JP2008294246A - End electrode forming method of low-temperature baked ceramic multilayer substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an end electrode forming method of a highly reliable LTCC substrate which can prevent occurrence of a crack in a castellation conductor layer even if the LTCC substrate is used as a ceramic multilayer substrate. <P>SOLUTION: A low temperature baked ceramic green sheet 11 is generated and a through hole 13 is formed so that it straddles a splitting line 12. The through hole 13 is filled with conductor paste and a conductor layer 14 is formed. The conductor layer with which the through hole is filled is opened by using a first pin or a metallic mold whose diameter is smaller than width of the through hole, and an opening part 15 is formed. Small holes 15a and 15b are formed on the splitting lines 12 at both ends in a longitudinal direction of the through hole by using a second pin whose size is equal to the first pin or is larger than it. The castellation conductor layers 14a and 14b are formed and they are laminated and press-fitted so as to form a ceramic green block. It is baked and is cut along the splitting lines 12. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  In the present invention, a ceramic green block is formed by laminating and pressing a plurality of layers of low-temperature fired ceramic (LTCC) green sheets, and fired at a relatively low temperature of about 800-1000 ° C., and then cut into individual substrates. The present invention relates to a low-temperature fired ceramic multilayer substrate (LTCC substrate), and more particularly to a method for forming an end face electrode thereof.

Conventionally, as an end face electrode of a ceramic multilayer substrate, it is known that a recess (castellation) is provided on the end face, and a castellation conductor layer (electrode) connected to the internal electrode is provided in the recess (Patent Document 1). The castoration conductor layer is formed by laminating and pressing multiple layers of ceramic green sheets to form a ceramic green block, forming through holes along the dividing line of the multi-chip substrate, and sucking the entire inner surface of the through hole. The conductor paste is printed by this method, and the input / output land pattern is printed. That is, this castellation conductor layer has a ceramic green box set on the suction plate and a screen mask set on the screen mask while applying an air suction force from the suction port formed on the suction plate into the through hole. Is applied to the inner peripheral surface of the through-hole (see column 0003 above).
JP 2001-77507 A

  However, when a low-temperature fired ceramic (LTCC) substrate that can be fired at a low temperature is used as the ceramic multilayer substrate, the thermal expansion coefficient differs greatly between the castellation conductor layer (Ag) and the LTCC substrate. Therefore, there is a problem that a crack progresses in the castellation conductor layer, and the conductive mechanism is broken by the crack, resulting in an open failure.

  The present invention has been made based on the above-mentioned circumstances, and even when an LTCC substrate is used as the ceramic multilayer substrate, cracks are prevented from occurring in the castellation conductor layer (Ag) due to the difference in thermal expansion coefficient. An object of the present invention is to provide a highly reliable method of forming an end face electrode of an LTCC substrate.

  In the method for forming an end face electrode of an LTCC substrate of the present invention, a low-temperature fired ceramic green sheet is prepared, a through hole is formed so as to straddle a dividing line for cutting the green sheet into a number of individual substrates, and a conductor is formed in the through hole. Filling the paste to form a conductor layer, opening the conductor layer filled in the through hole using a first pin or mold having a diameter smaller than the width of the through hole, forming an opening, Using a second pin having a size equal to or larger than the pin on the dividing line at both longitudinal ends of the through hole, a small hole is formed, and a castellation conductor layer is formed on a side edge of the through hole, A plurality of green sheets are laminated and pressed to form a ceramic green block, fired, and cut along the dividing line.

  According to the present invention, since the end face electrode of the LTCC substrate is formed with the above-described configuration, the difference in thermal expansion coefficient between the LTCC substrate and the castellation conductor layer (Ag) in the temperature cycle test of the LTCC substrate at the completion stage or the like. Can be released to the small hole portion, thereby preventing the castellation conductor layer from being cracked, and the problem that the conductive mechanism is broken by the crack can be solved.

  Further, a small hole is further formed in the middle portion of the castellation conductor layer using a second pin having a size equal to or larger than that of the first pin, whereby thermal expansion between the LTCC substrate and the castellation conductor layer is achieved. The effect of dispersing the stress generated from the difference in coefficients can be further increased, and a more reliable end face electrode of the LTCC substrate can be formed.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a method for forming an end face electrode of a low-temperature fired ceramic multilayer substrate according to the present invention in the order of steps.

  First, a ceramic green sheet is prepared by a method such as a doctor blade using a slurry in which resin, plasticizer, dispersant, etc. are added to ceramic powder made of alumina and glass material that can be fired at low temperature. The green sheet 11 is cut out. The green sheet 11 is a multi-piece sheet, and is finally cut into a large number of individual substrates by dividing lines 12 (see (a)).

  Next, a through hole 13 is formed so as to straddle the dividing line 12 using a punching die or a punching machine (see (b)). Then, the through hole 13 is filled with Ag paste using a metal mask or the like and dried to form the conductor layer 14 (see (c)). Then, the conductor layer 14 filled in the through hole 13 is continuously punched by using the first pin having a diameter smaller than the width of the through hole to form the opening 15 (see (d)). In this embodiment, it is preferable to form the opening 15 by opening the conductor layer using a pin having a diameter of about 0.3 mm with respect to the width of the through hole of about 0.4 mm.

  Next, small holes 15 a and 15 b are formed on the dividing line 12 at both ends in the longitudinal direction of the through hole 13 using a second pin having a size equal to or larger than the first pin, and the side edges of the through hole 13 are formed. Castoration conductor layers 14a and 14b are formed in the portion (see (e)). Further, small holes 15c and 15d are formed in the middle portion of the castellation conductor layers 14a and 14b using a second pin having a size equal to or larger than the first pin used for forming the opening of the conductor layer 14. Thus, the castellation conductor layers 14a and 14b on both sides of the dividing line 12 in the through hole 13 are insulated and separated in the middle thereof to form castellation conductor layers 14c, 14d, 14e, and 14f (see (f)). .

  Thereafter, an internal electrode pattern is formed by a method such as screen printing. Then, a plurality of green sheets produced by the above procedure are stacked and pressed by a uniaxial press or an isostatic press to form a ceramic green block. And a half cut is formed along the parting line 12, and it bakes in the range of 800-1000 degreeC. Furthermore, if necessary, a plating process, a dividing process, etc. are performed to complete an LTCC substrate having an internal circuit wiring pattern. Various electronic components are mounted on the surface layer as necessary.

  FIG. 2 shows a detailed structure example of the end face electrode portion of the LTCC substrate of the present invention. As an example, the distance A between the castellation conductor layers is about 0.3 mm, and the distance B between the castellations (recesses) is about 0.4 mm. Therefore, the thickness of the castellation conductor layer is about 0.05 mm. On the other hand, the diameters C and D of the small holes 15a, 15b, 15c, and 15d are equivalent to the first pin that forms the opening 15 by continuously punching and opening the conductor layer 14 filled in the through hole 13. Alternatively, it is formed using a second pin having a size larger than that, and the size is equal to or larger than the distance A between the castellation conductors.

In the simulation result of the above structural example, when the thermal expansion coefficient of the LTCC substrate is 5.5 × 10 ⁻⁶ / K and the thermal expansion coefficient of the castellation conductor layer (Ag) is 19.6 × 10 ⁻⁶ / K, the caster The thermal stress applied to the insulation conductor layer (Ag) is about 170 to 220 MPa.

By the way, in the HTCC board | substrate which consists of a normal alumina board | substrate, the thermal expansion coefficient of the main component material is an alumina 7.0 * 10 < ^-6 > / K, tungsten 4.5 * 10 < ^-6 > / K, molybdenum 5.5 * 10. a ^-6 / K, the thermal stress on the castellation conductor layers of the LTCC substrate is seen much larger compared to the case of the HTCC substrate.

  According to the present invention, there are provided two small holes (15a, 15b) on both sides of the castellation conductor layer (15a, 15b), preferably two (15c, 15d) in the middle of the castellation conductor layer. The stress resulting from the difference in thermal expansion coefficient with the conductor layer can be dispersed in each small hole portion, and the stress applied between the LTCC substrate and the conductor layer can be relaxed, and the castellation conductor layers 14c, 14d, and 14e. , 14f can be prevented from cracking.

  Therefore, this LTCC substrate is excellent in heat resistance and moisture resistance, and by using Ag having a low resistance loss as a wiring conductor, while taking advantage of good loss characteristics (frequency characteristics) in a high frequency circuit, the end face Reliability in the electrode can be increased. Further, in the present invention, for each layer of the green sheet, the conductor layer filled in the through hole is continuously punched using the first pin having a diameter smaller than the width of the through hole to form the opening, and the small hole is provided. The caster conductor layer is formed, and the caster conductor layer of the LTCC substrate is formed by laminating and press-bonding the cast conductor layer. Therefore, even when the longitudinal length of the through hole is variable, the same pin can be used efficiently. A castellation conductor layer can be formed.

  In addition, since one green sheet is relatively thin, about 50 to 200 μm, it is possible to fill a through hole by printing a conductor paste to form a conductor layer, and a castellation conductor layer for each green sheet. Therefore, the adhesion between the castellation conductor layer and the LTCC substrate can be improved. In addition, the castoration conductor layer can be efficiently formed without the need for a suction device or the like required for forming the castellation conductor layer of Patent Document 1.

  In the above embodiment, an example in which the opening of the conductor layer filled in the through hole is formed by continuously punching using a small-diameter pin has been described, but a mold may be used for forming the opening. Good.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

It is a top view which shows the process order of the end surface electrode formation method of the low-temperature baking ceramic multilayer substrate of one Embodiment of this invention. It is a top view which shows arrangement | positioning of the end surface electrode of the low-temperature baking ceramic multilayer substrate of one Embodiment of this invention.

Explanation of symbols

11 Green sheet 12 Dividing line 13 Through hole 14 Conductor layer 15 Small hole

Claims (4)

Create a low-temperature fired ceramic green sheet,
A through hole is formed so as to straddle a dividing line for cutting the green sheet into a large number of individual substrates,
Filling the through hole with a conductor paste to form a conductor layer,
Opening the conductor layer filled in the through hole using a first pin or mold having a smaller diameter than the width of the through hole, forming an opening,
A small hole is formed on the dividing line at both ends in the longitudinal direction of the through hole using a second pin having a size equal to or larger than the first pin, and a castellation conductor layer is formed on a side edge of the through hole. Form the
A method of forming an end face electrode of a low-temperature fired ceramic multilayer substrate, wherein a plurality of green sheets are laminated and pressed to form a ceramic green block, fired, and cut along the dividing line.   2. The low-temperature fired ceramic multilayer substrate according to claim 1, wherein a small hole is further formed in the middle portion of the castellation conductor layer using a second pin having a size equal to or larger than the first pin. End electrode forming method.   2. The method for forming an end face electrode of a low-temperature fired ceramic multilayer substrate according to claim 1, wherein the conductor paste is a silver paste. 2. An opening is formed by continuously punching using a first pin having a diameter smaller than the width of the through hole to open a conductor layer filled in the through hole. A method for forming an end face electrode of a low-temperature fired ceramic multilayer substrate.

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