JP2010232257A - Multilayer wiring board - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a multilayer wiring board for preventing peeling of a connection pad installed on the surface of an insulating substrate and controlling a large projection of through-conductor from the surface of the insulating substrate. <P>SOLUTION: Inner wiring layers 2 and the through-conductors 3 are installed inside the insulating substrate 1, formed of a plurality of glass ceramic insulating layers 11, 12, 13 and 14. The connection pad 4 having an area larger than a cross section of each through conductor 3 is arranged on the surface of the insulating substrate 1 so that it is connected to the through-conductor 3 in the multilayer wiring board. The connection pad 4 is provided with a first conductor layer 41, which is brought into contact with the through conductor 3, a glass ceramic intermediate layer 43 including a circular part 431 covering a peripheral edge of the first conductor layer 41 and two belt-like parts 432 crossing just above the through conductor 3, and a second conductor layer 42, which is electrically connected to the first conductor layer 41, in a region excluding the circular part 431 and the belt-like part 432. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a multilayer wiring board having a connection pad for connection to a surface mount component or an external circuit board.

  In recent years, with the miniaturization of electronic devices and the digitization of circuits, a high-density multilayer wiring board has been required, and the BGA (ball grid array) type is mainly used for mounting on an external circuit board. It has become.

  For example, a multilayer wiring board on which a semiconductor element is mounted includes an insulating base made of ceramics having a mounting portion on which the semiconductor element is mounted on the upper surface, and a copper led out from the semiconductor element mounting portion of the insulating base or its periphery to the lower surface, The structure includes a through conductor made of silver, gold or the like, and a plurality of connection pads formed on the lower surface of the insulating base and electrically connected to the through conductor.

  When mounting the multilayer wiring board on the external circuit board, the solder pads are used to reflow the connection pads provided on the upper surface of the external circuit board and the connection pads provided on the lower surface of the multilayer wiring board. Are soldered together.

Here, the thermal expansion coefficient of the multilayer wiring board is about 4 × 10 ⁻⁶ / ° C. to 12 × 10 ⁻⁶ / ° C., whereas the external circuit board is generally formed of a resin material such as a glass epoxy resin. Since the thermal expansion coefficient is about 15 × 10 ⁻⁶ / ° C. to 50 × 10 ⁻⁶ / ° C., it is greatly different.

  Therefore, when the heat generated during the operation of the semiconductor element repeatedly acts on the multilayer wiring board and the external circuit board, a large thermal stress is repeatedly generated in the horizontal direction due to the difference in thermal expansion between the two. And there existed a problem that a connection pad will peel from the periphery by repetition of this thermal stress.

  Therefore, in order to prevent the connection pad from peeling off from the outer edge, a multilayer wiring board in which the peripheral portion of the connection pad is covered with an insulating film has been proposed (see Patent Document 1 and Patent Document 2).

See JP-A-6-310614 See JP 2002-198637 A

  On the other hand, a multilayer wiring board having an insulating substrate made of glass ceramics shrinks in volume by about 40 to 50% due to sintering from the state of the glass ceramic green sheet laminate before sintering. At this time, the conductor material used for the through conductor is designed to adjust the composition and the raw material particle diameter so that the shrinkage rate approaches the shrinkage rate of the glass ceramic green sheet and allows simultaneous firing.

  However, the shrinkage rate of the glass ceramic green sheet is generally anisotropic, and there is a difference between the shrinkage rate in the direction parallel to the main surface of the multilayer wiring board (plane direction) and the shrinkage rate in the direction perpendicular to the thickness (thickness direction). There is a case. Here, when the shrinkage rate in the thickness direction of the glass ceramic green sheet is larger than the shrinkage rate in the plane direction, the shrinkage rate in the thickness direction of the glass ceramic green sheet is larger than the shrinkage rate in the thickness direction of the through conductor, When the thickness of the penetrating conductor after bonding becomes larger than the thickness of the insulating base, the penetrating conductor protrudes from the surface of the insulating base.

  Therefore, even if the peripheral portion of the connection pad is covered with an insulating film, even if peeling from the peripheral portion of the connection pad is prevented, the through conductor protrudes from the surface of the insulating base, so that the mounting reliability of the surface mount component and There has been a problem that the reliability of bonding with the external circuit board is lowered.

  The present invention has been made in view of such circumstances, and while preventing the connection pads provided on the surface of the insulating base from being peeled off, the through conductor is prevented from greatly protruding from the surface of the insulating base. An object is to provide a multilayer wiring board.

  In the present invention, an internal wiring layer and a through conductor are provided inside an insulating base composed of a plurality of glass ceramic insulating layers, and the cross section of the through conductor is connected to the through conductor on the surface of the insulating base. A multilayer wiring board provided with a connection pad having a large area, wherein the connection pad includes a first conductor layer in contact with the through conductor, an annular portion covering a peripheral portion of the first conductor layer, and the through conductor And a second ceramic layer electrically connected to the first conductor layer in a region excluding the annular portion and the belt-like portion. It is characterized by this.

  According to the present invention, since the peripheral portion of the first conductor layer is covered with the annular portion of the glass ceramic intermediate layer, first peeling of the first conductor layer is suppressed. And since the 2nd conductor layer is joined to the 1st conductor layer in the field near the peripheral part, exfoliation of the 2nd conductor layer is controlled.

  Further, since the glass ceramic intermediate layer includes two strips intersecting immediately above the through conductor, the intersecting portion of the two strips acts to suppress the protrusion of the through conductor during the sintering process. Thus, it is possible to obtain a multilayer wiring board in which the through conductor is prevented from greatly protruding from the surface of the insulating base.

It is a schematic sectional drawing of one Embodiment of the multilayer wiring board of this invention. It is a plane perspective view of the connection pad shown in FIG. It is an AA arrow schematic sectional drawing shown in FIG. FIG. 3 is a schematic cross-sectional view taken along line B-B shown in FIG. 2. It is a schematic sectional drawing of other embodiment of the multilayer wiring board of this invention.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  FIG. 1 is a schematic cross-sectional view of an embodiment of a multilayer wiring board according to the present invention. The multilayer wiring board shown in FIG. 1 is disposed inside an insulating substrate 1 composed of a plurality of glass ceramic insulating layers 11, 12, 13, and 14. The internal wiring layer 2 and the through conductor 3 are provided, and the connection pad 4 having an area larger than the cross section of the through conductor 3 is provided on the surface of the insulating base 1 so as to be connected to the through conductor 3.

  An insulating substrate 1 composed of a plurality of glass ceramic insulating layers 11, 12, 13, and 14 is obtained by sintering a glass ceramic green sheet or paste mainly composed of a crystalline glass powder on which crystals are deposited after firing and a ceramic filler. And has a crystalline phase and residual glass. Residual glass refers to glass that remains as glass without being deposited as crystals from crystalline glass by firing.

  The crystal phases contained in the glass ceramic insulating layers 11 to 14 include alumina, zirconia, quartz, cristobalite, cordierite, mullite, spinel, garnite, enstatite, forsterite, anorsite, slausonite, serdian, diopside, Examples include hardestite, montericite, akermanite, willemite, its solid solution, and substituted derivatives. Among these crystal phases, alumina, zirconia, cordierite, and serdian are preferable in terms of improving the bending strength, and forsterite, quartz, in terms of reducing transmission loss of high-frequency signals by reducing the dielectric constant. Diopside is preferred.

  Here, a plurality of crystal phases may coexist. Further, the crystal phase may be precipitated from a crystalline glass powder by firing, or may be precipitated by reaction with a ceramic filler, or may be included as crystals from the raw material (ceramic filler) stage. Good. Further, the amount of residual glass is preferably 10% by volume or less, particularly 5% by volume or less from the viewpoint of the bending strength and dielectric loss of the multilayer wiring board. This amount of residual glass can be determined from the XRD diffraction pattern by Rietveld analysis.

  An internal wiring layer 2 and a through conductor 3 are provided inside the insulating base 1. The internal wiring layer 2 and the through conductor 3 contain a low-resistance conductor such as Cu, Ag, Au or the like as a main component, and other metals, metal oxides, glass, and the like as long as the electrical resistance and thermal conductivity are not reduced. In addition, ceramics and the like may be included.

  As shown in FIGS. 2 to 4, connection pads 4 connected to the through conductors 3 are provided on the surface of the insulating base 1. The connection pad 4 is formed in an area larger than the cross section of the through conductor 3, and functions as a connection terminal with a surface-mounted component or an external circuit board.

  The connection pad 4 is a glass including a first conductor layer 41 that is in contact with the through conductor 3, an annular portion 431 that covers the peripheral portion of the first conductor layer 41, and two strips 432 that intersect just above the through conductor 3. The ceramic intermediate layer 43 and the second conductor layer 42 electrically connected to the first conductor layer 41 in the region excluding the annular portion 431 and the strip-like portion 432 are included.

  The first conductor layer 41 and the second conductor layer 42 are formed of the same material as the internal wiring layer 2 and the through conductor 3, and contain a low-resistance conductor such as Cu, Ag, Au as a main component, Usually, it is formed in a disk shape having a diameter of about 1.2 to 2 times the diameter of the through conductor 3 to be connected.

  And between the 1st conductor layer 41 and the 2nd conductor layer 42, the glass ceramic intermediate | middle layer 43 which has the cyclic | annular part 431 and the strip | belt-shaped part 432 is provided. The glass ceramic intermediate layer 43 refers to a region included in the connection pad 4 in the ceramic coating formed from the surface of the insulating base 1 around the connection pad 4, and is formed of the same material as the formation material of the insulating base 1. It has been done.

  Specifically, an annular portion 431 is provided so as to cover the peripheral edge portion of the first conductor layer 41. The annular portion 431 is for suppressing peeling of the first conductor layer 41 during manufacture and use. From the viewpoint of conduction (electrical characteristics) between the first conductor layer 41 and the second conductor layer 42 and the suppression of peeling of the first conductor layer 41, the inner diameter of the annular portion 431 is the same as that of the first conductor layer 41. It is preferably 75 to 90% of the outer diameter (the outer diameter of the annular portion 431).

  In addition, on the region of the first conductor layer 41 that is not covered with the annular portion 431, two belt-like portions 432 that intersect just above the through conductor 3 are provided. The two strips 432 act so that the intersecting portion of the two strips suppresses the protrusion of the through conductor 3 during the sintering process, and the through conductor 3 protrudes greatly from the surface of the insulating substrate 1. It is for suppressing. A sufficient protrusion suppression effect is obtained when the number of the belt-like portions 432 is two instead of one and intersects immediately above the through conductor 3. Here, from the viewpoint of conduction (electrical characteristics) between the first conductor layer 41 and the second conductor layer 42 and the suppression of the protrusion of the through conductor 3, the width of the belt-like portion 432 is the cross section of the through conductor 3. It is preferably 30 to 50% of the diameter.

  In addition, it is preferable that the two strip | belt-shaped parts 432 are provided so that it may orthogonally cross as shown in FIG. 1 from the point which suppresses peeling from any part of the 1st conductor layer 41 equally.

  A second conductor layer 42 is provided on the glass ceramic intermediate layer 43, and the second conductor layer 42 is electrically connected to the first conductor layer 41 in a region excluding the annular portion 431 and the belt-like portion 432. ing. Since the region excluding the annular portion 431 and the belt-like portion 432 is a region close to the peripheral portion of the second conductor layer 42, for example, the second conductor layer 42 is compared with the case where it is connected to the through conductor near the center. The peeling of is suppressed.

  Here, as shown in FIG. 5, the first conductor layer 41 has a larger area than the second conductor layer 42, and the inner periphery of the annular portion 431 and the outer periphery of the second conductor layer 42 are viewed from above. In the case where they substantially match, the second conductor layer 42 is joined to the first conductor layer 41 at a portion closer to the peripheral edge, and peeling of the second conductor layer 42 is further suppressed.

  The connection pad 4 refers to a region up to the outer periphery of the first conductor layer 41 or the second conductor layer 42 as viewed from above, and usually the outer periphery of the first conductor layer 41. It means the area up to. In addition to the connection pads 4, a surface wiring layer may be provided on the surface of the insulating substrate 1.

  Next, the manufacturing method of said multilayer wiring board is demonstrated.

  First, glass ceramic green sheets that become glass ceramic insulating layers 11, 12, 13, and 14 after firing are prepared. The glass ceramic green sheet is formed of a material mainly composed of crystalline glass powder 30 to 100% by mass and ceramic filler 0 to 70% by mass.

The glass powder, and the SiO ₂ 20 to 60 wt%, and the _Al 2 _{O 3} 10 to 25 wt%, the MgO 8 to 35 wt%, and 10 to 20 wt% of _BaO, B _{2 O 3,} Y _At least one selected from ₂ O ₃ , CaO, SrO, Na ₂ O, SnO ₂ , P ₂ O ₅ , ZrO ₂ and Li ₂ O is 0 to 20% by mass, and includes diopside, hardistonite, It is preferable to form at least one crystal among celsian, cordierite, anorsite, garnite, willemite, spinel, mullite, forsterite, and sourite. As the ceramic _{filler, Al 2 O 3, SiO 2} , MgTiO 3, CaZrO 3, CaTiO 3, BaTi 4 O 9, Mg 2 SiO 4, SrTiO 3, ZrTiO 4, ZrO 2, TiO 2, AlN, Si 3 Those containing at least one selected from N ₄ are preferred.

  Using this material as a main component, a volatile organic binder that easily volatilizes during firing, an organic solvent and, if necessary, a plasticizer are mixed to form a slurry, and this slurry is used by a lip coater method or a doctor blade method. Tape molding is performed and the glass ceramic green sheet is produced by cutting into a predetermined size.

  Next, a through hole having a desired shape is formed in the obtained glass ceramic green sheet by a method such as laser, punching or etching. Then, the through hole paste is filled in the through hole. As a through-conductor paste, a paste prepared by adding an organic binder, an organic solvent, and, if necessary, an organic or inorganic additive to Cu powder, Ag powder, Au powder or the like and kneading them with a three-roll is used. For the filling, a screen printing method using a metal mask or an emulsion mesh screen mask drilled at a location corresponding to the through hole is used. At this time, as a method of extruding the through-conductor paste through the mask, a method using a normal polyurethane plate-like (or sword-like) squeegee, or a method of pressurizing and injecting using a paste extrusion squeegee head Good. Further, the viscosity of the through conductor paste and the printing conditions are adjusted, and the filled through conductor paste is overfilled so as to protrude from the surface of the glass ceramic green sheet through the through hole. Thereafter, if necessary, the protruding paste for through conductor is pressed and pushed into the through hole.

  Next, on one main surface of the glass ceramic green sheet disposed in the inner layer, a conductive paste for forming the internal wiring layer 2 is applied by screen printing or the like, and one of the glass ceramic green sheets disposed in the surface layer is applied. A conductor paste for forming the first conductor layer 41 constituting the connection pad 4 is applied to the main surface by a screen printing method or the like. Here, the conductor paste is kneaded with three rolls by adding an organic binder, an organic solvent and, if necessary, an organic or inorganic additive to any of gold powder, silver powder, copper powder and aluminum powder. It is prepared in the same manner as the through-conductor paste or with a different viscosity.

  Further, in the glass ceramic green sheet in which the conductor paste for forming the first conductor layer 41 is applied by a screen printing method or the like, the annular portion 431 is formed on the conductor paste for forming the first conductor layer 41. And a glass ceramic paste for forming a glass ceramic intermediate layer 43 composed of the belt-like portion 432 is applied by screen printing or the like. Note that the glass ceramic paste is applied to a region other than the region to be the connection pad 4, and the coating region may extend not only around the connection pad 4 but also over the entire main surface of the glass ceramic green sheet.

  Furthermore, in the glass ceramic green sheet to which the glass ceramic paste is applied, the conductor paste for forming the second conductor layer 42 is made such that the outer periphery of the second conductor layer 42 is at least larger than the inner periphery of the annular portion 431. Apply by screen printing or the like. Note that the conductive paste for forming the second conductive layer 42 is the same as the conductive paste for forming the first conductive layer 41.

  The glass ceramic green sheets thus obtained are laminated in a predetermined arrangement to produce a glass ceramic green sheet laminate, and then fired. Specifically, after heat-treating at 400 to 750 ° C. to decompose and remove organic components in the glass ceramic green sheet laminate, it is sufficiently sintered and prevented from oversintering at 800 to 1000 ° C. Bake. In addition, the firing atmosphere is appropriately selected, such as an oxidizing atmosphere when Ag powder is the main component of the conductive paste, and a non-oxidizing atmosphere when Cu powder is the main component.

  According to the present invention, during firing, due to the anisotropy of the shrinkage rate of the glass ceramic green sheet, the through conductor paste is likely to protrude greatly from the surface of the glass ceramic green sheet laminate. It acts as if the glass ceramic paste that has started to be pressed is pressed down. Therefore, the protrusion of the through conductor 3 after firing from the insulating base 1 can be suppressed, and the mountability of the surface mount component and the connection reliability with the external circuit board can be improved.

As a forming material of the glass ceramic green sheet, 23.8% by mass of SiO ₂ , 8.4% by mass of Al ₂ O ₃ , 15.4% by mass of MgO, 26.5% by mass of BaO, 17.9% by mass. Glass powder having an average particle diameter of 2.5 μm, consisting of B ₂ O ₃ , 4.9 mass% CaO, 0.4 mass% SrO, 1.0 mass% SnO ₂ , 1.7 mass% ZrO _2. 60% by mass and 40% by mass of an Al ₂ O ₃ filler having an average particle diameter of 2.5 μm were prepared.

  An acrylic organic binder, a plasticizer, and an organic solvent were added to this glass ceramic green sheet forming material to prepare a slurry, which was thinned by a doctor blade method to prepare a glass ceramic green sheet. At this time, the ceramic green sheet was prepared to have a thickness of 125 μm.

  Next, beta quartz, barium borosilicate glass, and organic vehicle are added to Ag powder, and after stirring these, they are mixed with a three-roll mill until there is no aggregate of silver powder and organic binder, and paste is formed. Produced. The organic vehicle was composed of 5 parts by mass of ethyl cellulose as an organic binder and 95 parts by mass of α-terpineol as an organic solvent, and 15 parts by mass of this organic vehicle was added to 100 parts by mass of silver powder.

  Next, a through-hole having a diameter of 75 μm was formed in the glass ceramic green sheet with a laser, and the above-described conductor paste was filled in the through-hole. An on-contact printer equipped with a paste extrusion head was used for filling the conductor paste.

  Next, the glass ceramic green sheet in which the through hole was filled with the conductive paste was pressed with a flat plate mold, and the portion of the conductive paste that protruded from the glass ceramic green sheet surface was pressed into the through hole.

  Screen printing of the above-mentioned conductor paste as an internal wiring layer on the glass-ceramic green sheet disposed in the inner layer of the glass-ceramic green sheet laminate described later, among the plurality of glass-ceramic green sheets in which the through-hole is filled with the conductor paste Was applied.

  In addition, among the plurality of glass ceramic green sheets in which the through holes are filled with the conductive paste, the above-mentioned conductor as a first conductor layer is formed on the glass ceramic green sheet disposed on the surface layer of the glass ceramic green sheet laminate described later. The paste was applied to a diameter of 100 μm by screen printing.

  And the glass ceramic paste used as the cyclic | annular part and strip | belt-shaped part as a glass-ceramic intermediate layer was apply | coated by screen printing on the conductor paste used as a 1st conductor layer. The same slurry as the glass ceramic green sheet forming material was used as the glass ceramic paste. The annular portion is formed with an inner diameter of 75 μm and an outer diameter of 100 μm, and the line widths of the strip portions are 20, 30, and 40 μm (Sample Nos. 1, 2, and 3) so that the two strip portions intersect in a cross shape. It was made by changing. Further, a sample having no belt-like part (sample No. 4) was also produced.

  Further, on the conductor paste to be the first conductor layer and the glass ceramic intermediate layer, the conductor paste to be the second conductor layer was applied to a diameter of 100 μm by screen printing with the central axis aligned.

  In addition, it produced also about the thing (sample No. 5) which does not have a strip | belt-shaped part and an annular part and does not have a 2nd conductor layer.

  Next, after aligning these glass ceramic green sheets, four layers are laminated to produce a glass ceramic green sheet laminate, which is debindered at 400 ° C. in the atmosphere and then fired at 900 ° C. in the atmosphere. Thus, a multilayer wiring board was produced.

  In the obtained multilayer wiring board, surface irregularities were measured with a three-dimensional laser displacement meter. The measurement range was a range of 3 mm × 3 mm in which the connection pad at the center of the multilayer wiring board was formed, and the difference between the lowest point and the highest point in the obtained measurement data was defined as the protrusion amount (projection height). The results are shown in Table 1. Table 1 shows the maximum value of the protrusion amount (projection height) as a result of measuring five multilayer wiring boards, and a protrusion amount of less than 25 μm was regarded as a good product.

Moreover, in the obtained multilayer wiring board, the peel strength of the connection pads soldered by reflowing at 240 ° C. was evaluated by a solder tensile test. The results are shown in Table 1. Table 1 shows the average value of peel strength obtained by 20 tensile tests, and a peel strength of 69 N / cm ² or higher was determined as a good product. In all the samples shown in Table 1, peeling occurred between the first conductor layer and the insulating substrate.

  Further, in the obtained multilayer wiring board, the direct current resistance between the connection pad on the upper surface and the connection pad on the lower surface electrically connected by the through conductor was obtained with an ammeter. The results are shown in Table 1.

According to Table 1, sample no. In Nos. 1 to 3, the protrusion amount was 17 μm or less, and the peel strength by the tensile test was 74 N / cm ² or more, and good results of the protrusion amount and peel strength were obtained. In addition, it turns out that peeling strength is increasing, when the width | variety of a strip | belt-shaped part becomes large.

  On the other hand, the sample No. outside the scope of the present invention in which the annular portion, the band-like portion and the second conductor layer are not formed. In No. 5, the protrusion amount was as large as 25 μm, and the peel strength was as low as 3.7 μm.

  In addition, although the annular portion and the second conductor layer are formed, the sample No. outside the scope of the present invention is not formed with the band-shaped portion. In No. 4, the peel strength was in a range where there was no problem, but the protrusion amount was as large as 25 μm.

  From the DC resistance values measured for all samples, it can be seen that the narrower the band width, the smaller the resistance value. This is probably because the substantial transmission path becomes longer.

DESCRIPTION OF SYMBOLS 1 ... Insulating base | substrate 11, 12, 13, 14 ... Glass ceramic insulating layer 2 ... Internal wiring layer 3 ... Through-conductor 4 ... Connection pad 41 ... 1st conductor layer 42- .... Second conductor layer 431 ... annular part 432 ... band-like part

Claims (1)

An internal wiring layer and a through conductor are provided inside an insulating base made of a plurality of glass ceramic insulating layers, and a connection having a larger area than the cross section of the through conductor is connected to the through conductor on the surface of the insulating base. A multilayer wiring board provided with a pad, wherein the connection pad intersects a first conductor layer in contact with the through conductor, an annular portion covering a peripheral portion of the first conductor layer, and immediately above the through conductor. And a second ceramic layer electrically connected to the first conductor layer in a region excluding the annular portion and the belt-like portion. Multilayer wiring board.

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