JP2005071825A - Conductive paste, wiring board, and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide conductive paste having low resistance and capable of achieving high connection reliability, and to provide a wiring board using it. <P>SOLUTION: This conductive paste contains: low-melting-point metal A particles 5a containing at least tin and having melting points below 230°C; low-melting-point metal B particles 5b containing at least tin and having melting points lower than those of the particles 5a; low-resistance metal particles 5c having melting points over 230°C; and a resin. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a conductive paste capable of reducing via resistance and improving connection reliability in a wiring board including an insulating substrate containing at least a resin and a via filled with a conductive paste.

  In recent years, a so-called printed circuit board in which a wiring layer is formed on the surface of an insulating substrate containing a thermosetting resin such as an epoxy resin or a phenol resin is applied to a package or the like on which an electric element such as a wiring board or a semiconductor element is mounted. As a method of forming a wiring layer in such a printed circuit board, a copper foil is bonded to the surface of an insulating substrate and then etched to form a wiring circuit, or a copper foil formed on the wiring circuit is insulated. A method of transferring to a substrate, a method of forming a circuit on the surface of an insulating substrate by a metal plating method, and the like are used. In addition, with the increase in the number of wiring layers, wiring layers between different layers are also electrically connected by vias. This via is generally formed by opening a via hole at a predetermined location on an insulating substrate of a wiring board with a drill or the like and then plating the inner wall in the via hole.

  However, in the method as described above, the chemicals used for the plating treatment are expensive, and there are difficulties in productivity and economy such as a long treatment time. In addition, in the case of vias formed by plating the inner wall, in the case of a multilayer structure, it is necessary to perform resist formation, plating, and peeling polishing for each layer in order to form between arbitrary layers. Sexual deterioration. There is a problem as a conduction mechanism that conducts electricity between arbitrary layers of a multilayer structure in order to improve the density of the wiring layer.

  To solve this problem, a conductive paste in which a metal powder such as silver, copper, or solder is mixed with a thermosetting resin or activator is applied to the surface of an insulating substrate or filled into a via hole. There is a method of stacking and multilayering (see Patent Documents 1 and 2).

  The conductive paste for vias is generally composed of a mixture of metal powder and thermosetting resin. However, in the conductive paste of Patent Document 1, the amount of the thermosetting resin component in the conductive paste is 22. There is a problem that the electrical conductivity of the via is low because the contact property between the metal powders of the via is not sufficient and the contact property is low.

  Further, in the conductive paste of Patent Document 2, since the amount of the thermosetting resin component is reduced, the initial via resistance is low, but the bonding force between the metal particles of the via is not sufficient, the thermal cycle, etc. As a result, the resistance of the via changes.

In order to solve this problem, it has also been proposed that the conductive paste contains a low melting point solder such as Pb-Sn together with a powder such as Cu, and the Cu particles are connected to each other by solder to increase the conductivity of the via. (See Patent Document 3).
JP-A-8-315637 Japanese Patent No. 2603053 JP2002-109956

  However, the reliability is low when the low-melting-point solder wettability to the Cu particle surface that is the core of the via structure in the wiring board is insufficient, or the low-temperature soldering that connects the Cu particles is insufficient. There is a problem that necking is cut off due to heat cycle or the like, the electrical resistance is increased, and in the worst case, disconnection is caused.

  An object of the present invention is to solve such problems and to provide a conductive paste that realizes high connection reliability with low resistance and a wiring board using the same.

  The conductive paste of the present invention contains at least tin and low melting point metal A particles having a melting point of 230 ° C. or lower, low melting point metal B particles containing tin and having a melting point lower than that of the low melting point metal A particles, Resistive metal particles and a resin are contained.

  The conductive paste of the present invention preferably contains at least one kind of low-resistance metal particles selected from Cu, Ag, and Au.

  Moreover, as for the electrically conductive paste of this invention, it is desirable for the average particle diameter of the low melting metal A particle to be larger than the average particle diameter of the low melting metal B particle.

  In the conductive paste of the present invention, the average particle size of the low melting point metal B particles is desirably 80% or less of the average particle size of the low melting point metal A particles.

  Moreover, as for the electrically conductive paste of this invention, it is desirable that resin is a thermosetting resin.

  Moreover, as for the electrically conductive paste of this invention, it is desirable for resin to contain triallyl isocyanurate.

  In the conductive paste of the present invention, when the content of the low melting point metal A particles is M1, the content of the low melting point metal B particles is M2, and the content of the low resistance metal particles is M3, (M2) / ( It is desirable that the relationship of (M1 + M2) is 30 to 80% and (M3) / (M1 + M2 + M3) is 40 to 60%.

  Moreover, as for the electrically conductive paste of this invention, it is desirable for the difference of melting | fusing point of the low melting metal A particle and the low melting metal B particle to be 10 degreeC or more.

  In the conductive paste of the present invention, it is desirable that the low melting point metal B particles contain Bi.

  The conductive paste of the present invention has a total content of low melting point metal A particles, low melting point metal B particles, and low resistance metal particles of 85 to 95% by mass, and a resin content of 5 to 15% by mass. It is desirable.

  By using such a conductive paste for, for example, a wiring board or the like, a highly reliable and low resistance via can be formed.

  The wiring board of the present invention is a wiring board in which an insulating substrate containing at least a resin and a wiring layer are laminated, and a via is provided in the insulating substrate to electrically connect the wiring layers. The via is formed by filling the conductive paste described above.

  By producing a wiring board using the conductive paste described above, the resistance of the via can be reduced, the connection reliability of the via and the electrical connection structure can be improved, and a wiring having a low electrical resistance can be provided. In addition, a highly reliable wiring board can be provided.

  The method for manufacturing a wiring board according to the present invention includes a step of forming a via hole in an uncured or semi-cured insulating substrate containing at least a thermosetting resin, and after filling the via hole with the conductive paste. A step of depositing and forming a conductor layer on the surface of the insulating substrate including the via hole forming portion, and laminating and integrating the insulating substrates, and then heating the laminate to a curing temperature of the thermosetting resin. And a step of collectively curing.

  In such a method of manufacturing a wiring board, it is possible to reduce the change in the material physical properties of the wiring board inner layer part and the outer layer part that are generated at the time of sequential curing by batch curing, and to shorten the process time related to curing, A wiring board with low resistance and excellent connection reliability can be provided.

  The conductive paste of the present invention contains at least tin and low melting point metal A particles having a melting point of 230 ° C. or lower, low melting point metal B particles containing tin and having a melting point lower than that of the low melting point metal A particles, Resistive metal particles and a resin are contained.

  By using two or more low melting point metals having different melting points in this way, a thicker and stronger connection structure between conductive particles is realized compared to the case of using one kind of low melting point metal, and a low resistance via is provided. It is possible to provide a conductive paste that can realize the above.

  The conductive paste of the present invention preferably contains at least one kind of low-resistance metal particles selected from Cu, Ag, and Au. These metals or alloys have low resistance, and by including them in a conductive paste, a low resistance via and electrical connection structure can be provided.

  Moreover, as for the electrically conductive paste of this invention, it is desirable for the average particle diameter of the low melting metal A particle to be larger than the average particle diameter of the low melting metal B particle.

  Thus, the low resistance metal particles are connected to each other by making the average particle size of the low melting point metal A particles that melt at a higher temperature than the low melting point metal B particles larger than the average particle size of the low melting point metal B particles. The connection structure formed by the melting point metal A particles can be thick and strong, and the low melting point metal B can wet a wider range of low resistance metal particles and low melting point metal A particles at a lower temperature. become. Moreover, since the number of the low melting point metal B particles is increased, the effect is further remarkable.

  In the conductive paste of the present invention, the average particle size of the low melting point metal B particles is desirably 80% or less of the average particle size of the low melting point metal A particles.

  Thus, by setting the average particle size of the low melting point metal B particles to 80% or less of the average particle size of the low melting point metal A particles, the difference in the average particle size between the low melting point metal B particles and the low melting point metal A particles is increased. The above-described effect caused by the above becomes more prominent, and a via or an electrical connection structure having excellent connection reliability can be manufactured.

  Moreover, as for the electrically conductive paste of this invention, it is desirable that resin is a thermosetting resin.

  In such a conductive paste, as the temperature increases and the electrical conductive path is formed by the metal, the thermosetting resin also hardens, the rigidity increases, and the via and the electrical connection structure are not easily deformed. Deformation of vias and electrical connection structures due to application of thermal stress and external force can be suppressed, and connection reliability of vias and electrical connection structures can be improved.

  Moreover, as for the electrically conductive paste of this invention, it is desirable for resin to contain triallyl isocyanurate.

  Since triallyl isocyanurate has a low softening point, it is possible to adjust the conductive paste to a low viscosity to increase the fillability of via holes by screen printing and the like, and to eliminate the occurrence of voids. Secure contact.

  In the conductive paste of the present invention, when the content of the low melting point metal A particles is M1, the content of the low melting point metal B particles is M2, and the content of the low resistance metal particles is M3, (M2) / ( It is desirable that the relationship of (M1 + M2) is 30 to 80% and (M3) / (M1 + M2 + M3) is 40 to 60%.

  As described above, by setting (M2) / (M1 + M2) to 30% or more, the coating area of the low-melting-point metal A particles on the low-resistance metal particles can be expanded, and by setting it to 80% or less, low resistance is achieved. Since the connection structure between the metal particles can be thick and formed firmly, the resistance of the via and the electrical connection structure can be lowered, and the connection reliability of the via and the electrical connection structure can be improved.

  Further, by setting (M3) / (M1 + M2 + M3) to 40% or more, low resistance metal particles having a low resistance increase, so that the electrical resistance of the via can be lowered, and (M3) / (M1 + M2 + M3) is set to 60. % Or less, the necking that connects the low-resistance metal particles can be formed thick and firm, so the resistance of the via and the electrical connection structure can be lowered, and the connection reliability of the via and the electrical connection structure can be reduced. Can be improved.

  Moreover, as for the electrically conductive paste of this invention, it is desirable for the difference of melting | fusing point of the low melting metal A particle and the low melting metal B particle to be 10 degreeC or more.

  By setting the difference between the melting points of the low melting point metal A particles and the low melting point metal B particles to 10 ° C. or more, a relatively long time difference is provided between the softening and melting start temperatures of the low melting point metal A particles and the low melting point metal B particles. The low melting point metal B can sufficiently wet the surface of the low resistance metal particle and the low melting point metal A particle. Therefore, the connection between the low-resistance metal particles via the low-melting point metal B and the low-melting point metal A occurs more easily, and the connection reliability of the via or the electrical connection structure can be improved.

  In the conductive paste of the present invention, it is desirable that the low melting point metal B particles contain Bi. By containing Bi in the low melting point metal B particles, the viscosity of the low melting point metal B after melting can be reduced, so that the low melting point metal B wettability to the low resistance metal particles and the low melting point metal A particles The connection reliability of vias and electrical connection structures can be improved.

  The conductive paste of the present invention has a total content of low melting point metal A particles, low melting point metal B particles, and low resistance metal particles of 85 to 95% by mass, and a resin content of 5 to 15% by mass. It is desirable.

  Thus, the amount of the conductive powder such as the low melting point metal A particle, the low melting point metal B particle, and the low resistance metal particle is 85% by mass or more, and the amount of the resin is 15% by mass or less. Therefore, the conductive path is secured, and the resistance of the via and the electrical connection structure can be reduced. In addition, by setting the amount of conductive powder to 95% by mass or less and the amount of resin to 5% by mass or more, the viscosity of the conductive paste can be made appropriate. For example, the conductive paste is filled into the via hole by screen printing or the like. In doing so, the filling property can be improved and the generation of voids can be eliminated.

  The wiring board of the present invention is a wiring board in which an insulating substrate containing at least a resin and a wiring layer are laminated, and a via is provided in the insulating substrate to electrically connect the wiring layers. The via is formed by filling the conductive paste described above.

  In such a conductive paste, when heat treatment is performed, first, the low melting point metal B is softened and melted, and the low resistance metal particle surface and the low melting point metal A surface are softened and melted. The low melting point metal B layer is formed on at least a part of the surface of the low resistance metal particle and the low melting point metal A particle.

  In this way, the low resistance metal particles and the low melting point metal A surface adhere to the low melting point metal B which has been softened and melted to have a low viscosity, so that the low resistance metals, the low melting point metal A particles or the The low resistance metal particles and the low melting point metal A come into contact via the softened and melted low melting point metal B.

  As the temperature rises, the viscosity of the low melting point metal B further decreases and spreads on the surfaces of the low resistance metal particles and the low melting point metal A particles.

  When the melting point of the low melting point metal A particles is reached, the low melting point metal A softens and melts to form a necking that firmly connects the low resistance metal particles covered with the low melting point metal B. At this time, since the low melting point metal A has a higher melting point than the low melting point metal B, the low melting point metal A becomes a fluid having a higher viscosity than the low melting point metal B at the same temperature. Thus, the Cu particles can be firmly connected structurally and electrically. The connection with the low melting point metal A has a shape reflecting the raw material shape of the low melting point metal A because the deformation of the low melting point metal A is small, and a relatively thick and strong connection structure between the low melting point metal particles is realized. . In addition, a similar mechanism appears at the interface between the via of the wiring board and the wiring layer provided above and below the via, and the connection reliability between the via and the wiring layer is improved as well as the via.

  By producing a wiring board using the conductive paste described above, the resistance of the via can be reduced, the connection reliability of the via and the electrical connection structure can be improved, and a wiring having a low electrical resistance can be provided. In addition, a highly reliable wiring board can be provided.

  The method for manufacturing a wiring board according to the present invention includes a step of forming a via hole in an uncured or semi-cured insulating substrate containing at least a thermosetting resin, and after filling the via hole with the conductive paste. A step of depositing and forming a conductor layer on the surface of the insulating substrate including the via hole forming portion, and laminating and integrating the insulating substrates, and then heating the laminate to a curing temperature of the thermosetting resin. And a step of collectively curing.

  In such a method of manufacturing a wiring board, it is possible to reduce the change in the material physical properties of the wiring board inner layer part and the outer layer part that are generated at the time of sequential curing by batch curing, and to shorten the process time related to curing, A wiring board with low resistance and excellent connection reliability can be provided.

  The conductive paste of the present invention is used, for example, to form a via of a wiring board. As shown in FIG. 1A, the via paste 3 formed in the insulating layer 1 is filled with the conductive paste 5, A wiring layer 7 is formed above and below the via hole 3 and then heated to form a via 9 as shown in FIG. 1C. A wiring layer 7a formed on the upper surface of the via 9 and a lower surface of the via are formed. The wiring layer 7b thus formed is electrically connected.

  As shown in FIG. 1 (a), the conductive paste of the present invention contains at least tin and low melting point metal A particles 5a having a melting point of 230 ° C. or less, and at least tin, and low melting point metal A particles 5a. The low melting point metal B particles 5b having a lower melting point, the low resistance metal particles 5c having a melting point exceeding 230 ° C., and a resin (not shown).

  Although the resin is omitted in FIG. 1, the resin occupies a portion excluding conductive particles such as the low melting point metal A particles 5 a, the low melting point metal B particles 5 b, and the low resistance metal particles 5 c in the via hole 3. Yes.

  Since the low-resistance metal particles 5c contained in the conductive paste 5 do not melt at the time of heat treatment, the low-resistance metal particles 5c are materials that serve as the core or skeleton of the via 9 that is a conductive path, and have low resistance. As the low resistance metal particles 5c, a metal having a melting point higher than those of the low melting point metal A particles 5a and the low melting point metal B particles 5b is used.

  In particular, Cu is desirable because it is inexpensive, has low resistance, and is difficult to form a brittle intermetallic compound with Sn. Further, Ag is desirable from the viewpoint of low resistance and excellent oxidation resistance, and Au is desirable from the viewpoint of low resistance and excellent oxidation resistance and chemical resistance. Moreover, these powders may be mixed and these alloys may be sufficient.

  The low melting point metal A particles 5a and the low melting point metal B particles 5b are each made of a metal containing at least tin and having a melting point of 230 ° C. or less, and are softened and melted at a time difference during the heat treatment of the conductive paste 5. By deforming, the low-resistance metal particles 5 c that are the core or skeleton of the via 9 and the wiring layer 7 in contact with the via 9 are connected.

  The low melting point metal B particle 5b is low in order to express the function of wetting the surfaces of the low melting point metal A particle 5a and the low resistance metal 5c, and to bond the low resistance metal particle 5c and make necking thick and strong. It is important that the melting point is lower than that of the melting point metal A5a particles. Particularly, by making the difference between the melting points of 10 ° C. or more, the resistance of the via 9 is lowered, and the wiring board having the highly reliable via 9 can be easily obtained. Can be produced.

  The low-melting point metal A particles 5a and the low-melting point metal B particles 5b have a function of smoothly wetting and spreading between the wiring layers 7 disposed above and below the via holes 3 and the low-resistance metal particles 5c serving as the cores of the vias. Have.

  The low melting point metal B particle 5b of the present invention is melted before the low melting point metal A particle 5a, and the low melting point metal B particle 5b obtained by melting the surface of the low resistance metal particle 5c and the low melting point metal A particle 5a is wetted. The connection point is increased by forming a layer of the low melting point metal B particles 5b. Therefore, in order to increase the number of the low melting point metal B particles 5b, the average particle diameter of the low melting point metal B particles 5b is desirably smaller than the low melting point metal A particles 5a.

  In particular, the average particle size of the low melting point metal B particles 5b is desirably 80% or less of the average particle size of the low melting point metal A particles 5a, and more desirably 50% or less.

  Further, it is desirable to use a thermosetting resin that has high rigidity after being cured with excellent ability to protect and retain the conductive path.

  In addition, the thermosetting resin adjusts the conductive paste to a low viscosity in an uncured state, increases the filling property to the via hole 3 by screen printing or the like, and reduces the generation of voids. It is desirable to contain.

  Further, the conductive paste 5 of the present invention has a function of expanding the covering area of the low melting point metal A particles 5a to the low resistance metal 5c and forming a thick and strong necking for connecting the low resistance metal particles 5c, Therefore, (M2) / (M1 + M2) is preferably 30 to 80%, and more preferably 50 to 80%.

  Further, the conductive paste 5 of the present invention increases the number of contacts between the low-resistance metal particles 5c, decreases the electrical resistance of the via 9, and forms a thick and firm necking that connects the low-resistance metal particles 5c. , (M3) / (M3 + M1 + M2) is preferably 40 to 60%.

  Further, the low melting point metal A particle 5a and the low melting point metal B particle 5b of the present invention are such that the low melting point metal B particle 5b is melted before the low melting point metal A particle 5a, and the surface of the low resistance metal particle 5c and the low melting point metal A particle. The low melting point metal B particles 5b that have melted the surface of the 5a particles have a function of wetting and forming a layer of the low melting point metal B particles 5b. The melting point metal B particles 5b are desirably deformed, and the difference in melting point between the low melting point metal A particles 5a and the low melting point metal B particles 5b is desirably 10 ° C. or more.

  Moreover, it is desirable that the low melting point metal B particles 5b of the present invention contain Bi in order to wet other conductive particles.

  In addition, the conductive paste of the present invention has a conductive powder of 85 to 95% by mass in order to improve the filling property and eliminate voids when the conductive paste is embedded in the via hole 3 by screen printing or the like. It is desirable to contain 5-15 mass% of curable resin.

  The wiring board according to the present invention includes an insulating substrate 1 containing at least a resin, a plurality of wiring layers formed on the surface of or inside the insulating substrate 1, and the wiring layers are electrically connected by vias 9. Thus, the via 9 is formed using the conductive paste described above.

  Next, the manufacturing method of the wiring board of this invention is demonstrated.

First, as shown in FIG. 2A, the semi-cured insulating substrate 1 is drilled by a laser processing machine such as a UV-YAG laser, an excimer laser, or a CO ₂ laser to provide a via hole 3.

  Next, as shown in FIG. 2B, a conductive paste 5 is filled in the via hole 3.

  Next, as shown in FIG. 2 (c), a wiring layer 7 made of a metal foil bonded to a resin film 9 with an adhesive 11 is attached to one side or both ends of the via hole 3 filled with the conductive paste 5. Align, heat at 60 to 150 ° C., and pressurize at a pressure of 4.0 to 8.0 MPa. Then, as shown in FIG. 2 (d), the wiring layer 7 is embedded in the insulating substrate 1 by peeling the resin film 9 together with the adhesive 11.

  A plurality of wiring units a as shown in FIG. 2 (e) thus manufactured are manufactured and stacked as shown in FIG. 3 (f), and the thermosetting resin in the insulating layer is cured at once. By heating to a temperature, for example, 180 to 250 ° C. and pressurizing at a pressure of 1 to 10 MPa, a wiring board A as shown in FIG. 3G can be manufactured.

  With this heating, before heating, the low melting point metal A particles 5a and the low melting point metal B particles of the conductive paste 5 filled in the via holes 3 of the insulating substrate 1 as shown in FIG. 5b and the low-resistance metal particles 5c change.

  First, as shown in FIG. 1B, the low melting point metal B particles 5b begin to soften and deform, and the low melting point metal A particles 5a, the low resistance metal particles 5c, and the wiring layer 7 start to be bonded.

  Further, as the temperature rises, the low melting point metal A particle 5a is deformed, and as shown in FIG. 2C, the low melting point metal B particle 5b, the low resistance metal particle 5c, and the wiring layer 7 are interposed. Forms a thick and strong bond.

  Thus, by using the conductive paste 5 of the present invention, the via 9 having a low resistance and high reliability is formed, and a high-performance and highly reliable wiring board A as shown in FIG. can do.

  In addition, this invention is not limited to the said form, A various change is possible in the range which does not change the summary of invention. For example, when two or more kinds of melting points contain a low resistance metal having a melting point of 230 ° C. or lower, a low melting point metal having a melting point higher than 230 ° C. may be contained. Needless to say, three or more kinds of low melting point metals may be used.

  Of course, the form of the wiring board A can also be used for, for example, a structure in which a fine wiring layer is formed on the surface of the core board.

  A mixture of the copper powder as the low-resistance metal particles 5c, the low-melting point metal A particles 5a, the low-melting point metal B particles 5b, and the resin having the composition shown in Table 1 at a blending ratio shown in Table 1 is obtained with a propeller-type stirrer. The conductive paste 5 was produced by kneading.

  The resin used was a mixture of triallyl isocyanurate resin and peroxide PH25B as a catalyst, and the mixing ratio of triallyl isocyanurate resin and peroxide PH25B was 95: 5 vol%.

  The particle diameters of the low melting point metal A particles 5a and the low melting point metal B particles 5b were also changed within the range shown in Table 1.

  Thus, the produced conductive paste 5 was used in the following steps to produce a test wiring board.

  First, a via hole 3 was formed on a semi-cured insulating substrate 1 made of PPE (polyphenylene ether) having a thickness of 30 μm by drilling 100 μm with a UV-YAG laser processing machine.

  Next, the conductive paste 5 shown in Table 1 was filled in the via hole 3.

  Next, the wiring layer 7 made of a copper foil having a thickness of 10 μm and patterned on the front and back surfaces of the via hole 3 formed in the insulating substrate 1 was transferred at 150 ° C. and 6.0 MPa.

  Next, the insulating substrate 1 manufactured as described above is placed in 6 layers so that each via hole 3 and the wiring layer 7 are electrically connected, aligned, heated to 230 ° C., and 5.0 MPa. Was applied and laminated.

  Conduction reliability is evaluated by conducting a temperature cycle test (TCT) in which the initial conduction resistance and the sample are 30 minutes at a temperature of −55 ° C. and 30 minutes at a temperature of 125 ° C. (TCT). The conduction resistance of 9 was measured and evaluated by comparing the rate of change of conduction resistance before and after the test.

Table 1 shows initial conduction resistance per via hole and conduction resistance change rate before and after the test.

Sample No. using only one kind of low melting point metal which is outside the scope of the present invention. In 1 and 2, the initial resistance of the via 9 was as high as 10 × 10 ⁻⁶ Ωcm or more, and the resistance change rate after the thermal cycle test of the via 9 was as high as 5.4% or more.

In addition, although two types of low melting point metals are used, Sample No. No. 2 has a melting point of a low melting point metal having a high melting point exceeding 230 ° C. 3, the initial resistance of the via 9 was as high as 13.2 × 10 ⁻⁶ Ωcm or more, and the resistance change rate after the thermal cycle test of the via 9 was also as high as 6.7% or more.

On the other hand, sample No. using the conductive paste 5 of the present invention. 4 to 21 all have an initial resistance of 10 × 10 ⁻⁶ Ωcm or less and a conduction resistance change rate of 5% or less, and it can be seen that the via 9 has low resistance and high reliability.

  Sample No. 5 in which the difference in melting point between the low melting point metal A particles 5a and the low melting point metal B particles 5b was changed. In Samples Nos. 5 and 6, the difference in melting point between the low melting point metal A particles 5a and the low melting point metal B particles 5b is 5 ° C. Sample No. 5 which is 10 ° C. than 5 ° C. 6 is superior in both the initial resistance and the rate of change in resistance after thermal cycling.

  In addition, Sample No. 5 in which the average particle diameter of the low melting point metal A particles 5a and the low melting point metal B particles 5b was changed. From the results of 6 to 8, it can be seen that the smaller the average particle size of the low melting point metal B particles 5b is smaller than the average particle size of the low melting point metal A particles 5a, both the initial resistance and the rate of change in resistance after thermal cycling are excellent. . Sample No. 5 in which the average particle size of the low melting point metal B particles 5b is 80% of the average particle size of the low melting point metal A particles 5a. 7, the initial resistance and the rate of change in conduction resistance are decreased, and the average particle size of the low melting point metal B particles 5b is 50% of the average particle size of the low melting point metal A particles 5a. In 8, the initial resistance and the rate of change in conduction resistance were further reduced.

  Further, when the content of the low melting point metal A particles 5a is M1 and the content of the low melting point metal B is M2, the ratio of (M2) / (M1 + M2), that is, the low melting point metal A particles 5a and the low melting point metal B Sample No. 5 in which the ratio of the particles 5b was changed. In Samples Nos. 9 to 13, Sample No. 8-12 showed the lower initial resistance and the conduction | electrical_connection resistance change rate.

  Further, when the content of the low melting point metal A particles 5a is M1, the content of the low melting point metal B particles 5b is M2, and the content of the low resistance metal particles is M3, the ratio of (M3) / (M1 + M2 + M3), that is, Sample No. 5 in which the ratio of the sum of the low resistance metal particles, the low melting point metal A particles 5a, and the low melting point metal B particles 5b was changed. In Samples Nos. 14 to 17, Sample No. 15 and 16 showed lower initial resistance and conduction resistance change rate.

  In addition, the sample No. in which the resin amount was changed in the range of 3 to 20% by mass. 18-21, sample No. whose resin is 5-15 mass%. 17 to 20 showed low initial resistance and conduction resistance change rate.

  As for the sample containing Bi in the low melting point metal B particle 5b, Sample No. No. containing Bi in the low melting point metal B particle 5b. The initial resistance and conduction resistance change rate tended to be lower than 4.

It is the schematic diagram by which the electrically conductive paste of this invention is heated and becomes a via | veer. It is process drawing which shows the preparation methods of the wiring board of this invention. It is process drawing which shows the preparation methods of the wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 3 ... Via hole 5 ... Conductive paste 5a ... Low melting point metal A particle 5b ... Low melting point metal B particle 5c ... Low resistance metal particle 7 ... .... Wiring layer 9 ... Resin film 11 ... Adhesive a ... Wiring unit A ... Wiring board

Claims (12)

Low-melting point metal A particles containing at least tin and having a melting point of 230 ° C. or lower, low-melting point metal B particles containing at least tin and having a melting point lower than that of the low-melting point metal A particles, and low resistance exceeding 230 ° C. A conductive paste comprising metal particles and a resin. 2. The conductive paste according to claim 1, wherein the low-resistance metal particles contain at least one selected from Cu and Ag. The conductive paste according to claim 1 or 2, wherein the average particle size of the low melting point metal A particles is larger than the average particle size of the low melting point metal B particles. The conductive paste according to any one of claims 1 to 3, wherein the average particle size of the low melting point metal B particles is 80% or less of the average particle size of the low melting point metal A particles. The conductive paste according to claim 1, wherein the resin is a thermosetting resin. The conductive paste according to any one of claims 1 to 5, wherein the resin contains triallyl isocyanurate. When the content of the low melting point metal A particles is M1, the content of the low melting point metal B particles is M2, and the content of the low resistance metal particles is M3, (M2) / (M1 + M2) is 30 to 80%, (M3 ) / (M1 + M2 + M3) satisfies a relationship of 40 to 60%, and the conductive paste according to any one of claims 1 to 6. The conductive paste according to claim 1, wherein a difference in melting point between the low melting point metal A particles and the low melting point metal B particles is 10 ° C. or more. The conductive paste according to any one of claims 1 to 8, wherein the low melting point metal B particles contain Bi. 10. The content of the low melting point metal A particles, the low melting point metal B particles, and the low resistance metal particles is 85 to 95 mass% in total, and the resin content is 5 to 15 mass%. The electrically conductive paste in any one of these. An insulating substrate containing at least a resin and a wiring layer are laminated, and the wiring substrate is provided with a via in the insulating substrate for electrically connecting the wiring layers, wherein the via is the claim 1. A wiring board formed by filling the conductive paste according to any one of 1 to 10. A step of forming a via hole in an uncured or semi-cured insulating substrate containing at least a thermosetting resin, a step of filling the via hole with the conductive paste according to any one of claims 1 to 10, and A step of forming a conductor layer on the surface of the insulating substrate; and a step of laminating and integrating the insulating substrates and then heating to a curing temperature of the thermosetting resin to collectively cure the insulating substrate. A method for manufacturing a wiring board.

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