JP4545866B2 - Method for manufacturing circuit board for multilayer printed wiring board - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
  The present invention is a proposal for a method of manufacturing a double-sided circuit board and a single-sided circuit board that are used for manufacturing a multilayer printed wiring board.
[0002]
[Prior art]
  In response to recent demands for smaller, lighter, faster, and more advanced electronic devices, interstitial via hole structure (hereinafter referred to as “high-density wiring”) that can be easily replaced with high-density wiring instead of conventional multilayer printed wiring boards with through-hole structure A multilayer printed wiring board having abbreviated IVH structure has been proposed.
[0003]
  The multilayer printed wiring board having the IVH structure is a printed wiring board having a structure in which each interlayer insulating layer constituting the laminated body is provided with a via hole for electrically connecting conductor circuits. In such a printed wiring board, inner layer conductor circuit patterns or between inner layer conductor circuit patterns and outer layer conductor circuit patterns are electrically connected by via holes (belly via holes or blind via holes) that do not penetrate the wiring board. Is a feature. Therefore, such a multilayer printed wiring board having an IVH structure does not require a special region for forming a through hole, and each interlayer connection can be made only with a minute via hole. It is expected that high density and high-speed signal propagation can be easily realized.
[0004]
  However, the multilayer printed wiring board having the above IVH structure is caused by employing an uncured resin such as a glass epoxy prepreg in which a glass cloth is impregnated with an epoxy resin as an insulating resin base material in the manufacturing process. There was a problem.
  That is, a copper foil is bonded onto a prepreg by hot pressing, and a plurality of circuit boards on which conductive circuits are formed by etching are laminated with an adhesive, and then the laminated circuit boards are heated together. When multilayered by pressing, the phenomenon that the position of the via hole shifted in the XY direction was observed because the cured resin contracted. In order to cope with such a positional shift, it is necessary to increase the via land diameter in advance, so that precise wiring is difficult.
[0005]
  In addition, such a problemaboutThe inventors of the present application have previously described Japanese Patent Application No. 10-179192.By patent applicationThe improvement method was proposed.
  This improvementThe proposal is not a conventional insulating base material made of uncured resin, but a resin base material made of cured resin as a core material, and a conductor circuit is formed on one or both sides of the core material, and the conductor circuit For single-sided circuit boards or double-sided circuit boards connected by filled via holesthingIt is a technique for manufacturing a multilayer printed wiring board by appropriately combining and laminating a plurality of these sheets and collectively heating and pressing.
[0006]
[Problems to be solved by the invention]
  However, the above improvement proposals still have the following problems to be solved. In other words, according to the previously proposed technology, in the manufacture of a circuit board having conductor circuits on both sides of an insulating base material, a through hole is provided in the insulating base material, and a conductive paste is filled into the through hole by a method such as printing. Then, after forming the filled via hole, a copper foil was attached to both sides, and the conductor circuit was formed by etching the copper foil.
[0007]
  However, when such a double-sided circuit board is used as a core and a laminated circuit board having a conductor circuit formed on one side is laminated, a multilayer printed wiring board is manufactured.InTherefore, there is a practical problem that the core circuit board and the laminated circuit board must be manufactured on separate manufacturing lines, which increases the manufacturing cost of the multilayer printed wiring board.
[0008]
  Further, in the manufacturing process of such a circuit board, there is a problem that bubbles are involved in the conductive paste during stirring or printing before filling with the conductive paste, that is, bubbles are mixed.
  In general, the amount of air bubbles mixed into this conductive paste is larger when filling non-through holes than when filling through holes, but in any case, it is possible to reduce air bubbles as much as possible. Is necessary to stabilize the interlayer connection resistance.
[0009]
  As a technique to reduce the mixing of bubbles, so-called vacuum pressurization is performed by removing the bubbles entrained in the conductive paste by pressurizing the filled paste under reduced pressure while filling the conductive paste. Although a method of defoaming has been proposed, it is difficult to efficiently apply such a technique to filling the through-holes, and it is difficult to completely avoid residual bubbles mixed in the conductive paste. It is.
[0010]
  Therefore, the inventors do not employ a process of filling a conductive paste in a through hole provided in an insulating base material, and a double-sided circuit board and a single-sided circuit boardsoProposing a manufacturing method including a part of the same manufacturing process, that is, a process of providing a non-through hole in an insulating base material with a copper foil pasted on one side and filling the non-through hole with a conductive paste. is there.
[0011]
  The present invention has been made in view of the above-mentioned problems of the proposed improvement technique, and its main object is a circuit for a multilayer printed wiring board capable of reducing the manufacturing cost and stabilizing the interlayer connection resistance. It is to propose a method for manufacturing a substrate.
[0012]
[Means for Solving the Problems]
  As a result of intensive studies to achieve the above-mentioned object, the inventors have arrived at the present invention having the following contents. That is,
(A) A method for producing a circuit board for a multilayer printed wiring board according to the present invention comprises:
  Formed from fully cured hard resin materialIn manufacturing a circuit board for a multilayer printed wiring board having conductor circuits on both surfaces of a hard insulating base material, and via holes for electrically connecting the conductor circuits formed in the insulating base material, During the production process, at least the following steps (1) to (4):
(1) A resin adhesive layer in a semi-cured state is formed on the other surface of an insulating substrate having a copper foil attached to one surface, and a resin film is adhered onto the resin adhesive layer, and then the resin A step of forming a non-through hole reaching the copper foil by laser irradiation from above the film;
(2) After the non-through hole is filled with the conductive paste, the insulating base is exposed from the other surface of the insulating base of the filled conductive paste under reduced pressure. Pressurizing the surface of
(3) After peeling off the resin film from the surface of the insulating substrate, the conductive paste exposed from the other surface of the insulating substrate is covered with a copper foil, and the conductive paste and Forming a filled via hole for electrically connecting the copper foil;and
(4) etching the copper foil attached to the insulating resin to form a conductor circuit on both sides;
TheIt is characterized by including.
[0013]
  In the manufacturing method described above, it is desirable that after the step (1), the method includes a step of exposing the insulating base material to a plasma atmosphere and plasma cleaning the resin residue remaining in the non-through holes. The plasma cleaning process is preferably performed under the conditions of the output, the degree of vacuum, the reactive gas species, and the energization time such that the temperature of the circuit board is 60 ° C. or less.
[0014]
(B) Moreover, the manufacturing method of the circuit board for multilayer printed wiring boards of the present invention includes:
  Formed from fully cured hard resin materialWhen manufacturing a circuit board for a multilayer printed wiring board having a conductive circuit on one side of a hard insulating base material and via holes reaching the conductive circuit are formed in the insulating base material, during the manufacturing process, At least the following steps (1) to (3):
(1) A process of forming a conductor circuit by performing an etching process on an insulating base material having a copper foil attached to one surface;
(2) A semi-cured resin adhesive layer is formed on the other surface of the insulating substrate, and a resin film is adhered onto the resin adhesive layer, and then laser irradiation is performed on the resin film. Forming a non-through hole reaching the copper foiland
(3) The side of the filled conductive paste exposed from the other surface of the insulating base material under reduced pressure conditions after the conductive paste is filled into the non-through holes Pressurize the surface of,Forming a filled via hole for electrical connection with the conductor circuit;
TheIt is characterized by including.
[0015]
  In the above manufacturing method, it is desirable that the step (2) includes a step of exposing the insulating base material to a plasma atmosphere and plasma cleaning the resin residue remaining in the non-through holes. The plasma cleaning process is preferably performed under conditions of output, vacuum, reactive gas species, and energization time such that the temperature of the circuit board is 60 ° C. or lower.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
  The feature of the method for manufacturing a circuit board for a multilayer printed wiring board according to the present invention is that the circuit board serving as a core of the multilayer printed wiring board having all layers having an IVH structure, or a circuit board for lamination laminated on the core circuit board A circuit board suitable for use is manufactured in a partially shared process between a double-sided circuit board and a single-sided circuit board without providing a through hole in a hard insulating base material.It is in.
[0017]
  IeThe present inventionA copper foil is pasted on one surface of a hard insulating base material, and a semi-cured resin adhesive layer is formed on the other surface of the insulating base material.Made of resin filmAfter a protective film is pasted and a non-through hole reaching the copper foil from the protective film is formed, a conductive paste is filled in the non-through hole, and then the insulating substrate is filled with a conductive material under reduced pressure. The surface of the conductive paste exposed from the other surface of the insulating substrate to form a filled via hole,Peel off the protective film,A circuit board having a conductor circuit on both sides by etching the copper foil pasted on both surfaces of the insulating base material after covering the conductive paste exposed from the other surface of the insulating base material and pasting the copper foil It is characterized by manufacturing.
[0018]
  In addition, after a copper foil is pasted on one surface of a hard insulating substrate, a conductive circuit is formed by etching the insulating substrate, and then a semi-cured resin is formed on the other surface of the insulating substrate. Form an adhesive layer on itMade of resin filmAfter pasting a protective film and forming a non-through hole reaching the conductor circuit from the protective film, after filling the non-through hole with a conductive paste, the insulating substrate is filled with the conductive material under reduced pressure. A circuit board having a conductor circuit on one side is formed by pressurizing the surface of the conductive paste that is exposed from the other surface of the insulating base material and electrically connecting with the copper foil to form a filled via hole. It is characterized by manufacturing.
[0019]
  According to such a configuration, the double-sided circuit board and the single-sided circuit board can be manufactured through a partly common manufacturing process, so that the manufacturing cost can be reduced, and the insulating property in which the copper foil is pasted on one side Since the conductive paste is filled into the non-through holes provided in the base material by vacuum pressure defoaming, residual bubbles in the conductive paste can be suppressed as much as possible.
[0020]
  Also, before filling the non-through holes with the conductive paste, the resin remaining in the non-through holes without damaging the PET film or the resin adhesive by performing a desmear process by plasma cleaning in the non-through holes. Residue can be effectively removed, and a stable interlayer connection resistance can be obtained in synergy with filling of the conductive paste by vacuum pressure degassing.
[0021]
  The insulating base material used in the circuit board manufacturing method of the present invention is not a semi-cured prepreg as in the prior art, but a hard insulating base material formed from a completely cured resin material. By using a simple material, the final thickness of the insulating substrate due to the pressing pressure is eliminated when the copper foil is crimped onto the insulating substrate with a hot press, minimizing misalignment of via holes. By suppressing, the via land diameter can be reduced. Therefore, the wiring pitch can be reduced and the wiring density can be improved. In addition, since the thickness of the substrate can be kept substantially constant, when the non-through hole for forming the filled via hole is formed by laser processing, the laser irradiation conditions can be easily set.
[0022]
  As the insulating substrate, a glass cloth epoxy substrate having a thickness of 20 to 600 μm is preferably used. The reason is that when the thickness is less than 20 μm, the strength is reduced and handling becomes difficult, and the reliability with respect to the electrical insulation is reduced. When the thickness exceeds 600 μm, formation of fine via holes and filling of conductive paste are performed. This is because the thickness of the substrate itself is increased.
[0023]
  A copper foil is attached to one surface of the insulating base material via an appropriate resin adhesive, and a conductor circuit is formed by an etching process. Instead of sticking the copper foil on such an insulating substrate, a single-sided copper clad laminate in which the copper foil is previously stuck on the insulating substrate can also be used.
[0024]
  When manufacturing the double-sided circuit board according to the present invention, first, on the surface opposite to the surface of the insulating base material to which the copper foil is attached, a semi-cured resin adhesive layer is interposed.Made of resin filmA protective film is adhered and a non-through hole is formed by irradiating a laser on the protective film, but when manufacturing a single-sided circuit board, the copper foil is first etched to form a conductor circuit. Through the semi-cured resin adhesive layer on the surface opposite to the surface of the insulating base material on which this conductor circuit is formedMade of resin filmA protective film is adhered, and laser irradiation is performed on the protective film to form non-through holes.
  As will be described later, the resin adhesive is for bonding a copper foil to the surface of an insulating substrate. For example, the resin adhesive is formed from a bisphenol A type epoxy resin, and the thickness is preferably in the range of 10 to 50 μm.
[0025]
  In addition, the protective film applied on the resin adhesive layer functions as a printing mask that fills the non-through holes reaching the copper foil from the surface of the insulating base material, and is not applied to the insulating base material. After forming the through hole, the adhesive layer is peeled off from the adhesive layer. This resin film is preferably formed from a PET film having a pressure-sensitive adhesive layer thickness of 1 to 20 μm and a film thickness of 10 to 50 μm, for example.
  The reason is that depending on the thickness of the PET film, the amount of protrusion of the conductive paste from the surface of the insulating substrate is determined. Therefore, if the thickness is less than 10 μm, the amount of protrusion is too small and connection failure tends to occur. If the thickness exceeds 50 μm, the melted conductive paste spreads too much at the connection interface, so that a fine pattern cannot be formed.
[0026]
  The non-through hole formed on the glass epoxy substrate having the thickness in the above range has a pulse energy of 0.5 to 100 mJ, a pulse width of 1 to 100 μs, a pulse interval of 0.5 ms or more, and a shot number of 3 to 50. Preferably, it is formed by a carbon dioxide laser that is irradiated under the above conditions, and the aperture is desirably in the range of 50 to 250 μm.
  The reason is that if it is less than 50 μm, it becomes difficult to fill the non-through holes with the conductive paste and the connection reliability is lowered, and if it exceeds 250 μm, it is difficult to increase the density.
[0027]
  Before filling the non-through holes with conductive paste, it is desirable to perform desmear treatment to remove the resin residue remaining on the inner wall surface of the non-through holes from the viewpoint of securing connection reliability. Since it is performed in a state where the agent layer and the protective film are adhered, it is desirable to use dry desmear treatment using plasma discharge, corona discharge, or the like, for example. Among dry desmear treatments, plasma cleaning using a plasma cleaning device is particularly preferable.
[0028]
  In the above plasma cleaning, an insulating base material with non-through holes formed is placed on an electrode provided in a chamber of a known plasma cleaning device with its opening facing upward to insulate the copper foil. So that the temperature of the adhesive layer and the protective film applied on the insulating base material during laser processing is lower than the softening temperature of those resins. It is desirable to perform plasma cleaning while cooling the electrode itself. For this purpose, conditions such as output, degree of vacuum, reactive gas species, and energization time should be appropriately selected. According to such treatment, the oil residue is plasma-cleaned, and the positional deviation of the opening and the peeling of the protective film due to the softening of the resin adhesive can be effectively prevented. At this time, in order to dissipate the heat received by the insulating base material to the electrode in the chamber, it is more effective if it is placed via a heat conductive sheet made of a silicone resin containing metal particles.
[0029]
  After the desmear treatment for the non-through holes of the insulating base material, the conductive paste filled in the non-through holes by the vacuum pressure defoaming method is suitable for reducing the manufacturing cost and improving the yield. is there.
  The conductive paste is at least one selected from silver, copper, gold, nickel, and solder.
A conductive paste containing more than one kind of metal particles can be used.
[0030]
  In addition, as the metal particle, a metal particle whose surface is coated with a different metal can be used. Specifically, the metal particle which coat | covered the noble metal chosen from gold | metal | money and silver on the surface of a copper particle can be used.
  As the conductive paste, an organic conductive paste in which metal particles are added with a thermosetting resin such as an epoxy resin or a phenol resin, or a thermoplastic resin such as polyphenylene sulfide (PPS) can be used.
[0031]
  Such filling of the conductive paste into the non-through holes can be performed by any method such as a printing method using a metal mask or a method using a squeegee or a dispenser.
  The decompression condition and the pressure to be applied are determined according to the viscosity of the conductive paste, the type and amount of the solvent, the opening diameter and depth of the through hole and via hole, and the conductive paste under such appropriate conditions. The pressure can be applied, for example, using a known press device or a vacuum laminator for forming a dry film.
  Furthermore, if necessary, the time for eliminating bubbles can be shortened by heating the conductive paste filled in the openings to increase its fluidity.
[0032]
  When manufacturing a single-sided circuit board, after filling a non-through hole of the insulating base material with a conductive paste and then removing the protective film from the resin adhesive layer, the resin adhesive is in a semi-cured state Is exposed on the surface of the insulating substrate. A circuit board in which such a conductor circuit is formed on one side of an insulating base material is suitable as a circuit board for lamination, and the conductive paste filled in the via hole is exposed by a predetermined amount from the substrate surface. It is preferable to form a protruding conductor for connection.
[0033]
  Further, when manufacturing a double-sided circuit board, a semi-cured resin adhesive remaining on the insulating substrate by heating press after filling the non-through holes of the insulating substrate with a conductive paste Copper foil is affixed through the layers.
  The thickness of the copper foil is desirably 5 to 18 μm, and the heating press is performed under an appropriate temperature and pressure. More preferably, the conventional prepreg is used because the copper foil can be firmly bonded to the insulating substrate by performing only heat-pressing under reduced pressure and curing only the semi-cured resin adhesive layer. Manufacturing time is shortened compared to conventional circuit boards.
[0034]
  As described above, the copper foil attached to one surface of the insulating base material is subjected to an appropriate etching treatment together with the copper foil previously attached to the other surface of the insulating base material, Desired conductor circuits are formed on both sides.
  A circuit board in which a conductor circuit is formed on both surfaces of an insulating base material in this way is suitable as a core board when forming a multilayer printed wiring board. The via land (pad) as a part of the circuit is formed with a diameter of 50 to 250 μm.preferable.
[0035]
  Hereinafter, an example of a method for producing a double-sided circuit board for a multilayer printed wiring board according to the present invention will be specifically described with reference to FIG.
(1)In manufacturing a circuit board for a multilayer printed wiring board according to the present invention, on one side of the insulating substrate 10Copper foil 12Is used as a starting material (see FIG. 1 (a)).
  The insulating base material 10 is, for example, a glass cloth epoxy resin base material, a glass cloth bismaleimide triazine resin base material, a glass cloth polyphenylene ether resin base material, an aramid nonwoven fabric-epoxy resin base material, an aramid nonwoven fabric-polyimide resin base material. Although a rigid (hard) laminate substrate may be used, a glass cloth epoxy resin substrate is most preferred.
[0036]
  As for the thickness of the said insulating base material 10, 20-600 micrometers is desirable. The reason is that when the thickness is less than 20 μm, the strength is reduced and handling becomes difficult, and the reliability with respect to the electrical insulation is reduced. When the thickness exceeds 600 μm, formation of fine via holes and filling of conductive paste are performed. This is because the thickness of the substrate itself is increased.
[0037]
  Moreover, as for the thickness of the copper foil 12, 5-18 micrometers is desirable. The reason is that, when laser processing as will be described later is used to form a non-through hole for forming a via hole in an insulating base material, if it is too thin, it penetrates. This is because it is difficult to form a fine pattern.
  As the insulating base material 10 and the copper foil 12, in particular, a single-sided copper-clad laminate obtained by laminating an epoxy resin into a glass cloth to form a B stage and laminating a copper foil and heating and pressing. It is preferable to use a plate. The reason is that the position of the wiring pattern and the via hole is not shifted during handling after the copper foil 12 is etched as will be described later, and the positional accuracy is excellent.
[0038]
(2)A semi-cured adhesive, that is, a B-stage adhesive layer 14 is provided on the surface opposite to the surface on which the copper foil 12 of the insulating base material 10 is affixed. A protective film 16 is stuck on the top (see FIG. 1 (b)).
  This adhesive 14 is for adhering the copper foil which forms a conductor circuit, For example, an epoxy resin varnish is used and the layer thickness has the preferable range of 10-50 micrometers.
  This protective film 16 is used as a mask for printing a conductive paste described later, and for example, a polyethylene terephthalate (PET) film having an adhesive layer on the surface can be used.
  The PET film 16 is such that the pressure-sensitive adhesive layer has a thickness of 1 to 20 μm and the film itself has a thickness of 10 to 50 μm.
[0039]
(3)Next, laser irradiation is performed from above the PET film 16 affixed on the insulating base material 10, penetrates the PET film 16 and the adhesive layer 14, and reaches the copper foil 12 from the surface of the insulating base material 10. A through hole 18 is formed (see FIG. 1C).
  This laser processing is performed by a pulse oscillation type carbon dioxide laser processing apparatus. Processing conditionsIsIt is desirable that the pulse energy is 2.0 to 10.0 mJ, the pulse width is 1 to 100 μs, the pulse interval is 0.5 ms or more, and the number of shots is 10 to 50.
  The diameter of the non-through hole 18 that can be formed under such processing conditions is preferably 50 to 250 μm.
[0040]
(4)Above(3)In order to remove the resin residue remaining on the inner wall surface of the non-through hole 18 formed in the above step, a desmear process is performed.
  As this desmear treatment, dry desmear treatment using plasma discharge, corona discharge or the like is desirable from the viewpoint of securing connection reliability, and in particular, desmear treatment is performed by a novel plasma cleaning method developed by the present inventors. It is preferable.
[0041]
  In this plasma cleaning method, the insulating base material 10 in which the non-through holes 18 are formed is placed on an electrode provided in a chamber of a known plasma cleaning device with its opening facing upward, Adhesive layer pasting the foil 12 on the insulating substrate 10 and the above(3)The temperature of the adhesive layer 14 and the protective film 16 affixed on the insulating base material 10 during the laser processing in the step is such that the softening temperature of those resins, for example, lower than 60 ° C., This is a method in which plasma cleaning is performed while the electrode itself is cooled, and the resin residue is plasma-cleaned, and effectively prevents displacement of the opening and peeling of the protective film due to softening of the resin adhesive. Can do. At this time, in order to dissipate the heat received by the insulating base material 10 to the electrode in the chamber, it is more effective if it is placed via a heat conductive sheet made of a silicone resin containing metal particles.
[0042]
(5)Next, the conductive paste 20 is filled into the non-through holes 18 that have been desmeared by printing (see FIG. 1D).
  Thereafter, the entire substrate is fixed on a stage in a vacuum chamber (not shown), and 1 × 10³~ 5 × 10³Under a reduced pressure of Pa, the exposed side surface of the conductive paste 20 of the insulating substrate 10 is pressurized for several minutes by an appropriate press device (not shown).
[0043]
(6)Thereafter, after the PET film 16 is peeled off from the surface of the adhesive layer 14 (see FIG. 1 (e)), the copper foil 24 is pressure-bonded to one side of the insulating substrate 10 via the adhesive layer 14 by a hot press. Then, the adhesive layer 14 is cured (see FIG. 1 (f)).
  At that time, the copper foil 24 is bonded to the insulating substrate 10 through the cured adhesive layer 14, and the conductive paste 20 and the copper foil 24 are electrically connected. As for the thickness of this copper foil 24, 5-18 micrometers is desirable.
[0044]
(7)Next, an etching protective film is applied to each of the copper foils 12 and 24 applied to both surfaces of the insulating base material 10 and is covered with a mask having a predetermined circuit pattern. And 28 (including via land) are formed (see FIG. 1 (g)).
  In this processing step, first, a photosensitive dry film resist is applied to the surfaces of the copper foils 12 and 24, and then an etching resist is formed by exposing and developing along a predetermined circuit pattern. The metal layer is etched to form conductor circuit patterns 26 and 28 including via lands.
  The etching solution is preferably at least one aqueous solution selected from an aqueous solution of sulfuric acid monohydrogen peroxide, persulfate, cupric chloride, and ferric chloride. As a pretreatment for etching the copper foils 12 and 24 to form the conductor circuits 26 and 28, in order to facilitate the formation of a fine pattern, the entire surface of the copper foil is etched in advance to a thickness of 1 to 10 μm. Preferably, the thickness can be reduced to about 2 to 8 μm.
  The via land as a part of the conductor circuit has an inner diameter substantially the same as the via hole diameter, but the outer diameter is preferably formed in the range of 50 to 250 μm.
[0045]
(8)Next, the above(7)The surfaces of the conductor circuits 26 and 28 formed in this step are roughened (the roughened layer is not shown), and the double-sided circuit board 30 for the core is formed.
  This roughening treatment is to improve adhesion with the adhesive layer and prevent peeling (delamination) when multilayering.
  Examples of the roughening treatment method include soft etching treatment, blackening (oxidation) one-reduction treatment, formation of needle-like alloy plating made of copper-nickel-phosphorus (made by Sugawara Eugleite: trade name Interplate), manufactured by MEC There is surface roughening with an etchant named “MEC Etch Bond”.
[0046]
  In this embodiment, the roughening layer is preferably formed using an etching solution. For example, the surface of the conductor circuit is etched using an etching solution from a mixed aqueous solution of a cupric complex and an organic acid. It can be formed by processing. Such an etching solution can dissolve the copper conductor circuit under oxygen coexisting conditions such as spraying and bubbling, and the reaction is assumed to proceed as follows.
  Cu + Cu (II) A_n → 2Cu (I) A_{n / 2}
  2Cu (I) A_{n / 2} + N / 4O₂ + NAH (Aeration)
                    → 2Cu (II) A_n + N / 2H₂O
In the formula, A represents a complexing agent (acts as a chelating agent), and n represents a coordination number.
[0047]
  As shown in this formula, the generated cuprous complex dissolves by the action of an acid, and combines with oxygen to form a cupric complex, which again contributes to the oxidation of copper. The cupric complex used in the present invention is preferably an azole cupric complex. The etching solution comprising the organic acid-cupric complex can be prepared by dissolving a cupric complex of an azole and an organic acid (halogen ions as required) in water.
  Such an etching solution is, for example, 10 parts by weight of imidazole copper (II) complex, glycolic acid
It is formed from an aqueous solution in which 7 parts by weight and 5 parts by weight of potassium chloride are mixed.
  The double-sided circuit board for a multilayer printed wiring board according to the present invention is the above-mentioned(1)~(8)And is suitable as a circuit board for a core of a multilayer printed wiring board.
[0048]
  Next, a method of manufacturing a single-sided circuit board that is laminated on the front and back surfaces of such a double-sided circuit board will be described with reference to FIG.
(1) First, an etching protective film is pasted on the copper foil 12 stuck on one surface of the insulating base material 10, and is covered with a mask having a predetermined circuit pattern. (Including via land) is formed (FIG. 2).(a) to FIG.(See (b)).
  In this processing step, first, a photosensitive dry film resist is applied to the surface of the copper foil 12, and then exposed and developed along a predetermined circuit pattern to form an etching resist. The layer is etched to form a conductor circuit pattern 34 including via lands.
  The etching solution is preferably at least one aqueous solution selected from an aqueous solution of sulfuric acid monohydrogen peroxide, persulfate, cupric chloride, and ferric chloride.
  As a pretreatment for forming the conductor circuit 34 by etching the copper foil 12, the entire surface of the copper foil is etched in advance to have a thickness of 1 to 10 μm, more preferably 2 to 2 to facilitate the formation of a fine pattern. The thickness can be reduced to about 8 μm.
[0049]
(2) After forming the conductor circuit 34 on one side of the insulating base material 10, the double-sided circuit board(2)~(5)(See FIGS. 2 (c) to 2 (e)). After that, when the PET film 16 is peeled off from the surface of the adhesive layer 14, a conductive circuit is formed on one surface of the insulating substrate. The single-sided circuit board 40 having the filled via hole 22 formed in the conductive circuit 34 is formed (see FIG. 2F).
[0050]
  In the state where the PET film 16 is peeled off, the conductive paste 20 filled in the non-through holes 18 is obtained by adding approximately the thickness of the adhesive layer 14 and the thickness of the PET film 16 from the surface of the insulating substrate 10. The height of the protruding portion 36 (hereinafter referred to as “protruding conductor”) is preferably in the range of 5 to 30 μm.
  The reason is that if the thickness is less than 5 μm, poor connection is likely to occur, and if the thickness exceeds 30 μm, the resistance value becomes high, and when the protruding conductors 36 are thermally deformed in the hot press process, they extend too much along the surface of the insulating substrate. This is because a fine pattern cannot be formed.
[0051]
  Further, it is desirable that the protruding conductor 36 formed from the conductive paste 20 is in a pre-cured state. The reason is that the protruding conductor 36 is hard even in a semi-cured state, and its tip protrudes from the adhesive layer 14. Therefore, before the adhesive layer 14 is softened at the stage of the lamination press, another circuit board is laminated. This is because electrical contact with the conductor circuit (conductor pad) is possible. In addition to deformation during hot pressing, the contact area increases and the conduction resistance can be lowered, as well as variations in the height of the protruding conductors 36 can be corrected.
[0052]
  Thus, the single-sided circuit board 40 manufactured by the steps (1) and (2) has the conductor circuit 34 on one surface of the insulating base material 10 and the conductive paste on the other surface. A part of the protruding conductor 36 is formed so as to be exposed, and is laminated on the core circuit board 30 manufactured in advance to be multilayered.
[0053]
  FIG. 3 shows that a four-layer board in which three single-sided circuit boards 40, 42 and 44 are laminated on both sides of a core double-sided circuit board 30 has a heating temperature of 150 to 200 ° C. and a pressure of 1 M to 4 MPa. Originally, a multilayer printed wiring board integrated by one press forming is shown.
  Thus, by heating simultaneously with pressurization, the adhesive layer 38 of each single-sided circuit board is cured, and strong adhesion is performed between adjacent single-sided circuit boards. Note that a vacuum hot press is preferably used as the hot press.
[0054]
  In addition, instead of the adhesive layer 38 formed in advance on the surface of the insulating base material, after each single-sided circuit board is manufactured, in the stage of multilayering, the entire surface on the protruding conductor side of the insulating base material and Alternatively, an adhesive may be applied to the entire surface on the conductor circuit side and formed as an adhesive layer made of an uncured resin in a dried state. The adhesive layer is preferably pre-cured for easy handling, and the thickness is preferably in the range of 5 to 50 μm.
  In the above-described embodiment, the double-sided circuit board for core and the three-sided single-sided circuit board are used to form a multi-layered structure with four layers.
[0055]
【Example】
Example 1
(1) A single-sided copper-clad laminate obtained by laminating an epoxy resin in a glass cloth to form a B stage and laminating and pressing the copper foil is used as a substrate. The thickness of the insulating substrate 10 was 75 μm, and the thickness of the copper foil 12 was 12 μm.
[0056]
(2) An adhesive layer 14 having a thickness of 25 μm made of a B-stage epoxy resin is provided on the surface opposite to the surface on which the copper foil 12 of the insulating base material 10 is pasted, and the adhesive A PET film 16 having a thickness of 22 μm is pasted on the layer 14.
  The PET film 16 includes a pressure-sensitive adhesive layer having a thickness of 10 μm and a PET film base having a thickness of 12 μm.
[0057]
(3) Next, a non-through hole 18 for forming a via hole is formed by irradiating a pulse oscillation type carbon dioxide laser on the PET film 16 under the following laser processing conditions.
[Laser processing conditions]
  Pulse energy 4.0mJ
  Pulse width 15μs
  Pulse interval 2ms or more
  5 shots
[0058]
(4) Further, in order to remove the resin remaining on the inner wall of the non-through hole 18, a plasma cleaning process using a plasma apparatus is performed under the following conditions.
[Plasma cleaning conditions]
  Electrode cooling method: Water cooling
  Thermal conductive sheet: Silicone resin with metal particles
  Reaction gas: O₂And CF₄And mixed gas (O₂: CF₄= 70: 30)
  Vacuum degree in chamber: 7.3 × 10⁴Pa
  Output: 500W
  Energizing time: 3 minutes
  Circuit board temperature: 60 ° C
[0059]
(5) Next, the conductive paste 20 is filled into the through holes 18 using the PET film 16 as a printing mask to form filled via holes 22 of 150 μmφ. At that time, vacuum depressurization is performed under the following conditions.
[Vacuum pressure defoaming conditions]
  Degree of vacuum: 2.5 × 10³Pa
  Applied pressure: 2 MPa
[0060]
(6) After peeling the PET film 16 from the adhesive layer 14, a copper foil 24 having a thickness of 12 μm is heated and pressed on the adhesive layer 14 under the following conditions.
[Heat press conditions]
  Heating temperature: 180 ° C
  Heating time:
70 minutes pressure: 2 MPa
  Degree of vacuum: 2.5 × 10³Pa
  Thereafter, the copper foils 12 and 24 were appropriately etched to form conductor circuits 26 and 28 (including via lands), and the double-sided circuit board 30 was produced.
[0061]
(Example 2)
(1) After the step (1) of the first embodiment, the copper foil 12 affixed to one surface of the insulating base material 10 is appropriately etched to form the conductor circuit 34 (including via land). .
(2) Next, substantially the same process as in the steps (2) to (5) of Example 1 is performed, and the conductive paste 20 is filled into the non-through holes 18 and cured to 150 μmφ. The filled via hole 22 was formed, and the PET film 16 was further peeled to produce a single-sided circuit board 40.
[0062]
(Comparative Example 1)
(1)An adhesive is applied to both surfaces of an insulating base material made of a cured glass cloth epoxy resin base material (thickness 75 μm), dried at 100 ° C. for 30 minutes to form an adhesive layer 20 μm thick, Further, a PET film having a pressure-sensitive adhesive layer having a thickness of 10 μm and a thickness of 12 μm is laminated on the adhesive layer.
[0063]
(2)Next, a pulse oscillation type carbon dioxide laser is irradiated on the PET film to form a through hole for forming a via hole. Further, using the PET film as a printing mask, the inside of the through hole is filled with a conductive paste by printing to fill 150 μmφ. A via hole is formed.
[0064]
(3)After peeling the PET film from the adhesive layer, a copper foil having a thickness of 12 μm was heated to a heating temperature of 180 ° C., a heating time of 70 minutes, a pressure of 2 MPa, and a degree of vacuum of 2.5 × 10.³It heat-presses on an adhesive bond layer on the conditions of Pa.
(4)Thereafter, the copper foil on both sides of the substrate was appropriately etched to form conductor circuits and via lands, thereby producing a double-sided circuit board for core.
[0065]
  About the circuit board manufactured by the said Example 1, Example 2, and the comparative example 1, the grade of the resin residue which remains in a non-through-hole, and the degree of voidless were investigated with the X-ray microscope (EV-1100PC2: made by Uniheit). .
  As a result, in Example 1 and Example 2, almost no resin residue was found and the number of voids in 500,000 via holes was 0, but in Comparative Example 1, some resin residue was found. The number of voids in 10,000 via holes was 5.
[0066]
【The invention's effect】
  As described above, according to the present invention, the double-sided circuit board and the single-sided circuit board that are used for the production of the multilayer printed wiring board can be manufactured through a partly common manufacturing process, thereby reducing the manufacturing cost. In addition, since the conductive paste is filled in the non-through hole provided in the insulating base material with the copper foil pasted on one side by vacuum pressure degassing, bubbles remain in the conductive paste. As much as possible, the interlayer connection resistance can be stabilized.
[0067]
  Also, before filling the non-through holes with the conductive paste, the resin remaining in the non-through holes without damaging the PET film or the resin adhesive by performing a desmear process by plasma cleaning in the non-through holes. Residues can be effectively removed, and a more stable interlayer connection resistance can be obtained in synergy with filling of the conductive paste by vacuum pressure degassing.
[Brief description of the drawings]
FIG. 1 is a diagram showing a part of a manufacturing process of a double-sided circuit board for a multilayer printed wiring board according to the present invention.
FIG. 2 is a diagram showing a part of a manufacturing process of a single-sided circuit board for a multilayer printed wiring board according to the present invention.
FIG. 3 is a view showing a four-layer wiring board in which a double-sided circuit board and a single-sided circuit board according to the present invention are laminated.
[Explanation of symbols]
10 Insulating substrate
12 Copper foil
14 Resin adhesive
16 PET film
18 Non-through hole
20 Conductive paste
22 Filled via hole
24 Copper foil
26, 28 conductor circuit
30 Double-sided circuit board for core
34 Conductor circuit
36 Protruding conductor
40, 42, 44 Single-sided circuit board for lamination

Claims (5)

A multilayer in which a conductor circuit is provided on both surfaces of a hard insulating base material formed from a completely cured hard resin material , and via holes are formed in the insulating base material to electrically connect the conductor circuits. In manufacturing a circuit board for a printed wiring board, during the manufacturing process, at least the following steps (1) to (4):
(1) A resin adhesive layer in a semi-cured state is formed on the other surface of an insulating substrate having a copper foil attached to one surface, and a resin film is adhered onto the resin adhesive layer, and then the resin A step of forming a non-through hole reaching the copper foil by laser irradiation from above the film;
(2) After the non-through hole is filled with the conductive paste, the insulating base is exposed from the other surface of the insulating base of the filled conductive paste under reduced pressure. Pressurizing the surface of
(3) After peeling off the resin film from the surface of the insulating substrate, the conductive paste exposed from the other surface of the insulating substrate is covered with a copper foil, and the conductive paste and A step of forming a filled via hole for electrically connecting the copper foil, and (4) a step of etching the copper foil attached to the insulating base to form a conductor circuit on both sides of the insulating base,
A method for producing a circuit board for a multilayer printed wiring board , comprising:   2. The method according to claim 1, further comprising a step of plasma cleaning the resin residue remaining in the non-through holes by exposing the insulating substrate to a plasma atmosphere after the step (1). The manufacturing method of the circuit board for multilayer printed wiring boards of description. A circuit for a multilayer printed wiring board having a conductor circuit on one side of a hard insulating base material formed of a completely cured hard resin material , and having a via hole reaching the conductor circuit in the insulating base material In manufacturing the substrate, during the manufacturing process, at least the following steps (1) to (3), that is,
(1) A process of forming a conductor circuit by performing an etching process on an insulating base material having a copper foil attached to one surface;
(2) A semi-cured resin adhesive layer is formed on the other surface of the insulating substrate, and a resin film is adhered onto the resin adhesive layer, and then laser irradiation is performed on the resin film. Forming a non-through hole reaching the copper foil; and (3) filling the non-through hole with a conductive paste and then subjecting the insulating base material to a reduced pressure under reduced pressure conditions. the step of the surface of the other exposed from the face side of the insulating substrate is pressurized to form a filled via hole for electrical connection between the conductor circuit,
A method for producing a circuit board for a multilayer printed wiring board , comprising:   4. The method according to claim 3, further comprising the step of plasma cleaning the resin residue remaining in the non-through holes by exposing the insulating base material to a plasma atmosphere after the step (2). The manufacturing method of the circuit board for multilayer printed wiring boards of description.   5. The plasma cleaning process according to claim 2, wherein the plasma cleaning process is performed under conditions of an output, a degree of vacuum, a kind of reaction gas, and an energization time such that a temperature of the circuit board is 60 ° C. or less. The manufacturing method of the circuit board for multilayer printed wiring boards of description.

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