JP2009260382A - Wiring substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring substrate excellent in reliability by raising adhesiveness between a through-hole formed in an insulating substrate and a through conductor provided in the through-hole in the wiring substrate constituted by being equipped with the insulating substrate. <P>SOLUTION: In the wiring substrate 17 constituted by being equipped with: the insulating substrate 1; the through-hole 3 formed on the insulating substrate 1; and the through conductor 5 consisting of a first metal phase 5 formed in the through-hole 3, it is characterized that an inner wall of the through-hole 3 and the through conductor 5 are connected with each other via an intermediate region 6 constituted by containing a second metal layer 6a and inorganic powder 6b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an organic material-based wiring board, and more particularly to a wiring board for mounting a large-scale semiconductor (LSI), and more particularly to a wiring board in which through-holes are narrow and the through-holes are formed at high density. .

  LSIs can process a large amount of information in a short time due to advances in fine wiring processing technology and an increase in operating frequency. A terminal called I / O supplies a large amount of information and power for processing it to a semiconductor. This I / O is expected to increase rapidly in recent years as LSI technology advances. On the other hand, conventionally, an organic material-based wiring board for mounting electronic components such as semiconductor elements has a through-hole penetrating from the upper surface to the lower surface of a glass-epoxy plate, for example. The wiring conductors on both sides were connected to each other.

  For such a wiring board, a double-sided copper-clad plate with copper foils attached to both upper and lower surfaces of an insulating base made of glass-epoxy plate is prepared, and a through-hole penetrating vertically through the double-sided copper-clad plate is drilled. Then, a plating layer made of copper is deposited on the upper and lower copper foils and on the inner surface of the through hole by electroless plating and electrolytic plating, and the plating layers are deposited on the upper and lower copper foils. In addition, a through conductor made of a plating layer is formed on the inner surface of the through hole, and then a photolithography technique is applied to the copper foil deposited on the upper and lower surfaces of the insulating base and the plating layer deposited on the copper foil. It is manufactured by partially etching to form a wiring conductor. Furthermore, in order to form finer wiring, a buildup layer is also formed by a generally known method called a buildup method.

  By the way, as the number of I / Os of LSI increases, in such an organic material-based multilayer wiring board, the density of the through conductors is increased by narrowing the interval between the through conductors (pitch of the through conductors). Is required.

  This is because if the density of the through conductors is not high, the density of the wiring for connecting to the I / O terminal cannot be increased, and as a result, the density of the I / O terminal must be lowered to a density capable of wiring. This is because it cannot be obtained.

  Further, if the density of the through conductors is not high, it is necessary to draw the wiring from the LSI terminal to the outside and then to the mother board side, and the wiring length cannot be shortened. Shortening the wiring length is an indispensable element for preventing deterioration due to transmission of a signal reaching the GHz level.

  For this reason, it is necessary to increase the density of the through conductors. However, if the interval between the through conductors is narrowed, it is difficult to ensure electrical insulation between the through conductors. In order to ensure insulation, it is necessary to reduce the diameter of the through hole as much as possible. At present, attempts have been made to make the diameter of the through hole as small as about 75 to 130 μm. A drilling method using a gas laser has been studied (see Patent Documents 1, 2, and 3).

JP-A-9-05172 JP-A-8-323488 JP-A-6-334301

  However, even when the methods of Patent Documents 1, 2, and 3 are used, there is a problem that the electrical insulation between the through conductors deteriorates if the interval (pitch) between the through conductors is narrowed in order to increase the density of the through conductors. there were.

  This is because the copper plating formed as the through conductor and the insulating base do not have sufficient connection reliability, and a gap is easily generated between the through conductor and the insulating base.

  If there is a gap in this part, when left in a general room for a long time, moisture is condensed in the gap between the through conductor and the insulating base, and an electrochemical short circuit due to the moisture occurs. In addition, various chemicals used in the manufacturing process may remain in this gap, and even if this chemical solution remains in a small amount, it is an ionic component such as chlorine, so that it easily becomes a starting point for electrochemical corrosion. It was promoting the deterioration of insulation.

  The present invention has been devised in view of such conventional problems, and an object of the present invention is to improve the adhesion between the copper plating forming the through conductor and the insulating base, thereby improving the contact between the through conductor and the insulating base. Providing a highly reliable wiring board that eliminates gaps and does not cause a decrease in insulation, and enables the pitch of through conductors to be reduced, thereby reducing LSI size and improving electrical characteristics in the high-frequency region. There is in making it possible.

  A wiring board according to an aspect of the present invention includes an insulating base, a through hole formed in the insulating base, and a through conductor made of a first metal phase formed in the through hole. In the substrate, the inner wall of the through hole and the through conductor are connected via an intermediate region containing a second metal phase and an inorganic powder.

  A wiring board according to an embodiment of the present invention includes an insulating layer, a through hole formed in the insulating layer, and a through conductor made of a first metal phase formed in the through hole. In the substrate, the inner wall of the through hole and the through conductor are connected via an intermediate region containing a second metal phase and an inorganic powder.

  According to the wiring board of the present invention, the intermediate region containing the second metal phase and the inorganic powder, i.e., through the intermediate region of the through-conductor and the through-hole and the through-hole both have high connection affinity, By connecting the through conductor, there is no gap between the through conductor and the through hole, and the reliability of the wiring board is improved.

It is sectional drawing explaining one form of the wiring board of this invention. It is a principal part expanded sectional view of the wiring board of this invention. It is a principal part expanded sectional view of the other form of the wiring board of this invention. It is process drawing explaining the manufacturing method of the wiring board of this invention. It is process drawing explaining the manufacturing method of the wiring board of this invention. It is sectional drawing explaining the other form of the wiring board of this invention.

  For example, as shown in FIG. 1, the wiring board of the present invention is formed by penetrating an insulating substrate 1 containing a glass cloth, a first resin, and a first inorganic powder, and the insulating substrate 1. A through hole 3, a through conductor 5 formed in the through hole 3, an intermediate layer 6 connecting the inner wall of the through hole 3 and the through conductor 5, and a core wiring layer 7 formed on both surfaces of the insulating substrate 1. The insulating layer 9 formed on the main surface of the insulating substrate 1, the through hole 11 formed through the insulating layer 9, the via conductor 13 formed in the through hole 11, and the main surface of the insulating layer 9 The wiring conductor layer 15 is formed on the wiring conductor layer 15.

  In such a wiring board, the insulating substrate 1 and the insulating layer 9 are composed of the core wiring layer 7 and the wiring conductor layer 15 disposed so as to sandwich the insulating substrate 1 and the insulating layer 9, and the through conductor 5 and the via conductor provided so as to penetrate each of them. 13 and has a function of electrically insulating.

  The core wiring layer 7, the wiring conductor layer 15, the through conductor 5, and the via conductor 13 are arbitrarily connected to each other to form a wiring circuit.

  In the wiring board 17 of the present invention, forming the intermediate layer 6 containing at least the second metal phase and the second inorganic powder between the inner wall of the through hole 3 and the through conductor 5, By forming the intermediate layer 6 between the inner wall of the through hole 3 and the through conductor 5, which has been important and has been conventionally easy to peel off and is one of the major factors that reduce the reliability of the wiring board 17, The separation of both is effectively suppressed, and the reliability of the wiring board is remarkably improved.

  For example, as shown in FIG. 2, the intermediate layer 6 includes at least a second metal phase 6a and a second inorganic powder 6b. The second metal phase 6 a is the same as the first metal phase 5 constituting the through conductor 1, and the second inorganic powder 6 b is the first inorganic phase constituting the insulating substrate 1. It is derived from the powder 1b, and the second inorganic powder 6b is dispersed in the matrix of the second metal phase 6a. In other words, the first metal layer 5 forming the through conductor 5 has the first metal layer 5 formed therein. The inorganic powder 1b is dispersed. Therefore, the intermediate layer 6 is excellent in affinity with the insulating base 1 and the through conductor 5, and firmly bonds the insulating base 1 and the through conductor 5, which have conventionally been easily peeled off. In addition, when the thermal expansion coefficient of the intermediate layer 6 is between the insulating base 1 and the through conductor 5, a function to relieve the thermal stress generated between the insulating base 1 and the through conductor 5 is also expressed. Furthermore, the reliability of the wiring board 17 can be improved.

  In FIG. 2, the second inorganic powder 6b of the intermediate layer 6 is depicted as being isolated, but it is needless to say that the second inorganic powder 6b may be in contact with each other. Furthermore, it is most desirable that the second inorganic powders 6b form a neck at the contact point and have a three-dimensional network structure from the viewpoint of strength as a structure and manufacturing reasons described later.

The first inorganic powder 1b, and as the second inorganic powder _6b, and inorganic powders of a general crystalline, such as SiO 2, _Al 2 _{O 3,} amorphous _SiO 2, E glass, S glass, etc. Amorphous inorganic powder can be used. In the inorganic powder, crystalline or amorphous SiO ₂ excellent in electrical characteristics such as dielectric constant is preferably used.

In order to form a neck between the second inorganic powders 6b, it is desirable to use an amorphous inorganic powder having a low melting point, and amorphous SiO ₂ having excellent electrical characteristics and low thermal expansion is the most desirable. Preferably used. Further, glass containing SiO ₂ as a main component and containing a small amount of B ₂ O ₃ or the like for vitrification can be used as well.

  By setting the average particle size of the second inorganic powder 6b to 3 μm or less, even if there is a difference in the thermal expansion coefficient between the second inorganic powder 6b and the second metal phase 6a, the second inorganic powder 6b Since excessive thermal stress can be prevented from concentrating between 6b and the second metal phase 6a, problems such as breakage of the through conductor 5 can be effectively prevented. In addition to the above effects, the number of the second inorganic powders 6b increases when the same amount of the second inorganic powder 6b is used. The contact points between the inorganic powders 6b increase and the second inorganic powders 6b form a neck to form a strong structure, so that the strength of the intermediate layer 6 also increases and the reliability of the wiring board 17 is improved. be able to.

  Further, by using the first metal phase 5 constituting the through conductor 5 for the second metal phase 6a constituting the intermediate layer 6, the bonding strength between the intermediate layer 6 and the through conductor 5 can be improved. it can. Further, since the second metal phase 6a of the intermediate layer 6 is also a part of the circuit of the wiring board 17, it is desirable to form it with low resistance copper or silver in order to reduce the resistance of the circuit.

  As shown in FIG. 3, the intermediate layer 6 contains the second resin 6c in addition to the second metal phase 6a and the second inorganic powder 6b. The affinity with can be further improved. The second resin 6c is preferably the same as the first resin 1a in terms of improving the affinity between the intermediate layer 6 and the insulating substrate 1.

  Further, it is desirable that the second resin 6c is present more on the insulating base 1 side. Accordingly, in the intermediate layer 6, it is particularly desirable that the second metal phase 6 a is gradually reduced in amount on the insulating base 1 side.

  By setting the thickness of the intermediate layer 6 having such a structure to 3 μm or more, the through conductor 5 and the insulating base 1 can be firmly connected, and the reliability of the wiring board 17 can be improved. . Furthermore, by setting the thickness of the intermediate layer 6 to 5 μm or more, particularly 10 μm or more, the wiring board 17 having remarkably excellent reliability can be obtained.

  Further, by setting the thickness of the intermediate layer 6 to 30 μm or less, it is not necessary to make the through holes 3 larger than necessary, and the wiring density can be increased. In addition, since it is not necessary to reduce the size of the through conductor 5 more than necessary, the electrical resistance of the through conductor 5 can be reduced, and the characteristics of the wiring board 17 can be improved. From these points, it is further desirable that the thickness of the intermediate layer 6 is 20 μm or less, particularly 15 μm or less.

  The manufacturing method of the wiring board 17 of the present invention will be described in detail below.

  First, as shown to Fig.4 (a), the insulating base | substrate 1 containing a glass cloth (not shown), the 1st resin 1a, and the 1st inorganic powder 1b is prepared, for example. This insulating substrate 1 is a first resin that is a mixed resin of, for example, a first inorganic powder 1b and a thermosetting resin such as an epoxy resin, a bismaleimide triazine resin / polyphenylene ether resin, or an imide resin on a glass cloth. The thickness impregnated with 1a is 0.05 to 2.0 mm.

The insulating base 1 contains the first inorganic powder 1b in an amount of 20% by volume or more, further 40% by volume or more, particularly 50% by volume or more. Desirable to form. Further, in order to improve the strength of the three-dimensional network structure formed by combining the inorganic powders 6a, it is desirable to further include 55% by volume or more.

Further, as the first inorganic powder 1b, general crystalline inorganic powder such as SiO ₂ and Al ₂ O ₃ and amorphous inorganic powder such as amorphous SiO ₂ , E glass, and S glass are used. Can be used. In the crystalline inorganic powder, SiO ₂ excellent in electrical characteristics such as dielectric constant is preferably used. Needless to say, complex oxides such as forsterite and spinel may be used. In the figure, the first inorganic powder 1b is described as a spherical shape. Of course, a spherical shape is desirable from the viewpoint of moldability. For example, the first non-spherical first powder produced by crushing is used. Inorganic powder 1b may be used. Further, the mixing of the first inorganic powder 1b is desirably uniform, but it may be uniform when viewed macroscopically, and there is no problem even if there is a microscopically nonuniform portion. Even in such a microscopically non-uniform case, the intermediate layer 6 can be formed, and the adhesion between the insulating substrate 1 and the through conductor 5 can be enhanced.

  Next, as shown in FIG. 4B, the through hole 3 is formed in the insulating substrate 1 using laser light. At this time, although the first resin 1a and the first inorganic powder 1b of the insulating base 1 are completely removed at the central portion of the through hole 3, the center of the through hole 3 from the wall surface of the through hole 3 is removed. The second inorganic powder 6b derived from the first inorganic powder 1b is not removed but remains exposed from the wall surface of the through-hole 3 to form an intermediate layer precursor 7. ing.

  In order to form the intermediate layer precursor 7, it is necessary to remove the resin 1a and leave the second inorganic powder 6b derived from the first inorganic powder 1b. According to the method for manufacturing the wiring board 17 of the present invention, when the through hole 3 is formed, it is important to remove the resin 1a by heat particularly in a portion inside the through hole 3 where the intermediate layer 6 is to be formed later. is there.

  For example, when laser light is used, the resin 1a and the inorganic powder 1b are removed from the insulating substrate 1 by heat to form the through holes 3. Later, the wall surfaces of the through holes 3 to be the intermediate layer 6 are formed. In the vicinity, by adjusting the irradiation interval to such an extent that only the resin 1a can be removed, or by adjusting the irradiation energy as appropriate, the inorganic powder is formed on the wall surface of the through hole 3 as shown in FIG. The intermediate layer precursor 7 formed from 6a and the gap 6d can be easily formed.

  In addition, it is desirable to form the through hole 3 having a diameter of 75 to 130 μm through the insulating substrate 1. When the diameter of the through hole 3 is made as fine as 75 to 130 μm, the size of the through hole 3 is small. Therefore, the through conductors 5 can be arranged with high density, and a wiring board having extremely high density wiring can be obtained.

  In order to form the through holes 3 in the insulating base 1 and the metal phase foil (not shown) formed on the main surface of the insulating base 1, for example, the main surface of the metal phase foil absorbs laser light energy well. A method of applying a laser processing sheet made of a resin having a black color or a color close to black and irradiating a carbon dioxide laser beam on the laser processing sheet, or an arithmetic average roughness Ra of the main surface of the metal phase foil After the surface is roughened in the range of 0.2 to 2 μm, the metal phase foil is heat-treated at an oxidizing atmosphere of 150 ° C. for about 30 minutes, and the surface absorbs the laser beam energy well, such as black or brown Either one of the methods of irradiating carbon dioxide laser light as a color having a color close to black is used, and a predetermined position is irradiated with carbon dioxide laser light having an output of 6 to 30 mJ with a pulse width of 40 to 240 μsec. Penetrating A method of drilling the through hole 3 is employed.

At this time, by setting the output of the carbon dioxide laser beam to 6 mJ or more, the through hole 3 can be drilled to a sufficient size. Moreover, the hole diameter of the through-hole 3 in the insulating base | substrate 1 can be accurately formed by setting it as 30 mJ or less. Therefore, it is preferable that the carbon dioxide laser light to be irradiated has an output of 6 to 30 mJ and a pulse width of 40 to 240 μsec.

  Needless to say, the optimum output of the laser light varies depending on the content and characteristics of the first inorganic powder 1b contained in the insulating substrate 1. For example, in the case of a glass containing a modified oxide, a smaller output is desirable. Even in the case of the same amorphous powder, it is necessary to slightly increase the output in the case of an inorganic powder that contains no or almost no modified oxide, and in the case of a crystalline inorganic powder, it is even larger. Output is required.

  Needless to say, the particle size and surface state of the inorganic powder also affect the formation of the neck.

  In addition, in order to make the through-hole 3 have a shape that expands toward both the upper and lower surfaces, when drilling by laser processing, the energy per laser beam and the number of shots may be adjusted.

  In laser processing, a carbon dioxide laser is advantageous in terms of cost, but it is also possible to use a YAG laser capable of finer processing. In addition, it is said that a laser using a harmonic higher than three times that of a YAG laser is generally less affected by heat during processing, but even in such a case, the insulating substrate 1 is affected by heat. The intermediate layer 6 can be formed.

  As described above, when the through-hole 3 is formed, the first inorganic powder 1b heated when removing the first resin 1a around the first inorganic powder 1b is in contact with each other and is sufficiently When heated, the neck is formed at the contact point, and the intermediate layer precursor 7 having a three-dimensional network structure is formed.

  In addition, when the 1st inorganic powder 1b used as the 1st inorganic powder 1b used for the insulation base | substrate 1 is easy to soften rather than the crystalline 1st inorganic powder 1b, it is easily 2nd. Since a neck can be formed between the inorganic powders 6b and the intermediate layer precursor 7 becomes a strong structure, problems such as separation of the intermediate layer precursor 7 during the manufacturing process can be suppressed, and an intermediate thickness of any thickness Since the layer precursor 7 can be formed, even the thick intermediate layer 6 can be easily and accurately manufactured.

  Similarly, in order to form a neck between the second inorganic powders 6b, it is important to produce the insulating substrate 1 using the first inorganic powder 1b having a high sinterability and an average particle diameter of 3 μm or less. is there. Furthermore, in order to increase the strength of the intermediate layer precursor 7, it is desirable to use the first inorganic powder 1b of 2 μm or less, particularly 1 μm or less.

  In addition, the second inorganic powder 6b of the intermediate layer 6 may be uniformly dispersed and separated, or a plurality of second inorganic powders 6b may aggregate to form a plurality of three-dimensional Needless to say, the skeleton may be present in a non-uniform manner.

  Moreover, in the example of FIG.1 and FIG.4 (b), although the wall surface of the through-hole 3 is drawn as a straight line, in the insulation base | substrate 1, the 1st inorganic powder 1b is not necessarily disperse | distributed uniformly, In particular, when viewed microscopically, the dispersion is non-uniform. When the through-hole 3 is formed in the insulating base 1 having such a configuration, the presence of the first resin 1a is not uniform, and when viewed microscopically, the insulating base 1 is structurally and thermally conductive. From the viewpoint of the above, it is non-uniform, and in the process of forming the through-hole 3, as shown in FIG.

  Therefore, the intermediate layer 6 having the form as shown in FIG. 3 in which the second metal phase 6a is reduced can be formed on the insulating substrate 1 side of the intermediate layer 6.

By using SiO ₂ having a low dielectric constant and dielectric loss tangent as the first inorganic powder 1b, a high-performance wiring board 17 having excellent high frequency characteristics can be produced. In addition, when amorphous SiO ₂ is used, there is an advantage that a robust intermediate layer precursor 7 can be formed because a neck can be formed at a temperature lower than that of crystalline SiO ₂ in addition to electrical characteristics.

Moreover, as these first inorganic powder 1b, for example, since it is possible to use amorphous SiO ₂ crystalline SiO ₂ and low thermal expansion coefficient of the high thermal expansion coefficient, thermal expansion coefficient of the intermediate layer 6 through It is desirable to adjust appropriately so as to be intermediate between the conductor 5 and the insulating substrate 1.

Since the strength of the neck formed between the second inorganic powders 6b described above, that is, the degree of bonding depends on the heat resistance and size of the second inorganic powder 6b, by adjusting the material and particle diameter, Can be optimized. For example, when the inorganic component is SiO ₂ , it is desirable that 20% by volume or more of SiO ₂ having an average particle diameter of 3 μm or less is contained in the first resin 1a. When the inorganic component is Al ₂ O ₃ , it is desirable to use a finer powder having an average particle diameter of 2 μm or less because it has higher heat resistance and higher softening temperature than SiO ₂ . In the case of glass powder in which B ₂ O ₃ or the like is mixed with SiO ₂ , since the softening point is low, the particle diameter may be large, and those having an average particle diameter of about 5 μm can be used.

  Next, by sequentially forming a palladium catalyst, electroless plating, and electrolytic plating in the through hole 3, as shown in FIG. 5 (c), the void surrounded by the second inorganic powder 6b becomes non-filled. The intermediate layer 6 is formed by filling with the metal phase 6a formed by electrolytic plating or electrolytic plating.

  Furthermore, through-plating conductors 5 as shown in FIG. 5D can be formed by performing electrolytic plating.

  Further, if necessary, an insulating layer 9 is formed on the main surface of the insulating base 1 on which the through hole 3, the through conductor 5, and the intermediate layer 6 are formed, and the via conductor 13 and the wiring conductor layer 15 are formed by a conventionally known method. By being formed, for example, the wiring board 17 of the present invention shown in FIG. 1 can be manufactured.

  Further, for example, as shown in FIG. 6, the space formed by the through conductor 3 may be filled with the embedded resin 19, or the conductive paste may be filled instead of the embedded resin 19.

  Note that a resin-based flame retardant such as bromine or phosphorus is generally added to the resin-based wiring board 17 in order to impart flame retardancy. Since these additives behave as part of the resin component, they do not affect the formation of the intermediate layer of the inorganic powder and metal phase of the present invention. For this reason, various flame retardants can be added to the substrate material used in the present invention.

  In the example described above, a so-called core substrate having a glass cloth has been described. However, it is obvious that the present invention can be applied to an insulating layer containing an inorganic powder and a resin. Needless to say, the present invention can also be applied to a build-up layer of a so-called build-up substrate produced by laminating an insulating layer on the surface.

  The intermediate layer 6 is desirably formed on the entire inner wall of the through-hole 3, but the through-conductor 5 and the through-hole 3 are separated even if a region where the intermediate layer 6 does not exist is formed in part. It only has to be suppressed. Needless to say, the glass cloth may have a structure containing an intermediate layer.

In the example described above, the first metal phase 5 and the second metal phase 6a are formed of the same metal, and the first inorganic powder 1b and the second inorganic powder 6b are described as the same inorganic material. However, it goes without saying that these may be formed of different metals and different inorganic materials. When the inorganic powder and the metal layer are formed of different materials, for example, the coefficient of thermal expansion can be controlled with a high degree of freedom. In addition, what is necessary is just to change the kind of metal plated, when forming a metal phase with a different metal. In the case of inorganic powder, even if the same inorganic material is used, the crystalline inorganic powder can be changed to amorphous in the step of forming the through holes. Moreover, when forming an intermediate | middle layer, the intermediate | middle layer 6 containing the 2nd inorganic powder 6b can be formed by mixing the inorganic powder used as the 2nd inorganic powder 6b with a plating solution, plating. .

  In order to evaluate the wiring board of the present invention, an evaluation board was prepared, and reliability evaluation was performed using this board.

(1) Production of insulating substrate: Four types of varnish made of various resins such as cyanate, epoxy, polyimide, and PPE were prepared. Furthermore, various powders having an average particle diameter shown in Table 1 made of SiO ₂ , Al ₂ O ₃ , amorphous SiO ₂ , E glass, and S glass were prepared. Note that amorphous or powder not described as glass is crystalline inorganic powder. Then, these powders were subjected to a coupling treatment with a silane coupling agent, and then mixed so that the volume fraction relative to the resin became the content shown in Table 1. The varnish after mixing the resin and the inorganic powder was impregnated into a standard glass cloth called “2116” and then dried to prepare a prepreg having a thickness of about 0.1 mm. Four prepregs are stacked, and a copper foil having a thickness of 12 μm is placed on the front and back of the laminate, and hot pressing is performed at a predetermined temperature (200 ° C.) for about 1 hour. An insulating substrate on which a copper foil was formed was produced.

  (2) Production of evaluation substrate: After removing the surface of the copper foil formed on the front and back surfaces of the insulating substrate with copper foil produced by the above method by about 9 μm, etching is performed at 160 ° C. in order to improve laser light absorption. The copper foil surface was oxidized under conditions of 10 minutes, and then a through hole having a hole diameter of 95 μm was formed by a carbon dioxide gas laser. Note that the carbon dioxide laser and YAG laser drilling conditions were a pulse width of 75 μs, an output of 6 mJ, and a shot count of 8 shots unless otherwise specified.

  Sample No. In No. 28, a through-hole was formed using a carbon dioxide laser, but the drilling conditions were a pulse width of 75 μs, an output of 4 mJ, and a shot count of 12 shots.

  Sample No. In No. 29, a through-hole was formed using a carbon dioxide laser, but the drilling conditions were a pulse width of 75 μs, an output of 32 mJ, and a shot count of 4 shots.

  Sample No. In No. 25, a 90 μm diameter microdrill was drilled at a rotational speed of 300,000 revolutions per minute.

  After that, the insulating substrate in which the through holes are formed is immersed in a 80 ° C. roughening solution made of a potassium permanganate solution and subjected to a roughening treatment for 10 minutes. In this order, a palladium catalyst, an electroless copper plating, and an electrolytic copper plating are sequentially applied. An intermediate layer and a through conductor were formed on the wall surface of the through hole.

  In addition, the intermediate layer was not confirmed in the sample in which the content of the inorganic powder was less than 20% by volume.

Thereafter, filling resin is filled in the through holes, unnecessary portions of the filling resin are removed by polishing, and the wiring conductor composed of the copper foil and the plating layer formed on the front and back surfaces of the insulating base is set to a predetermined thickness. An evaluation substrate having a structure in which wiring patterns are formed by the subtractive method and through conductors formed in a lattice shape at a pitch of 175 μm are electrically connected in the horizontal direction is manufactured.

  In addition, 1000 through-holes were formed in each evaluation board, and wiring was formed so that each was electrically connected in series.

  (3) Evaluation: In the evaluation substrate, the cross section of the through hole was polished, and an intermediate layer of 10 through conductor holes was observed using a scanning electron microscope (SEM) at 200 × and 1000 × magnification. The maximum thickness of the intermediate layer observable thereby was measured at a magnification of 10,000 times to obtain the thickness of the intermediate layer. For the evaluation of the insulation reliability, all the evaluation substrates were pretreated under the conditions of JEDEC Level 3 before the test was input. Subsequently, HAST of 130 degreeC, 85%, 5.5V, and 168 hours was implemented. A sample was taken out after 168 hours, and the insulation resistance between the through conductors was measured for each of 10 evaluation boards, and those that were 10 8 ohms or less were regarded as defective. The measurement was carried out for the insulation resistance at each pitch, and Table 1 shows the result of a 175 μm pitch as a representative example.

  Sample No. without an intermediate layer, which is outside the scope of the present invention. 1, 2, 15, 25, 28, and 29 all had extremely poor insulation reliability and low reliability. Further, when the cross section of the sample after HAST was observed, peeling was confirmed at the interface between the through hole and the through conductor, and it was observed that copper migration occurred along the glass cloth. Sample No. 80 containing 80% by volume of inorganic powder was added. In No. 10, the amount of inorganic powder was too large to form the insulating substrate itself.

Of these samples, Sample No. In 1, 2, and 15, it is considered that the intermediate layer was not formed because the amount of inorganic powder contained in the insulating substrate was small. In addition, Sample No. in which a through-hole was formed by a drill was used. In No. 25, it is considered that the intermediate layer was not formed due to insufficient heat generation. In addition, the sample No. in which the output of the laser beam was changed. In Nos. 28 and 29, it is considered that the intermediate layer was not formed because the output of the laser beam was not in an appropriate range.

  On the other hand, sample no. 3 to 9, 11 to 14, 16 to 24, 26, and 27, there are some samples that are slightly inferior in reliability, but there are sample Nos. With no intermediate layer. Compared with 1, 2, 15, 25, 28, and 29, migration between the through holes is remarkably reduced, and insulation reliability is also improved.

  Hereinafter, the sample of the present invention will be described in detail.

Sample No. _{2 in} which SiO ₂ powder having an average particle diameter of 1 μm was added to the insulating substrate in the range of 20 to 70 vol% In 3-9, the thickness of the intermediate layer increased as the amount of the inorganic powder increased, and an intermediate layer of 3-30 μm was observed, and there was no migration, and a wiring board excellent in reliability was obtained.

Sample No. 1 in which the particle size of the SiO ₂ powder was changed in the range of 0.5 to 5.0 μm. From the results of 11 to 14, it can be seen that a thick intermediate layer can be easily formed by using an inorganic powder having a small particle size. Among these samples, sample No. 1 in which the particle size of the SiO ₂ powder was 5.0 μm. In FIG. 14, although the intermediate layer is formed, since the inorganic powder has a large particle size, a three-dimensional skeleton structure of the inorganic powder having sufficient thickness and strength is not formed, and there is no problem in insulation reliability. However, separation was observed between the through hole and the through conductor, though only slightly.

Sample No. using crystalline Al ₂ O ₃ In Nos. 16 and 17, it was possible to form an intermediate layer by using a fine inorganic powder of 0.3 μm and containing 20% by volume or more in an insulating substrate. Further, sample Nos. Using E glass and S glass having a low softening point compared to crystalline inorganic powder and amorphous SiO ₂ powder containing no modified oxide. In Nos. 18 and 19, an intermediate layer having a thick and strong structure was easily formed, and a wiring board having excellent insulation reliability was obtained.

Further, Sample No. using 0.3 μm amorphous SiO ₂ powder was used. In 20-22, even if the resin used for the insulating substrate was changed, excellent characteristics were obtained without any influence. In addition, the sample No. using YAG laser light for forming the through hole was used. In 23 and 24, good characteristics were obtained although the thickness of the intermediate layer was slightly reduced.

Sample No. using crystalline SiO ₂ powder was used. As compared with the case of using amorphous SiO ₂ powder, the thicknesses of the intermediate layers 26 and 27 are thin, but the intermediate layers are sufficiently thick and have high insulation reliability.

DESCRIPTION OF SYMBOLS 1 ... Insulation base | substrate 1a ... 1st resin 1b ... 1st inorganic powder 3 ... Through-hole 5 ... Through-conductor, 1st metal phase 6 ... Intermediate | middle layer 6a ... Second metal phase 6b ... second inorganic powder 6c ... second resin 7 ... intermediate layer precursor

Claims (14)

In a wiring board comprising an insulating base, a through hole formed in the insulating base, and a through conductor made of a first metal phase formed in the through hole,
The wiring board, wherein an inner wall of the through hole and the through conductor are connected via an intermediate region containing a second metal phase and an inorganic powder.   2. The wiring board according to claim 1, wherein the second metal phase is reduced on the insulating base side of the intermediate region than on the through conductor side of the intermediate region.   The wiring substrate according to claim 1, wherein the intermediate region has a thickness of 3 to 30 μm.   The wiring substrate according to claim 1, wherein an average particle diameter of the inorganic powder is 3 μm or less.   The wiring board according to claim 1, wherein the inorganic powder is glassy. The wiring board according to claim 1, wherein the inorganic powder contains SiO ₂ as a main component.   The wiring board according to claim 1, wherein the second metal phase and the first metal phase are made of the same metal. In a wiring board comprising: an insulating layer; a through hole formed in the insulating layer; and a through conductor made of a first metal phase formed in the through hole.
The wiring board, wherein an inner wall of the through hole and the through conductor are connected via an intermediate region containing a second metal phase and an inorganic powder.   The wiring board according to claim 8, wherein the second metal phase is reduced on the insulating base side of the intermediate region than on the through conductor side of the intermediate region.   The wiring substrate according to claim 8 or 9, wherein the intermediate region has a thickness of 3 to 30 µm.   The wiring substrate according to claim 8, wherein an average particle diameter of the inorganic powder is 3 μm or less.   The wiring board according to claim 8, wherein the inorganic powder is glassy. The wiring board according to claim 8, wherein the inorganic powder contains SiO ₂ as a main component.   The wiring board according to claim 8, wherein the second metal phase and the first metal phase are made of the same metal.

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