JP2010027637A - Conductor paste, and method of manufacturing ceramic substrate using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conductor paste and a method of manufacturing a ceramic substrate using the paste reducing a void in a through-hole in the burned ceramic substrate having the through-hole. <P>SOLUTION: In the method of manufacturing the ceramic substrate, carrying out burning treatment by filling the through-hole in the burned ceramic substrate having the through-hole with the conductor paste, the conductor paste is used, containing: a conductive metal powder; an organic component; and a solvent, wherein metal coagulation products are each formed by joining together some of particles of conductive metal powder with the organic component and the average grain diameter of the metal coagulation products is in a range of 20-52 μm. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a conductor paste and a method for manufacturing a ceramic substrate using the conductor paste. In particular, the present invention relates to a method for manufacturing a ceramic substrate having no voids in a through hole filled with a conductive paste.

  FIG. 5 shows a conventional method for producing a conductor paste. The first step 5 in the figure is a step of kneading the metal powder 1, the organic component 2 and the solvent 3 to obtain a kneaded conductor paste 4. In the next second step 25, the viscosity of the kneaded conductor paste 4 obtained in the first step 5 is adjusted with the solvent 3 to obtain the conductor paste 30.

  FIG. 6 shows a conventional method for manufacturing a ceramic substrate. The first step 18 in the figure is a step of preparing a fired ceramic substrate 17 with through holes provided with through holes 16 in the fired ceramic substrate 15. The second step 33 is a step of filling the through-hole 16 with the conductor paste 30 obtained in FIG. 5 and firing it at a temperature at which the conductor paste 30 can be fired to obtain a filled ceramic substrate 32. A printing method is generally used as a method of filling the conductor paste 30. In the next third step 35, the desired surface layer conductors 21 are formed at both ends of the through holes 16 on the surface of the filled ceramic substrate 32, and then fired at a temperature at which the surface layer conductors 21 can be fired. In this way, a ceramic substrate 34 with a surface layer conductor is obtained. A printing method is generally used as a method for forming the surface layer conductor 21. In the next fourth step 37, the plated layer 24 is formed on the surface of the surface conductor 21 to obtain a completed ceramic substrate 36.

  In the ceramic substrate 36 prepared as described above, voids are generated in the through holes 16. The mechanism by which this void occurs will be described with reference to FIG. FIG. 7 schematically shows the cross section in the through hole 16 and the state of the filled conductor paste 30 in the first to fourth steps in the method of manufacturing the ceramic substrate described in FIG.

  The second step 33 in the figure shows a state in which the metal powder inside the conductor paste 30 filled in the through holes 16 by the printing method is evenly dispersed. At this time, no void is generated. A second 'step 39 in the drawing shows a state where the conductor paste 30 is dried. The drying of the conductive paste 30 occurs because all the solvent in the inside has evaporated. Therefore, the metal powder 1 moves toward the center as shown by the arrow at the same time as the volume of the conductor paste 30 decreases. For this reason, a large void 38 is generated on the surface of the conductor paste 30. The shape of the void 38 generated here is maintained even when the conductive paste 30 is fired. Further, even if the surface layer conductor 21 is formed at both ends of the conductor paste 30 in the through hole 16 in the next third step, the void 38 cannot be completely filled.

  When such voids occur, the following problems occur. That is, in the fourth step, which is a subsequent step, an electroless Ni / Au plating layer 24 is formed on the surface of the surface conductor 21 in order to improve solder erosion resistance and solder wettability. When the Ni plating solution enters and remains in 38, a state where no Au plating is formed (no plating) occurs. In such a non-plated portion, since Ni is exposed on the surface layer portion, corrosion occurs and deteriorates the solder wettability. In addition, the plating solution, cleaning solution, etc. accumulate in the void 32, so that the plating solution, the cleaning solution, etc. are vaporized during the subsequent reflow process such as component mounting or solder ball mounting. ). Further, when the void 38 is generated, the connection strength between the conductor paste 30 in the through hole 16 and the surface layer conductor 21 is lowered, so that the connection reliability between the conductor paste 30 in the through hole 16 and the surface layer conductor 21 is lowered.

Conventionally, the technique shown in FIG. 8 is known as a method for preventing the void 38 in the through hole 16. This prevents voids by adjusting the particle size of the conductor paste. It is disclosed to use a conductor paste composed of a first metal powder 34 having an average particle diameter of 2 μm or less and a second metal powder 35 having an average particle diameter of 5 to 10 μm (for example, see Patent Document 1). .).
JP-A-8-97528

  However, the conventional configuration is effective when the conductor paste and the green sheet are fired at the same time. However, when applied to a fired ceramic substrate, there is a problem that void generation cannot be completely suppressed. It was.

  An object of the present invention is to solve the above-described conventional problems, and to provide a conductor paste for suppressing voids in a through-hole in a fired ceramic substrate with a through-hole and a method for manufacturing a ceramic substrate using the same. To do.

  In order to solve the conventional problems, in the conductive paste containing the conductive metal powder of the present invention, an organic component and a solvent, an average particle size of 20 to 52 μm in which the metal powder is bonded with the organic component. The metal agglomerates are included.

  Moreover, this invention is a manufacturing method of the ceramic substrate which fills the said through-hole of the baked ceramic board | substrate provided with the through-hole, and performs a baking process, The said conductive paste is a conductor paste of Claim 1 to 2 It is characterized by using.

  According to the conductor paste of the present invention and the method of manufacturing a ceramic substrate using the same, by effectively suppressing voids generated when the conductor paste is filled into the through holes 16 of the fired ceramic substrate 17 with through holes, A ceramic substrate that suppresses non-plating that occurs in the plating 24 on the surface of the surface conductor 21 and solder voids that occur when components are mounted by soldering, and that has high connection reliability between the conductor paste in the through hole 16 and the surface conductor 21. Can be manufactured.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings and tables. In addition, about the same thing as the past, description is simplified using the same code | symbol.

(Embodiment 1)
A method for producing the conductor paste of the present invention is shown in FIG. The first step 5 in the figure is a step of preparing the kneaded conductor paste 4 by mixing the metal powder 1, the organic component 2 and the solvent 3. As the metal powder 1, at least one metal powder from Ag, Pt, Pd, and Au is used.

  In this example, Ag having an average particle diameter of 8 μm was used as a main component, and Pd was further added by several percent. Although the organic component 2 used ethyl cellulose, it is not particularly limited to this. The solvent 3 is terpineol, but is not limited to this, and any material that can dissolve the organic component 2 may be used. The kneaded conductor paste 4 was produced by kneading with three rolls in order to sufficiently disperse the metal powder 1, the organic component 2 and the solvent 3.

  The next second step 10 is a step of producing an aggregate 9 from the kneaded conductor paste 4. In this step, the kneaded conductor paste 4 produced in the first step 5 is dried 6 and then pulverized 7 to be powdered. Thereafter, the size is adjusted 8 to obtain an aggregate 9. In this example, drying 6 was performed at 150 ° C. for 1 hour, and pulverization 7 was performed in a mortar. Moreover, the molecular sieve was used for the sizing 8 of this sample. Aggregates 9 (20 μm or less, 20 to 52 μm and 52 to 90 μm) having three types of particle diameters were prepared by three types of molecular sieves having openings of 20 μm, 52 μm, and 90 μm.

  In the next third step 12, the agglomerate 9 obtained in the second step 10 and the kneaded conductor paste 4 obtained in the first step 5 are mixed to obtain the agglomerate-added conductor paste 11. . Since the particle size and added amount of the aggregate 9 at this time are important, details will be described later.

In the final fourth step 14, the solvent 3 is added to the aggregate-added conductor paste 11 obtained in the third step 12, and the viscosity is adjusted to obtain a conductor paste 13 for use in a ceramic substrate. This is because the viscosity is high because the solid content of the aggregated conductor paste 11 is high. Generally, the viscosity of the conductor paste for use in the printing method is 500P
A · s or less is desirable.

  FIG. 2 shows a method for manufacturing a ceramic substrate using the conductive paste 13 produced in the fourth step 14. The first step 18 is a step of providing a through-hole 16 in the fired ceramic substrate 15 to obtain a fired ceramic substrate 17 with a through-hole. Specifically, examples of the material of the fired ceramic substrate 15 include alumina, aluminum nitride, and glass ceramic. The substrate size of the fired ceramic substrate 15 was a size of 4 inches on a side, which is generally called a 4 inch size. The substrate thickness in this example was 0.8 mm. The size of the through holes 16 was 0.3 mmφ, the pitch between the through holes 16 was 1.27 mm, and the through holes 16 were produced by laser processing.

  The second step 20 is a step of filling the through holes 16 of the fired ceramic substrate 17 with through holes with the conductor paste 13 and firing at the firing temperature of the conductor paste 13 to obtain a filled ceramic substrate 19. Filling the through holes 16 with the conductor paste 13 was performed by a printing method. The plate making used in the printing method used a 0.1 mmt metal mask. The firing temperature of the conductor paste 13 was 850 ° C.

  The third step 23 is a step in which the surface layer conductor 21 is formed on both surfaces of the through hole 16 of the filled ceramic substrate 19 and then fired at the firing temperature of the surface layer conductor 21 to obtain the ceramic substrate 22 with the surface layer conductor. The surface conductor 21 was formed by a printing method using a paste mainly composed of Ag. The surface conductor 21 was fired at 850 ° C.

  The fourth step 26 is a step of forming the plated layer 24 on the surface of the surface layer conductor 21 to obtain the ceramic substrate 25. The plating layer 24 was formed by electroless Ni / Au plating.

  As described in the step of obtaining the aggregate-added conductor paste 11 of FIG. 1, the particle size and the amount of the aggregate 9 are greatly involved in the generation of voids in the through holes 16 filled with the conductor paste 13. Details will be described below.

  The aggregate 9 (20 μm or less, 20 to 52 μm and 52 to 90 μm) having three kinds of particle diameters obtained in the second step 10 of FIG. 1 is added to the kneaded conductor paste 4 obtained in the first step 5. In addition, a conductor paste 13 was prepared in which the addition amount at that time was changed from 0 to 40 wt%. Using these conductor pastes 13, a filled ceramic substrate 19 was manufactured by the manufacturing method of FIG. The relationship between the generation of voids in the through holes 16 of the filled ceramic substrate 19 and the viscosity during printing was evaluated as follows.

  To confirm the presence or absence of voids, after firing the conductor paste 13, first the surface state was visually confirmed and the internal state was confirmed with an X-ray inspection apparatus. A substrate on which the surface voids 38 and the internal voids 29 were not confirmed by visual inspection and X-ray inspection was marked with ◯. The board | substrate with which the surface void 38 was confirmed visually was set as x. Although the surface void 38 was not visually confirmed, the substrate on which the internal void 29 was confirmed by the X-ray inspection was designated as xx. Moreover, the board | substrate which cannot be filled with a conductor paste inside a through-hole by printing was set to xxx. The addition amount of 0 wt% means that the aggregate 9 is not added to the kneaded conductor paste 4, and means the conventionally kneaded conductor paste 4.

  When the particle diameter of the aggregate 9 is 20 μm or less, 20 to 52 μm, and 52 to 90 μm, the evaluation results are shown in Table 1, Table 2, and Table 3 when the addition amount is changed from 0 to 40 wt%.

From the results shown in Table 1, when the average particle size of the aggregate 9 was 20 μm or less, the generation of surface voids 38 was observed or the conductive paste could not be printed regardless of the addition amount. That is, in the range where the viscosity of the conductor paste 13 is 200 to 500 Pa · s, the surface void 38 is generated,
When the viscosity of the conductor paste 13 was 600 Pa · s, printing was not possible because the viscosity was too high.

  From the results in Table 2, when the average particle size of the aggregate 9 was in the range of 20 μm to 52 μm, printing could not be performed in the same manner as in Table 1 when the viscosity of the conductor paste 13 was 600 Pa · s regardless of the amount added. Further, when the viscosity of the conductor paste 13 was in the range of 400 to 500 Pa · s, when the addition amount was 10 to 30 wt%, surface voids 38 were not generated, which was good. When the viscosity of the conductor paste 13 was 300 Pa · s, the addition amount was in the range of 20 to 30 wt%, and the surface voids 38 were not generated, which was good. In other ranges, generation of surface voids 38 was observed.

  From the results in Table 3, when the average particle size of the aggregate 9 is in the range of 52 μm to 90 μm, the generation of surface voids 38 was observed or the conductor paste could not be printed regardless of the addition amount. That is, when the viscosity of the conductor paste 13 is in the range of 200 to 500 Pa · s, the surface void 38 is generated when the addition amount is up to 5 wt%, and the internal void 29 is observed when the addition amount is more than that. When the viscosity of the conductor paste 13 was 600 Pa · s, printing could not be performed as in Table 1.

  A mechanism capable of suppressing the generation of voids according to the present invention will be described with reference to FIGS. FIG. 3 is a schematic cross-sectional view of the through hole in the second process 20 to the fourth process 26 in the manufacturing process described in FIG.

  The second step 20 is a step of filling the through hole 16 with the conductive paste 13 by a printing method in the through hole 16. The conductive paste 13 includes the aggregate 9 created in the second step of FIG. The agglomerate 9 is dried by heat treatment in the second step 10 of FIG. 1 to gel the organic component 2 inside, and then the metal powders 1 form a nodule to solidify. The agglomerate 9 in the form of a metal powder nodule does not re-dissolve the cured organic component 2 even if the conductor paste 13 is prepared by adjusting the viscosity of the agglomerated conductor paste 11 with the solvent 3. Remain inside.

  The next second step 28 shows a state after the conductor paste 13 is dried. When the conductive paste 13 is dried, the solvent is volatilized and the volume of the conductive paste 13 is reduced. At the same time, the aggregate 9 and the metal powder 1 try to move toward the center as shown by arrows. However, since the aggregate 9 is a large lump, the surface void 38 is not generated on the surface of the conductor paste 13 in the through hole 16 due to the so-called bridging effect in which the movement in the arrow direction is inhibited.

  The third step 23 is a step of forming the surface layer conductor 21 on the surface of the through hole 16. However, since the surface void 38 and the internal void 29 are not generated, a good connection is ensured. Further, in the fourth step 26, the plating layer 24 is formed on the surface of the surface conductor 21 by electroless Ni / Au plating. However, since the surface void 38 and the internal void 29 are not generated, the surface void is not generated. 38, the state in which the Au plating is not formed (no plating) does not occur when the Ni plating solution enters and remains in the internal void 29. Since no plating occurs, solder wettability is not deteriorated, and plating liquid, cleaning liquid, etc. are accumulated in the surface void 38 and the internal void 29, so that reflow for component mounting and solder ball mounting in a later process is performed. -Occasionally, there is no occurrence of defects (solder voids) in which the plating solution, the cleaning solution, etc. are vaporized and voids are formed inside the solder.

  However, an internal void 29 is generated inside the through hole 16 depending on the amount of the aggregate 9 added to the conductor paste 13 and the particle size. As shown in Table 2, when the particle size of the aggregate 9 added to the conductor paste 13 was 20 to 52 μm, the internal void 29 was generated when the added amount of the aggregate 9 was 40 wt%. Further, as shown in Table 3, when the particle size of the aggregate 9 is 52 to 90 μm, the internal void 29 is generated when the added amount of the aggregate 9 is 10 wt% or more. This mechanism will be described with reference to FIG.

  As shown in the second step 20 in the figure, the proportion of the aggregate 9 in the through-hole increases, so that the proportion of the metal powder 1 filling the space between the aggregates 9 decreases, and the metal powder 1 A sparse part 27 occurs. In this state, when the solvent 3 is volatilized by drying in the next second 'step 28, an internal void 29 is generated in the portion 27 where the metal powder 1 is sparse. The internal void 29 once generated remains with its shape maintained in the third step 23 for forming the surface conductor 21 and the fourth step 26 for forming the plating layer 24.

  As shown in Tables 1 to 3, the conditions under which the surface voids 38 and the internal voids 29 are not generated change depending on the addition amount and the particle size of the aggregate 9 because the above mechanism works. That is, when the addition amount of the aggregate 9 is small, the bridging effect is not observed, and the surface void 38 is generated. When the addition amount of the aggregate 9 is large, the ratio of the metal powder 1 filling between the aggregates 9 is reduced. An internal void 29 of the through hole is generated. Therefore, the aggregate 9 addition amount has an appropriate range. In the present invention, the appropriate amount of the agglomerate 9 is in the range of 10 to 30 wt% of the entire conductor paste.

  Moreover, when the particle size of the aggregate 9 is small, the surface void 38 is generated without the bridging effect. On the other hand, when the particle size of the aggregate 9 is large, the ratio of the metal powder 1 filling the space between the aggregates 9 is reduced, and the internal voids 29 of the through holes are generated. Therefore, the particle size of the aggregate 9 must be in an appropriate range. In the present invention, the appropriate average particle size of the aggregate 9 was 20 to 52 μm.

  Next, the influence of the conductor paste of the present invention on the resistance value of the conductor in the through hole 16 will be described with reference to Table 4. In Table 4, the range in which the added amount of the aggregate 9 of the conductor paste 13 is 0 to 40 wt% and the viscosity of the conductor paste 13 is 200 to 500 Pa · s is the range in which the through holes 11 can be printed. In the sample, when the addition amount of the aggregate 9 shown in Table 2 is 0 to 40 wt%, the void state of the conductor paste 13 in the through hole 16 of the filled ceramic substrate 19 and the aggregate 9 of the conductor paste 13 are shown. This is the same as the evaluation of the relationship between the addition amount of 0 to 40 wt% and the viscosity during printing. The resistance value of the conductor in the through hole 16 was measured by the 4-terminal method using a low resistance meter on the ceramic substrate 22 with a surface layer conductor prepared in the third step 23. The measurement was performed regardless of the presence or absence of the surface void 38 and the internal void 29 in the through hole 16.

  As a result of the measurement, the addition amount of the aggregate 9 without generation of the surface void 38 and the internal void 29 is 10 to 15 wt%, the viscosity of the conductor paste 13 is 400 to 500 Pa · s, and the addition amount of the aggregate 9 is 20 to 30 wt%. %, The resistance value of the conductor in the through hole 16 is 0.6 to 0.8 mΩ in the range of 300 to 500 Pa · s of the viscosity of the conductor paste 13, whereas the surface void 38 and the internal void 29 are generated. In other ranges, the resistance value of the conductor in the through hole 16 is 0.6 to 0.8 mΩ. In particular, even in the case of 0 wt% in which no agglomerate 9 is added, the resistance value of the conductor in the through hole 16 is 0.6 to 0.8 mΩ, which is equivalent, so the agglomerate 9 is added to the kneaded conductor paste 4 It can be seen that there is no influence on the resistance value of the conductor in the through hole 16 by doing so.

  The conductor paste and the method for producing a ceramic substrate using the conductor paste according to the present invention are useful for producing a ceramic substrate having no voids in the through holes filled with the conductor paste. The ceramic substrate obtained by the present invention is particularly useful for reducing plating defects and solder voids generated by voids.

Manufacturing process diagram of conductor paste shown in Embodiment 1 of the present invention Manufacturing process diagram of ceramic substrate shown in Embodiment 1 of the present invention Detailed view of the manufacturing process of the ceramic substrate shown in Embodiment 1 of the present invention Detailed view of the manufacturing process of the ceramic substrate shown in Embodiment 1 of the present invention Manufacturing process diagram of conventional conductor paste Manufacturing process diagram of conventional ceramic substrate Detailed view of conventional ceramic substrate manufacturing process Sectional drawing of the conductor paste of patent document 1

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Metal powder 2 Organic component 3 Solvent 4 Kneaded conductor paste 9 Aggregate 11 Aggregate-added conductor paste 13 Conductor paste 15 Ceramic substrate 16 Through-hole 21 Surface layer conductor 24 Plating 29 Internal void 38 Surface void

Claims (3)

In a conductive paste containing conductive metal powder and organic components and solvent,
A conductor paste comprising metal aggregates having an average particle size of 20 to 52 μm, wherein the metal powders are bonded together by the organic component. 2. The conductor paste according to claim 1, wherein the metal aggregate is in a range of 10 to 30 wt% of the entire conductor paste. In the method for manufacturing a ceramic substrate, a conductive paste is filled in the through-hole of the fired ceramic substrate having a through-hole and a firing process is performed.
The said conductive paste is a manufacturing method of the ceramic substrate using the conductive paste of Claim 1 or 2.

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