JP4480415B2 - Wiring board manufacturing method - Google Patents

Description

  The present invention relates to a method for manufacturing a wiring board for mounting electronic components such as semiconductor elements and resistors.

  Conventionally, as a wiring board used for mounting electronic components such as semiconductor elements and resistors, from an insulating base material in which a glass cloth woven with warp yarns and weft yarns made of glass fiber bundles is impregnated with a thermosetting resin Through-holes with through-hole conductors attached to the inner surface are formed from the upper surface to the lower surface of the laminated substrate in which a plurality of alternately laminated insulating bases and wiring conductors made of copper foil are laminated. There is known a multilayer printed wiring board in which wiring conductors positioned are electrically connected by through-hole conductors. In such a multilayer printed wiring board, first, an insulating base having a copper foil deposited on the surface thereof is prepared, and the copper foil deposited on the surface of the insulating base is etched to form a wiring conductor having a predetermined pattern. A multilayer substrate is manufactured by laminating and laminating a plurality of insulating substrates each having a wiring conductor formed thereon with an adhesive made of a thermosetting resin in between, and then a through-hole penetrating the multilayer substrate is formed by drilling. Thereafter, the through hole conductor is formed by depositing copper plating on the inner surface of the through hole to electrically connect the wiring conductors located above and below.

  By the way, with recent miniaturization and higher density of electronic devices, there is an increasing demand for improvement in wiring density for wiring boards for mounting electronic components such as semiconductor elements. However, in the multilayer printed wiring board described above, through-hole conductors for connecting the upper and lower wiring conductors are provided through the multilayer substrate, and the area occupied by the through-holes in each insulating base becomes large. It was difficult to increase the wiring density.

In order to solve such problems, instead of the through-hole structure penetrating the front and back of the multilayer substrate, through holes are formed only in necessary portions for each insulating base layer, and the through conductors are filled in the through holes. A wiring board having an inner via hole structure in which the upper and lower wiring conductors are electrically connected is put into practical use. In such a wiring board having an inner via hole structure, a through hole is formed by laser processing on an uncured insulating base material obtained by impregnating a glass cloth woven with warp yarns and weft yarns made of glass fiber bundles with a thermosetting resin. After that, the through-holes are filled with a conductive paste for through conductors containing metal powder and thermosetting resin, and then a wiring conductor made of copper foil is coated on the upper and lower surfaces of the insulating substrate by a transfer method. Next, a plurality of insulating base materials to which wiring conductors are attached are laminated, and the insulating base material and the conductor paste are thermally cured by heating while pressing from above and below. In order to impregnate the glass cloth for the insulating substrate with the thermosetting resin, the long glass cloth is pulled out from the roll of the glass cloth wound in a roll shape and impregnated with the thermosetting resin varnish. A method of drying through a heating zone after being immersed in a bath is employed.
JP 2002-187966 A JP 2002-314222 A

  However, the insulating base material constituting the insulating base is a state in which tension is applied in the direction in which the glass cloth is drawn out, that is, in the warp direction when the glass cloth woven with warp and weft is impregnated with the thermosetting resin. A thermosetting resin varnish is impregnated and dried. For this reason, the uncured insulating base material after the varnish is dried is in a state where stress due to the tension applied when the varnish is impregnated remains. And when an insulating base material having such a residual stress is used to produce a wiring board, a plurality of insulating base materials for forming each insulating base are stacked and heated while pressing from above and below. As the thermosetting resin is once fluidized before curing, the stress remaining on the insulating substrate is released, and as a result, a phenomenon occurs that the glass cloth contracts greatly in the warp direction of the glass cloth. For this reason, the through conductor and the wiring conductor formed on the insulating base made of an insulating base material are likely to be greatly displaced from a predetermined position, and the wiring conductor and the through conductor are not connected accurately and reliably. There was a problem that the electrical connection reliability of the was low.

  Furthermore, since the shrinkage in one direction of the insulating base material is large, the produced wiring board is greatly warped, and it is difficult to mount an electronic component such as a semiconductor element on the wiring board. It was.

  The present invention has been devised in view of such conventional problems, and its purpose is that the through conductor and the wiring conductor are connected accurately and reliably, and the electrical connection reliability of both is high, It is an object of the present invention to provide a wiring board with small warpage and easy mounting of electronic components.

The method for manufacturing a wiring board according to the present invention includes a step of preparing a plurality of insulating base materials in which a glass cloth woven with glass warp and glass weft is impregnated with an uncured thermosetting resin, a step of forming a plurality of said warp and uncured insulating substrate direction of the weft is stacked so as to be perpendicular to each other of the insulating substrate which are adjacent the insulating base in the laminating direction of the insulating After the step of forming a plurality of bases, the step of pressing while heating the insulating base body to a temperature equal to or higher than the flow start temperature of the thermosetting resin while leaving the base body uncured, and the pressed uncured insulating base body , Forming a plurality of through holes penetrating the insulating substrate in the thickness direction, filling the through holes with a conductive paste containing an uncured thermosetting resin, and filling the through holes with the conductive paste. Before uncured A step of depositing a wiring conductor made of copper foil on the surface of an insulating substrate by transfer method, the steps of the wiring conductors are stacked with the insulating substrate are deposited, laminated the insulating substrate and the through hole it is characterized in that it comprises a and a step of thermally curing the conductive paste filled in.

  The method for producing a wiring board according to the present invention comprises an insulating substrate formed by laminating a plurality of insulating base materials impregnated with uncured thermosetting resin on a glass cloth woven with glass warp and glass weft. Is pressed while being heated to a temperature equal to or higher than the flow start temperature of the thermosetting resin, and the thermosetting resin contained in each insulating substrate of the insulating substrate flows during the pressing. The residual stress on each insulating substrate is released. Then, through holes are formed in the insulating substrate and filled with a conductor paste, and further, a wiring conductor is deposited on the surface of the insulating substrate by transfer, and finally the insulating substrate and the conductor paste are thermally cured. When the insulating substrate and the conductive paste are thermally cured, the insulating substrate does not shrink in one direction. Therefore, the through conductor and the wiring conductor formed on the insulating base do not greatly deviate from the predetermined position, the through conductor and the wiring conductor are connected accurately and reliably, and the electrical connection reliability between them is high, and the warp is prevented. A small wiring board on which electronic components can be easily mounted can be provided.

  In addition, the method of manufacturing a wiring board according to the present invention provides the warp and weft of the glass cloth of the insulating substrate adjacent to each other in the laminating direction. When they are orthogonal to each other, when the insulating substrate is thermally cured, the shrinkage of the insulating bases adjacent in the stacking direction interacts and is averaged, so that it is possible to provide a wiring board with extremely stable shrinkage. .

  Next, a method for manufacturing a wiring board according to the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 is a cross-sectional view showing an embodiment of a wiring board manufactured by the manufacturing method of the present invention, in which 1 is a glass cloth, 2 is a thermosetting resin, 3 is an insulating substrate, 4 is An insulating substrate, 5 is a wiring conductor, and 6 is a through conductor.

  A wiring board manufactured by the manufacturing method of the present invention has a wiring conductor made of copper foil on the upper and lower surfaces of an insulating substrate 4 formed by laminating a plurality of insulating base materials 3 impregnated with a glass cloth 1 with a thermosetting resin 2. The wiring conductors 5 positioned above and below the insulating base 4 are electrically connected to each other by a through conductor 6 provided on the insulating base 4. In this example, the insulating base 4 is formed by laminating two insulating base materials 3, four such insulating bases 4 are laminated, and a solder resist layer 7 is formed on the outermost layer. An example is shown.

  The glass cloth 1 constituting the insulating base material 3 is formed by weaving warps and wefts made of a bundle of glass fibers into a plain weave, twill weave, satin weave, etc., and gives the insulating base 3 mechanical strength. It functions as a reinforcing member for reducing the coefficient of thermal expansion of the insulating substrate 3. When the thickness of the glass cloth 1 is less than 10 μm, the warp and weft tend to be very thin and difficult to weave uniformly. When the thickness is greater than 50 μm, the insulating base 4 is unnecessarily thick and the wiring board is thin. Tends to be difficult. Therefore, the thickness of the glass cloth 1 is preferably 10 to 50 μm. Moreover, in order to improve the adhesiveness with the thermosetting resin 2, it is preferable that the surface of the glass cloth 1 is subjected to a silane coupling treatment. Moreover, although the glass cloth 1 normally uses glass called E glass, D glass, S glass, high dielectric constant glass, or the like may be used.

  The thermosetting resin 2 impregnated in the glass cloth 1 is made of an epoxy resin, a bismaleimide triazine resin, a modified polyphenylene ether resin, or the like, and imparts good insulating properties to the insulating base material 3 and the insulating base materials 3 to each other. Also, it functions as an adhesive for firmly bonding the insulating substrate 4 and the wiring conductor 5 together.

  The insulating base 4 formed by laminating a plurality of insulating base materials 3 functions as a support for supporting the wiring conductor 5 and the through conductor 6, and the wiring conductor 5 made of copper foil is formed on the upper and lower surfaces thereof. A through conductor 6 made of a conductive material containing metal powder and a thermosetting resin is formed from the upper surface to the lower surface. In this wiring board, the three-dimensional high-density wiring is formed by electrically connecting the wiring conductors 5 positioned above and below the insulating base 4 via the through conductors 6 penetrating the insulating base 4. It is possible.

  The solder resist layer 7 formed on the outermost layer of the wiring board is made of, for example, 30 to 70% by mass of inorganic powder such as silica or talc in a mixture of a photosensitive resin such as an acrylic-modified epoxy resin and a photoinitiator. It is made of an insulating material containing a filler, and has a function of improving the electrical insulation reliability between the outermost wiring conductors 5 and improving the bonding strength between the outermost wiring conductor 5 and the insulating substrate 4.

  Next, a method for manufacturing the above-described wiring board according to the manufacturing method of the present invention will be described. First, as shown in FIG. 2 (a), two insulating base materials 3 each prepared by impregnating an uncured thermosetting resin 2 into a glass cloth 1 woven with warp yarns and weft yarns made of glass fiber bundles are prepared. To do. Note that a surfactant, an inorganic filler, or the like may be added to the thermosetting resin 2. Such an insulating substrate 3 is heated after the long glass cloth 1 is drawn out from the roll of the glass cloth 1 wound in a roll and immersed in an impregnation tank containing a varnish of the thermosetting resin 2. It is manufactured by drying the thermosetting resin 2 through the zone. At this time, the uncured thermosetting resin 2 is impregnated and dried in a state where tension is applied in the direction in which the glass cloth 1 is pulled out, that is, in the warp direction. Therefore, the uncured insulating base material 3 after the thermosetting resin 2 is dried is in a state in which stress due to tension applied when the thermosetting resin 2 is impregnated remains.

  Next, as shown in FIG. 2 (b), two insulating substrates 3 are laminated to form an uncured insulating substrate 4, and the insulating substrate 4 is left uncured and the thermosetting resin 2 is formed. Press while heating to a temperature above the flow start temperature. At this time, the thermosetting resin 2 contained in each insulating base material 3 of the insulating base 4 flows by heating and pressing, and the residual stress on each insulating base material 3 is released. The insulating base 4 is such that the warp and weft directions of the glass cloth 1 of the laminated insulating base 3 are orthogonal to the warp and weft of the glass cloth 1 of the upper and lower insulating bases 3, respectively. It is preferable to be laminated. Thus, by laminating | stacking so that the direction of the warp and weft of the glass cloth 1 of the insulating base material 3 may be orthogonal to the warp and weft of the glass cloth 1 of the upper and lower insulating base materials 3, respectively, it is mentioned later As described above, when the insulating base 4 is thermally cured, the shrinkage of the upper and lower insulating base materials 3 interacts and is averaged, so that it is possible to provide a wiring board with extremely stable shrinkage.

  Next, as shown in FIG. 2C, a plurality of through holes H for forming through conductors 6 are formed in the pressed uncured insulating base 4 by laser processing.

  Next, as shown in FIG. 2 (d), a conductor paste 6p containing an uncured thermosetting resin inside the through hole H formed in the uncured insulating base 4 is adopted by screen printing. Fill. The conductor paste 6p is, for example, a metal powder made of an alloy of tin, silver, bismuth and copper and a triazine type such as triallyl cyanurate, triallyl isocyanurate, trisepoxypropyl isocyanurate, tris (2-hydroxyethyl) isocyanurate. And a thermosetting resin. In addition, when the content of the metal powder in the conductor paste 6p is less than 80% by mass, the connection between the metal powders is hindered by the thermosetting resin and the electrical resistance of the through conductor 6 tends to be high. If it exceeds 95% by mass, the viscosity of the conductor paste 6p tends to increase so that it is difficult to satisfactorily embed it in the through-hole provided in the insulating substrate 4. Therefore, the content of the metal powder in the conductor paste 6p is preferably 80 to 95% by mass. Moreover, when the metal powder contained in the conductor paste 6p is made of an alloy of tin, silver, bismuth and copper, it is preferable to contain 70 to 90% by mass of tin. Furthermore, the average particle size of the metal powder is preferably 5 to 10 μm.

  Next, as shown in FIG. 2E, the wiring conductor 5 is deposited on the surface of the uncured insulating base 4 in which the through-hole H is filled with the conductive paste 6p by using a transfer method. In order to deposit the wiring conductor 5 on the surface of the insulating substrate 4 by a transfer method, first, a copper foil having a thickness of about 10 to 30 μm to be the wiring conductor 5 is applied to one side of a transfer film made of a heat resistant resin such as polyethylene terephthalate. The wiring conductor 5 is formed on the transfer film by adhering via an adhesive, and then etching the copper foil into a predetermined pattern using a photolithography technique, thus forming on the transfer film A method is adopted in which the wiring conductor 5 thus formed is embedded in the surface of the uncured insulating substrate 4 by thermocompression bonding using a hot press and then peeled off from the transfer film. In thermocompression bonding, it is better to perform only pressurization prior to heating. When heating is performed first, the transfer film is stretched by heat, and accurate alignment between the wiring conductor 5 and the through conductor 6 tends to be difficult. Therefore, it is preferable to perform only the pressurization prior to the heating in the thermocompression bonding.

  Next, as shown in FIG. 2 (f), a plurality of uncured insulating bases 4 filled with the conductor paste 6p for the through conductors 6 and transferred with the wiring conductors 5 in this way are prepared and the structure shown in FIG. As shown in (g), the insulating base 4 and the conductive paste 6p are thermoset by pressing while heating them at a temperature of 150 to 200 ° C. for several hours using a hot press machine, whereby a plurality of insulations are obtained. A wiring substrate is completed in which the base body 4 and the wiring conductor 5 are laminated and integrated, and the wiring conductors 5 positioned above and below the insulating base body 4 are electrically connected by a through conductor 6 penetrating the insulating base body 4. At this time, the laminated insulating bases 4 are formed of the thermosetting resin while the stress remaining on the insulating bases 3 when the glass cloth 1 is impregnated with the thermosetting resin 2 leaves the insulating bases 4 uncured. 2 is preliminarily released by pressing while being heated to a temperature equal to or higher than the flow start temperature of 2. Therefore, when the insulating base 4 and the conductive paste 6p are thermoset, the insulating base 4 contracts in one direction. There is nothing. Therefore, according to the method for manufacturing a wiring board of the present invention, the through conductor 6 and the wiring conductor 5 formed on the insulating base 4 do not greatly deviate from predetermined positions, and the through conductor 6 and the wiring conductor 5 are accurately and reliably connected. In addition, it is possible to provide a wiring board that is connected to each other, has high electrical connection reliability, and has low warpage and easy mounting of electronic components. Furthermore, when the warp and weft directions of the glass cloth 1 of the insulating base 3 in each insulating base 4 are laminated so as to be orthogonal to the warp and weft of the glass cloth 1 of the upper and lower insulating bases 3, respectively, When the insulating substrate 4 is thermally cured, the shrinkage of the upper and lower insulating base materials 3 interacts and is averaged, so that it is possible to provide a wiring board with extremely stable shrinkage.

  Finally, as shown in FIG. 2 (h), a solder resist layer 7 may be applied to the upper and lower surfaces of the wiring board as required. Such a solder resist layer 7 is formed by depositing an uncured resin film made of a photosensitive resin, a photoinitiator, and an inorganic powder filler on the surface of the outermost insulating base 4, or by using a photosensitive resin and light. An uncured resin varnish composed of an initiator and an inorganic powder filler is applied to the surface of the outermost insulating base 4 to form an uncured photosensitive resin layer, and then the uncured photosensitive resin layer is formed. An opening is formed by exposing and developing to expose a part of the wiring conductor 5 on the outermost layer, followed by ultraviolet curing and heat curing.

  Thus, according to the wiring board of the present invention, the wiring conductor 5 and the through conductor 6 are connected accurately and reliably, the electrical connection reliability between them is high, and the warp is small and the electronic component can be easily mounted. A wiring board can be provided.

  The wiring board of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. For example, in the above-described embodiment, an insulating substrate is used. 4 is formed by laminating two insulating bases 3, but the insulating base 4 may be formed by laminating three or more insulating bases 3. Furthermore, in the above-described embodiment, the wiring substrate 5 of the present invention is formed by laminating a plurality of insulating bases 4 each having a wiring conductor 5 made of copper foil on the upper and lower surfaces and a through conductor 6 formed from the upper surface to the lower surface. However, the wiring board of the present invention may be formed by the wiring base 5 made of copper foil on the upper and lower surfaces and the insulating base 4 having only one layer in which the through conductors 6 are formed from the upper surface to the lower surface. Furthermore, an insulating layer made of a thermosetting resin and copper are formed on the surface of a wiring board in which a wiring conductor 5 made of copper foil is formed on the upper and lower surfaces and an insulating substrate 4 in which through conductors 6 are formed from the upper surface to the lower surface is laminated. A build-up wiring board may be formed by laminating build-up wiring portions made of wiring conductors made of plating.

It is sectional drawing which shows the embodiment of the wiring board manufactured by the manufacturing method of this invention. (A)-(h) is sectional drawing for every process which shows the manufacturing method of the wiring board of this invention.

Explanation of symbols

1: Glass cloth 2: Thermosetting resin 3: Insulating substrate 4: Insulating substrate 5: Wiring conductor 6: Through conductor 6p: Conductor paste for through conductor 6

Claims (1)

Preparing a plurality of insulating base materials in which a glass cloth woven with glass warp and glass weft is impregnated with an uncured thermosetting resin;
And wherein the step of the warp and the direction of the weft between the insulating substrate to form a plurality of uncured insulating substrate formed by laminating with each other perpendicularly to the adjacent plurality of the insulating substrate in the laminating direction,
After the step of forming a plurality of the insulating bases, the step of pressing while heating the insulating base to a temperature equal to or higher than the flow start temperature of the thermosetting resin without being cured;
Forming a plurality of through-holes penetrating the insulating base in the thickness direction in the pressed uncured insulating base;
Filling a conductive paste containing an uncured thermosetting resin in the through hole;
Attaching a wiring conductor made of copper foil to the surface of the uncured insulating base filled with the conductive paste in the through-hole by a transfer method;
A step of laminating a plurality of the insulating bases to which the wiring conductors are deposited;
Thermosetting the laminated insulating substrate and the conductive paste filled in the through hole ; and
A method for manufacturing a wiring board, comprising:

Images