JP5409117B2 - Manufacturing method of ceramic green sheet and ceramic multilayer substrate - Google Patents

Description

  The present invention relates to a ceramic green sheet and a method for producing a ceramic multilayer substrate using the ceramic green sheet to produce a ceramic multilayer substrate.

  In recent years, in order to meet the demand for higher functionality and lower cost, ceramic multilayer substrates have been increasingly manufactured in a smaller size at a lower cost. This ceramic multilayer substrate forms a number of through-holes for forming through conductors such as conductor vias in the ceramic green sheet, and after filling the through-holes with a conductive paste, forms a conductor pattern to be a wiring conductor etc. Then, a plurality of ceramic green sheets are laminated and fired.

  Conventionally, as a method of forming a through conductor, a method of punching a ceramic green sheet with a metal pin having a diameter approximately equal to the diameter of the through conductor to be formed has been adopted. As the diameter has decreased, it has become difficult to manufacture very fine pins, and even if it has been manufactured, the manufacturing cost has increased.

  Therefore, instead of the punching method using a pin, a method of forming a through hole using a laser beam capable of further reducing the diameter of the through hole has been adopted. When the laser beam is irradiated onto the ceramic green sheet, the laser beam is absorbed by the ceramic green sheet, the temperature of the irradiated portion is increased, and the raw material of the ceramic green sheet is volatilized to form a through hole.

  However, since the ceramic green sheet often has low laser beam absorbability, the through hole may not be easily formed. Therefore, conventionally, a method of adding a laser light absorber to a ceramic green sheet (see, for example, Patent Document 1), a laser light absorber is applied to one surface of the ceramic green sheet, and laser light is applied from the other surface side. A method (for example, Patent Document 2) in which a via is formed by the volatile power of a laser light absorber by irradiation is employed.

JP 7-106192 A JP-A-2-303696

  However, in the above-described conventional technique, when a laser light absorbent is added to the ceramic green sheet as in the invention described in Patent Document 1, the degreasing property of the laser light absorbent is poor. The caking property is lowered and the sintering temperature is changed. As a result, problems such as warpage of the ceramic multilayer substrate increase, dimensional accuracy decreases, and insulation decreases. For this reason, there is a problem that the amount of the laser light absorber added to the ceramic green sheet cannot be increased.

  In the case of a method of applying a laser light absorbent to one side of a ceramic green sheet as in the invention described in Patent Document 2, the laser light absorbent is applied after the laser light absorbent coating step and the formation of the through hole. Since the removal step of the laser light absorber to be removed is necessary, the manufacturing cost of the ceramic multilayer substrate increases due to an increase in the manufacturing steps. In addition, a component such as a laser beam absorbent that has volatilized during the formation of the through-hole by laser light adheres to the inner wall of the through-hole and the periphery of the through-hole in the main surface of the ceramic green sheet. As a result, there is a problem that the sinterability of the ceramic green sheet is deteriorated, resulting in deterioration of insulating properties of the ceramic green sheet.

  Therefore, the present invention has been devised in view of the above-mentioned conventional problems, and the object thereof is to reduce the content of the laser light absorber and efficiently suppress the deterioration of the degreasing property. By providing a ceramic green sheet that can be formed and that can be sintered while suppressing variation in dimensions, and a method for manufacturing a ceramic multilayer board using the ceramic green sheet is there.

In addition, the ceramic green sheet of the present invention is provided on the opposite side of the main surface irradiated with the laser light in the ceramic green sheet containing the laser light absorber in which the through hole is formed by irradiating the laser light. The first layer and the remaining second layer, and the first layer has a higher content of the laser light absorber than the second layer, has a lower sintering start temperature, and has a laser. A plurality of layers having different contents of light absorber and sintering start temperature are bonded, and the plurality of first layers are directed toward the main surface opposite to the main surface irradiated with the laser light. , it is characterized in that the content of the laser beam-absorbing agent sintering initiation temperature with increased are stacked so as to be lower.

In the ceramic green sheet of the present invention, in the above configuration, the softening point of the glass included in the plurality of first layers is lower than the softening point of the glass included in the second layer. the first layer together have different softening point of the glass, towards the main surface opposite to the main surface on which laser light is irradiated, it characterized in that the softening point of the glass are laminated so as to be lower Is.

Moreover, the ceramic green sheet of the present invention has the above-described configuration, wherein the plurality of first layers include an oxidizing agent that promotes degreasing, and the plurality of first layers include the oxidizing agent. different amounts, in which the content of the oxidizing agent, wherein the laser light is laminated so that much toward the main surface opposite to the main surface to be irradiated.

Moreover, the ceramic green sheet of the present invention is characterized in that, in the above configuration, the oxidizing agent is copper oxide.

  In the method for producing a ceramic multilayer substrate of the present invention, the ceramic green sheet of the present invention is irradiated with laser light to form a through hole, and then the through hole is filled with a conductive paste, and then the conductive paste is filled. A laminate is produced by laminating a plurality of the aforementioned ceramic green sheets, and the laminate is then fired.

  According to the ceramic green sheet of the present invention, in the ceramic green sheet containing a laser light absorber, through-holes are formed by irradiating laser light, the main surface opposite to the main surface irradiated with laser light. The ceramic green sheet has a first layer on the surface layer and a second layer that is the remainder of the first layer, and the first layer has a higher content of laser light absorber than the second layer and a lower sintering start temperature. Through-holes can be efficiently formed while reducing the degreasing property by reducing the content of the laser light absorber in the. That is, by forming the first layer containing the laser light absorber on the surface layer of the main surface opposite to the main surface irradiated with the laser light of the ceramic green sheet, the content of the laser light absorber is reduced. A reduction in degreasing during sintering can be suppressed.

  In addition, by lowering the sintering start temperature of the first layer than that of the second layer, the first layer can be sintered earlier than the second layer, and the influence on the sinterability of the second layer can be suppressed. it can. In addition, since the first layer behaves like a constraining substrate with respect to the second layer, variations in dimensions of the second layer can be suppressed. That is, when the second layer starts sintering, since the first layer has already started sintering, the influence of degreasing of the first layer is reduced, so that the second layer is sufficiently sintered. As a result, the insulating properties of the ceramic green sheet can be improved. In addition, since the first layer can suppress the shrinkage of the second layer in the XY direction (plane direction) at the temperature at which the second layer is sintered, the dimensions of the ceramic multilayer substrate manufactured using the ceramic green sheet Accuracy is improved.

  In the ceramic green sheet of the present invention, when the softening point of the glass contained in the first layer is lower than the softening point of the glass contained in the second layer, the sintering start temperature of the first layer is higher than that of the second layer. It can be made faster, and the dimensional accuracy of the ceramic multilayer substrate is further improved.

  Moreover, when the 1st layer contains the reducing agent which accelerates | stimulates degreasing, since the ceramic green sheet of this invention can improve a degreasing property more, it improves the insulation of a ceramic green sheet more easily. be able to. Moreover, since the addition amount of a laser beam absorber can be increased without degreasing, a through-hole can be formed more easily.

Further, the ceramic green sheet of the present invention, the oxidizing agent is, when the copper oxide or molybdenum oxide, when it is the temperature of the thermal decomposition of the laser beam-absorbing agent, since the act as an oxidizing agent, the addition amount of the oxidizing agent Even if the amount is smaller, the degreasing property of the laser light absorber can be improved more easily, and the insulating property of the ceramic green sheet can be easily improved.

  Further, the ceramic green sheet of the present invention is a ceramic green sheet containing a laser light absorbent, in which a through hole is formed by irradiating laser light, on the main surface opposite to the main surface irradiated with laser light. On the other hand, as the content of the laser light absorber is increased and the sintering start temperature is lowered, the content of the laser light absorber in the ceramic green sheet is decreased to suppress the degreasing property. A through-hole can be formed efficiently. That is, a portion containing a large amount of the laser light absorber is formed on the main surface side opposite to the main surface irradiated with the laser light of the ceramic green sheet, thereby reducing the content of the laser light absorber and firing. It is possible to suppress a decrease in degreasing properties during the setting. Further, the diameter of the through hole is hardly changed in the thickness direction of the ceramic green sheet.

  Moreover, the main surface irradiated with the laser light by lowering the sintering start temperature on the main surface opposite to the main surface irradiated with the laser light lower than the main surface side irradiated with the laser light. Sintering on the main surface side opposite to the main surface side irradiated with the laser beam is made faster than the main surface side opposite to the main surface irradiated with the laser beam. The influence can be suppressed. In addition, since the main surface side opposite to the main surface irradiated with the laser beam behaves like a restraint substrate with respect to the main surface side irradiated with the laser light, the side of the main surface irradiated with the laser light Variation in dimensions can be suppressed.

  In addition, the ceramic green sheet of the present invention has a glass softening point that is lower from the main surface irradiated with laser light toward the opposite main surface, and is opposite to the main surface irradiated with laser light. The sintering start temperature on the main surface side can be made lower than that on the main surface side irradiated with the laser beam. As a result, the shrinkage in the XY direction can be suppressed by the portion having a low softening point, so that the dimensional accuracy of the ceramic multilayer substrate is further improved.

Moreover, the ceramic green sheet of the present invention contains an oxidant that promotes degreasing, and the content of the oxidant increases from the main surface irradiated with the laser light toward the opposite main surface. Sometimes, the degreasing property can be further improved, so that the insulating property of the ceramic green sheet can be improved more easily. Moreover, since the addition amount of a laser beam absorber can be increased without degreasing, a through-hole can be formed more easily.

Further, the ceramic green sheet of the present invention, the oxidizing agent is, when the copper oxide or molybdenum oxide, when it is the temperature of the thermal decomposition of the laser beam-absorbing agent, since the act as an oxidizing agent, the addition amount of the oxidizing agent Even if the amount is smaller, the degreasing property of the laser light absorber can be improved more easily, and the insulating property of the ceramic green sheet can be easily improved.

  According to the method for manufacturing a ceramic multilayer substrate of the present invention, the ceramic green sheet of the present invention is irradiated with laser light to form through holes, and then the through holes are filled with a conductive paste, and then the conductive paste is filled. A multilayered body is produced by laminating a plurality of the ceramic green sheets thus prepared, and then the laminated body is fired, so that a ceramic multilayer substrate having excellent dimensional accuracy can be manufactured.

FIGS. 1A to 1D are cross-sectional views for each manufacturing process showing an example of an embodiment of a method for manufacturing a ceramic multilayer substrate of the present invention.

  Embodiments of a ceramic green sheet according to the present invention will be described below with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view for each process showing an example of an embodiment of a method for producing a ceramic multilayer substrate of the present invention. In FIG. 1, 1 is a ceramic green sheet, 2 is a first layer, 3 is a second layer, 4 is a through hole, 5 is a wiring conductor, 6 is a conductor paste, 7 is a laser beam, and 8 is a laminate. Yes.

  The ceramic green sheet 1 as an example of the present embodiment is a ceramic green sheet 1 containing a laser light absorber, in which a through-hole 4 is formed by irradiating the laser light 7, and the laser light 7 is mainly irradiated. It has the 1st layer 2 in the surface layer of the main surface 1b on the opposite side to the surface 1a, and the 2nd layer 3 of the remainder, and the 1st layer 2 contains laser beam absorber content rather than the 2nd layer 3 Therefore, the sintering start temperature is low.

  With this configuration, the through-hole 4 can be efficiently formed while reducing the content of the laser light absorber in the ceramic green sheet 1 and suppressing the degreasing deterioration. That is, the first layer 2 containing the laser light absorber is formed on the surface layer of the main surface 1b opposite to the main surface 1a irradiated with the laser light 7 of the ceramic green sheet 1, thereby containing the laser light absorber. Decreasing the degreasing property during sintering can be suppressed by reducing the amount.

  In addition, by making the sintering start temperature of the first layer 2 lower than that of the second layer 3, the sintering of the first layer 2 is made faster than the second layer 3 and the sinterability of the second layer 3 is improved. The influence can be suppressed. In addition, since the first layer 2 behaves like a constraining substrate with respect to the second layer 3, variations in the dimensions of the second layer 3 can be suppressed. That is, when the second layer 3 starts sintering, since the first layer 2 has already started sintering, the effect of degreasing the first layer 2 is reduced. It becomes possible to sinter, and the insulation of the ceramic green sheet 1 can be improved. Moreover, since the 1st layer 2 can suppress shrinkage | contraction to the XY direction (plane direction) of the 2nd layer 3 at the temperature which the 2nd layer 3 sinters, the ceramic produced using the ceramic green sheet 1 The dimensional accuracy of the multilayer substrate is improved.

  The ceramic green sheet 1 of the present embodiment generally has a thickness of about 10 to 200 μm, but the thickness of the first layer 2 is preferably about 5 to 100 μm. By setting it within this range, the content of the laser light absorber in the ceramic green sheet 1 can be reduced, and the through-holes 4 can be efficiently formed while suppressing a decrease in degreasing properties. It can be suppressed that the content of the laser light absorber in is excessive and the degreasing property is lowered.

  The content of the laser beam absorbent contained in the first layer 2 is preferably 0.1 to 10% by mass, and by setting the content within this range, the through holes 4 can be efficiently formed by the absorption effect of the laser beam 7. It is also possible to reduce the content of the laser light absorber and suppress the degreasing deterioration.

  The content of the laser light absorber contained in the second layer 3 is preferably 0 to 7% by mass, and by making it within this range, the following effects are exhibited. When the ceramic green sheet 1 is irradiated with the laser beam 7, the material temperature of the ceramic green sheet 1 rises, and the material is scattered by the explosive force to form holes, but the laser beam on the back surface (main surface 1b) side. When the absorption rate of 7 is high, the explosive force on the back surface side is high, so that the straight through hole 4 is easily formed. On the contrary, if the absorption rate of the laser beam 7 on the front surface (main surface 1a) side is high, a hole is likely to be formed near the surface, but the absorption rate on the back surface is low, so the diameter of the through hole 4 increases on the front surface side. The diameter of the through hole 4 is reduced on the back surface side, and a tapered through hole 4 is formed. When the tapered through-hole 4 is formed, poor filling of the conductive paste filled in the through-hole 4 occurs, or the diameter of the through-hole 4 is large on the surface side, so that it is close to the through-hole 4. A short circuit occurs with the wiring conductor 5 and the like that should not be electrically connected.

  The irradiation energy (output) of the laser beam 7 is preferably about 0.1 to 30 W. By setting it within this range, it is possible to efficiently raise the temperature of the irradiated portion of the ceramic green sheet 1 by the irradiation of the laser beam 7, and that the ceramic green sheet 1 is deformed by the thermal effect of the laser beam 7. Can be suppressed.

  The wavelength of the laser beam 7 is preferably about 100 to 10,000 nm. By setting it within this range, the laser light 7 can be efficiently absorbed by the laser light absorbent, and deformation of the ceramic green sheet 1 due to the thermal effect of the laser light 7 can be suppressed. The wavelength of the laser beam 7 is more preferably 380 to 780 nm, which is the wavelength range of visible light. Since the laser beam 7 is visible, the workability of forming the through hole 4 and the operability of the laser device are improved. It is advantageous.

  The pulse width of the laser beam 7 is preferably about 1 psec to 100 nsec. By making it within this range, the irradiation part of the ceramic green sheet 1 can be efficiently heated by the irradiation of the laser light 7, and the deformation of the ceramic green sheet due to the influence of heat by the laser light 7 is suppressed. can do.

The laser apparatus for generating a laser beam 7, YAG laser device, UV-YAG laser device, carbon dioxide (CO ₂₎ laser device, it is possible to use a fiber laser device.

  Hereinafter, the ceramic green sheet 1 of this Embodiment is demonstrated according to the manufacturing method of the ceramic green sheet 1. FIG.

  First, as shown in FIG. 1A, a ceramic green sheet 1 is prepared.

  The ceramic green sheet 1 of the present embodiment can be manufactured as follows. The first ceramic slurry mixed with ceramic powder, glass powder, filler powder, organic binder, solvent, laser light absorber and the like was coated on the support to form the first layer 2 and then produced in the same manner. The second ceramic slurry can be produced by applying the second ceramic slurry on the first layer 2 to form the second layer 3.

  Further, the first layer 2 formed on one support (support A) is stacked on the second layer 3 of another support (support B) on which the second layer 3 is formed, and is pressurized and applied. It is also possible to produce the ceramic green sheet 1 by transferring the second layer 3 onto the first layer 2 by peeling the support B after heating.

  Here, in order to adjust the dispersibility of the ceramic powder and the hardness and strength of the ceramic green sheet 1, a dispersant or a plasticizer may be added to the ceramic slurry.

Examples of the ceramic powder used for the ceramic green sheet 1 include Al ₂ O ₃ , AlN, glass ceramic powder (a mixture of glass powder and filler powder), etc. In the case of manufacturing a capacitor, composite perovskite ceramic powders such as BaTiO ₃ system and PbTiO ₃ system can be used, and they are appropriately selected according to the characteristics required for the object to be manufactured.

Examples of the glass component of the glass powder include SiO ₂ —B ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ system, SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —MO system (however, M represents Ca, Sr, Mg, Ba or Zn), SiO ₂ —Al ₂ O ₃ —M ¹ O—M ² O system (provided that M ¹ and M ² are the same or different, and Ca, Sr, Mg, Ba or Zn), SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —M ¹ O—M ² O system (where M ¹ and M ² are the same as above), SiO ₂ —B ₂ O _3- M ³ ₂ O system (where M ³ represents Li, Na or K), SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ —M ³ ₂ O system (where M ³ is the same as above) And Pb-based glass, Bi-based glass, and the like.

  Here, although the first layer 2 has a lower sintering start temperature than the second layer 3, specifically, the softening point of the glass contained in the first layer 2 is determined by the softening of the glass contained in the second layer 3. By making it lower than the point, the sintering start of the first layer 2 can be made earlier than the sintering start of the second layer 3, and the dimensional accuracy of the ceramic multilayer substrate is further improved.

  The difference between the sintering start temperature of the first layer 2 and the sintering start temperature of the second layer 3 may be about 10 to 200 ° C. In this case, the shrinkage of the second layer 3 in the XY direction can be suppressed, and the occurrence of cracks due to the difference in thermal expansion between the first layer 2 and the second layer 3 after the sintering of the first layer 2, etc. Can be suppressed.

  Therefore, for example, the sintering start temperature of the first layer 2 is about 400 to 700 ° C., and the sintering start temperature of the second layer 3 is about 410 to 900 ° C.

  Also, the crystallization temperature of the first layer 2 should be lower than the softening point of the glass contained in the second layer 3, and in this case, when the second layer 3 starts to shrink, the first layer 2 Since crystallization of the second layer 3 can further suppress the shrinkage of the second layer 3 in the XY direction, the dimensional accuracy is further improved.

Examples of filler powder include Al ₂ O ₃ , SiO ₂ , composite oxide of ZrO ₂ and alkaline earth metal oxide, composite oxide of TiO ₂ and alkaline earth metal oxide, and Al ₂ O. _And ceramic powders such as composite oxides (for example, spinel, mullite, cordierite) containing at least one selected from ₃ and SiO ₂ .

  As the organic binder, those conventionally used for the ceramic green sheet 1 can be used. For example, acrylic (a homopolymer or copolymer of acrylic acid, methacrylic acid or esters thereof, specifically acrylic Homopolymers such as acid ester copolymers, methacrylate ester copolymers, acrylic ester-methacrylic ester copolymers, etc.), polyvinyl butyral, polyvinyl alcohol, acrylic-styrene, polypropylene carbonate, cellulose, etc. Or a copolymer is mentioned. Considering decomposition and volatility in the firing step, an acrylic organic binder is more preferable.

  The solvent is not particularly limited as long as the ceramic powder and the organic binder can be well dispersed and mixed, and examples thereof include organic solvents such as toluene, ketones, alcohols, and water. Among these, solvents having a high evaporation coefficient such as toluene, methyl ethyl ketone, isopropyl alcohol and the like are preferable because the drying step after applying the ceramic slurry can be performed in a short time.

  The laser light absorber is composed of a component that absorbs the laser light 7, and an optimum material can be selected depending on the type of the laser light 7 to be used. Moreover, as a material of a laser beam absorber, either an inorganic material such as metal or an organic material such as resin can be used.

  For example, if the wavelength of the laser beam 7 is 355 nm, an inorganic material powder such as zinc oxide, titanium oxide, tungsten oxide or an organic material such as a pigment such as benzophenone or benzotriazole is used as the laser beam absorber. can do.

  The addition amount of the laser light absorber is not limited as long as it does not inhibit the degreasing property and sintering of the ceramic green sheet 1, and may be approximately 0.1 to 10% by mass. The laser light absorber can be added to either the first layer 2 or the second layer 3.

  In addition, although the degreasing process (drying process dried at the temperature of about 400 degreeC) of the ceramic green sheet 1 is normally performed before a sintering process, you may carry out in the first half with a sintering process.

In the ceramic green sheet 1 of the present embodiment, preferably, the first layer 2 contains an oxidant that promotes degreasing during sintering, so that oxygen released from the oxidant is ceramic green. By combining with the laser light absorber in the sheet 1 and carbon in the other organic components, carbon dioxide is formed and the carbon component in the ceramic green sheet 1 is reduced, so that the degreasing property can be further improved. Therefore, the insulation of the ceramic green sheet 1 can be improved more easily. Moreover, by adding an oxidizing agent, the amount of the laser light absorbent added can be increased without reducing the degreasing property, and therefore the through-hole 4 can be formed more easily.

Here, as an oxidizing agent, often when selecting a copper oxide or molybdenum oxide, when it is the temperature of the thermal decomposition of the laser beam-absorbing agent, since the act as an oxidizing agent, even in smaller amount, more readily laser beam The degreasing property of the absorbent can be improved, and the insulating properties of the ceramic green sheet 1 can be easily improved.

  The addition amount of the laser light absorber may be about 0.1 to 20% by mass. In this case, the degreasing property can be improved and the sinterability of the ceramic green sheet 1 by the reducing agent is not lowered.

  Examples of the method for forming the ceramic green sheet 1 by applying the ceramic slurry include a doctor blade method, a lip coater method, and a die coater method. In particular, an extrusion method such as a die coater method, a slot coater method, or a curtain coater method may be used. In this case, since these are non-contact application methods, a second ceramic slurry is applied on the first layer 2. Thus, when forming the second layer 3, the ceramic green sheet 1 can be formed without mixing the first layer 2 and the second layer 3.

  Further, the ceramic green sheet 1 of another example of the present embodiment is irradiated with the laser beam 7 in the ceramic green sheet 1 including the laser beam absorbent, in which a through hole is formed by irradiating the laser beam 7. In this configuration, the content of the laser light absorber increases and the sintering start temperature decreases toward the main surface 1b opposite to the main surface 1a.

  With the above configuration, the through hole 4 can be more easily formed even when the amount of the laser light absorber added is reduced, and the diameter of the through hole 4 in the main surface 1a and the main surface 1b are increased. The diameter of the through hole 4 can be adjusted to be substantially the same.

  As a method of making the sintering start temperature low as the content of the laser light absorber increases toward the main surface 1b opposite to the main surface 1a irradiated with the laser beam 7, There is a method in which a plurality of ceramic slurries each containing glass having different sintering start temperatures, that is, different softening points, are sequentially applied and formed.

  The content of the laser beam absorbent in the region of the main surface 1a irradiated with the laser beam 7 is preferably about 0.1 to 5% by mass, and heating within the main surface 1a by the laser beam 7 becomes strong by setting the content within this range. The diameter of the through hole 4 in the main surface 1a can be prevented from becoming too large.

  The content of the laser light absorber in the portion of the main surface 1b opposite to the main surface 1a irradiated with the laser beam 7 is preferably about 1 to 15% by mass. The through-hole 4 can be efficiently formed while reducing the content and suppressing the degreasing deterioration.

  The difference in sintering start temperature between the main surface 1a portion and the main surface 1b portion of the ceramic green sheet 1 may be about 10 to 200 ° C. In this case, shrinkage in the XY direction of the main surface 1a side portion can be suppressed, and the main surface 1a side portion and the main surface 1b side portion after sintering of the main surface 1b side portion can be suppressed. Generation of cracks due to a difference in thermal expansion can be suppressed.

  Therefore, for example, the sintering start temperature at the site of the main surface 1a is about 400 to 700 ° C., and the sintering start temperature at the site of the main surface 1b is about 410 to 900 ° C.

Next, as shown in FIG.1 (b), the laser beam 7 is irradiated and the through-hole 4 is formed. The wavelength of the laser beam 7 can be appropriately selected depending on the diameter of the through-hole 4 to be formed, the material of the ceramic green sheet 1 and the like. For example, when the diameter of the through-hole 4 is 50 μm or more, a CO ₂ laser device having a wavelength of about 10,000 nm can be used, and when the diameter is 50 μm or less, a UV-YAG laser device having a wavelength of about 355 nm can be used. Further, a support (hereinafter also referred to as a carrier) such as an organic film may be bonded to at least one main surface of the ceramic green sheet 1 and used. By doing so, it is possible to suppress deformation of the ceramic green sheet 1 due to the thermal effect generated when the through-holes 4 are formed, and a support is bonded to the surface irradiated with the laser light. If the support is removed after the processing, it is possible to prevent the processing waste of the ceramic green sheet 1 generated during the laser light irradiation from accumulating on the ceramic green sheet 1. Further, when the through hole 4 is formed by bonding a support to the main surface 1b opposite to the main surface 1a irradiated with the laser beam 7, there is a support so that when the substrate is volatilized by irradiation with the laser beam 7, Ascending air current of the steam is strengthened, and it becomes easy to remove the processing waste adhering to the wall surface of the through hole 4.

  Next, as shown in FIG. 1C, the through hole 4 is filled with a conductive paste 6, and a conductor component is introduced into the through hole 4.

  Examples of the conductive material contained in the conductive paste include one or more of W, Mo, Mn, Au, Ag, Cu, Pd, Pt, etc., and in the case of two or more, they are mixed. It may be in any form, such as a form in which the conductive paste is formed, a form in which the conductive paste includes two or more kinds of alloys, a form in which coatings made of individual conductive pastes are laminated, and the like. The conductor powder is manufactured by an atomization method, a reduction method, or the like, and may be subjected to treatments such as oxidation prevention and aggregation prevention as necessary. Moreover, fine powder or coarse powder may be removed by classification or the like to adjust the particle size distribution. The particle size of the conductor powder can be measured by a particle size measuring device such as a microtrack device.

  As the organic binder, those conventionally used for conductive pastes can be used. For example, acrylic (a homopolymer or copolymer of acrylic acid, methacrylic acid or esters thereof, specifically acrylic acid Ester copolymer, methacrylate ester copolymer, acrylic ester-methacrylic ester copolymer, etc.), polyvinyl butyral, polyvinyl alcohol, acrylic-styrene, polypropylene carbonate, cellulose, or other homopolymers or A copolymer is mentioned. In view of decomposition and volatility in the firing step, acrylic and alkyd organic binders are more preferable. The amount of the organic binder to be added varies depending on the conductor powder, but may be an amount that can disperse the conductor powder without any problem in the decomposability of the organic binder.

  As the organic solvent, it is only necessary that the above-mentioned conductor powder and the organic binder can be dispersed and mixed well, and plasticizers such as terpineol, butyl carbitol acetate and phthalic acid can be used. In consideration of the drying property of the solvent after filling the through holes 4 with the conductive paste 6, a low boiling point solvent such as terpineol is preferable.

  Further, a conductive paste to be the wiring conductor 5 is formed on the upper surface of the through hole 4 by screen printing or the like. As the conductive paste used as the wiring conductor 5, the same paste as the conductive paste 6 filled in the through hole 4 can be used.

  Finally, as shown in FIG.1 (d), the laminated body 8 is produced by aligning and stacking several ceramic green sheets 1, and heating and pressurizing and crimping | bonding them. At this time, pressurization (0.1 to 1 MPa) is applied to the laminate 8 so as not to shift the positions of the ceramic green sheets 1 in the laminate 8 and to ensure that the plurality of ceramic green sheets 1 can be laminated reliably. This makes it possible to perform more accurate and reliable crimping.

  Finally, the multilayer body 8 is fired to produce a ceramic multilayer substrate. The firing process includes an organic component removal process (degreasing process) and a ceramic powder sintering process. The organic component removing step is performed by heating the laminated body 8 in a temperature range of 100 to 800 ° C. to decompose and volatilize the organic component. In addition, the sintering temperature in the sintering process varies depending on the ceramic composition, and is performed within a range of about 800 to 1600 ° C. The firing atmosphere varies depending on the ceramic powder and the conductor material, and is performed in the air, in a reducing atmosphere, in a non-oxidizing atmosphere or the like, and may contain water vapor or the like in order to effectively remove organic components.

  Ceramic multilayer substrates, electronic components, and the like obtained by firing are exposed to the surface of the wiring conductor 5 exposed on the surface thereof, to prevent corrosion of the wiring conductor 5, or to external substrates and electronic components such as solder and metal wires. For good connection with the connection means, etc., it is preferable to apply a plated layer of Ni, Au.

When a low-temperature sintered material is used as the ceramic material, a ceramic with higher dimensional accuracy can be obtained by stacking and firing a constrained ceramic green sheet on the upper and lower surfaces of the laminate 8 and removing the constrained ceramic green sheet after firing. A multilayer substrate can be obtained. The constrained ceramic green sheet is a ceramic green sheet mainly composed of a hardly sinterable inorganic material such as Al ₂ O ₃ and does not shrink during sintering. The laminated body 8 in which the constraining ceramic green sheets are laminated is suppressed in shrinking in the plane direction (xy direction) by the constraining ceramic green sheet that does not shrink, and shrinks only in the laminating direction (z direction). Variation is suppressed.

  In addition to the hard-to-sinter inorganic component, the constrained ceramic green sheet may contain a glass component having a softening point equal to or lower than the sintering temperature, for example, the same glass powder as the glass powder contained in the ceramic green sheet 1. When the glass powder is softened and bonded to the ceramic green sheet 1 during sintering, the bonding between the ceramic green sheet 1 and the constraining ceramic green sheet becomes strong, and a more reliable restraining force is obtained. The amount of glass at this time is preferably 0.5 to 15% by mass by external addition to the inorganic component including the hardly sinterable inorganic component and the glass component, and the binding force is improved and the firing shrinkage of the constraining green sheet Is suppressed to 0.5% or less.

  After firing, the constrained ceramic green sheet is removed. Examples of the removal method include polishing, water jet, chemical blasting, sand blasting, wet blasting (a method of spraying abrasive grains and water by air pressure) and the like.

Reference examples of the ceramic green sheet of the present invention will be described below.

A ceramic green sheet was prepared as follows. Ceramic powder made of Al ₂ O ₃ , glass powder made of SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ , filler powder made of SiO ₂ , acrylic organic binder, solvent made of toluene, and laser made of zinc oxide The first ceramic slurry mixed with a light absorber and the like was printed on a support made of polyethylene terephthalate by a screen printing method and applied to form a first layer having a thickness of 25 μm. The 1st layer shall contain 5 mass% of laser beam absorbers.

  A second ceramic slurry prepared in the same manner was printed on the first layer and applied to form a second layer having a thickness of 50 μm. The 2nd layer shall contain 1 mass% of laser beam absorbers.

Further, by setting the softening point of the glass (SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ glass) included in the first layer to 450 ° C., the sintering start temperature is set to 500 ° C., and included in the second layer. By setting the softening point of glass (SiO ₂ —B ₂ O ₃ —Al ₂ O ₃ glass) to 700 ° C., the sintering start temperature was set to 725 ° C.

  Thus, a ceramic green sheet having a thickness of 75 μm composed of the first layer and the second layer was produced.

  A UV-YAG laser device is used as a laser device for generating laser light, a laser beam having a wavelength of 355 nm and an irradiation energy (output) of 3 W is set to a pulse width of 100 nsec per through hole, and a 50 μm through hole is formed in the ceramic green sheet. 1000 pieces were formed.

  And when the diameter of the through hole in the main surface (front surface) of the ceramic green sheet irradiated with laser light and the diameter of the through hole in the main surface (back surface) opposite to the main surface were measured, 1000 The average value of the through holes was 15 μm.

  Next, the ceramic green sheet was sintered at 900 ° C. for 1 hour to produce a ceramic substrate. As a result, the rate of change in dimension in the plane direction of the ceramic substrate was about 0.2%.

Moreover, the ceramic green sheet of the comparative example was produced as follows. In the same manner as in Reference _Example, comprises _{SiO 2 -B 2 O 3 -Al 2} O 3 glass, to produce a ceramic green sheet having a thickness of 75μm without the laser beam-absorbing agent, a ceramic green sheet, the reference example In the same manner, 1000 through holes were formed.

  And when the diameter of the through hole in the main surface (front surface) of the ceramic green sheet irradiated with laser light and the diameter of the through hole in the main surface (back surface) opposite to the main surface were measured, 1000 A difference of 25 μm occurred in the average value of the individual through holes, and a tapered through hole was formed.

  Next, when the ceramic substrate was fabricated by sintering the ceramic green sheet at 900 ° C. for 1 hour, the rate of change in the dimension in the plane direction of the ceramic substrate was about 0.3%.

1: Ceramic green sheet 1a: main surface 1b irradiated with laser light: main surface opposite to main surface irradiated with laser light 2: first layer 3: second layer 4: through hole 5: wiring conductor 6 : Conductive paste 7: Laser beam 8: Laminate

Claims (5)

  In a ceramic green sheet containing a laser beam absorbent, in which a through hole is formed by irradiating a laser beam, a first layer provided on the side opposite to the main surface irradiated with the laser beam and the remaining second layer The first layer has a higher content of the laser light absorber than the second layer and a lower sintering start temperature, and the content of the laser light absorber and the start of sintering. A plurality of layers having different temperatures are bonded to each other, and the plurality of first layers have a content of the laser beam absorbent toward a main surface opposite to the main surface irradiated with the laser light. A ceramic green sheet characterized by being laminated so as to increase the sintering start temperature as it increases. The softening point of the glass contained in the plurality of first layers is lower than the softening point of the glass contained in the second layer, and the first layers of the plurality of glass layers have different softening points. The ceramic green sheet according to claim 1 , wherein the ceramic green sheets are laminated so that a softening point of the glass is lowered toward a main surface opposite to the main surface irradiated with light.   The plurality of first layers include an oxidant that promotes degreasing. The plurality of first layers have different contents of the oxidant, and the content of the oxidant is different from that of the laser beam. The ceramic green sheets according to claim 1 or 2, wherein the ceramic green sheets are laminated so as to increase toward a main surface opposite to the main surface to be irradiated.   The ceramic green sheet according to claim 3, wherein the oxidizing agent is copper oxide.   A ceramic green sheet according to any one of claims 1 to 4 is irradiated with laser light to form a through hole, and then the through hole is filled with a conductive paste, and then the conductive paste is filled. A method for producing a ceramic multilayer substrate, comprising: laminating a plurality of the ceramic green sheets thus produced to produce a laminate, and then firing the laminate.

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