JP2005191115A - Wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board having a high reliability by suppressing the separation of an interconnection conductor around a through-hole from an insulation substrate, and to provide its manufacturing method. <P>SOLUTION: The wiring board at least comprises the insulation substrate 1 which contains resin, the through-hole 3 formed in the insulation substrate 1, a through-conductor 5 attached on the inner wall of the through-hole 3, and an interconnection layer 13 which includes a metal foil 9 and is formed on a principal plane of the insulation substrate 1. In the periphery of the through hole out of the principal plane of the insulation substrate 1, a through-hole periphery interconnection layer 14 consisting of a plating layer 11 is formed. The through-hole conductor 5 and the interconnection layer 13 are connected via the through-hole periphery interconnection layer 14. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  TECHNICAL FIELD The present invention relates to an organic material-based wiring board and a method for manufacturing the same, and in particular, a wiring board excellent in reliability without peeling between an insulating substrate and a through-hole peripheral wiring layer as a wiring layer in a peripheral part of the through-hole. It relates to the manufacturing method.

  Conventionally, as an organic material-based wiring board for mounting electronic components such as semiconductor elements, copper foils are formed on both upper and lower surfaces of an insulating substrate made of, for example, a glass-epoxy plate and having through holes penetrating from the upper surface to the lower surface. A wiring board is used in which a wiring conductor made of a plating layer applied thereon is attached and a through conductor made of a plating layer that connects the upper and lower wiring conductors is attached to the inner surface of the through hole. Yes.

  Such an organic material-based wiring board is prepared by preparing a double-sided copper-clad board with copper foils attached on both upper and lower sides of an insulating substrate made of glass-epoxy board, and penetrating vertically through the double-sided copper-clad board. Holes are drilled and then plated on the upper and lower copper foils by depositing a copper plating layer on the upper and lower copper foils and on the inner surface of the through holes by electroless plating and electrolytic plating. A through conductor made of a plating layer is formed on the inner surface of the through hole, and then the copper foil applied to the upper and lower surfaces of the insulating substrate and the plating layer applied to the copper foil are photolithography. It is manufactured by employing a technique and partially etching to form a wiring conductor.

  Moreover, a buildup wiring board is manufactured by forming a buildup resin layer and a buildup wiring layer on both surfaces of the wiring board. In such a wiring board, the through hole to which the through conductor is attached is usually filled with a filling resin such as an epoxy resin.

By the way, in such an organic material-based multilayer wiring board, in order to increase the wiring density in response to the demand for reduction in size and thickness of the electronic device, for example, the insulating substrate has a thickness of about 0.2 to 1 mm. Attempts have been made to make the hole diameter as small as 75 to 130 μm. Moreover, in order to form such a small through-hole with a diameter of about 75 to 130 μm, for example, a drilling method using a carbon dioxide laser is employed (see Patent Document 1).
JP 2000-91750 A

  However, when forming a through hole in a double-sided copper-clad substrate, when the through hole is formed by conventional drilling and laser processing, the copper foil and When the adhesion strength with the insulating substrate is extremely deteriorated and the thermal history during mounting of the semiconductor element is received, the stress generated by the difference in the thermal expansion coefficient between the insulating substrate and the copper foil, particularly at the periphery of the through hole There is a problem in that a crack is generated between the insulating substrate and the copper foil, and the crack is the starting point, causing the through conductors for conduction on the front and back sides of the wiring substrate to be disconnected, resulting in poor conduction.

  The present invention has been devised in view of such conventional problems, and its purpose is to provide adhesion strength between a copper foil and an insulating substrate due to heat, vibration, impact, etc. when a through hole is formed in a double-sided copper-clad substrate. It is an object of the present invention to provide a wiring board and a manufacturing method of the wiring board that do not cause disconnection of a through conductor due to a decrease.

  The wiring substrate of the present invention includes at least an insulating substrate containing a resin, a through hole formed in the insulating substrate, a through conductor attached to the inner wall of the through hole, and a main surface of the insulating substrate. In a wiring board comprising a wiring layer provided with the formed metal foil, a through-hole peripheral wiring layer made of a plating layer is formed on the peripheral edge of the through-hole in the main surface of the insulating substrate, The through conductor and the wiring layer are connected via the through hole peripheral wiring layer.

  Further, it is desirable that the width of the through hole peripheral wiring layer is 3 μm or more.

  Moreover, as for the wiring board of this invention, a plating layer consists of an electroless plating layer and an electroplating layer, and it is desirable that it is copper plating.

  In addition, the method for manufacturing a wiring board according to the present invention includes a step of forming a through hole in a double-sided copper-clad substrate including an insulating substrate containing a resin and a metal foil formed on a main surface of the insulating substrate, A step of roughening the double-sided copper-clad substrate, and etching a part of the copper foil of the roughened double-sided copper-clad substrate to remove the copper foil at the periphery of the through-hole, thereby insulating the periphery of the through-hole An electroless copper plating layer and an electrolytic copper plating layer are sequentially formed on the double-sided copper-clad substrate from which the copper foil at the periphery of the through hole is removed, and a step of exposing the main surface of the substrate. A step of forming a conductor peripheral wiring layer and a wiring layer; a step of embedding a hole-filling resin in the through-hole; and polishing a surface layer of the double-sided copper-clad substrate to remove unnecessary portions of the hole-filling resin; A polishing step for setting the thickness of the layer to a predetermined thickness, and That.

  In the method for manufacturing a wiring board according to the present invention, the through hole is preferably formed by laser processing.

  In the method for manufacturing a wiring board according to the present invention, it is preferable that the polishing of the surface layer of the double-sided copper-clad substrate and the etching of copper are alternately repeated a plurality of times in the polishing step.

  Conventionally, the reliability of the wiring board has been reduced due to a decrease in the adhesion strength between the copper foil around the through hole and the insulating board generated due to heat, vibration, impact, etc. that are generated when the through hole is formed in the double-sided copper-clad board. According to the present invention, the copper foil with reduced adhesion strength is removed in advance, and the through hole peripheral wiring layer is formed around the through hole periphery again by the plating method. The adhesion reliability between the peripheral insulating substrate and the through hole peripheral wiring layer can be remarkably improved, and the reliability of the wiring substrate can be improved.

  Further, in the present invention, by setting the width from the through hole of the through hole peripheral wiring layer to 3 μm or more, the metal foil with reduced adhesion can be removed, and the reliability of the wiring board can be improved.

  In addition, by forming the through-hole peripheral wiring layer with an electroless plating layer and an electrolytic plating layer, a wiring layer with low electrical resistance and low electrical noise can be easily formed at low cost.

  In addition, according to the manufacturing method of the present invention, it is possible to easily form a through hole peripheral wiring layer having excellent adhesion reliability with an insulating substrate at the periphery of the through hole, and to provide a wiring substrate excellent in reliability. Can do.

  In particular, the copper foil in the roughening process of the double-sided copper-clad board is made by roughening the double-sided wiring board after forming the through-hole, and etching the part of the copper of the double-sided copper-clad board after the roughening process. It is possible to remove not only the adhesion strength of the insulating substrate but also the pole surface portion of the insulating substrate having deteriorated characteristics required as a resin, and the characteristics of the insulating substrate can be recovered.

  Then, by etching the copper foil after this roughening step, the copper foil at the periphery of the through hole can be easily removed at a width of about 3 to 5 μm at the periphery of the through hole.

  In addition, the step of embedding a hole-filling resin in the through-hole and the copper foil at the periphery of the through-hole remove the unnecessary portion of the hole-filling resin by polishing the surface layer of the double-sided copper-clad substrate, and the wiring layer has a predetermined thickness By using the polishing step, the through hole peripheral wiring layer and the wiring layer including the metal foil can be made substantially flush with each other, and sufficient flatness can be obtained when forming the build-up wiring layer.

  Moreover, the copper foil around a through-hole becomes easy to be etched by processing to the through-hole to a double-sided copper clad board | substrate by laser processing. In particular, the ease of etching of the copper foil in the case where the through hole is formed with a carbon dioxide laser becomes remarkable. It is a thermal action during laser processing that opens a hole in the copper foil to form a through-hole, but the copper foil around the through-hole also receives a heat action to oxidize the surface, and the copper action also changes the copper crystal arrangement. This is considered to be because etching is easily performed.

  Therefore, it is desirable to form a through hole in the double-sided copper-clad substrate by using a laser, particularly a carbon dioxide gas laser.

  Further, in the polishing step, the polishing of the surface layer of the double-sided copper-clad substrate and the etching of the copper are alternately repeated a plurality of times to remove unnecessary portions of the hole-filling resin and to make the thickness of the surface layer copper a predetermined thickness. Rather than removing unnecessary portions of the hole filling resin and making the copper thickness a predetermined thickness only by polishing, it is better to remove the unnecessary portions of the hole filling resin by alternately performing polishing and copper etching and to make the copper thickness a predetermined thickness. The total working time is shortened and the copper thickness becomes more uniform. As the copper etching solution, a mixed solution of sulfuric acid-hydrogen peroxide solution or an aqueous solution of ammonium persulfate is desirable, and etching with a uniform copper thickness can be performed.

  In the wiring board of the present invention, for example, as shown in FIG. 1, a through hole 3 is provided in an insulating substrate 1, and a through conductor 5 that electrically connects both surfaces of the insulating substrate 1 is provided in the through hole 3. Is provided. A space formed by surrounding the through conductor 5 is filled with an embedded resin 7.

  A wiring layer 13 made of a metal foil 9 and a plating layer 11 is formed on both surfaces of the insulating substrate 1. The peripheral portion of the through hole 3 has no metal foil 9 and a through hole peripheral wiring layer 14 made of a plating layer 11 is formed.

  In the wiring board of the present invention, the metal foil 9 is not provided at the peripheral portion of the through hole 3, and the wiring layer 13 provided with the metal foil 9 and the through conductor 5 are connected via the through hole peripheral wiring layer 14. It is important to.

  For example, when a wiring board is manufactured from a double-sided copper-clad substrate, the insulating substrate 1 and the metal foil 9 are formed particularly at the periphery of the through hole 3 due to heat, vibration, impact, etc. generated when the through hole 3 is formed. In this structure, instead of the metal foil 9 having poor adhesion strength at the periphery of the through-hole 3, a through-hole peripheral wiring layer 14 made of a plating layer is newly provided. By forming, it becomes a wiring board which has the through-hole periphery wiring layer 14 excellent in the adhesive strength with the insulating substrate 1 in the through-hole peripheral part, and can improve the reliability of a wiring board markedly.

  The through-hole peripheral wiring layer 14 is preferably formed by a plating method because it is easy to form. In particular, an electroless plating layer and an electrolytic plating layer are sequentially deposited on the main surface of the insulating substrate 1. It is desirable to form. Moreover, it is desirable that copper having a low resistance is a main component.

  Further, the base of the electrolytic plating layer may be formed by a sputtering method or a vacuum deposition method.

  In addition, the wiring conductor 13 formed on the main surface of the insulating substrate 1 is formed by, for example, depositing a plating layer 11 such as copper plating on a copper foil 9 having a thickness of 3 to 18 μm, and is mounted on the wiring substrate. It functions as a part of a conductive path for electrically connecting an electrode of a component (not shown) to a wiring conductor (not shown) of an external electric circuit board, and the wiring conductor layer 13 on the upper surface side has an electronic component. Are formed via an electronic component connection pad connected via a conductive bonding member such as solder and a wiring pattern drawn from the electronic component connection pad. External connection pads and the like are formed which are connected to the wiring conductor of the external electric circuit board via a conductive bonding member such as solder.

  Note that the copper foil 9 constituting the wiring conductor 13 has a thickness of 5 μm or more, so that the copper foil 9 is subjected to copper during micro-etching performed as a pretreatment for forming the electroless copper plating layer after the through hole 3 is formed in the wiring conductor 13. The foil 9 is etched so that pinholes in the copper foil 9 or defects in the copper foil 9 do not occur, and sufficient coverage and adhesion of the copper plating layer 11 to the copper foil 9 can be secured. On the other hand, when the thickness is 20 μm or less, the layer 11 such as the copper plating layer 11 can be satisfactorily formed on the copper foil 9. Therefore, the thickness of the copper foil 9 constituting the wiring conductor 13 is desirably in the range of 5 to 20 μm, and optimally in the range of 10 to 15 μm.

  In addition, when the total thickness of the copper foil 9 constituting the wiring conductor 13 and the plating layer 11 deposited thereon is less than 8 μm, the wiring conductor 13 has high electrical resistance, and on the other hand, exceeds 30 μm. It becomes difficult to form the wiring conductor 13 in a high-density wiring pattern. Therefore, the total thickness of the copper foil 9 constituting the wiring conductor 13 and the plating layer 11 deposited on the copper foil 9 is preferably in the range of 8 to 30 μm.

  The insulating substrate 1 used for the wiring board of the present invention is, for example, a flat plate having a thickness of 0.2 to 0.8 mm in which a glass cloth is impregnated with a resin such as an epoxy resin, a bismaleimide triazine resin, or a polyphenylene ether resin. is there.

  The insulating substrate 1 has a thickness of 0.2 mm or more so that a plurality of through holes 3 are formed through the insulating substrate 1 and the metal foil 9 or the wiring conductors 13 are formed on both upper and lower surfaces of the insulating substrate 1. Can be prevented from being warped or deformed due to the influence of heat or external force applied when forming the hole filling resin 7 or the like, and the flatness required for the wiring board Can be secured. Further, by setting the thickness of the insulating substrate 1 to 0.8 mm or less, when the through conductor 5 is formed inside the through hole 3, the plating solution can easily enter the inner wall of the through hole 3. It can be formed satisfactorily. Therefore, the thickness of the insulating substrate 1 is preferably in the range of 0.2 to 0.8 mm.

  Insulating substrate 1 is made of a resin material such as epoxy resin, bismaleimide triazine resin, polyphenylene ether resin or the like impregnated into glass cloth. If the penetration is included so that the transmittance is substantially equal, the through-hole 3 is made substantially uniform when the through-hole 3 is drilled with a laser beam in the insulating substrate that is a laminate of the insulating substrate 1 and the metal foil 9. It is possible to form a good size. Therefore, in the resin such as epoxy resin, bismaleimide triazine resin or polyphenylene ether resin impregnated into the glass cloth of the insulating substrate 1, a filler made of silica, alumina, aramid resin or the like is irradiated with laser light between the glass cloth portion and the resin portion. It is preferable to make it contain so that the transmittance | permeability may become substantially equivalent.

  Moreover, the insulating substrate 1 which does not contain glass cloth may be sufficient, and a thermal expansion coefficient can also be adjusted suitably using the insulating substrate 1 which consists of a liquid crystal polymer. Alternatively, it is also possible to adjust characteristics such as a coefficient of thermal expansion and strength by using a plurality of types of these insulating substrates 1.

  Further, it is desirable to form a through hole 3 having a diameter of 75 to 130 μm through the insulating substrate, and the through conductor 5 is formed by applying metal plating to the inner wall of the through hole 3. The through hole 3 is provided to provide a lead-out path for leading the through conductor 5 from the upper surface to the lower surface of the insulating substrate 1 and is drilled by laser processing.

  The through-hole 3 has a diameter of 75 to 115 μm at the substantially central portion of the cross section of the insulating substrate 1 and is substantially the same size, and expands outward so as to be 90 to 130 μm at the opening of the insulating substrate 1. It is preferable to keep the diameter.

  And when the hole diameter of the through-hole 3 is made as fine as 75 to 130 μm in this way, the size of the through-hole 3 becomes small, so that the through conductors 5 can be arranged at high density, and the extremely high density A wiring board having wiring can be obtained.

  Moreover, when the through-hole 3 forms the through-conductor 5 when depositing a plating metal inside the through-hole 3 and forming the through-conductor 5 due to the diameter expanding toward the outside, The plating solution enters the inside of the through hole 3 favorably, and as a result, the through conductor 5 can be satisfactorily deposited and formed in the through hole 3. In addition, when the diameter of the through hole 3 is 75 μm or more, when forming the through conductor 5 by filling the inside of the through hole 3 with a plating metal, a plating solution for forming the through conductor 5 is formed inside the through hole 3. The through conductor 5 can be satisfactorily formed by depositing the plated metal inside the through hole 3, and when the thickness is 130 μm or less, the through conductor 5 and the wiring conductor 13 are arranged at high density. It becomes possible. Therefore, the diameter of the through hole 3 is preferably in the range of 75 to 130 μm.

  Further, when the diameter at the opening of the through hole 3 is 10 μm or more larger than the diameter at the substantially central portion in the thickness direction of the insulating substrate 1, the through conductor 3 is formed by filling the inside of the through hole 3 with a plating metal. At this time, the plating solution for forming the through conductor 5 enters the inside of the through hole 3 favorably, so that the through conductor 5 can be satisfactorily deposited and formed in the through hole 3. When the diameter of the opening is larger than the diameter of the central portion in the thickness direction of the insulating substrate and the difference is 50 μm or less, the through-hole 3 having such a shape can be stably formed. Become. Therefore, it is preferable that the diameter at the opening of the through hole 3 is 10 to 50 μm larger than the diameter at the substantially central portion in the thickness direction of the insulating substrate 1.

  Further, the through conductor 5 deposited and formed in the through hole 3 is made of a plating metal such as copper plating, and serves as a connection conductor for electrically connecting the wiring conductors 13 positioned above and below the insulating substrate 1 with each other. Function. Since the through hole 3 has a shape that expands toward the outside as described above, the plated layer 5 is deposited and formed satisfactorily by depositing the plating layer 5 in the through hole 3.

  Next, a method for manufacturing the wiring board of the present invention for manufacturing the wiring board shown in FIG. 1 will be described in detail with reference to FIGS. 2 (a) to 5 (g). In this embodiment as well, an example is shown in which a thin wiring board having a diameter of 75 to 130 μm and a fine through hole 3 and a thickness of 0.2 to 0.8 mm is manufactured.

  First, as shown in FIG. 2 (a), for example, glass cloth is impregnated with an epoxy resin, a resin such as a bismaleimide triazine resin or a polyphenylene ether resin, on both surfaces of an insulating substrate 1 having a thickness of 0.2 to 0.8 mm. A double-sided copper-clad substrate 15 on which a copper foil 9 that is a metal foil 9 having a thickness of 5 to 20 μm is deposited is prepared.

  The insulating substrate 1 has a thickness of 0.2 mm or more, so that when the insulating substrate 1 and the copper foil 9 are penetrated, a plurality of through holes 3 are formed, or when the hole filling resin 7 is formed. The risk of warping or deformation of the wiring board due to the influence of heat or external force applied to the wiring board to prevent the flatness required of the wiring board from being ensured can be reduced, and the thickness can be reduced to 0. By setting the thickness to .8 mm or less, when the through conductor 5 is formed by depositing the plating layer 5 on the inner wall of the through hole 3 as will be described later, it is difficult for the plating solution to enter the through hole 3. In this case, disconnection is not likely to occur. Therefore, it is preferable to use the insulating substrate 1 having a thickness of 0.2 to 0.8 mm.

  Further, by setting the thickness of the copper foil 9 to 5 μm or more, the copper foil 9 is etched at the time of microetching performed as a pretreatment for forming the plating layer after the through-hole 3 is formed, so that pinholes or defects are formed in the copper foil 9. Can be prevented, and the adhesion property and adhesion of the plating on the copper foil 9 can be increased.

  Moreover, when the thickness of the copper foil 9 is 20 μm or less, when the through hole 3 is drilled by laser processing, the through hole 3 having a diameter of 75 to 130 μm can be stably formed. Therefore, it is desirable to use a copper foil 9 having a thickness of 5 to 20 μm.

  For example, the copper foil 9 has a thickness of about 8 to 40 μm attached to the entire upper and lower surfaces of the insulating substrate 1, and the copper foil 9 is made of a copper etching solution such as sulfuric acid-hydrogen peroxide solution. It is formed by etching so that the film thickness becomes uniform and processing so that the thickness becomes 5 to 20 μm.

  Next, as shown in FIG. 2B, a through hole 3 having a diameter of 75 to 130 μm penetrating the double-sided copper-clad substrate 15 and expanding toward the outside in the surface layer of the insulating substrate 1 is drilled by laser processing. .

  In this case, a carbonized layer 17 having a thickness of about several μm or less is formed on the inner wall of the through hole 3 along with the laser processing. Further, due to the thermal shock of the laser processing during the through hole processing, the adhesion strength between the copper foil 9 and the insulating substrate 1 at the periphery of the through hole 3 is low.

  Thus, when the diameter of the through hole 3 is as fine as 75 to 130 μm, the through conductor 5 and the wiring conductor 13 can be arranged with high density when the through conductor 5 and the wiring conductor 13 are formed. Thus, a high-density wiring board can be obtained. Moreover, since the hole diameter of the through-hole 3 is expanding outward, when the through-conductor 5 is formed by filling the inside of the through-hole 3 with a plating metal, a plating solution for forming the through-conductor 5 is used. As a result, the through conductor 5 can be satisfactorily formed in the through hole 3.

  In addition, when the hole diameter of the through hole 3 is 75 μm or more, when forming the through conductor 5 by depositing a plating metal on the inner layer of the through hole 3, a plating solution for forming the through conductor 5 is used in the through hole 3. The inside of the through hole 3 can be satisfactorily formed, and the through conductor 5 can be satisfactorily formed inside the through hole 3. On the other hand, when the thickness is 130 μm or less, the through conductor 5 and the wiring conductor 13 can be arranged with high density. Therefore, the diameter of the through hole 3 is preferably in the range of 75 to 130 μm.

  Further, when the diameter of the opening of the through hole 3 is 10 μm or more larger than the diameter of the substantially central portion in the thickness direction of the insulating substrate 1, a plated metal is deposited on the inner layer of the through hole 3 to form the through conductor 5. At the time of forming, the plating solution for forming the through conductor 5 can enter the inside of the through hole 3 well and form the through conductor 5 inside the through hole 3. When the diameter at the opening is larger than the diameter at the substantially central portion in the thickness direction of the insulating substrate 1 within a range not exceeding 50 μm, the through hole 3 having such a shape can be stably formed. . Therefore, it is preferable that the diameter of the opening of the through hole 3 is about 10 to 50 μm larger than the diameter of the substantially central portion of the insulating substrate 1.

  In order to form the through-hole 3 in the insulating substrate 1 and the copper foil 9, a laser processing sheet made of a resin having a black color or a color close to black, for example, which absorbs laser beam energy satisfactorily on the copper foil 9 is used. A method of attaching and irradiating the laser processing sheet with a carbon dioxide laser beam, or roughening the surface of the copper foil 9 with an arithmetic average roughness Ra in the range of 0.2 to 2 μm, and then the copper Either a method in which the foil 9 is heat-treated at an oxidizing atmosphere of 150 ° C. for about 30 minutes and the surface thereof is irradiated with a carbon dioxide laser beam as a color having a color close to black, such as black or brown, which absorbs the energy of the laser beam satisfactorily. Using this method, a method of piercing the through-hole 3 by irradiating a predetermined position with a carbon dioxide laser beam with an output of 8 to 30 mJ with a pulse width of 40 to 240 μs is employed.

  At this time, by setting the output of the carbon dioxide laser beam to 8 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 insulated substrate 1 can be accurately formed by setting it as 30 mJ or less. Therefore, it is preferable that the carbon dioxide laser beam to be irradiated has an output of 8 to 30 mJ and a pulse width of 40 to 240 μsec.

  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.

  For example, first, as shown in the enlarged cross-sectional view of the main part in FIG. 6A, the copper foil 9 and the insulating substrate 1 are irradiated by irradiating several pulses of laser light having an output of 8 to 30 mJ and a pulse width of 40 to 500 μsec. The through-hole 3 having a shape that expands toward the upper and lower surfaces on the upper surface side of the insulating substrate 1 is formed. At this time, since the laser beam energy is applied more on the upper surface side of the insulating substrate 1 than on the lower surface side, the through-hole 3 has a shape that expands toward the outside on the upper surface side of the insulating substrate 1. Further, since the copper foil 9 is less likely to be drilled than the insulating substrate 1, the diameter of the through hole 3 is smaller than that of the insulating substrate 1 at the portion of the copper foil 9, and the copper foil 9 protrudes inside the through hole 3. It becomes a shape.

  Next, as shown in the enlarged cross-sectional view of the main part in FIG. A part of the irradiated laser beam is reflected by the copper foil 9 protruding to the inside of the through hole 3 on the lower surface side of the insulating substrate 1 and passes through the lower surface side of the insulating substrate 1. It becomes a shape which expands in diameter toward the upper and lower both sides.

  Furthermore, by removing the copper foil 9 on the lower surface side of the insulating substrate 1 with a laser, the diameter of the double-sided copper-clad substrate 15 is increased toward the upper and lower surfaces on the upper and lower sides of the insulating substrate 1 as shown in FIG. The through-hole 3 in which the upper and lower hole diameters are substantially the same can be formed.

  For example, the through-hole 3 is formed on a double-sided copper-clad substrate 15 having a copper foil 9 having a thickness of 10 μm deposited on the upper and lower surfaces of an insulating substrate 1 made of a glass-epoxy plate having a thickness of 0.4 mm using a carbon dioxide laser. In this case, the pulse width per pulse of the laser may be 40 to 240 μsec, the energy value may be 8 to 30 mJ, and the number of shots may be 3 to 10. At this time, if the number of shots of laser light irradiation is too small, the diameter of the lower surface side of the through-hole 3 cannot be increased well toward the outside, and if the number of shots is too large, the diameter of the lower surface side of the through-hole 3 is increased. It becomes too much.

  Moreover, by setting it as this laser condition, the protrusion width | variety of the metal foil 9 protruded to the through-hole 3 mentioned later can be suppressed within 30 micrometers.

  Further, by using a carbon dioxide laser, the laser processing conditions are a pulse width of 40 to 240 μs, an output of 8 to 30 mJ, and a shot number of 3 to 10 shots, so that the protruding width of the metal foil 9 protruding into the through hole 3 is within 30 μm. It is possible to stably form the through holes 3 in the double-sided copper-clad substrate 15.

  That is, the copper foil 9 can be stably opened by setting the pulse width to 240 μs or less. Further, by setting the output to 8 mJ or more, it is possible to stably perforate up to the back surface of the double-sided copper-clad substrate 15. Further, by setting the number of shots to 3 shots or more, since the laser light reaches the back surface of the double-sided copper-clad substrate 15, it is possible to stably perforate the back surface of the double-sided copper-clad substrate 15. In addition, when the number of shots is 10 shots or less, the openings can be formed similarly, and the energy is so large that the through holes 3 formed in the double-sided copper-clad substrate 15 become too large as in the case of exceeding 10 shots, thereby forming fine wiring. There is no such thing as impossible. Further, the metal foil 9 around the through-hole 3 is altered by processing under the laser conditions described above, and the altered metal foil 9 around the through-hole 3 is etched during the etching for removing the protruding metal foil 9 described later. The etching rate is increased and the insulating substrate 1 around the through hole 3 is exposed.

  In FIG. 6, the carbonized layer 17 is omitted.

  Then, the carbonized layer 17 on the inner wall of the through-hole 3 is removed by roughening using, for example, a roughening solution made of a potassium permanganate solution or a sodium permanganate solution, thereby showing a partial cross-sectional view of FIG. A double-sided copper-clad substrate 15 from which the carbonized layer 17 has been removed is obtained.

  Here, an etching resist 20 is formed on the surface of the metal foil 9. The etching resist 20 is desirably formed so that there is an opening of 3 μm or more around the through hole 3. Next, the metal foil 9 is removed by etching including a portion protruding from the through hole 3. As the etching solution, when the metal foil 9 is the copper foil 9, an etching solution made of a mixed solution of sulfuric acid and hydrogen peroxide, a cupric chloride aqueous solution or a ferric chloride aqueous solution is preferably used. Thereafter, by peeling off the etching resist 20, the metal foil 9 can be removed at the peripheral edge of the through hole 3 to expose the insulating substrate 1, as shown in FIG.

  Even when the etching resist is not used, the insulating substrate 1 shown in the partial cross-sectional view of FIG. 3D can be obtained by setting the laser conditions, the copper foil thickness conditions, and the etching conditions as follows. The conditions are shown below. The width of the metal foil 9 protruding into the through hole 3 is preferably suppressed to 2.5 times or less the thickness of the metal foil 9. The presence of the metal foil 9 protruding in the through-hole 3 of the copper foil 9 allows penetration when roughening using a roughening solution comprising a potassium permanganate solution or a sodium permanganate solution as shown in FIG. Convection is likely to occur at the portion of the metal foil 9 protruding into the hole 3, and the carbonized layer 17 can be more reliably removed, and the metal foil 9 and the extremely thin portion of the surface layer of the insulating substrate 1 with reduced adhesion strength Can be removed. However, when the length of the metal foil 9 protruding into the through hole 3 exceeds 2.5 times the thickness of the metal foil 9, the metal foil 9 protruding into the through hole 3 is sufficiently removed during copper etching. Difficult to do.

  The specification for removing the metal foil 9 protruding from the through hole 3 by etching is that the metal foil 9 formed on the surface of the insulating substrate 1 is etched by contact with an etching solution from one direction, whereas the metal foil 9 formed on the surface of the insulating substrate 1 is etched. Since the protruding metal foil 9 is etched by contact with an etching solution from three directions, it is etched using a rate of 2 to 3 times that of the copper foil 9 formed on the surface of the insulating substrate 1. is there.

  Therefore, when the protruding width of the metal foil 9 protruding into the through hole 3 exceeds 2.5 times the thickness of the copper foil formed on the surface of the double-sided copper-clad substrate 15, the metal foil 9 protruding into the through hole is removed by etching. In doing so, the etching amount of the metal foil 9 protruding into the through hole 3 is increased, and the copper foil 3 formed on the surface of the insulating substrate 1 is excessively etched. Note that, as described above, the method for suppressing the protruding width of the metal foil 9 protruding into the through hole 3 to 30 μm or less can be performed by adjusting the conditions of the carbon dioxide laser. That is, using a carbon dioxide laser, the length of the metal foil 9 protruding into the through hole 3 is set to the surface of the insulating substrate 1 by setting the pulse width to 40 to 240 μs, the output to 8 to 30 mJ, and the number of shots to 3 to 10 shots. It is possible to stably form the through-hole 3 drilled in the insulating substrate 1 while keeping the thickness within 2.5 times the thickness of the copper foil 3 formed in the above.

  In this way, the removal of the carbonized layer 17 on the inner wall of the through hole 3, the carbonized layer 17 adjacent to the eaves-shaped portion of the copper foil 9, the copper foil 9 at the peripheral edge of the through hole, and the insulating substrate 1 at the peripheral edge of the through hole The surface layer can be removed. By setting it as such a process, the through conductor 5 and the through-hole periphery wiring layer 14 and wiring layer 13 which are mentioned later can be formed favorably. In this etching, a mixed solution of sulfuric acid and hydrogen peroxide solution or an etching solution made of a cupric chloride aqueous solution or a ferric chloride aqueous solution is suitably used.

  Next, as shown in FIG. 4 (e), after removing the carbonized layer 17 and the metal foil 9 at the periphery of the through hole, the inside of the through hole 3, the portion where the insulating substrate 1 at the periphery of the through hole is exposed, An electroless plating layer 11 a (not shown) and an electrolytic copper plating layer 11 b (not shown) are sequentially deposited on the surface of the metal foil 9 to form a through conductor 5 in the through hole 3, and on the surface of the copper foil 9. An electroless copper plating layer 11 a having a thickness of 1 to 3 μm and an electrolytic copper plating layer 11 b having a thickness of 20 to 30 μm are sequentially deposited to form the plating layer 11 and form the wiring layer 13. At the same time, a through-hole peripheral wiring layer 14 composed of the electrolytic copper plating layer 11a and the electrolytic copper plating layer 11b is formed at the peripheral edge of the through-hole.

  At this time, the carbonized layer 17 is removed from the inner wall of the through-hole 3, and further, the metal foil 9 at the periphery of the through-hole and the ultrathin portion of the surface layer where the adhesion strength of the insulating substrate 1 at the periphery of the through-hole is reduced are removed in advance. As a result, the through conductor 5 and the through hole 3, and the through hole peripheral wiring layer 14 and the insulating substrate 1 can be firmly bonded.

  In order to deposit the electroless copper plating layer 11a, for example, a palladium active solution containing ammonium chloride-based palladium acetate is used, and the inner wall of the through-hole 3 and the part where the insulating substrate 1 on the peripheral edge of the through-hole is exposed, A palladium catalyst may be attached to the surface of the copper foil 9, and an electroless copper plating layer 11a may be deposited thereon using a copper sulfate-based electroless copper plating solution. At this time, since the diameter of the through hole 3 is increased toward the outside at the opening of the double-sided copper-clad substrate 15, the electroless copper plating solution satisfactorily enters the through hole 3, and as a result, the electroless The copper plating layer 11a can be satisfactorily deposited with a substantially uniform thickness.

  Moreover, as an electrolytic copper plating solution for depositing the electrolytic copper plating layer 11b, for example, a copper sulfate-based electrolytic copper plating solution may be used. At this time, since the diameter of the through hole 3 is increased toward the outside at the opening of the double-sided copper-clad substrate 15, the electrolytic copper plating solution enters the through hole 3 favorably. As a result, the through hole 3 The inside can be satisfactorily filled with the electrolytic copper plating layer.

  Next, as shown in FIG. 4 (f), after filling and filling the hole filling resin 7 in the through hole 3, the surface of the wiring layer 13, the through hole peripheral wiring layer 14 and the hole filling resin 7 is polished, Flatten. By this polishing, unnecessary portions of the hole filling resin can be removed, and the thicknesses of the wiring layer 13 and the through hole peripheral wiring layer 14 can be set to predetermined thicknesses. In the polishing step, polishing and copper etching are alternately repeated a plurality of times to remove unnecessary portions of the hole-filling resin 7, and the thickness of the surface wiring layer 13 and the through hole peripheral wiring layer 14 is set to a predetermined thickness. Rather than removing unnecessary portions of the hole-filling resin 7 only by polishing and setting the thickness of the wiring layer 13 and the through-hole peripheral wiring layer 14 to a predetermined thickness, the total work time is improved by alternately performing polishing and copper etching. As a result, the thickness of the wiring layer 13 and the through hole peripheral wiring layer 14 becomes more uniform. As the copper etching solution, a mixed solution of sulfuric acid-hydrogen peroxide solution or an aqueous solution of ammonium persulfate is desirable, and etching with a uniform copper thickness can be performed.

  Finally, as shown in FIG. 5G, the wiring conductor 13 is formed by a conventionally known subtracting method, semi-additive method, or the like. Thus, according to the method for manufacturing a wiring board of the present invention, the metal foil 9 having reduced adhesion strength with the insulating substrate 1 can be easily removed at the peripheral portion of the through hole, and the newly exposed insulating substrate of the peripheral portion of the through hole. Since the through-hole peripheral wiring layer 14 can be formed on the substrate 1 by plating, the insulating substrate 1 and the through-hole peripheral wiring layer 14 can be firmly bonded to each other at the peripheral portion of the through-hole. Can be provided easily.

  Further, even if a build-up resin layer and a build-up wiring layer are laminated on the main surface of such a wiring board to produce a build-up wiring board, wiring in the through-hole 3 or around the through-hole is formed on the build-up resin layer. A wiring board in which no cracks are generated from between the conductor 13 and the insulating substrate 1 can be obtained.

  In the above-mentioned embodiment, the through-hole 3 has a diameter of 75 to 130 μm and a thickness of 0.2 to 0.8 mm as an example. However, the present invention is not limited to the above-described embodiment. Needless to say, various modifications can be made without departing from the scope of the present invention.

  Moreover, in the above-mentioned Example, although the through-hole 3 was formed by laser processing, when the through-hole 3 is formed by drilling, it cannot be overemphasized that the same effect is acquired.

  In order to evaluate the wiring board of the present invention, a sample was prepared and the following evaluation was performed.

  The through-hole 3 was formed in the double-sided copper-clad board | substrate 15 which comprises the copper foil 9 with a thickness of 10 micrometers on the main surface, and whose thickness is 0.4 mm by the carbon dioxide laser. Carbon dioxide laser drilling conditions were such that the pulse width was 160 μs, the output was 20 mJ, and the number of shots was six.

  The diameter of the produced through hole 3 was 90 μm. Thereafter, the carbon dioxide laser processed double-sided copper-clad substrate 15 was subjected to a roughening treatment for 10 minutes with an 80 ° C. roughening solution made of a potassium permanganate solution. Next, an etching resist 20 in which the exposed width of the copper foil 9 around the through-hole 3 is changed is formed on the main surface of the copper foil 9, and the copper foil 9 is made with a copper etching solution made of a sulfuric acid-hydrogen peroxide mixed solution. Was etched to expose the insulating substrate 1 at the periphery of the through hole with the exposure width shown in Table 1.

  Thereafter, the etching resist 20 is stripped, and the electroless copper plating layer 11a and the electrolytic copper plating layer 11b are exposed to the wall surface of the through hole 3, the exposed portion of the insulating substrate 1 at the periphery of the through hole, and the copper foil 9 Deposited on the surface.

  Thereafter, the hole filling resin 7 is embedded in the through hole 3, unnecessary portions of the hole filling resin 7 are removed by polishing, the through hole peripheral wiring layer 14 and the wiring conductor 13 are set to a predetermined thickness, and a wiring pattern is formed by a conventionally known subtract method. And a test piece as a core substrate was obtained.

  Ten test pieces each having different exposed widths of the insulating substrate 1 around the through-hole 3 shown in Table 1 were prepared, a heat resistance test assuming mounting on a semiconductor element and a printed board, and a temperature. After performing the cycle test, the peeled state between the insulating substrate 1 and the through-hole peripheral wiring layer 14 at the periphery of the through-hole was confirmed by cross-sectional observation with an SEM (scanning electron microscope).

The heat resistance test assuming mounting on a semiconductor element and mounting on a printed board was conducted three times through reflow conditions in which the peak temperature was 260 ° C. and the holding time was 200 ° C. or more and 60 seconds or more. Further, the temperature cycle test was performed at −55 ° C./125° C. under the condition of 1000 cycles.

  Sample No. in which a metal foil was formed on the peripheral edge of the through hole, which was outside the scope of the present invention. In No. 1, 10/10 peeling between the wiring conductor and the insulating substrate was confirmed by observing the cross section of the through hole after the temperature cycle, and it was confirmed that the reliability was poor.

  On the other hand, sample No. 1 provided with the through hole peripheral wiring layer of the present invention. In Nos. 2 to 5, no peeling between the wiring conductor and the insulating substrate was confirmed by cross-sectional observation of the through hole after the temperature cycle.

It is a principal part enlarged view of the wiring board of this invention. It is process drawing explaining the process of the manufacturing method of the wiring board of this invention. It is process drawing explaining the process of the manufacturing method of the wiring board of this invention. It is process drawing explaining the process of the manufacturing method of the wiring board of this invention. It is process drawing explaining the process of the manufacturing method of the wiring board of this invention. It is process drawing explaining the punching process which forms a through-hole among the manufacturing methods of the wiring board of this invention. It is process drawing explaining the roughening process of removing a carbonized layer among the manufacturing methods of the wiring board of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Insulating substrate 3 ... Through-hole 5 ... Through-conductor 7 ... Embedded resin 9 ... Metal foil 11 ... Plating layer 11a ... Electroless plating layer 11b ... Electrolytic plating Layer 13 ... Wiring layer 14 ... Through-hole peripheral wiring layer 15 ... Double-sided copper-clad substrate 17 ... Carbonized layer

Claims (6)

An insulating substrate containing at least a resin; a through hole formed in the insulating substrate; a through conductor deposited on an inner wall of the through hole; and a metal foil formed on a main surface of the insulating substrate. In the wiring substrate comprising the wiring layer, a through-hole peripheral wiring layer made of a plating layer is formed on the peripheral portion of the through-hole in the main surface of the insulating substrate. A wiring board, wherein the through conductor and the wiring layer are connected via each other. 2. The wiring board according to claim 1, wherein the width of the through hole peripheral wiring layer is 3 [mu] m or more. The wiring board according to claim 1 or 2, wherein the plating layer is composed of an electroless plating layer and an electrolytic plating layer, and is a copper plating. A step of forming a through hole in a double-sided copper-clad substrate made of an insulating substrate containing a resin and a metal foil formed on the main surface of the insulating substrate; a step of roughening the double-sided copper-clad substrate; Etching part of the copper foil of the roughened double-sided copper-clad substrate to remove the copper foil at the periphery of the through hole, exposing the main surface of the insulating substrate at the periphery of the through hole; An electroless copper plating layer and an electrolytic copper plating layer are sequentially formed on the double-sided copper-clad substrate from which the copper foil at the periphery of the hole is removed, and a through conductor, a through conductor peripheral wiring layer, and a wiring layer are formed. A step of embedding a hole-filling resin in the through-hole, a polishing step of polishing a surface layer of the double-sided copper-clad substrate to remove unnecessary portions of the hole-filling resin, and a wiring layer having a predetermined thickness A method of manufacturing a wiring board, comprising: The method for manufacturing a wiring board according to claim 4, wherein the through hole is formed by laser processing. The polishing step wherein the polishing of the surface layer of the double-sided copper-clad substrate and the etching of the copper are alternately repeated a plurality of times to remove unnecessary portions of the hole-filling resin and to make the copper thickness of the surface layer a predetermined thickness. A method for manufacturing a wiring board according to 4 or 5.

Images