JP4900227B2 - Multilayer ceramic substrate manufacturing method, multilayer ceramic substrate, and electronic component using the same - Google Patents

Description

  The present invention relates to a method for manufacturing a multilayer ceramic substrate in which a plurality of ceramic layers are laminated. The present invention also relates to a multilayer ceramic substrate manufactured by this manufacturing method and an electronic component using the same.

  Today, multilayer ceramic substrates are used in various electronic components such as antenna switch modules, PA (Power Amplifier) modules, and filter modules in mobile communication terminal devices such as mobile phones.

  In such a multilayer ceramic substrate, a plurality of ceramic layers are laminated, wiring layers are formed between the layers, and the wiring layers are connected by via wiring. In particular, LTCC (Low Temperature Co-fired Ceramics) can be sintered together with a wiring material or the like at a low temperature and is therefore suitable as a material for the ceramic layer in such a configuration.

  A functional element such as a semiconductor chip is mounted on such a multilayer ceramic substrate and functions as an electronic component. In order to mount such a functional element on the surface, a connecting conductor portion is provided on the surface, and the connecting conductor portion is connected to internal wiring formed inside the multilayer ceramic substrate by via wiring. The internal wiring and the connecting conductor are patterned so that the electronic component operates properly.

  As an example, FIG. 6 shows a cross-sectional structure (a) of a conventional multilayer ceramic substrate and a partial shape (b) seen from above. In the multilayer ceramic substrate 90, for example, two ceramic layers 91a and 91b are laminated, and an internal wiring 92 is formed between the ceramic layers 91a and 91b. A connecting conductor portion 93 is formed on the surface of the ceramic layer 91 b, and the internal wiring 92 and the connecting conductor portion 93 are connected by a via wiring 94. The surface of the connecting conductor portion 93 is connected to the semiconductor chip itself and wiring from the semiconductor chip by solder. For this reason, a gold (Au) or nickel (Ni) plating layer that has good solder wettability and can be satisfactorily joined by solder is formed on the surface of the connecting conductor portion 93. Although not shown in FIG. 6, the total number of ceramic layers is three or more, internal wirings are formed between the respective layers, and the internal wirings are connected by via wirings penetrating the ceramic layers. is there.

  Further, as shown in FIG. 6B, the connecting conductor portion 93 and the via wiring 94 are both circular, and the diameter of the connecting conductor portion 93 is larger. This is because the via wiring 94 needs to be reduced in size from the viewpoint of high integration, but a certain amount of area is required for soldering on the connecting conductor portion 93. . For this reason, for example, the diameter of the via wiring 94 is about 100 μm, and the diameter of the connecting conductor 93 is about 300 μm.

  Both the connecting conductor portion 93 and the via wiring 94 are formed of a silver paste, and are integrally fired when the ceramic layer is sintered. The via wiring is formed by filling an opening corresponding to the via wiring with silver paste. The connecting conductor portion is formed by forming a silver paste layer of the shape by screen printing. At this time, printing is performed by aligning the screen with the already formed via wiring.

  Using this structure, it was possible to manufacture an electronic component formed by mounting a large number of semiconductor chips on a multilayer ceramic substrate and joining them using solder.

  However, in recent years, along with the high integration of such electronic components, it has become necessary to refine the patterns of internal wiring and connecting conductor portions. For example, it is necessary to set the diameter of the connecting conductor portion to 300 μm or less and the interval to 200 μm or less. In such a case, the overlay accuracy between the via wiring and the connecting conductor is a problem.

  For this reason, Patent Document 1 discloses a multilayer ceramic substrate that is sintered in two stages in order to form a surface conductor pattern with high accuracy. That is, a plurality of first ceramic green sheets on which internal wirings are formed are stacked and laminated, and a second ceramic green sheet on which external wiring on the surface layer is formed is stacked on both main surfaces of the ceramic substrate. This is a method for manufacturing a ceramic multilayer substrate in which a body is formed and the laminate is further sintered. However, with this method, it is actually difficult to press the green green sheet densely onto the sintered ceramic substrate, and it is practically difficult to bake them without peeling defects or thermal damage. is there.

JP 2006-140513 A

  On the other hand, the accuracy of the alignment between the printing screen for forming the connecting conductor portion and the via wiring can be increased by improving the accuracy of the printing apparatus, but this is particularly the case when printing silver paste. Is likely to occur. The cause of this bleeding is that the silver paste overflowing from the via opening obstructs the adhesion of the screen. For this reason, the pattern may move due to bleeding in the squeegee movement direction (direction in which the silver paste is applied) in printing. For this reason, the center of the connecting conductor portion and the via wiring may shift as shown in FIG. When this shift becomes as large as the radius of the connecting conductor portion, the electrical resistance increases at this portion. That is, the electrical resistance is increased due to poor overlay accuracy between the via wiring and the connecting conductor.

  When the printing screen and the via wiring for forming the connecting conductor portion have higher density, it is necessary that the connecting conductor portion has a diameter of 200 μm or less and an interval of 100 μm or less. Therefore, the influence of this overlay accuracy cannot be ignored as the electronic parts are highly integrated as described above.

  From the above, in the conventional multilayer ceramic substrate, when the internal wiring and the wiring pattern of the connecting conductor portion are miniaturized, the overlay accuracy is insufficient.

  The present invention has been made in view of such problems, and a method for manufacturing a multilayer ceramic substrate, which solves problems such as bleeding and improves the overlay accuracy of via wiring and connecting conductors, and multilayer ceramic substrate And it aims at providing the electronic component using the same.

In order to solve the above problems, the present invention has the following configurations.
SUMMARY OF THE INVENTION according to claim 1 is a method for producing a multi-layer ceramic substrate to form a first ceramic green sheet in a range of thickness of 20~120μm comprising a ceramic layer of the outermost surface after firing, straight a via opening forming step of forming a diameter 6 0 .mu.m or less of the opening, the the first ceramic green sheet, the diameter of the connecting conductor part after firing viewed in the stacking direction of the and the multilayer ceramic substrate below 1 00Myuemu A surface layer ceramic green sheet forming step of forming a first metal layer formed in a wider area than the opening and a second metal layer filling the via opening by one screen printing, and firing wherein said thicker than the first ceramic green sheet second ceramic green sheets for the ceramic layer adjacent to the ceramic layer of the outermost surface is formed after, before And lower ceramic green sheets forming step of forming a third metal layer made of the internal wiring after firing the second ceramic green sheet, is crimped by laminating a pre-Symbol superficial ceramic green sheets the lower ceramic green sheets, wherein An upper ceramic sheet laminate forming step for forming an upper ceramic sheet laminate having a total thickness of more than 56 μm, to which the first to third metal layers are connected, and the upper ceramic sheet laminate separately from the outermost surface A lower ceramic sheet forming step of forming a lower ceramic sheet that becomes an adjacent ceramic layer on a surface opposite to the ceramic layer adjacent to the ceramic layer and the uppermost ceramic layer; and the upper ceramic sheet laminate and the lower portion crimp the ceramic sheet, firing the multilayer ceramic body unsintered formed by laminating Consists in a method for manufacturing a multilayer ceramic substrate, characterized in that it comprises a binding step.
According to such a method, by performing a step of forming an upper ceramic sheet laminate comprising a surface ceramic green sheet and a lower ceramic green sheet under predetermined conditions,
Screen printing can be performed once, so that the bleeding problem can be solved and the overlay accuracy between the via wiring and the connecting conductor can be improved.

The gist of the invention described in claim 2 is that the first to third metal layers are electrically independent from a metal layer serving as an internal wiring in the lower ceramic sheet. 1. The method for producing a multilayer ceramic substrate according to 1 .

The gist of the invention described in claim 3 is that when at least the surface ceramic green sheet is pressure-bonded and the lower ceramic green sheet is laminated and pressure-bonded to the surface ceramic green sheet in the upper ceramic sheet laminate forming step. 3. The method according to claim 1 or 2, wherein the step is performed in a reduced pressure atmosphere.
According to such a method, even when the surface ceramic green sheet is thin, generation of wrinkles and gaps at the time of adhesion can be prevented, adhesion is good, and overlay accuracy is further improved.

The gist of the invention described in claim 4 resides in a multilayer ceramic substrate manufactured by the method for manufacturing a multilayer ceramic substrate according to any one of claims 1 to 3.
Such a multilayer ceramic substrate can be easily manufactured with high accuracy.

The gist of the invention described in claim 5 is that a plurality of the electrically conductive connecting conductor portions are arranged on the outermost surface, and a minimum interval between the connecting conductor portions is 200 μm or less. Item 4. A multilayer ceramic substrate according to Item 4.
In such a multilayer ceramic substrate, surface-mounted components can be mounted particularly at high density, and highly functional and high performance electronic components can be obtained.

  A gist of the invention described in claim 6 is that a surface mount component including at least one of a semiconductor chip, a chip capacitor, and a chip resistor is mounted on the multilayer ceramic substrate according to claim 5. It exists in electronic parts.

  Since the present invention is configured as described above, even when the wiring pattern of the internal wiring and the connecting conductor is miniaturized, the overlay accuracy between the via wiring and the connecting conductor is high, and the electric resistance of the wiring is high. A low multilayer ceramic substrate can be obtained. In addition, an electronic component having high reliability can be obtained by using it.

  The present invention will be described below with reference to specific embodiments. However, the present invention is not limited to these embodiments.

  In this manufacturing method, a via opening forming step, a surface ceramic green sheet forming step, a lower ceramic green sheet forming step, an upper ceramic sheet laminate forming step, a lower ceramic sheet forming step, and a sintering step are sequentially performed. FIG. 1 is a process cross-sectional view showing a surface ceramic green sheet forming process in the method for manufacturing a multilayer ceramic substrate according to the embodiment of the present invention. In addition, the right side in FIG. 1 also shows an external view around the via wiring in each process. This manufacturing method is used for forming a metal layer to be a connection wiring portion and a via wiring after firing in a thin green sheet layer that becomes a ceramic layer after firing in a multilayer ceramic substrate.

  FIG. 2 is a see-through perspective view showing the structure of the multilayer ceramic substrate manufactured by this manufacturing method. Here, only one side of the multilayer ceramic substrate 10 (upper side in FIG. 2) is described, but the same structure can be applied to the other side. In the multilayer ceramic substrate 10, an internal wiring 13 is formed between a ceramic layer 11 adjacent to the outermost ceramic layer and an outermost ceramic layer (surface ceramic layer) 12. One end of the via wiring 14 is connected to the internal wiring 13, the other end is connected to the connecting conductor portion (pad portion) 15, and the internal wiring 13 is provided with a pair of via wirings 14. Here, in this multilayer ceramic substrate 10, a surface ceramic layer 12, which is the outermost ceramic layer, is provided on the surface, and the connecting conductor portion 15 is embedded in the surface ceramic layer 12, The surface of 12 and the surface of the connecting conductor portion 15 are in the substantially same plane. This structure includes a lower ceramic green sheet that becomes a ceramic layer 11 after sintering, a surface ceramic green sheet layer that becomes a surface ceramic layer 12 after sintering, a third metal layer that becomes an internal wiring 13 after firing, and a conductor part for connection The first metal layer to be 15 and the second metal layer to be the via wiring 14 are formed in the form shown in FIG. It should be noted that the surface of the surface ceramic layer 12 and the surface of the connecting conductor portion 15 are substantially on the same plane so that there is no problem in soldering or the like even if there is a step between them. Specifically, the step is about 10 μm or less.

Note that the shapes of the connecting conductor portion 15 and the via wiring 14 are both circular when viewed from a direction perpendicular to the surface of the surface ceramic layer 12 in FIG. However, since the semiconductor chip or the like is joined by solder on the connecting conductor portion 15, it is necessary to make the connecting conductor portion 15 large enough to be soldered even when the density is increased. It is slightly larger than the diameter of the wiring 14. Specifically, the connecting conductor portion 15 has a diameter of 100 μm or less, and the via wiring 14 has a diameter of 60 μm or less. Note that the diameter of the connecting conductor portion is not limited to a circular shape but includes a rectangular shape. The diameter therefor is a numerical value when converted to circular same area. The same applies to via wiring. In addition, a metal plating layer mainly composed of gold (Au) and / or nickel (Ni) is provided on the surface of the connecting conductor portion 15 so as to improve solder wettability and to form a good solder joint. Is preferably formed.

  The method for manufacturing a multilayer ceramic substrate according to the embodiment of the present invention is particularly characterized in a process of forming a metal layer to be the via wiring 14 and the connecting conductor portion 15 (via opening forming process to upper ceramic laminate forming process). Have.

In this manufacturing method, as shown in FIG. 1A, a first ceramic green sheet 21 having a thickness of 20 to 120 μm is prepared. The first ceramic green sheet 21 becomes the surface ceramic layer 12 in the multilayer ceramic substrate 10 in FIG. 2 after firing. The ceramic green sheet 21 is made of a material containing LTCC (Low Temperature Co-fired Ceramics), for example, alumina (Al ₂ O ₃ ), silicon oxide (SiO ₂ ), or the like. Specifically, it is composed of oxides of aluminum (Al), silicon (Si), strontium (Sr), and titanium (Ti), which are 10 to 60% by mass in terms of Al ₂ O _{3 and in} terms of SiO ₂ , respectively. It is a material consisting of 25 to 60% by mass, 10 to 50% by mass in terms of SrO, and 20% by mass or less in terms of TiO ₂ . This layer is formed by sintering a green sheet made of this material at a temperature of about 900 ° C. The green sheet is obtained, for example, by molding a slurry in which the above oxide powder is dispersed in an organic binder made of, for example, polyvinyl butyral resin and a plasticizer made of di-n-butyl phthalate.

  Next, as shown in FIG. 1B, an opening 22 corresponding to the via wiring 14 is provided in the first ceramic green sheet 21 (via opening forming step). The opening 22 is formed by laser processing, for example, and penetrates the ceramic green sheet 21. A view of the shape of the opening 12 at this time as viewed from above in FIG. 1 is shown on the right side of FIG. The diameter of the opening is approximately 60 μm. The ceramic green sheet 21 is formed on the support film 40, and the support film 40 is preferably a PET (polyester) film that is chemically stable and highly plastic. Note that this process can be performed more easily when the first ceramic green sheet 21 is thinner. If the thickness is greater than 120 μm, this opening becomes difficult.

  Next, as shown in FIG. 1 (c), the second metal layer is formed in the first metal layer and the opening 22 using the screen 42 and the squeegee 45 to form the silver paste 52 in the shape of the connecting conductor 15. Fill. This operation is performed by one screen printing (surface ceramic green sheet layer forming step). An opening provided with a mesh is formed in the screen 42, and this opening corresponds to the shape (circular shape) of the connecting conductor portion 15. At this time, the screen 42 is arranged in alignment with the opening 22. Here, if the ceramic green sheet 21 is thick, the amount of the silver paste 52 required to fill the opening 22 increases. However, if the ceramic green sheet 21 is thin, the silver paste 52 necessary for the ceramic green sheet 21 is reduced. The amount is reduced. Further, since the opening of the screen 42 corresponds to the shape of the connecting conductor 15, the silver paste 52 has a shape shown in FIG. That is, the shapes of the via wiring 14 and the connection wiring portion 15 are simultaneously formed by one screen printing. Here, the surface ceramic green sheet 21 a is formed by forming a silver paste metal layer on the first ceramic green sheet 21.

  A view of the shape around the opening 22 at this time as viewed from above in FIG. 1 is shown on the right in FIG. Here, the center of the connection wiring portion 15 and the center of the opening portion 22 do not necessarily coincide with each other, and in general, there is a misalignment. As a cause of this deviation, there is insufficient alignment accuracy between the screen 42 and the opening 22 and bleeding that occurs in the silver paste 52.

  However, among these, the bleeding of the silver paste 52 can be reduced if the amount of the silver paste 52 to be used is small. Therefore, if the green sheet layer 21 is thin, this bleeding can be reduced. Therefore, in this case, if the alignment accuracy between the screen 42 and the opening 22 is sufficient, sufficient overlay accuracy can be obtained.

  Therefore, the silver paste 52 used as the via | veer wiring 14 and the connection conductor part 15 can be formed in the surface layer ceramic green sheet 21a with the above manufacturing method.

  As a comparative example, process cross-sectional views of an example of a conventional manufacturing method for forming a metal layer to be a via wiring and a connecting conductor portion are similarly shown in FIGS.

  3 (a) and 3 (b) are the same as FIGS. 1 (a) and 1 (b). That is, an opening 32 corresponding to the via wiring 14 is provided in the ceramic green sheet 31. However, the thickness of the ceramic green sheet and the diameter of the opening are different.

  Next, in FIG.3 (c), using the screen 43 and the squeegee 45, the opening part 22 is filled with the silver paste (metal layer) 53 by screen printing. An opening provided with a mesh is formed in the screen 43, and this opening has a slightly larger shape (circular shape) than the opening 32. At this time, the screen 43 is arranged in alignment with the opening 32. Here, when the green sheet layer 31 is thick, a large amount of silver paste 53 is required to fill the opening 32. Therefore, since the bleeding of the silver paste 52 becomes large while it is sufficiently filled, the pattern of the formed silver paste becomes larger than the opening of the screen and deviates from the opening 32. Therefore, in order to reduce this bleeding, the opening in the screen 43 is set to the minimum size necessary for filling the opening 32. That is, the size of the opening is set to be larger than the diameter of the opening 32 by taking account of misalignment. Accordingly, in this case, the silver paste layer 53 cannot be formed into the shape of the connecting wiring portion 15 at the same time as filling the opening as the size of the connecting conductor portion 15.

  Therefore, as shown in FIG. 3D, the opening 32 is filled with the silver paste 53, but a silver paste layer having the shape of the connecting conductor portion 15 cannot be formed. Further, due to misalignment and bleeding between the screen 43 and the opening 32, the center of the silver paste 53 and the center of the opening 32 are shifted as shown on the right side of FIG.

  Therefore, as shown in FIG. 3E, screen printing is performed again using a new screen 43 and a squeegee 45, and a silver paste 54 is applied. The screen 43 is formed with an opening provided with a mesh, and this opening corresponds to the connecting conductor portion 15. At this time, the screen 43 is arranged in alignment with the opening 32.

  Thereby, the silver paste 54 becomes the shape of the connecting conductor portion 15. However, the alignment between the screen 43 and the opening 32 (FIG. 3C) and the alignment between the screen 43 and the opening 32 (FIG. 3E) are performed independently. Therefore, depending on the misalignment between the screen 43 and the opening 32, as shown on the right side of FIG. 3 (f), the center of the silver paste 54 that becomes the connecting conductor 15 and the center of the opening 32 again. It may shift. In this case, the via wiring 14 formed after firing and the connection wiring portion 15 are not sufficiently overlapped, and the wiring resistance at this point increases.

  When the structure shown in FIG. 2 is formed by the conventional manufacturing method shown in FIG. 3, if the diameter of the connecting wiring portion or the via wiring is large, the misalignment between the screen and the opening or the silver paste Bleeding is not a big problem. However, when these diameters are small, the diameter of the connection wiring portion is 100 μm or less, and the diameter of the via wiring is 60 μm or less, the via wiring 14 and the connection wiring portion must be reduced unless misalignment and bleeding are reduced. 15 is insufficiently superposed.

  On the other hand, if a part of the manufacturing method (surface ceramic green sheet forming step) according to the embodiment of the present invention shown in FIG. 1 is used, the via wiring 14 and the connection wiring portion 15 are overlapped. A metal layer with sufficiently high accuracy can be obtained. This manufacturing method is particularly suitable when the ceramic green sheet layer 31 is thin.

  Further, in the conventional manufacturing method (FIG. 3), screen printing is performed twice, whereas in the manufacturing method (FIG. 1) according to the embodiment of the present invention, the same screen printing is performed once. Create a structure. Therefore, the manufacturing cost can be reduced.

  The structure shown in FIG. 2 is formed using the structure (surface ceramic green sheet) formed by the manufacturing method of FIG. 1 and having a silver paste (metal layer) to be a via wiring and a connecting conductor portion formed on the ceramic green sheet layer. The process for manufacturing the multilayer ceramic substrate will be described below. FIG. 4 is a process sectional view showing this manufacturing method.

  First, as shown in FIG. 4A, by the manufacturing method shown in FIG. 1, a silver paste 61 composed of a first metal layer serving as a connecting conductor portion and a second metal layer serving as a via wiring is formed as a first paste. A surface ceramic green sheet 63 formed on the ceramic green sheet 62 is manufactured (via opening forming step and surface ceramic green sheet forming step). Here, the silver paste 61 is preferably a silver paste in which the amount of silver powder in the paste is 88% by mass or more. For example, 88 to 94% by mass of Ag powder having an average particle size of less than 3.0 μm and Pd powder of 0.1 to 3% by mass are contained, and the total amount of the Ag powder and Pd powder is 88.1. A silver paste of ~ 95% by mass is used. If the silver concentration of the silver paste is inadequate, the via wiring conductor may be pulled and a recess may be formed in the connecting conductor after sintering. However, if the paste has a high silver concentration as described above, the filling property is good. This problem is reduced. In addition, this process is especially easily performed by being performed on the support film 40.

  On the other hand, as shown in FIG. 4B, a silver paste (third metal layer) 65 in the shape of the internal wiring 14 is formed on the second ceramic green sheet 64 that becomes the ceramic layer 11 in FIG. 2 after sintering. Are produced separately by screen printing (lower ceramic green sheet forming step). The second ceramic green sheet 64 is preferably made of the same material as the first ceramic green sheet 62. The same applies to the silver paste 65. In addition, this process is also easily performed by being performed on the support film 40.

  In the manufacturing method of the present invention, the surface ceramic green sheet 63 is preferably relatively thin, and is thinner than the lower ceramic green sheet 66, and it is preferable to combine them so that the total thickness of both is 60 μm or more. . In this way, there is an upper ceramic sheet laminate forming step in which the lower ceramic green sheet 66 is laminated on the thin surface ceramic green sheet 62 and pressure-bonded. At this time, there may be a crease or a void (air pocket) between the surface ceramic green sheet 63 and the lower ceramic green sheet 66, or a surface where the surface ceramic green sheet 63 is partially lifted to cause poor adhesion. As a countermeasure, if the pressure at the time of pressure bonding is increased, such a portion can be eliminated, but in that case, the thin surface ceramic green sheet 63 may be torn. Accordingly, the thickness of the surface ceramic green sheet (first ceramic green sheet) 63 is preferably 20 μm or more.

  Therefore, in the upper ceramic sheet laminate forming step shown in FIGS. 4C to 4J, a vacuum lamination pressure bonding method is performed in which at least the surface ceramic green sheet 63 and the lower ceramic green sheet 66 are pressure-bonded in a reduced pressure atmosphere. It is preferable to adopt. First, in FIG.4 (c), the adhesive sheet 41 for temporarily fixing the ceramic green sheet laminated | stacked on the vacuum press machine lower part 52 is installed. The pressure-sensitive adhesive sheet 41 can be easily peeled off from the laminate after completion of the lamination. Next, the surface ceramic green sheet 63 is placed on the adhesive sheet 41 with the silver paste layer 61 side down.

  Next, as shown in FIG. 4 (d), with the press machine upper part 51 sandwiching the adhesive sheet 41 and the surface ceramic green sheet 63 between the press machine lower part 52, both ends are supported by the elastic body 53. The space where the pressure-sensitive adhesive sheet 41 and the surface ceramic green sheet 63 are installed is depressurized by evacuation. Thereafter, pressure is applied to the surface ceramic green sheet 63 in the vertical direction in FIG. 4 as shown in FIG. In this step, for example, at a temperature of 30 to 90 ° C., a pressure of 0.98 to 9.8 MPa is applied and pressure bonding is performed for 5 to 100 seconds.

  Thereafter, as shown in FIG. 4 (f), the inside of the vacuum press is opened to the atmosphere, and the support film 40 is peeled from the surface ceramic green sheet 63.

  Through the above steps, the silver paste layer 61 (first metal layer) is embedded in the surface ceramic green sheet 63. Further, by reducing the pressure in the space in which the surface ceramic green sheet 63 is installed, even when the surface ceramic green sheet 63 is as thin as 80 μm or less, there is no gap between the adhesive sheet 41 and the adhesion can be improved. it can. That is, by reducing the pressure, the adhesion can be increased with a low pressure, so that even a thin surface ceramic green sheet does not break.

  Next, as shown in FIG. 4 (g), the lower ceramic green sheet 66 (second ceramic) with the support film 40 formed in FIG. 4 (b) is formed on the laminated surface ceramic green sheets 63. Align and install the green sheet).

  Next, as shown in FIG. 4 (h), the top ceramic green sheet 63 and the lower ceramic green sheet 66 are sandwiched between the press machine upper part 51 and the press machine lower part 52, and both ends are supported by the elastic bodies 53. In a state, the space where the ceramic green sheet is installed is decompressed by evacuation. Thereafter, as shown in FIG. 4I, pressure is applied to the surface ceramic green sheet 63 and the lower ceramic green sheet 66 in the vertical direction in FIG. 4 (upper ceramic sheet laminate forming step). In this step, for example, at a temperature of 30 to 90 ° C., a pressure of 0.98 to 9.8 MPa is applied and pressure bonding is performed for 5 to 100 seconds. As a result, an upper ceramic sheet laminate 67 composed of the surface ceramic green sheet 63 and the lower ceramic green sheet 66 is formed.

  Thereafter, as shown in FIG. 4 (j), the inside of the vacuum press is opened to the atmosphere, and the support film 40 is peeled from the upper ceramic sheet laminate 67.

  Through the above steps, the silver paste layer 61 (connecting conductor portion) is embedded in the upper ceramic sheet laminate 67 composed of the surface ceramic green sheet 63 and the lower ceramic green sheet 66. At this time, even if the surface ceramic green sheet 63 is thin, the lower ceramic green sheet 66 is thicker and has a total thickness of 60 μm or more. Further, by reducing the pressure in the space in which the ceramic green sheet is installed, even if the surface ceramic green sheet 63 is thin, the lower ceramic green sheet 66 is thicker than that, so that a total thickness of 60 μm or more is secured. It can accept the deformation of the green sheet, eliminate the gap between them, and improve the adhesion. That is, by reducing the pressure, the adhesion can be increased with a low pressure.

  Thereafter, a predetermined number of ceramic green sheets (lower ceramic sheets) lower than this are laminated and pressure-bonded in the same process, and finally the adhesive sheet 41 is peeled off. Alternatively, the lower ceramic sheet laminate 68 is formed by separately laminating and pressing (lower ceramic sheet forming step), and laminating and crimping in the same manner as described above, and finally as shown in FIG. A multilayer ceramic body 69 before sintering is formed. In FIG. 4 (k), the upper and lower sides are shown as being opposite to FIGS. 4 (a) to (j).

  Although simplified here, the lower ceramic sheet laminate 68 is appropriately provided with a metal layer serving as an internal wiring constituting the high frequency circuit, and in the same manner as above, a green sheet provided with a silver paste layer Are suitably laminated and pressure-bonded. In addition, in the lamination pressure bonding of the third and subsequent ceramic green sheets from the top, the pressure bonding can be performed without reducing the pressure. This is because the thickness of the second ceramic green sheet is sufficient, and the metal layers after the third layer are easily embedded in the ceramic green sheet layer, and the adhesion between the ceramic green sheet layers is increased.

  Thereafter, the multilayer ceramic body 69 described above is sintered (sintering step). This condition is, for example, about 900 ° C. for 2 hours in an air firing atmosphere. As a result, a multilayer ceramic substrate in which the upper ceramic sheet laminate and the lower ceramic sheet laminate are integrally sintered together is obtained.

  A metal plating layer is formed on the connection conductor portion of the multilayer ceramic substrate by electroless plating. However, when the connecting conductor portion is formed of a material having good solder wettability, the metal plating layer is not necessarily essential. In the above example, the structure near the surface of the multilayer ceramic substrate was mentioned. However, the structure inside the multilayer ceramic substrate and the structure on the opposite surface can be sintered together by the above-described sintering process. If so, it is optional.

  In the above manufacturing method, in particular, the thickness of the surface ceramic layer 12, that is, the surface ceramic green sheet 63 is preferably thin. By reducing the thickness, particularly when the silver paste 61 is screen-printed, the opening can be easily filled and bleeding can be reduced. Therefore, it is possible to increase the overlay accuracy between the connecting conductor 15 and the via wiring 14 in particular. In addition, it is particularly easy to form the connection conductor portion 15 in a form embedded in the surface ceramic layer 12. For this reason, it is preferable that the thickness of the surface ceramic layer 12 be 20 to 120 μm or less. However, if the thickness is too thin, it is difficult to form a structure in which the via wiring 14 and the connecting conductor portion 15 are laminated. Therefore, the thickness of the surface ceramic layer 12 is preferably 20 μm or more.

  In the above example, the first and second metal layers serving as the via wiring and the connecting conductor portion, and the third metal layer serving as the internal wiring were made of a silver paste having an amount of silver powder of 88% by mass or more. It is not limited to this. Any material that can be patterned by printing or the like and can be used as wiring after the ceramic layer is sintered can be used instead of the silver paste.

  According to the above manufacturing method, it is possible to obtain a multilayer ceramic substrate having high overlay accuracy between the via wiring and the connecting conductor portion and low electrical resistance of the wiring. Therefore, a plurality of connection wiring portions can be arranged on the outermost surface, and surface-mounted components such as semiconductor chips, chip capacitors, chip resistors can be mounted at high density, and high-performance electronic components can be formed. It becomes possible.

  The above multilayer ceramic substrate was manufactured by the above manufacturing method. The above-mentioned LTCC material is used as the ceramic green sheet material. A slurry is prepared by adding 15 parts by weight of polyvinyl butyral resin and 10.5 parts by weight of di-n-butyl phthalate to 100 parts by weight of the LTCC material. A sheet was formed. The thickness of the second ceramic green sheet serving as the internal ceramic layer was in the range of 20 to 190 μm, and the thickness of the first ceramic green sheet serving as the surface ceramic layer was in the range of 20 to 120 μm. An opening with a diameter of 60 μm was formed by laser processing. At this time, whether or not the opening could be formed was evaluated. Thereafter, a desired pattern and via wiring were formed by screen printing. Then, by using the above-mentioned vacuum lamination pressure bonding method, a multilayer ceramic substrate was manufactured by changing the thickness of the lamination of the surface ceramic green sheet and the lower ceramic green sheet. At this time, the pressure reduction condition of the atmosphere in the vacuum lamination pressure bonding method was set to 80 kPa pressure reduction from atmospheric pressure, and a pressure of 6.1 MPa was applied to the laminated body at a temperature of 70 ° C. for 60 seconds. Then, the presence or absence of tearing or peeling in the ceramic green sheet was confirmed, and whether or not the upper ceramic sheet laminate was formed was evaluated. It was. Thereafter, a plurality of second ceramic green sheets were laminated, a lower ceramic sheet laminate was added to form a multilayer ceramic body, and sintered under the conditions described above. And it evaluated whether the conductor part for a connection after sintering became a regulation dimension. In this evaluation, a case where the design value deviates by ± 15 μm or more is indicated as x.

The above evaluation results are shown in Table 1.

  In the via opening forming step, in the embodiment of the present invention, a via having an opening hole diameter of φ60 μm can be formed by laser, and a via having a diameter of φ60 μm or less can be similarly formed. In contrast, in Comparative Example 5 in which the thickness of the surface ceramic green sheet was 148 μm, a φ60 μm via by a laser could not be formed.

In the upper ceramic sheet laminate forming step, the thickness of the surface ceramic green sheet, which is an example of the present invention, is 20 to 120 μm, the thickness of the second ceramic green sheet is 20 μm or more, and the surface ceramic green sheet and the second ceramic green sheet In the range where the total thickness of the ceramic green sheets exceeded 56 μm, there was no tearing or peeling, and a multilayer ceramic substrate could be produced through the subsequent sintering process. On the other hand, in Comparative Example 1 in which the total thickness was small and in Comparative Example 6 in which the surface ceramic green sheet was thin, the sheet was torn and could not be laminated when the support film was peeled off after pressure bonding. Further, in Comparative Examples 2 and 3 having a small total thickness, good adhesion between the adhesive sheet and the surface ceramic green sheet or between the surface ceramic green sheet and the second ceramic green sheet is obtained when the support film is peeled after pressure bonding. A possible air pocket occurred. This is considered to be because the total thickness of the surface layer and the second green sheet is not sufficient, and the step of the electrode pattern could not be absorbed at the time of pressure bonding.

  Next, the overlay accuracy is shown in a photograph of the vicinity of the connecting conductor portion on the surface of the multilayer ceramic substrate after firing. FIG. 5A shows the shape in Comparative Example 4 in which the via wiring and the connecting conductor portion are formed by printing twice, and corresponds to the case of FIG. Here, the dotted line is the shape of the opening corresponding to the via wiring, the broken line is the shape of the silver paste 52 (first silver paste) in FIGS. 3D and 3F, and the solid line is the silver paste 53 in FIG. The shape of (second silver paste). As described above, it can be confirmed that the misalignment is large.

  On the other hand, a photograph of the vicinity of the connecting conductor portion after firing in Example 5 which is an example of the present invention is shown in FIG. Although both the connecting conductor portion and the via wiring are smaller than the example of FIG. 5A, it was confirmed that these could be formed with sufficient overlay accuracy.

It is process sectional drawing which shows the via opening formation process and the surface layer ceramic green sheet formation process in the manufacturing method of the multilayer ceramic substrate which concerns on embodiment of this invention. It is a section perspective view showing the structure of the multilayer ceramic substrate manufactured by the manufacturing method of the multilayer ceramic substrate concerning an embodiment of the invention. It is process sectional drawing which shows the manufacturing method of the multilayer ceramic substrate which concerns on embodiment of this invention. It is process sectional drawing which shows an example of the manufacturing method of the conventional multilayer ceramic substrate. It is a shape photograph near the via opening in the comparative example (a) and the example (b). It is sectional drawing which shows the structure of a common multilayer ceramic substrate.

Explanation of symbols

10, 90 Multilayer ceramic substrate 11, 91a, 91b Ceramic layer 12 Surface ceramic layer 13, 92 Internal wiring 14, 94 Via wiring 15, 93 Connecting conductor portion 21, 31 Ceramic green sheet 22, 32 Opening 40 Support film 41 Adhesive Sheet 42, 43 Screen 45 Squeegee 52, 53, 54 Silver paste (metal layer)
61 Silver paste (first metal layer)
62 First ceramic green sheet layer 63 Surface ceramic green sheet 64 Second ceramic green sheet layer 65 Silver paste (second metal layer)
66 Lower ceramic green sheet 67 Upper ceramic sheet laminate 68 Lower ceramic sheet laminate 69 Multilayer ceramic body

Claims (6)

A method of manufacturing a multi-layer ceramic substrate,
The first ceramic green sheet in a range of thickness of 20~120μm that after firing the ceramic layer of the outermost surface to form a via opening forming step of forming a following opening diameter 6 0 .mu.m,
A first metal layer formed on the first ceramic green sheet so as to have a diameter of 100 μm or less that becomes a conductor part for connection after firing and wider than the opening as viewed in the stacking direction of the multilayer ceramic substrate. And a surface ceramic green sheet forming step of forming a second metal layer filling the via opening by one screen printing,
A second ceramic green sheet thicker than the first ceramic green sheet, which becomes a ceramic layer adjacent to the outermost ceramic layer after firing, is formed, and becomes an internal wiring after firing on the second ceramic green sheet. Forming a lower ceramic green sheet to form a third metal layer;
Upper ceramic sheet forming the front Symbol superficial ceramic green sheet and is crimped by laminating the lower layer ceramic green sheets, upper ceramic sheet laminate in which the first to the total thickness of which is connected to the third metal layer exceeds 56μm A laminate forming step;
Separately from the upper ceramic sheet laminate, a lower ceramic forming a lower ceramic sheet that becomes a ceramic layer adjacent to the outermost ceramic layer and an adjacent ceramic layer on the surface opposite to the outermost ceramic layer. Sheet forming step;
The upper ceramic sheet laminate and the lower ceramic sheet are pressure-bonded, and a sintering step of firing the laminated unsintered multilayer ceramic body,
A method for producing a multilayer ceramic substrate, comprising: 2. The multilayer ceramic substrate according to claim 1, wherein the first to third metal layers are electrically independent from a metal layer serving as an internal wiring in the lower ceramic sheet . In the upper ceramic sheet laminate forming step,
The multilayer according to claim 1 or 2, wherein at least the surface ceramic green sheet is pressure-bonded and the lower ceramic green sheet is laminated and pressure-bonded on the surface ceramic green sheet in a reduced pressure atmosphere. A method for manufacturing a ceramic substrate.   A multilayer ceramic substrate manufactured by the method for manufacturing a multilayer ceramic substrate according to any one of claims 1 to 3.   5. The multilayer ceramic substrate according to claim 4, wherein a plurality of electrically independent connection conductor portions are arranged on an outermost surface, and a minimum interval between the connection conductor portions is 200 μm or less.   An electronic component comprising a multilayer ceramic substrate according to claim 5 and a surface-mounted component including at least one of a semiconductor chip, a chip capacitor, and a chip resistor.