JP2013131605A - Multilayer printed wiring board including anisotropic conductive film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a multilayer printed wiring board holding many metal particles, and thereby capable of suppressing an increase in conductive resistance value after reflow.SOLUTION: In a multilayer printed wiring board, a first insulating substrate including, on one face thereof, a wiring pattern and a projecting bump formed in a part of the wiring pattern and a second insulating substrate including, on a face facing the wiring pattern on the first insulating substrate, a wiring pattern and a receiving conductor land receiving the projecting bump are disposed to face each other, a metal particle-containing anisotropic conductive film is held between at least a tip of the projecting bump and the receiving conductor land, and an interlayer insulating resin layer is disposed on a side of the projecting bump.

Description

  The present invention relates to a multilayer printed wiring board manufactured by a batch lamination method using an anisotropic conductive film as a part of an interlayer connection.

  In some portable electronic devices, there are an increasing number of multilayer printed wiring boards that require a relatively short delivery time. Many multi-layer printed wiring boards using the batch lamination method have been manufactured in order to meet customer demand for short delivery times.

  FIG. 4 shows the prior art, in which thick circuits 702a and 702b and thin circuits 703a and 703b are formed on both surfaces of an insulating substrate 701, and the upper and lower sides thereof are sandwiched through sheet-like anisotropic conductive films 704a and 704b. Conductive particles 705a and 705b are sandwiched between conductor circuits 706a and 706b in the outer layer to form a buildup substrate 700 in which conduction between layers is obtained (see Patent Document 1).

  A printed wiring board 800 of the prior art shown in FIG. 5 has a wiring pattern 801 formed of copper foil. On the surface of the substrate other than the wiring pattern 801, an insulating resin 802 made of an epoxy resin is laminated on almost the entire surface excluding a portion where a connection portion is to be formed later. A portion where a connection portion is to be formed later is formed with a convex portion 803 of a conductive paste containing copper narrower than the exposed portion of the copper foil in a dotted or convex shape. The convex portion 803 of the conductive paste may be made of other materials such as lead and silver, and may be any conductive material. The conductor paste is printed thickly so as to protrude beyond the height of the surrounding insulating resin 802 after drying. The convex portion 803 is completely covered, the anisotropic conductive resin 804 is formed to the same height as the insulating resin 802, and the printed wiring board 800 can be obtained by stacking together (see Patent Document 2).

JP 2001-326469 A Japanese Patent Laid-Open No. 11-112150

  The prior art shown in FIG. 4 obtains a conductive resistance value between layers by sandwiching sheet-like anisotropic conductive films 704a and 704b between convex vias or circuits and an upper conductor layer. . However, when a pressure is applied to the substrate in the lamination process, the resin of the anisotropic conductive film is discharged out of the interlayer connection portion, and a considerable number of metal particles also flow out of the interlayer connection portion. Therefore, the necessary metal particles cannot be sandwiched between the convex via or circuit and the upper conductor layer, and the rate of change in the conduction resistance value after reflow is greatly unstable. .

  In the prior art shown in FIG. 5, an anisotropic conductive paste is applied only to an interlayer connection portion, and the other interlayer insulating layer portion is a printed wiring board made of an epoxy resin. However, since there is no difference in the thickness of the anisotropic conductive paste applied to the layer insulating layer portion and the interlayer connection portion, when sandwiched between the conductive paste formed in a convex shape, However, since the metal particles are discharged together with the pressure of the laminating press process and the metal particles also flow together, the necessary number of metal particles are sandwiched between the conductive paste formed in a convex shape and the copper foil. In other words, there is a problem that the rate of change of the conduction resistance value after reflow increases.

  The present invention solves the above-described conventional problems by providing a first insulating substrate including a wiring pattern and a convex bump formed on a part of the wiring pattern on one surface, and the first insulating substrate. A second insulating substrate having a wiring pattern and a receiving conductor land that receives the convex bump is disposed opposite to a surface of the insulating substrate facing the wiring pattern, and at least a tip portion of the convex bump. And a receiving conductor land, an anisotropic conductive film containing metal particles is sandwiched, and an interlayer insulating resin layer is disposed on the side of the convex bump. This is solved by a printed wiring board.

  According to the present invention, the anisotropic conductive film is formed thinner than the interlayer insulating layer between the convex bump and the receiving conductor land, and as a result, there are many between the tip portion of the convex bump and the receiving conductor land. Since the metal particles are sandwiched between the bumps and the receiving conductor lands by the resin contained in the anisotropic conductive film, the rate of change in the conduction resistance value can be suppressed. Become.

The schematic cross-sectional process explanatory drawing which shows the manufacture example of this invention multilayer printed wiring board. FIG. 2 is a schematic cross-sectional process explanatory diagram subsequent to FIG. 1. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic sectional explanatory view of a multilayer printed wiring board according to the present invention. Schematic cross-sectional explanatory drawing of the conventional multilayer printed wiring board. The schematic cross-section explanatory drawing of another conventional multilayer printed wiring board.

  Hereinafter, manufacturing examples of the multilayer printed wiring board of the present invention will be described with reference to FIGS. 1A to 1D and FIGS. 2E to 2F, and structural examples of the multilayer printed wiring board of the present invention will be described with reference to FIG. Will be described.

As shown in FIG. 1A, first, an insulating substrate 100 having conductor layers on both front and back surfaces is prepared, and a wiring pattern 101 is formed on one surface thereof. Convex bumps 102 are disposed in the portions corresponding to the above. The height of the bump is preferably about 30 to 40 μm on the wiring pattern 101 and the bump diameter is preferably about φ100 to 250 μm.
Next, a roughening process is performed on the front and back conductor layers of the insulating substrate 100. As the roughening treatment step, physical polishing or chemical polishing is appropriately selected. However, in order to form a stable roughening layer (not shown), it is preferable to perform chemical polishing treatment (for example, cupric copper). Etching with a solution in which a complex and an organic acid salt are mixed is effective in order to improve the adhesion between the interlayer insulating resin and the conductor layer because the roughened surface has uniform irregularities.
In addition, the front and back of the said insulating substrate 100 are connected by the filling of copper plating by a via fill or a conductive paste.

Next, as shown in FIG. 1B, the insulating resin 103 is applied to the convex bumps 102 of the insulating substrate 100 in a state where the bumps are opened by 50 to 150 μm larger than the bump diameter. The thickness of the insulating resin 103 applied in the applying process is preferably about 70 to 80 μm on the wiring pattern 101 in order to ensure interlayer insulation resistance. Depending on the application method of the insulating resin 103 and the resin composition, the insulating resin 103 can be formed in a plurality of times. (For example, by screen printing, using a screen plate having convex bump portions opened from the bump diameter, the first insulating layer is formed by applying the insulating resin 103, and after temporary drying, the opening diameter is the same in the same step. The thickness of the interlayer insulating resin layer can also be stably secured by forming the second insulating layer in a state where the pressure is reduced.
Here, it is desirable that the interlayer insulating resin 103 is mainly mixed with 50 to 70 wt% of a spherical inorganic filler. By mixing the inorganic filler into the interlayer insulating resin 103, the fluidity of the anisotropic conductive resin 104 and the resin of the interlayer insulating resin 103 can be controlled in the subsequent stacking process. Further, since the interlayer insulating resin 103 contains an inorganic filler, the coefficient of linear expansion due to a temperature change of the interlayer insulating layer as a completed multilayer printed wiring board can be reduced. By suppressing the shrinkage due to heat of the interlayer connection resin, there is little influence on the interlayer connection portion, which leads to stabilization of the change rate of the conduction resistance value.

Next, the applied insulating resin 103 is temporarily dried at 100 ° C. to 130 ° C. for 15 minutes to 80 minutes, and then, as shown in FIG. 1C, the anisotropic conductive material including the metal particles 105 in the convex bump 102 portion. Resin 104 is applied. The anisotropic conductive resin 104 is preferably formed with a thickness of 20 to 30 μm in a coated state. In particular, in order to prevent the metal particles 105 from being discharged out of the interlayer connection portion together with the resin component contained in the anisotropic conductive resin 104 in the subsequent lamination step, the tip of the convex bump 102 is different. It is effective to thinly apply the anisotropic conductive resin 104 (20 to 30 μm in the applied state) in order to suppress the change rate of the conduction resistance value.
Next, the anisotropic conductive resin 104 is temporarily dried at 100 to 130 ° C. for 10 to 50 minutes.

Next, as shown in FIG. 1D, an insulating substrate 200 including a receiving conductor land 106 facing the convex bump 102 provided on the insulating substrate 100 is prepared. The insulating substrate 200 has a wiring pattern 101 and a receiving conductor land 106 formed in advance on the surface facing the convex bump 102. Although the conductor layer provided on the insulating substrate 200 is also roughened by physical or chemical polishing, it is preferable to perform chemical polishing to form a stable roughened layer (not shown). (For example, etching with a liquid containing a cupric complex and an organic acid salt is effective for improving the adhesion between the interlayer insulating resin and the conductor layer because the roughened surface has uniform irregularities) .
The front and back surfaces of the insulating substrate 200 are connected by filling with copper plating with via fill or conductive paste.

Next, the convex bumps 102 provided on the insulating substrate 100 and the receiving conductor lands 106 provided on the insulating substrate 200 are positioned. As this positioning method, for example, a method of recognizing a positioning mark with an optical camera or X A positioning method at the hole position by the line camera is appropriately selected. Or you may position by the lamination | stacking method by the pin lamination of the next process.
Subsequently, it laminates with a lamination press. Lamination conditions are appropriately selected according to the composition of the epoxy resin used. For example, the holding condition at high temperature (main curing condition) is preferably 180 ° C. for 45 minutes or more, and the heating rate up to the holding temperature is preferably about 3 ° C./min.
Due to the heating / pressurization in the lamination step, the anisotropic conductive resin 104 has a lower melt viscosity than the interlayer insulating resin 103, so that the excess resin contained in the anisotropic conductive resin 104 is removed from the interlayer connection portion. As shown in FIG. 2E, the required number of metal particles 105 are sandwiched between the convex bumps 102 and the receiving conductor lands 106, thereby suppressing the rate of change in the conduction resistance value. There is an effect to.

  Next, as shown in FIG. 2F, after the laminating process, through holes are formed, panel plating is performed on the entire surface, through plated through holes 301 are formed, and an outer layer wiring pattern 302 is formed by a photomask etching process. The four-layer multilayer printed wiring board 300 of the present invention can be obtained through a process of forming and further forming a solder resist 303 as an outer layer.

  Next, the structure of the multilayer printed wiring board 300 of the present invention obtained in the above manufacturing process will be described with reference to FIG.

Reference numeral 100 denotes a first insulating substrate having a wiring pattern 101 and a convex bump 102 formed on a part of the wiring pattern 101 on one surface.
Reference numeral 200 denotes a second insulating substrate, and a conductor land 106 that receives the wiring pattern 101 and the convex bumps 102 of the first insulating substrate 100 on a surface facing the wiring pattern 101 of the first insulating substrate 100. It has.
The front and back surfaces of the first insulating substrate 100 and the second insulating substrate 200 are connected to each other by filling with copper plating with via fill or conductive paste.
The first insulating substrate 100 and the second insulating substrate 200 are arranged to face each other, and an anisotropic conductive film 204 including metal particles 105 is provided between at least the tip portion of the convex bump 102 and the receiving conductor land 106. While being sandwiched, an interlayer insulating resin layer 203 is disposed on the side of the convex bump 102.

  The first insulating substrate 100 and the second insulating substrate 200 further include a through-plating through hole 301, an outermost layer wiring pattern 302, and a solder resist 303 as a conductive connection between the front and back sides, and a multilayer printed wiring having four layers as a whole. It is a plate 300.

  With such a configuration of the multilayer printed wiring board 300, a large number of metal particles 105 are sandwiched between the convex bumps 102 and the receiving conductor lands 106, and a convex shape is formed by the resin contained in the anisotropic conductive resin 104. Since the bumps 102 and the receiving conductor lands 106 are joined, it is possible to prevent the conduction resistance value after reflowing from extremely increasing from the initial conduction resistance value.

  The anisotropic conductive film 204 is preferably made of a composition of metal particles 105, an epoxy resin, a curing agent, and a solvent. That is, since the anisotropic conductive film 204 does not contain an inorganic filler, there is an effect of preventing the metal particles 105, the convex bumps 102, and the receiving conductor lands 106 from being disturbed. As a result, more metal particles 105 can be sandwiched between the convex bumps 102 and the receiving conductor lands 106, leading to stabilization of the conduction resistance value.

  The anisotropic conductive film 204 preferably contains the same resin as that contained in the interlayer insulating resin layer 203. That is, by making the resin contained in the anisotropic conductive film 204 and the resin contained in the interlayer insulating resin layer 203 the same resin, the resin discharged to the outside of the interlayer connection portion by the pressure during the lamination process can be reduced. Even if mixed, compatibility is good and there is no problem in insulation reliability.

  In addition, the anisotropic conductive film 204 preferably has a viscosity that is lower than that of the interlayer insulating resin layer 203, which is softened at a temperature of 70 ° C. to 180 ° C., which is a temperature during the lamination process. That is, since the anisotropic conductive film 204 is softer at the above-described temperature than the interlayer insulating resin layer 203, the excess resin contained in the anisotropic conductive film 204 outside the interlayer connection portion. As a result, the necessary conductive particles are sandwiched between the convex bump 102 and the receiving conductor land 106, and a stable conduction resistance value can be secured.

  The metal particles 105 contained in the anisotropic conductive film 204 are preferably harder than copper plating and / or copper foil on which the convex bumps 102 or the receiving lands 106 are formed. That is, by using metal particles 105 that are harder than the convex bumps 102 and / or the receiving conductor lands 106, the metal particles 105 bite into the convex bumps 102 or the receiving conductor lands 106, so that the conduction resistance value is stabilized.

  The metal particles 105 contained in the anisotropic conductive film 204 are preferably gold-coated. That is, since the metal particles 105 are coated with gold, the surface oxidation of the metal can be suppressed, and the conduction change rate after reflow can be suppressed by stabilizing the initial conduction resistance value.

  As described above, the four-layer printed wiring board of the present invention can be obtained by providing the anisotropic conductive resin 104 and the interlayer insulating resin 103 between the double-sided insulating substrate 100 and the double-sided insulating substrate 200 and laminating them together. . In particular, the interlayer connection portion can obtain the conduction resistance of the collectively laminated portion by sandwiching the anisotropic conductive resin 104 between the convex bumps 102 and the receiving conductor lands 106.

  The present invention is not limited to this four-layer substrate. For example, two-sided insulating substrates 100 are prepared on the upper and lower sides of a four-layer multilayer printed wiring board, and anisotropic conductive layers are respectively formed in the interlayer connection portion and the interlayer insulating layer portion. An 8-layer multilayer printed wiring board can also be obtained by applying the resin 104 and the interlayer insulating resin 103 and laminating them together (not shown). Further, three double-sided insulating substrates 100 are prepared on the double-sided insulating substrate 200, and anisotropic conductive resin 104 and interlayer insulating resin 103 are applied to the insulating substrate 100 on the interlayer connection portion and the interlayer insulating layer portion, respectively. Also, an eight-layer multilayer printed wiring board can be obtained by stacking together (not shown). That is, it is needless to say that a multilayer printed wiring board having a necessary configuration can be obtained by appropriately combining the insulating substrate 100 and another insulating substrate.

Test Example For the following test substrates 1 to 5 (n = 10), the initial conduction resistance value and the change rate of the conduction resistance value after reflow were measured. In addition, as reflow conditions, the treatment was performed twice at a peak temperature of 260 ° C. The results are shown in Table 1.

Test substrate 1: An anisotropic conductive film made of a composition of gold-coated metal particles, epoxy resin (same as resin contained in an interlayer insulating resin layer), curing agent and solvent, and convex bumps of the first insulating substrate 3 printed circuit board test substrate 2 shown in FIG. 3 formed to a thickness of 25 μm: same as test substrate 1 except that the thickness of the anisotropic conductive film is 70 μm (same as the thickness of the interlayer insulating resin layer) Test substrate 3: Same as test substrate 4, except that the composition of the epoxy resin used for the anisotropic conductive film and the composition of the epoxy resin used for the interlayer insulating resin layer are different. Same as test substrate 1 except that the resin further contains an inorganic filler. Test substrate 5: Same as test substrate except that metal particles not coated with gold are used.

  From Table 1 above, as the anisotropic conductive film, a composition containing the same metal resin as that contained in the gold-coated metal particles and the interlayer insulating resin layer and containing no inorganic filler was used. It is clear that the thinner one can further suppress the conduction change rate after reflow.

100: first insulating substrate 101: wiring pattern 102: convex bump 103: interlayer insulating resin 104: anisotropic conductive resin 105: metal particles 106: receiving conductor land 203: interlayer insulating resin layer 204: anisotropic conductive Film 300: Multilayer printed wiring board 301: Through-plating through hole 302: Outermost layer wiring pattern 303: Outer layer solder resist

Claims (6)

  A first insulating substrate having a wiring pattern and convex bumps formed on a part of the wiring pattern on one surface, and a wiring on a surface facing the wiring pattern of the first insulating substrate. A second insulating substrate having a pattern and a receiving conductor land that receives the convex bump is disposed oppositely, and metal particles are disposed between at least the tip of the convex bump and the receiving conductor land. A multilayer printed wiring board, wherein an anisotropic conductive film is sandwiched, and an interlayer insulating resin layer is disposed on a side of the convex bump.   The multilayer printed wiring board according to claim 1, wherein the anisotropic conductive film is composed of a composition of metal particles, an epoxy resin, a curing agent, and a solvent.   The multilayer printed wiring board according to claim 1, wherein the anisotropic conductive film contains the same resin as that contained in the interlayer insulating resin layer.   The viscosity which has been softened at 70 ° C. to 180 ° C., which is the temperature during the lamination step of the anisotropic conductive film, is lower than that of the interlayer insulating resin. The multilayer printed wiring board as described.   5. The metal particle contained in the anisotropic conductive film is harder than copper plating and / or copper foil of the convex bump or the receiving conductor land. 6. Multilayer printed wiring board.   The multilayer printed wiring board according to any one of claims 1 to 5, wherein the metal particles contained in the anisotropic conductive film are coated with gold.