 , SrCO 3 , BaCO 3 , La 2 O 3 , ZrO 2 , TiO 2 , MgO, PbO, ZnO, Li 2 O 3 , Na 2 CO 3 , and K 2 CO 3 . The mixture of Al 2 O 3  and glass powder is added with poly vinyl butylal binder, plasticizer, and organic solvent for dispersion, thus providing slurry. The above described composition is illustrative, and may be replaced with any other appropriate example for providing slurry. 
   The slurry is applied on a base film  21  made of, for example, PET material with a doctor blade or the like, and is dried, thus providing a ceramic green sheet  20  having predetermined desired thickness and size, as shown in  FIG. 3 . The base film  21  is not limited to the PET material but may be made of any other appropriate material. 
   Next, the green sheet  20  is perforated by punching or laser beam machining to have through-holes  22  formed therein, as shown in  FIG. 4 . Pilot holes  27  may be provided in the base film  21  for multi-layer assembly if necessary. 
   The through-holes  22  are then filled with silver paste to develop via-electrodes  23 , as shown in  FIG. 5 . Then, a pattern of the internal electrodes  24  are formed by, for example, screen printing, as shown in  FIG. 6 . The internal electrodes  24  are patterned with paste made of Ag-based conductive material, however the paste may be made of any conductive material other than the Ag-based material which can be baked simultaneously with the green sheet  20 . 
   The base films  21  having green sheets  20 A- 20 D, the via electrodes  23 , and the internal electrodes  24  are aligned by inserting guide pins through the pilot holes  27 , as shown in  FIG. 7 . Then, the green sheet  20 A is placed on a stack pallet  25 . Then, the green sheet  20 B is placed on the green sheet  20 A on the stack pallet  25  while pilot holes  27  aligned with the guide pins  26  inserted. Then, similarly, the green sheet  20 C is stacked on the green sheet  20 B, and the green sheet  20 D is stacked on the green sheet  20 C. 
   As above, a multi-layer block  28  including the green sheets  20 A- 20 D is provided, as shown in  FIG. 8 . The land electrodes  4  are provided on the upper surface of the multi-layer block  28 . The pilot holes  27  are provided in the base film  21  according to the embodiment, however, may be provided in the green sheets  20 A- 20 D. Then, pressures F are applied to the multi-layer block  28  for having the green sheets  20 A- 20 D have an uniform density and for eliminating de-lamination between any adjacent ones of the green sheets  20 A- 20 D. Accordingly, the green sheets  20 A- 20 D are pressed and joined together. 
   The multi-layer block  28  is then degreased at a temperature ranging from 350° C. to 600° C., and baked at a temperature ranging from 850° C. to 950° C., hence providing the ceramic substrate  13  including the internal electrodes  24  of the Ag-based material, as shown in  FIG. 9 . 
   Then, a recess  30  is formed by applying laser beam  29  at a portion of the ceramic substrate  13  between the land electrodes  4 , as shown in  FIG. 10 . The laser beam  29  forms the recess  30  in a short period of time. 
   The end electrodes  15  of the component  6  are connected to the electrodes  4  with solders  7 . Then, the recess  30  is filled with the resin  11 , such as epoxy resin or silicone resin, and the resin  11  is cured. This allows the resin  11  filled in the recess  30  to prevents short-circuit between the electrodes  4  since the resin prevents the solders  7  from flowing between the electrodes  4  when being heated for mounting another component on the substrate  13  at a succeeding step. 
   In order to mount the component  8 , a recess  30  is formed at beneath the component  8  and in the substrate  13 , and filled with the resin  9  for improving the bonding strength and reliability of the mounting. This arrangement allows the resin  9  to be filled and cured between the component  8  and the substrate  13  with producing of no gap, hence contributing to the improvement in the bonding strength and operational reliability of the ceramic module  1 . 
   As shown in  FIG. 11 , for forming the land electrodes  4 , a land electrode  4 A having a large size may be formed on the ceramic substrate  13 , and is then baked. Then, the land electrode  4 A is divided into the electrodes  4  at the same time when the recess  30  is formed by the laser beam  29  in the substrate  13 , as shown in  FIG. 12 . That is, the electrodes  4  and the recess  30  can be formed simultaneously. This operation allows the recess  30  to be formed precisely between the land electrodes  4  without consideration of thinning of the conductive paste or accuracy of the patterning even when the land electrodes  4  have small sizes. 
   Then, the component  6  and the active component  8  (not shown) are mounted while the resin  11  is filled in the recess  30  as well as beneath the component  6 , as shown in  FIG. 13 . They are molded with a resin molding  12  and cut by dicing into the ceramic modules  1  having a predetermined size. 
   The electrodes  4  and  4 A may be baked together with the ceramic substrate  13  or after the ceramic substrate  13  is baked. 
     FIGS. 14 to 16  are cross sectional views of the ceramic module for illustrating another method for manufacturing the module according to the embodiment. When the through-holes  22  are formed in the green sheet shown in  FIG. 4  by punching or laser beam, a though-hole  22 A may be formed in the green sheet  20 D, which is to be placed at the outermost layer, at a portion where the recesses  10 A and  10 B is to be provided, as shown in  FIG. 14 . Then, similarly to processes illustrated in  FIGS. 5-11 , the via-electrodes  23  is formed in the through-holes  22 , as shown in  FIG. 15 , and the internal electrodes  24  are formed, as shown in  FIG. 16 . Then, the green sheets  20 A- 20 D are stacked and baked. That is, the through-hole  22 A serves as the recesses  10 A and  10 B in the multi-layer block  28 . Then, the components  6  and  8  are mounted, as shown in  FIG. 13 , and the resins  9  and  10  are then applied. Finally, they are encapsulated in the resin molding  12 , thus providing the ceramic module  1 . According to the above method, the recesses  10 A and  10 B can be provided without forming recesses after the green sheets  20 A- 20 D are baked. 
   The recess  30  may be formed in the multi-layer block  28  by laser beam machining before the block is baked. After the baking of the multi-layer block  28 , the components  6  and  8  are mounted, the resins  9  and  11  are applied, and the resin molding  12  is provided, thus providing the ceramic module  1 . 
   As shown in  FIG. 17 , the recess  30  between the land electrodes  4  may be formed by locating a die  41  between the land electrodes  4  and pressing the die downwardly while the multi-layer block  28  is pressed. Alternatively, as shown in  FIG. 12  the recess  30  may be formed by laser beam between the land electrodes  4 . The recess  30  can be formed before and after the pressing of the block. After the baking of the multi-layer block  28 , the components  6  and  8  are mounted, the resins  9  and  11  are applied, and the resin molding  12  is formed, thus providing the ceramic module  1  having the recesses  10 A and  10 B between the land electrodes  4  readily and easily.