JP4936756B2 - Manufacturing method of ceramic capacitor element for built-in multilayer wiring board - Google Patents

Description

  The present invention relates to a capacitor element used in various AV devices, home appliances, communication devices, computers, and electronic devices such as peripheral devices.

  Conventionally, a wiring board has a plurality of wiring conductors formed inside and on the surface of an insulating layer made of a ceramic material such as alumina or an organic resin material such as glass epoxy resin, and an insulating layer is formed between upper and lower wiring conductors. Electrically connected through through conductors formed on the board, and mounting and mounting electronic elements such as semiconductor elements, capacitors and resistance elements on the surface of this wiring board, and connecting these electrodes to each wiring conductor Thus, an electronic device used for an electronic device is formed.

  However, in recent years, electronic devices have been required to be small, thin, and lightweight as represented by mobile communication devices, and wiring boards mounted on such electronic devices are also required to be small and high in density. It has come to be.

In order to meet such requirements, Japanese Patent Application Laid-Open No. 11-217262 discloses a chip inside the wiring board for the purpose of reducing the number of electronic elements mounted on the surface of the wiring board and reducing the size of the wiring board. It has been proposed to mount a capacitor element.
JP 11-217262 A

In recent years, a further miniaturization of electronic devices has been demanded, and along with the miniaturization of the wiring board, the capacitor element incorporated in the wiring board has also been demanded to be miniaturized.

  However, in order to incorporate a chip-like capacitor element as disclosed in JP-A-11-217262 into a wiring board and make an electrical connection with a wiring conductor or through conductor inside the wiring board, the upper surface of the capacitor element and / Or it is necessary to form a surface electrode made of solder or conductive paste on the lower surface by a method such as a screen printing method, but as the capacitor element is miniaturized, it becomes difficult to form a fine surface electrode. There is a problem that it is difficult to reduce the size of the built-in capacitor element.

  In order to form electrodes on the upper surface and / or lower surface of the capacitor element, first, the internal electrode is exposed by polishing the side surface of the capacitor element, and then connected to the internal electrode on the side surface of the capacitor element. An end face electrode must be formed, and then a surface electrode connected to the end face electrode must be formed on the upper surface and / or the lower surface of the capacitor element, resulting in a problem that the process becomes complicated.

  Furthermore, since the thermal expansion coefficients of the capacitor element and the insulating layer are different, when a thermal shock test, which is a high-temperature and low-temperature cycle test, is performed, a large stress is caused between the capacitor element and the insulating layer due to the difference in the thermal expansion coefficient Has occurred, and there has been a problem of disconnection between the electrode of the capacitor element and the wiring conductor disposed on the surface of the insulating layer.

  In recent years, electronic devices such as communication devices have been used in a high frequency region having a frequency of several hundred MHz or more with an increase in communication speed. In such a high frequency region, the electrode of the capacitor element is used. The inductance component due to the length of the wiring conductor that connects to electronic components such as semiconductor elements can no longer be ignored, and when chip capacitor elements are built-in, the electrode leads from each electrode layer of the capacitor element to the end electrode on the side of the capacitor element Furthermore, since there is electrode routing such as electrode drawing to the upper surface and / or lower surface of the capacitor element, the inductance component due to the length of the routing electrode increases, and ΔV = LdI / dt (ΔV is power supply noise, L is the inductance, I is the current value, and t is the time). The noise ΔV becomes so large that it cannot be ignored, which causes problems such as malfunctions in electronic devices such as communication devices.

  The present invention has been devised in view of the problems of the prior art, and its purpose can contribute to the provision of a small and lightweight multilayer wiring board with a built-in capacitor element that is excellent in connection reliability and electrical characteristics. It is to make a capacitor element.

The present invention relates to a ceramic capacitor element for built-in multilayer wiring board, which is formed by firing an unfired laminated body in which a plurality of electrode layers and a plurality of ceramic dielectric layers are alternately laminated, and is used inside a multilayer wiring board. A method of preparing an unfired laminate in which a plurality of electrode layers and a plurality of ceramic dielectric layers are alternately laminated, and a laser on the unfired laminate with respect to the electrode layers you fill a conductive paste from the opening of the parallel long side with respect to the vertical and step direction cross-sectional shape to form the through-holes are trapezoidal, the electrode layer of the cross-sectional shape of the trapezoidal in the through hole Te a step, wherein the conductive paste is fired together with the laminate unfired prior internal to the multilayer wiring board, it includes a step of forming a lead electrode portion to the end face of the stacking direction to the external connection terminal And features.

The present invention is parallel in the manufacturing method of the multilayer wiring board built ceramic capacitor element, for the cross-sectional shape forming the trapezoidal shape of the lead electrode portions, among the four sides constituting the trapezoid, with respect to the electrode layer ratio of two sides of a long side and a short side (the long side / short side), characterized in that you set to 1.2 to 3 times.

According to the present invention, a method of manufacturing a ceramic capacitor element for incorporating a multilayer wiring board includes a step of forming a through-hole having a trapezoidal cross-sectional shape in a direction perpendicular to an electrode layer by a laser on an unfired laminate. And a step of filling the through hole with the conductive paste from the opening on the long side parallel to the electrode layer having a trapezoidal cross-sectional shape. As a result, when the conductive paste is filled from the opening on the long side parallel to the electrode layer having a trapezoidal cross-sectional shape, the conductive paste is filled to the opening on the short side of the through hole. Since the opening on the side is narrow, the conductive paste can be prevented from leaking unnecessarily outside the through hole. Therefore, the filling rate of the conductive paste can be increased, and as a result, the resistance of the lead electrode portion can be reduced, so that a capacitor element with a smaller inductance component can be manufactured .

  In addition, it is not necessary to provide an end face electrode on the side surface of the capacitor element and route the electrode, and the lead electrode can be formed at the shortest distance immediately above the electrode layer, so that the inductance component can be reduced and the high frequency Even in the region, it can be made excellent in electrical characteristics with small power source noise.

  Furthermore, since the cross-sectional shape in the direction perpendicular to the electrode layer of the lead electrode portion of the capacitor element is trapezoidal, the lead electrode portion is formed by filling the through holes formed in the capacitor element with solder or conductive paste. In this case, the solder or conductive paste can be satisfactorily filled by filling from the long side of the through hole, and as a result, the resistance of the lead electrode portion is smaller and the inductance component is smaller. can do.

  Furthermore, in the above configuration, since the maximum value of the surface roughness of the ceramic dielectric layer surface of the built-in capacitor element is larger than 0.2 μm, the adhesion between the insulating layer and the capacitor element becomes strong, and the temperature cycle test is performed. Even if stress occurs due to the difference in thermal expansion coefficient between the two, the insulating layer is constrained by the capacitor element, and the capacitor element electrode and the wiring conductor disposed on the surface of the insulating layer are separated. And there is no disconnection.

  Next, the multilayer wiring board of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an example of an embodiment of a multilayer wiring board according to the present invention. In this example, a case where one capacitor is built is shown. FIG. 2 is a cross-sectional view showing an example of an embodiment of the capacitor element built in the multilayer wiring board with built-in capacitor of the present invention. In these drawings, reference numeral 1 is an insulating layer, 2 is a wiring conductor, 3 is a through conductor, and 7 is a capacitor element. The capacitor element built-in multilayer wiring board 8 of the present invention is mainly constituted by these. The multilayer wiring board 8 with a built-in capacitor according to this example is formed by laminating three insulating layers 1, and a cavity 4 is formed in at least one layer of the insulating layer 1. 7 is buried.

  The capacitor element 7 incorporated in the multilayer wiring substrate 8 with a built-in capacitor is a rectangular parallelepiped having a length, width, and height of 1 to 5 μm, respectively. As shown in a sectional view in FIG. 2, the electrode layer 5 and the ceramic dielectric layer 6 Are alternately stacked.

As the material of the ceramic dielectric layer 6, various dielectric ceramic materials can be used. For example, a ceramic composition such as BaTiO ₃ , LaTiO ₃ · CaTiO ₃ · SrTiO ₃ , or a composition of BaTiO ₃ . Examples thereof include barium titanate-based materials such as solid solutions in which Ba, which is an element, is partially substituted with Ca and Ti is partially substituted with Zr or Sn, and lead-based perovskite-type structural compounds.

  Moreover, as a material which forms the electrode layer 5, metals, such as Pd, Ag * Pt * Ni * Cu * Pb, and those alloys are used, for example.

  Further, the capacitor element 7 has a lead electrode portion 10 formed by filling a through hole 9 penetrating in a vertical direction with respect to a large number of electrode layers 5. This is important in the present invention.

  According to the multilayer wiring board 8 with a built-in capacitor of the present invention, the capacitor element 7 has the lead electrode portion 10 formed by filling the through holes 9 penetrating in the vertical direction with respect to the multiple electrode layers 5, Since the electrode layer 5 and the through conductor 3 and / or the wiring conductor 2 are electrically connected via the lead electrode portion 10, there is no need to print the end face electrode or the surface electrode on the capacitor element 7, so that the process is performed. In addition to simplification, the capacitor element 7 can be miniaturized because a fine extraction electrode 10 having a diameter of several tens of μm can be easily formed. As a result, the capacitor element built-in multilayer wiring substrate 8 can be miniaturized. In addition, it is not necessary to provide an end face electrode on the side surface of the capacitor element 7 and route the electrode, and the lead electrode 10 can be formed at the shortest distance directly above the electrode layer 5, so that the inductance component can be reduced. Thus, even in a high frequency region, it is possible to achieve excellent electrical characteristics with low power supply noise.

  The through hole 9 formed in the capacitor element 7 is formed by punching a laminated body composed of the electrode layer 5 and the ceramic dielectric layer 6 or performing laser punching by UV-YAG laser, excimer laser, carbon dioxide gas laser, or the like. It is preferably formed by a laser drilling process in order to form the fine through-hole 9 by a method such as an installation process. Further, the diameter of the through hole 9 is several tens of μm to several mm, and may be appropriately determined according to the size of the capacitor element 7.

  The through hole 9 may be subjected to an ultrasonic cleaning process, a desmear process, or the like after the punching process or the laser drilling process in order to improve the electrical connection between the conductor filled inside and the electrode layer 5. .

  Moreover, as a conductor with which the through-hole 9 is filled, metals, such as Pd, Ag * Pt * Ni * Cu * Pb, and those alloys are used, and especially the viewpoint of making the electrical connection with the electrode layer 5 favorable. Is preferably made of the same material as the electrode layer 5.

  The conductor filled in the through hole 9 is filled with a conductive paste in which metal powder is dispersed in an organic vehicle in which an organic binder resin is dissolved in an organic solvent, by a method such as screen printing. Is formed. In addition to these, various dispersants, activators, plasticizers and the like may be added to the vehicle as necessary.

  Further, the organic binder resin used for the conductive paste has a role of uniformly dispersing the metal powder and imparting an appropriate viscosity and rheology for embedding in the through-hole 9. For example, acrylic resin, phenol resin, alkyd resin, rosin Examples include ester, ethyl cellulose, methyl cellulose, PVA (polyvinyl alcohol), and polyvinyl butyrate. In particular, it is preferable to use an acrylic resin from the viewpoint of improving the dispersibility of the metal powder.

  Further, the organic solvent used in the conductive paste has a role of dissolving the organic binder resin to disperse the metal powder particles and making the entire mixed system into a paste, such as α-terpineol or benzyl alcohol. Alcohol-based, hydrocarbon-based, ether-based, ester-based such as BCA (butyl carbitol acetate), naphtha, etc. are used. Especially from the viewpoint of improving the dispersibility of metal powder, alcohol-based such as α-terpineol It is preferable to use a solvent.

  Furthermore, the conductive paste can be a paste to which glass frit or ceramic frit is added in order to increase the adhesive strength to the capacitor ceramic after embedding and firing. In this case, the glass frit or ceramic frit is not particularly limited, and for example, borosilicate-based or zinc borosilicate-based glass, titania, barium titanate-based oxides such as barium titanate can be used as appropriate. .

Such a capacitor element 7 is manufactured by the following method. First, a dielectric layer 6 which is created made by well-known sheet forming method, for example, BaTiO ₃ in the dielectric ceramic green sheet surface, a predetermined shape created made the Ni metal paste by a screen printing method by a known paste operation made Method To form an unfired electrode layer, which are then laminated in a predetermined order and pressed to obtain a laminate. Then, after forming a plurality of through holes 9 at predetermined positions by laser in this laminated body, the through holes 9 are washed with water by ultrasonic cleaning. The through holes 9 are made of, for example, Ni metal powder, acrylic resin, and α-terpineol. The conductive paste is filled by screen printing. Thereafter, these are manufactured by firing at a temperature of 800 to 1600 ° C.

Note that conductors filled in the through-hole 9, after baking the organic binder resin and a solvent is removed, become the lead electrode portions 10, the capacitor element built - in multilayer at the end of the lead electrode portions 10 exposed to the capacitor element 7 surface It is electrically connected to the through conductor 3 and / or the wiring conductor 2 of the wiring board 8.

  Further, in the present invention, it is preferable and important that the cross-sectional shape of the vertical method with respect to the electrode layer 5 of the extraction electrode portion 10 is a trapezoid. According to the multilayer wiring board 8 of the present invention, since the cross-sectional shape in the direction perpendicular to the electrode layer 5 of the extraction electrode portion 10 is trapezoidal, the through-hole 9 formed in the capacitor element 7 is filled with the conductive paste. Thus, when forming the lead electrode portion 10, the conductive paste can be satisfactorily filled by filling from the opening with the longer bottom of the through hole 9, and as a result, the filling rate of the conductive paste is increased. The resistance of the extraction electrode portion 10 can be reduced and the inductance component can be further reduced.

The trapezoidal cross-sectional shape of the extraction electrode portion 10 is preferably 1.2 to 3 times the length of the shorter bottom side, and is less than 1.2 times the extraction electrode portion 10. There is a tendency that can not satisfactorily filled with a conductive paste forming the through hole 9, and there are difficulties and Do that tends to reduce the size of the capacitor element 7 diameter becomes large through hole 9 exceeds 3 times . Accordingly, it is preferable that the trapezoidal cross-sectional shape of the extraction electrode portion 10 is 1.2 to 3 times the length of the shorter bottom side. Further, the extraction electrode portion 10 may be formed so that either the longer base or the shorter base is located on the upper surface or the lower surface of the capacitor element 7.

The surface of the capacitor element 7, the maximum value R _max is larger than 0.2μm arithmetic mean roughness R of the surface of the ceramic dielectric layer 6, preferably 0.5μm or more, preferably not less than 1.0μm and most .

According to the multilayer wiring board 8 with a built-in capacitor element of the present invention, the surface of the ceramic dielectric layer 6 of the built-in capacitor element has a maximum value R _max of the surface roughness R larger than 0.2 μm. Even if it is performed, the adhesion between the insulating layer 1 and the capacitor element 7 is improved, so that the insulating layer 1 is constrained to the capacitor element 7 even if the thermal expansion coefficient of the insulating layer 1 is larger than the thermal expansion coefficient of the capacitor element 7. As a result, the stress generated by the difference in thermal expansion coefficient is reduced, and there is no disconnection between the electrode of the capacitor element 7 and the wiring conductor 2 disposed on the surface of the insulating layer 1. If the maximum value R _max of the surface roughness R of the ceramic dielectric layer 6 exceeds 5 μm, the capacitor element tends to be cracked or chipped. Therefore, the maximum value R _max of the surface roughness R is set to 5 μm. The following is preferable.

  The surface of the ceramic dielectric layer 6 on the surface of the capacitor element is formed at a stage of the green sheet laminate before firing by a method such as roughening treatment by brush polishing on the surface of the laminate or pressing a flat plate processed in advance. The surface roughness can be set to a desired surface roughness by physically baking or baking the surface of the green sheet laminated body with a laser to form a non-through hole and then firing. In addition, the ceramic material used for the ceramic dielectric layer 6 has higher heat resistance during firing and is more reactive with ceramic powder having an average particle size of 10 μm or more, or a part of the ceramic material used for the ceramic dielectric layer 6. Then, the ceramic powder having an average diameter of 10 μm or more may be adhered to the surface of the green sheet laminate so as to be partially embedded and fired to obtain a desired surface roughness. Further, the surface of the capacitor element after firing the green sheet laminate may be roughened by a physical method such as sandblasting or a chemical method such as etching.

Next, the manufacturing method of the multilayer wiring board 8 with a built-in capacitor element according to the present invention will be described in detail with reference to FIG. Figure 3 is a cross-sectional view of each process for fabricating a capacitor element built multilayer wiring board 8 in FIG.

  First, as shown in a cross-sectional view in FIG. 3A, an uncured precursor sheet to be an insulating layer 1 is prepared, and this precursor sheet is penetrated into a desired portion by a diameter of about 17 to 150 μm by laser processing. Hole 11 is drilled.

  Such an uncured precursor sheet that forms the insulating layer 1 is made of an organic resin material such as an epoxy resin, a bismaleimide triazine resin, a thermosetting polyphenylene ether resin, or a liquid crystal polymer resin, and improves mechanical strength. Silane and titanate coupling agents, antioxidants to improve thermal stability, light stabilizers such as UV absorbers to improve light resistance, halogens to improve flame retardancy or Phosphoric acid flame retardants, antimony compounds, flame retardant aids such as zinc borate, barium metaborate, zirconium oxide, higher fatty acids, higher fatty acid esters, higher fatty acid metal salts, fluorocarbons to improve lubricity Lubricants such as surfactants, aluminum oxide and silicon oxide for adjusting thermal expansion coefficient and / or improving mechanical strength・ Fillers such as titanium oxide, barium oxide, strontium oxide, zirconium oxide, calcium oxide, zeolite, silicon nitride, aluminum nitride, silicon carbide, aluminum borate, barium stannate, barium zirconate, strontium zirconate, or fibers You may contain base materials, such as a glass cloth etc. which woven glass-like glass into cloth shape, and the nonwoven fabric which consists of a heat resistant organic resin fiber.

  Such a precursor sheet is manufactured by the following method when, for example, a composite material of a thermosetting resin and an inorganic insulating powder is used as an insulating material. First, a mixture obtained by adding a thermosetting resin to the inorganic insulating powder described above together with a solvent so that the amount of the inorganic insulating powder is 17 to 80% by volume is obtained, and this mixture is used as a kneader (kneader) or means such as three rolls. To make a paste. Then, this paste is formed into a sheet by using a sheet forming method such as a rolling method, an extrusion method, an injection method, or a doctor blade method, and then dried by heating to a temperature at which the thermosetting resin is not completely cured. A precursor sheet to be the insulating layer 1 is manufactured. The paste is preferably prepared by adding a solvent such as toluene, butyl acetate, methyl ethyl ketone, methanol, methyl cellosolve acetate, isopropyl alcohol, methyl isobutyl ketone, or dimethylformamide to the composite material of thermosetting resin and inorganic insulating powder. The fluid having a predetermined viscosity is preferably 100 to 3000 poise depending on the sheet molding method.

  Next, as shown in a cross-sectional view in FIG. 3B, the through-hole 11 is filled with a conductive paste made of copper, silver, gold, solder, or the like by using a conventionally known screen printing method or the like. Conductor 3 is formed.

  Next, as shown in a cross-sectional view in FIG. 3C, a wiring conductor 2 to be attached to the front and back surfaces of the precursor sheet is prepared. Then, as shown in the cross-sectional view of FIG. 3D, the wiring conductor 2 is superimposed and transferred onto the front and back surfaces of the precursor sheet so that the necessary wiring conductor 2 and the through conductor 3 are electrically connected. To do.

  In this embodiment, the wiring conductor 2 is formed by a transfer method. Such a wiring conductor 2 is formed by the method described below. First, an electrolytic metal foil having a thickness of 1 to 35 μm, which is manufactured by plating or the like on the surface of a support 12 such as a release sheet and is made of one or more alloys selected from copper, gold, silver, aluminum and the like. And a resist layer is formed on the surface so as to be a mirror image pattern of a desired wiring pattern, and then a mirror image wiring conductor 2 of a predetermined wiring pattern is formed by etching and resist removal. Next, the deposition of the wiring conductor 2 on the front and back surfaces of the precursor sheet is performed by superimposing the support 12 on which the wiring conductor 2 is formed on the front and back surfaces of the precursor sheet, and then the pressure is 0.5 to 10 MPa. After pressurizing and heating at a temperature of 60 to 150 ° C., the support 12 is peeled off, so that the wiring conductor 2 is attached to the precursor sheet as shown in the sectional view of FIG. At this time, it is important that the through conductor 3 is in an uncured state that is not completely cured.

  As the support 12, known materials such as polyethylene terephthalate, polyethylene naphthalate, polyimide, polyphenylene sulfide, vinyl chloride, and polypropylene can be used. The thickness of the support 12 is suitably 10-100 μm, preferably 25-50 μm. If the thickness of the support 12 is less than 10 μm, the wiring conductor 2 formed by deformation or bending of the support 12 is likely to break, and if the thickness exceeds 100 μm, the flexibility of the support 12 is lost. There is a tendency that peeling of the support 12 becomes difficult. In addition, in order to form the electrolytic metal foil on the surface of the support 12, a known adhesive such as acrylic, rubber, silicon, or epoxy may be used.

  Then, as shown in a sectional view in FIG. 3 (f), a plurality of precursor sheets manufactured through the steps (a) to (f) and the capacitor element 7 are prepared, and then the extraction electrode portion Position and place the tip of 10 through conductor 3 and wiring conductor 2 and stack precursor sheets, hot for 30 minutes to 24 hours under conditions of temperature 150 to 300 ° C and pressure 0.5 to 10 MPa The precursor sheet and the conductive paste are completely cured by pressing to complete the capacitor element built-in multilayer wiring board 8 of the present invention shown in a sectional view in FIG.

  Further, the cavity 4 for accommodating the capacitor element 7 may be formed by a laser method or a punching method at a location where the capacitor element 7 of the precursor sheet is accommodated before the precursor sheet is laminated.

  The multilayer wiring board 8 with a built-in capacitor element according to the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention. Then, the multilayer wiring substrate 8 with a built-in capacitor element is manufactured by laminating the three insulating layers 1, but the multilayer wiring substrate 8 with a built-in capacitor may be fabricated by laminating four or five or more insulating layers. In the above-described embodiment, the insulating layer including the capacitor is one layer, but may be two layers (including a continuous layer) or more.

  Furthermore, the number of lead electrode portions 10 formed in the built-in capacitor element 7 may be two or more per electrode.

It is sectional drawing which shows an example of embodiment of the multilayer wiring board with a built-in capacitor | condenser element of this invention. It is sectional drawing which shows an example of embodiment of the capacitor | condenser element incorporated in the multilayer wiring board with a built-in capacitor | condenser element of this invention. (A)-(g) is sectional drawing for every process for demonstrating the manufacturing method of the multilayer wiring board with a built-in capacitor | condenser element of this invention, respectively.

Explanation of symbols

1 ... Insulating layer
2 .... Wiring conductor
3 ... Penetration conductor
4 ..... Cavity
5 ... ・ ・ ・ ・ ・ Electrode layer
6 ..... Ceramic dielectric layer
7 ・ ・ ・ ・ ・ ・ ・ ・ Capacitor element
8 ········ Capacitor element built-in multilayer wiring board
9 ・ ・ ・ ・ ・ ・ ・ ・ ・ Through hole
10 ・ ・ ・ ・ ・ ・ ・ ・ Extraction electrode part

Claims (2)

A method of manufacturing a ceramic capacitor element for built-in multilayer wiring board, which is formed by firing an unfired multilayer body in which a plurality of electrode layers and a plurality of ceramic dielectric layers are alternately laminated, and is used inside a multilayer wiring board. There ,
Preparing an unfired laminate in which a plurality of electrode layers and a plurality of ceramic dielectric layers are alternately laminated;
A step of direction the cross section perpendicular to said electrode layer by laser to form a through-hole is a trapezoidal shape with respect to the stack of unfired,
A step you filling a conductive paste from the opening of the parallel long side with respect to the electrode layer of the cross-sectional shape of the trapezoidal in the through hole,
Wherein by fired with the laminate of unfired conductive paste before built into the multilayer wiring board, characterized by comprising a step of forming a lead electrode portion to the end face of the stacking direction to the external connection terminal Manufacturing method of ceramic capacitor element for built-in multilayer wiring board. In the manufacturing method of the ceramic capacitor element for multilayer wiring board built-in of Claim 1 ,
Regarding the cross-sectional shape forming the trapezoidal shape of the lead electrode portion, among the four sides constituting the trapezoid, the ratio of the long side and the short side parallel to the electrode layer (long side / short side) is method for manufacturing a multilayer wiring board built ceramic capacitor element characterized in that you set to 1.2 to 3 times.

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