JP2002064263A - Printed wiring board and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a printed wiring board having proper hole-filling properties and high reliability. SOLUTION: A plurality of through-holes 3, 4, etc., of different diameters are formed on a board 2. A through-hole plating 5 is applied to the large- diameter through-holes 3 and the small-diameter through-holes 4 to make conductive the front side and the backside of the board 2. Filling materials 6 and 7 contain at least a thermoplastic resin component, such as epoxy resin and a filler component, such as silica fillers. The filler in the filling material 6, filled in the large-diameter through-holes 3 has a lower grain size standard deviation than that of the filler in the filling material 7, filled in the small- diameter through-holes 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a printed wiring board in which conduction between the front and back of a core substrate is achieved by through-hole plating and the inside of the through-hole is filled with a filler, and a method of manufacturing the same. In particular, it is useful when forming through holes with different hole diameters in the same substrate, and furthermore, when forming a small diameter through hole coaxially in the through hole, and high reliability is required for an MPU IC package or the like. It can be used as a printed wiring board.

[0002]

2. Description of the Related Art A method for manufacturing a multilayer printed wiring board includes:
There are the following methods. First, a through-hole serving as a through-hole is formed in a copper-clad laminate or the like serving as a core substrate, and then an inner wall is plated (through-hole plating) to form a conductor layer.
This through hole is filled with a paste for filling the through hole. After the substrate is flattened in this way, a multilayer printed wiring board is obtained by alternately building up an insulating layer and a conductor layer on the upper layer.

In a printed wiring board manufactured by the above method, when peeling occurs at the interface between the through-hole plating and the through-hole filler, a plating solution or the like soaks into the peeled gap or peels off in a reliability test. In some cases, cracks may develop in the upper build-up layer from the starting point, resulting in failure. For this reason, a method is known in which unevenness is formed on the surface of through-hole plating to improve the adhesion at the interface.

On the other hand, with the recent miniaturization of wiring circuits, fine through-hole processing with a laser is known as a technique for reducing the diameter of the through-hole (for example, Japanese Patent Application Laid-Open No. 61-176186). Furthermore, in order to reduce the cost of laser processing, wiring boards that use both mechanical drilling and laser processing, and small-diameter through-holes formed in large-diameter through-holes, are used to reduce the size or improve electrical characteristics. Wiring board (for example, see Japanese Unexamined Patent Publication No.
4, Japanese Patent Application Laid-Open No. 4-317359, etc.) are demanded for printed wiring boards in which through holes having different diameters are mixed in one board.

[0005]

In order to fill a through-hole with a paste for filling the through-hole, a screen printing method is generally used. However, when filling in a through hole with a small diameter by laser processing, a large aspect ratio (= length of through hole / diameter of through hole), and irregularities formed on the surface of the through hole plating,
In some cases, it may not be possible to sufficiently fill the back surface of the substrate.

To prevent such inconveniences, there are conceivable a method of applying an overcoat from the surface of the substrate and pushing it in, and a method of compensating for unfilling of the back surface of the substrate by printing on the back surface. A large void may be generated, and a defect may occur in a later process or a reliability test. Although it is considered that the viscosity of the filling paste should be reduced in order to enhance the filling property, the sufficient effect cannot be obtained by itself.

An object of the present invention is to provide a printed wiring board having good hole filling properties and high reliability by filling an optimum paste according to the hole diameter in a printed wiring board having through holes having different hole diameters. It is in.

[0008]

In order to solve the above-mentioned problems, a printed wiring board according to the present invention has a plurality of through-holes, and at least two through-holes having different hole diameters have a large diameter. It is characterized in that the standard deviation of the particle size of the filler in the filling material filled in the through hole is smaller than the standard deviation of the particle size of the filler in the filling material filled in the small through hole.

A first method of manufacturing a printed wiring board according to the present invention comprises a plurality of through holes, in which a filling material (precursor material: for example, a paste) is filled and cured. In the method of manufacturing a printed wiring board manufactured by the method, the standard deviation of the particle diameter of the filler in the filling material to be filled in the large-diameter through-hole is at least two through-holes having different hole diameters. It is characterized by being smaller than the standard deviation of the particle size of the filler in the material. The filling material can be a through-hole filling paste containing, for example, an uncured thermosetting resin and a filler.

According to the present invention, by filling and hardening the optimum filling material into the through holes having different hole diameters, it is possible to secure good filling and filling properties and to manufacture a highly reliable printed wiring board. It becomes possible. The standard deviation of the particle size of the filler in the filling material is a value reflecting the particle size distribution of the filler.The smaller the value of the standard deviation, the easier the uneven distribution of the filler, and the larger the standard deviation, the more easily the filler tends to be more uniformly dispersed. It is in. For small diameter through holes with relatively small inner diameters, the use of fillers with a large standard deviation of the particle size allows the filler to be dispersed well and makes it difficult for the through holes to be clogged. improves.

On the other hand, in a large-diameter through-hole having a relatively large inner diameter, if a filler having a too large standard deviation of the particle size is employed, the volume filling rate of the filler in the through-hole becomes insufficient, and the filler material after curing becomes harder. Large dents may occur. However, in a large-diameter through-hole, the relative ratio of the area in the through-hole to the total volume of the filler to be filled increases, so that clogging of the filler in the through-hole due to wall friction is less likely to occur as in a small-diameter through-hole. Therefore, in the present invention, by using a filling material having a relatively small filler particle diameter standard deviation in a large-diameter through-hole, the volume filling rate of the filler in the through-hole is increased, and the above-described dent generation Is prevented or suppressed. In other words, a filling material having a relatively large standard deviation of the filler particle size is used for small-diameter through holes, and a filling material having a relatively small standard deviation of the filler particle size is used for large-diameter through holes. By manufacturing a printed wiring board by using this method, it is possible to achieve both improvement in print filling properties and suppression of dents generated in the filling material (filling material) after curing.

The standard deviation of the particle size of the filler is determined by observing the cross section of the cured filling material portion in the through hole of the substrate with an optical microscope or a scanning electron microscope (SEM), and measuring the particle size appearing in the observed image. Can be calculated based on In this example, the particle size (particle size) of the filler refers to the maximum distance between the external shape of the particle appearing in the observed image and a circumscribed parallel line that does not cross the inside of the particle in various positional relationships. Is defined as dmax and the minimum interval is defined as dmin, and is defined as a value of (dmax + dmin) / 2.

Next, the second method of the present invention for producing a printed wiring board is to provide a filling material (a paste for filling through holes (hereinafter also simply referred to as a paste)) containing at least a thermosetting resin and a filler. , The volume content of the filler in the filling material is V _F , and the filling rate of the filler is DT _F
/ _{D F,} the tap density of the filler DT _F, the true density of the filler and _{D F,} as _{Y = V F / (DT F} / D F),
It is characterized in that the value of Y of the filling material that fills and hardens the small-diameter through hole is smaller than the value of Y of the filling material that fills and hardens the large-diameter through hole. In this case,
Each filling material in which the standard deviation of the particle size of the filler in the filling material to be filled in the large-diameter through hole is smaller than the standard deviation of the particle size of the filler in the filling material to be filled in the small-diameter through hole can also be used.

The second of the above-mentioned production method of the present invention is taken from the viewpoint of the powder packing density in through holes,
(DT _F / D _F ) This is an index corresponding to the relative tap density of the filler, that is, the critical packing density when the filler is ideally filled, which is measured by dry measurement without adding a solvent or a resin. Therefore, the value of _{Y = V F / (DT F} / D F) represents the actual filling material, or filler to what extent the ratio based on the limit packing density is contained. Y
The smaller the value of, the smaller the filling ratio of the filler in the filling material, which is separated from the critical packing density, means that the filler is less likely to be clogged in the through-holes, and the printability Is improved, and good filling and filling properties can be obtained. That is, it is advantageous in a small-diameter through-hole in which filler clogging is likely to occur.
On the other hand, since clogging of the filler is unlikely to occur in a large-diameter through-hole, the use of a filler having an extremely small Y value results in a large dent generated in the hole filling material (filling material) after curing, which is rather disadvantageous. There are cases.

Therefore, in a large diameter through hole, Y
By using a paste having a relatively large value of Y and a paste having a relatively small Y value in a small-diameter through hole, it is possible to improve the print filling property of a printed wiring board to be manufactured and to fill the hole after curing. It has become possible to suppress dents occurring in the material. Note that the value of Y is 0.4 to 1.3.
In this range, the value of Y of the filling material that fills and hardens the small-diameter through hole is preferably smaller than the value of Y of the filling material that hardens and fills the large-diameter through hole. It is preferable to ensure filling and filling.

The large-diameter through hole can be formed by, for example, mechanical drilling. Its diameter is 250μ
m or more (usually 1 mm or less), preferably 250 to 500
μm, more preferably 250 to 350 μm. In this case, the value of Y of the paste filled and cured in the large-diameter through-hole is preferably 0.7 or more and 1.3 or less, and more preferably 0.7 or more and 1.2 or less. If the value of Y is 1.
If it exceeds 3, the fluidity of the paste may be extremely reduced, and the filling and filling properties may be significantly reduced. When the value of Y is less than 0.7, the filling material (filling material) after filling and curing.
In some cases, the dent that occurs on the surface becomes large.

The small-diameter through hole can be formed by, for example, laser processing. Its diameter is 250μm
(Usually 50 μm or more). In that case, the value of Y of the paste filled and cured in the small-diameter through-hole is preferably 0.4 or more and less than 0.7, and more preferably 0.4 or more and 0.6 or less. When the value of Y is 0.7 or more, the print filling property is reduced, and a through-hole may not be sufficiently filled with the paste (consequently, the cured filling material). In addition, in the small diameter through hole, the value of Y is 0.1.
Even if the value is 4, no pitting occurs in the filling material after the filling and curing, but if the value of Y is too small, the sedimentation of the filler tends to occur. Therefore, it is desirable to add a known anti-settling agent.

The thermosetting resin used for producing the printed wiring board of the present invention is preferably an epoxy resin and a curing agent thereof. Epoxy resins generally have low curing shrinkage, and therefore can suppress dents during curing. In particular, it is desirable to use an aromatic epoxy resin in terms of heat resistance, moisture resistance, and chemical resistance. Furthermore, in order to make the paste solvent-free, a liquid epoxy resin (BPA type,
BPF type and PN type) are desirable. The curing agent for the epoxy resin is preferably a catalyst system, particularly an imidazole curing agent, from the viewpoints of heat resistance, chemical resistance, and solvent-free.

On the other hand, as the filler used for producing the printed wiring board of the present invention, for example, crystalline silica,
Amorphous silica, fused silica, alumina, talc, aluminum hydroxide, magnesium hydroxide, calcium carbonate,
Inorganic fillers such as magnesium carbonate, calcium silicate, magnesium silicate, calcium oxide, magnesium oxide, aluminum nitride, aluminum borate whiskers, boron nitride, silicon carbide, silicon nitride, copper, silver, nickel, zinc, tin, etc. Metallic fillers and the like can be used. As other components, if necessary, an antifoaming agent,
Minor additives such as leveling agents and anti-settling agents may be added. It is known to add a volatile component for adjusting the viscosity, but it is desirable that the volatile component is 1.0% or less (substantially no solvent). When a volatile component is added, voids and cracks are generated in the cured product when the paste is filled and cured.

The volume content _{V F} of the filler contained in the _{paste, V F = (W F /} D F) / ((W F / D F) + (W R / D
_{R) + (W A / D} A)), can be calculated based on. W represents the weight ratio of each component contained in the paste, D represents the true density of each component contained in the paste, suffix F represents the filler component, suffix R represents the thermosetting resin component, and suffix A Represents other components. As for the true density (D), a theoretical value may be used if its component is known. For example, epoxy resin: 1.2, silica: 2.2, copper: 8.9 (g / cm ³ ).

The dry filling rate of the filler (DT _F /
D _F) is determined from the measured values of the tap density DT _F of the filler. The tap density can be measured by the following method. 1. Fill the filler into a 20 ml graduated cylinder. 2. The graduated cylinder was raised from a height of 4.5 cm to 500
Tap twice. 3. The volume of the filler in the measuring cylinder is read from the scale of the measuring cylinder, and the weight of the filler at that time is measured. 4. Obtain DT _F by dividing the weight of the filler by volume of the filler in the graduated cylinder.

The dry filling rate of the filler (DT _F /
D _F ) can be a limiting measure of the volume content of fillers that can be added to the paste. Therefore, the value of Y reflects the amount of filler actually added to the limit of filler addition to the paste. That is,
A value of Y near 1 indicates that the filler has been sufficiently added, and a value of less than 1 indicates that there is still room for addition. That is, the value of Y indicates the relative amount of the filler in the filling material.
In the present invention, fine silica (for example, having a particle size of 50 nm or less) used as an antisettling agent is not regarded as a filler, but is treated as another component.

The printed wiring board of the present invention obtained by adopting the above-mentioned manufacturing method of the present invention has a plurality of through holes having different hole diameters. Assuming that the maximum value is Vmax and the minimum value is Vmin, (Vmax−Vmin) / Vm
The value represented by ax may be 0 to 0.7. That is, by adjusting the volume content of the filler as described above, regardless of the size of the through-hole, the variation in the filler filling density of each through-hole can be suppressed to be within the above-described range. In the large and small through-holes, it is possible to preferably achieve both good filling properties and suppression of dents generated in the filling material after curing. The above range is preferably from 0 to 0.
6 is good.

In the printed wiring board of the present invention, the filling material contains at least a thermosetting resin and a filler, and the absolute value of the difference between the coefficient of thermal expansion of the filling material and the coefficient of thermal expansion in the thickness direction of the substrate is 20 ppm / C. or lower, desirably, the difference in thermal expansion between the filling material (cured body) and the substrate (core substrate) is negative. If the values deviate from these values, cracks may occur in the solder resist or the like on the through holes in the thermal cycle test, which is not preferable. In addition,
As the core substrate to be used, a highly ripened laminated board such as a glass / BT substrate or a high Tg glass / epoxy substrate (FR-5) is desirable. The coefficient of thermal expansion in the Z direction of the high heat-resistant laminate is, for example, about 47 to 52 ppm, and in this case,
The thermal expansion coefficient of the cured product of the paste for filling through holes is 3
It is particularly desirable to be about 3 to 68 ppm, and more preferably about 33 to 52 ppm.

The thermal expansion coefficient of the filling material (hardened body) is would substantially determined by the volume content of the filler _{(V F),} if you want a thermal expansion coefficient in the vicinity of 45ppm, the _{V F} 35%
It is almost fixed in the vicinity (about 25 to 45%). Therefore,
In order to make a difference in the value of Y between the large diameter and the small diameter through holes, it is desirable to use fillers having different filling rates in the through holes of each diameter. In other words, the paste filler that is filled and hardened into the large-diameter through hole has a filling rate of 2%.
Fillers of 0 to 50% are filled into small through holes and hardened, and the filling ratio of the paste is 40 to 70%.
It is desirable to use those.

In the printed wiring board of the present invention, a first filling material is filled inside the large diameter through hole, a small diameter through hole is formed inside the first filling material, and the inside of the small diameter through hole is formed. Is filled with a second filler material, and the particle size standard deviation of the filler in the first filler material is
It can be configured to be smaller than the standard deviation of the particle size of the filler in the second filling material. That is, a small diameter through hole is formed in the filling material in the large diameter through hole,
When the present invention is applied to a printed wiring board having a coaxial structure (through-hole coaxial structure) in which the inside of the small-diameter through-hole is further filled with a filler material via a conductive layer, the print-filling property is more effectively improved, and after curing, The effect of suppressing dents generated in the filling material (filling material) also becomes more remarkable.

Further, the present invention can be applied to the case where the surface of the through-hole plating is formed with irregularities in order to improve the adhesion at the interface between the through-hole plating and the filling material. Filling properties are obtained, and the printed wiring board has high reliability. The thickness of the core substrate used in the present invention is not particularly limited.
Particularly good filling properties are exhibited in through holes formed in a substrate of 5 mm or more (usually 1.0 mm or less), particularly 0.7 mm or more.

Conventionally, in small through-holes having irregularities on the surface, the filling property of the paste often decreases. The reason is not clear, but is presumed as follows. When the filling paste is pressed into the through-hole by printing, it is considered that the paste near the inner wall of the through-hole causes fine turbulence due to the unevenness, and the paste is filled while the paste enters the concave portion of the unevenness. Since the unevenness of the through-hole plating is finer than the particle size of the filler, only the resin component of the paste enters the recess, and as a result, a region having a large filler content is likely to be formed near the unevenness. . In filling a large diameter through-hole, the region where the filler content is large due to its large diameter is relatively small, and its effect is negligible (that is, it is difficult to clog), and therefore the influence on the filling property is small. Seem. On the other hand, it is considered that the influence cannot be ignored in a small-diameter through-hole, and clogging of the through-hole occurs in a region where the filler content is increased, so that the paste cannot be filled any more.
Thus, as in the present invention, if a paste having a reduced Y value (that is, a paste in which an excess of the resin component is added) is used, the excess resin component enters the unevenness of the inner wall.
Even if a region having a large filler content is formed, clogging does not occur, and good print filling properties can be ensured.

On the other hand, the reason why the dent generated when the paste is hardened in the small-diameter through-hole is not clear, but is presumed as follows. The dent generated when the paste is cured is caused by the resin component of the paste flowing out around the core substrate (so-called bleed-out). When dents occur, surface energy loss occurs due to an increase in the surface area of the paste (spreading of the resin and occurrence of dents). However, when the dents occur because the energy reduction due to the wetting of the substrate and the resin is greater than that, Conceivable. It is considered that when the diameter of the through hole becomes smaller, the surface energy loss due to the depression increases (because the radius of curvature of the depression becomes smaller). Therefore,
It is considered that the small diameter through hole overcomes the energy reduction due to the wetting of the substrate and the resin, and suppresses the dent.

[0030]

Embodiments of the present invention will be described below with reference to the embodiments shown in the drawings. FIG. 1 is a sectional view schematically showing a main part of a printed wiring board according to a first embodiment of the present invention. A plurality of through-holes 3 and 4 having different hole diameters are formed in the substrate 2 of the printed wiring board 1, and the large-diameter through-hole 3 and the small-diameter through-hole 4 are subjected to through-hole plating 5 so that Is conducted. The insides of the through holes 3 and 4 are filled with filling materials 6 and 7, respectively.

The filling materials 6, 7 for filling the through holes 3, 4 contain at least a thermosetting resin component such as an epoxy resin and a filler component such as a silica filler.
Here, the standard deviation of the particle size of the filler in the filling material 6 filled in the large-diameter through hole 3 is smaller than the standard deviation of the particle size of the filler in the filling material 7 filled in the small-diameter through hole 4. . Further, when the maximum value of the volume content of the filler in the filling materials 6 and 7 filled in the through holes 3 and 4 is Vmax and the minimum value is Vmin, (Vmax−
The value represented by (Vmin) / Vmax is set to 0 to 0.7.

FIG. 2 shows a printed wiring board 1 according to the present invention.
FIG. 12 is a cross-sectional view schematically showing a main part of a second example of No. 0. In the printed wiring board 10, a small-diameter through hole 40 is provided coaxially inside a large-diameter through hole 30 provided in the substrate 20. That is,
Inside the large-diameter through hole 30 provided in the substrate 20,
The first filling materials 60a and 60b for the large-diameter through holes are filled, the small-diameter through holes 40 are formed inside the first filling materials 60a and 60b, and the small-diameter through holes are further formed inside the small-diameter through holes 40. And a second filling material 70 for filling. The large-diameter through-hole 30 and the small-diameter through-hole 40 are plated with through-holes 50 and 51, respectively, so that the front and back of the substrate 20 are electrically connected.

Also in this case, the first filling materials 60a, 60b
And the second filler 70 includes at least a thermosetting resin component and a filler, and the standard deviation of the particle diameter of the filler in the first filler 60a, 60b is the standard deviation of the particle diameter of the filler in the second filler 70. It is said to be smaller. Further, in the through-hole coaxial structure, in addition to the above-described case, after forming a large-diameter through-hole, a build-up insulating layer may be formed on the front and back surfaces of the substrate 20 and then a small-diameter through-hole may be formed.

In the through holes of the first and second embodiments, as shown in FIG.
It is also possible to add 0. In particular, in the case of a small-diameter through hole, clogging is likely to occur due to the provision of irregularities in the through hole. However, in the case of the present embodiment, since a filler material to which a resin component is excessively used is used, The surplus resin component 9 is provided on the irregularities 100 on the inner wall 40.
0 is included, and even if an area where the filler component 80 is unevenly distributed and the filler content is large is formed, clogging does not occur, and good print filling property is secured. Needless to say, even in the large-diameter through holes 3 and 30, good filling properties can be ensured by using a filling material having a relatively large resin component.

[0035]

EXAMPLES The following evaluation was performed on the printed wiring board of the present invention. (Evaluation of Fillability) The substrate was a BT resin substrate having a thickness of 800 μm. After drilling holes by mechanical drilling and laser processing, copper plating is applied to make 300μ
Substrates having through-hole diameters of m and 100 μm were prepared, respectively. On the conductor surface of each obtained substrate,
The surface was treated by a chemical surface roughening treatment (for example, using an acid such as formic acid) to form irregularities.

The filling paste was printed on the through holes of the prepared substrate by a screen printer. As the filling paste, those kneaded with the compositions shown in Table 1 were used.
The filled substrate was semi-cured at 120 ° C. for 40 minutes. Next, the surface of the core substrate was polished using a belt-type polishing apparatus (rough polishing), and was then flattened by buff polishing (finish polishing). Next, the semi-cured filling paste was cured at 150 ° C. for 5 hours. The through holes of each of the prepared samples were visually inspected from the back surface of the substrate for filling and filling with a magnifying glass having a magnification of 200 times.

(Measurement of Thermal Expansion) Further, pastes 1 to 7 for filling through holes shown in Table 1 were cast into a film,
The film was thermally cured at 150 ° C. for 5 hours to obtain a film-like cured product having a thickness of 100 μm. From this, a test piece having a width of 5 mm was cut out and subjected to TMA measurement. Measurement conditions are span 15m
m, cooled to −55 ° C. with a tensile load of 5 g applied in the longitudinal direction of the test piece, and cooled to 12 ° C. at a rate of 10 ° C./min.
The film was heated to 5 ° C. or higher, the elongation was measured, and the thermal expansion coefficient of the film-shaped cured product (filling material) was calculated from the following formula 1. Equation 1: thermal expansion coefficient = ((elongation rate of test piece at 125 ° C.)
− (Elongation at −55 ° C.)) / (125 − (− 55))

Next, the thermal expansion coefficient of the core substrate in the X and Y directions was measured in the same manner as described above. However, the thickness of the test piece was 800 μm, which is the same as the substrate thickness. The thermal expansion coefficient in the Z direction of the core substrate is −5 g in a state where a compression load of 5 g is applied in the Z direction of the substrate.
Cool to 55 ° C. and heat at a rate of 10 ° C./min.
The temperature was increased to at least ℃, the elongation was measured, and the above equation was used to calculate the same. The thermal expansion coefficient of the core substrate is 14 ppm in the XY directions,
Z direction: 48 ppm.

[0039]

[Table 1]

The paste raw materials used are as follows. The silica filler is spherical silica S1 (Tatsumori Corporation: SOC2) and spherical silica S2 (Electrochemical Industry Co., Ltd .: FB-35X), and the copper filler is spherical copper powder C1 (Nippon Atomize Processing Co., Ltd .: SFR) -CU-5)
And dendritic copper powder C2 (Japan Energy Co., Ltd .: #
D), epoxy resin is bisphenol A type epoxy resin E1 (Yukaka Shell Co., Ltd .: E-828) and bisphenol F type epoxy resin E2 (Yukaka Shell Co., Ltd .: E-8)
07), imidazole-based curing agent H1 (Shikoku Chemicals Co., Ltd .: 2P4MZ) and imidazole-based curing agent H
2 (Shikoku Kasei Kogyo Co., Ltd .: 2P4MHZ), the anti-settling agent was fine silica A (Nippon Aerosil Co., Ltd .: RY200)
S).

Table 2 shows the obtained results. Also in Table 2, the volume content of the filler determined from the composition of Table 1 _(V F), the filler filling factor determined from the tap density of the filler _(DT F _{/ D} F), was determined from these Y _{= V} F /
The value of (DT _F / D _F ) and the value of the standard deviation of the particle size of the filler calculated by the laser diffraction type particle size meter are shown.

[0042]

[Table 2]

The pastes 1, 3, 7, and 10 have a relatively small standard deviation of the particle diameter of the filler or a relatively large Y value. The prevention of dents later was good, but 10
The 0-μm-diameter through hole had poor print filling properties and could not be filled. The paste 4 was made to have a low viscosity by using a low-viscosity epoxy resin and reducing the amount of the anti-settling agent, but it was still impossible to fill the through-holes having a diameter of 100 μm.

The pastes 2, 5, 6, and 8 have a relatively large standard deviation of the particle size of the filler or a relatively small value of Y. The prevention of dents later was good, but 300
With the μm diameter, the print filling property was slightly inferior to the pastes 2 and 6, and it was necessary to reduce the printing speed.

Since the paste 9 had a Y value of 0.3, a large dent was observed in a through hole having a diameter of 300 μm, and a dent was observed in a through hole having a diameter of 100 μm. In Paste 11, since the value of Y was set to 1.4, the fluidity of the paste was reduced, and the filling and filling properties were reduced. The paste 12 was subjected to a thermal cycle test on the obtained substrate. As a result, cracks occurred in the solder resist and the like on the through holes.

From the above results, it is preferable to use a paste having a relatively small particle diameter standard deviation or a relatively large Y value for a large diameter through hole having a hole diameter of 300 μm. It can be seen that it is preferable to use a paste having a relatively large particle diameter standard deviation or a relatively small Y value. Further, the absolute value of the difference in thermal expansion coefficient between the cured product and the substrate is 20
It is desirable to use a paste that gives ppm / ° C.

More specifically, the printed wiring board 10 of the second embodiment shown in FIG. 2 was manufactured using the pastes 1 and 6 as follows. Thickness 80 as core substrate
Using a 0 μm BT resin substrate, drilling holes in it by mechanical drilling, and then applying copper plating,
μm through hole diameter (becomes large diameter through hole 30)
A substrate having a through-hole plating (conductor) 50 having a thickness of 18 μm was prepared. The conductor surface of the obtained substrate is subjected to a surface roughening treatment with formic acid to form irregularities, and paste 1 (the first filling material (to be the first filling material 60a)) is formed on the through-holes of the prepared substrate by a screen printing machine. )
Was printed. The substrate filled in this way is filled with 120
After semi-curing under conditions of 40 ° C. × 40 minutes, and then polishing the surface of the core substrate using a belt-type polishing device (rough polishing),
It was flattened by puff polishing (finish polishing). Next, the semi-cured filling paste was cured at 150 ° C. for 5 hours.

After drilling a hole in this substrate by laser processing so as to substantially penetrate the center of the large-diameter through hole, and applying copper plating, the through-hole diameter of 100 μm (to become a small-diameter through-hole 40) and the thickness of 18 μm. A substrate having a through-hole plating (conductor) 51 was prepared. Irregularities are formed on the conductor surface of the obtained substrate by surface roughening treatment, and paste 6 (second filling material (second filling material 60
b) was printed. The substrate filled in this way is semi-cured under the conditions of 120 ° C. × 40 minutes, and then the surface of the core substrate is polished using a belt-type polishing device (rough polishing), followed by puff polishing (finish polishing). Flattened. Next, the semi-cured filling paste is heated to 150 ° C.
It was cured under the conditions of × 5 hours. By forming a conductive circuit on the conductive layer on the substrate surface by a known subtractive method, a wiring board (printed wiring board) 10 having a coaxial through hole was manufactured. A build-up layer (insulating layer or conductor layer) is formed on the wiring board by using a known build-up technique (insulating layer forming technique, subtractive, additive, semi-additive, etc.) to form a multilayer wiring board. Is also good.

One substrate 20 manufactured in this manner is
Pre-hole in which through holes 30 and 40 with different diameters are mixed
The wiring board 10 has good filling and filling properties.
The above trouble did not occur. In addition, thermal shock test
Peeling and cracking even after 1000 cycles
And high reliability. In this case, the pace
G1 filler volume content V_FOf 35% paste 6
Filler volume content V _FIs 29%, and (Vmax
-Vmin) / Vmax is 0.17.

That is, in a large-diameter through hole,
A paste containing a filler having a relatively small value of the particle size standard deviation and having a relatively large value of Y is used. On the other hand, in a small-diameter through hole, the value of the particle size standard deviation is relatively large, and By using a paste containing a filler having a relatively small value of, it is possible to ensure good print filling properties.

The printed wiring board of the present invention is not limited to the above embodiment. For example, in the case of a wiring board having three or more types of through-hole diameters, at least two types of through-holes satisfy the conditions of the present invention. Just do it. For example, in a substrate having at least three types of through-holes of “large”, “medium”, and “small” diameters, Use the same paste for "large" and "medium"
"Small", filler particle size standard deviation is "large", "medium"
Use a paste that is larger than or larger than Y, that is, smaller than “large” or “medium”. 2. Use the same paste for "medium" and "small"
“Large”, standard deviation of filler particle size is “Medium”, “Small”
Use a paste that is smaller than or smaller than Y value of “medium” or “small”. 3. In the "large", the filler particle diameter standard deviation is smaller than "medium", or using a paste in which the value of Y is larger than "medium", and in "medium" the filler particle diameter standard deviation is smaller than "small", Alternatively, a paste in which the value of Y is larger than “small” is used. As described above, by satisfying the conditions of the present invention for at least two through holes having different hole diameters, it is possible to ensure excellent filling and filling properties. In this case, "large" and "small" are through-hole coaxial structures, "large"
“Middle” may have a through-hole coaxial structure, and “middle” and “small” may have a through-hole coaxial structure.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view showing a first embodiment of the printed wiring board of the present invention.

FIG. 2 is a schematic sectional view showing a second embodiment of the printed wiring board of the present invention.

FIG. 3 is a schematic cross-sectional view showing one embodiment of a through hole.

[Explanation of symbols]

 1,10 Printed wiring board 2,20 Board (core board) 3,30 Large diameter through hole 4,40 Small diameter through hole 5,50 Through hole plating 6,7 Filling material 60a, 60b First filling material 70 Second filling material

Claims (9)

[Claims] 1. A method for filling at least two through holes having a plurality of through holes and having different hole diameters, wherein the standard deviation of the particle diameter of the filler in the filling material filled in the large diameter through hole is the filling amount filled in the small diameter through hole. A printed wiring board having a particle diameter smaller than a standard deviation of a filler in a material. 2. A method according to claim 1, wherein a plurality of through-holes having different hole diameters are provided, and the maximum value of the volume content of the filler in the filling material filled in each through-hole is Vmax, and the minimum value is Vmin, where (Vmax−Vmin) / Vmax. The printed wiring board according to claim 1, wherein a value represented by is 0 to 0.7. 3. The filling material contains at least a thermosetting resin and a filler, and the absolute value of the difference between the coefficient of thermal expansion of the filling material and the coefficient of thermal expansion in the thickness direction of the substrate is 20 ppm /
The printed wiring board according to claim 1, wherein the temperature is lower than or equal to ℃. 4. A first filling material is filled inside the large diameter through hole, and the small diameter through hole is formed inside the first filling material. 4. The method according to claim 1, wherein the second filler is filled with the filler, and the standard deviation of the particle diameter of the filler in the first filler is smaller than the standard deviation of the particle diameter of the filler in the second filler. A printed wiring board according to any of the claims. 5. A method for manufacturing a printed wiring board, comprising: a plurality of through holes having different hole diameters; and filling and curing a filling material in the through holes, wherein the filling material comprises at least a thermosetting resin. and a filler, the volume content V _F of the filler of the filling _material, the dry packing ratio DT F _{/ D} F of the _filler, the tap density of the filler DT _F, the true density of the filler D and _F, as _{Y = V F / (DT F} / D F), the value of Y of filling material filling curing the small diameter through hole, than the value of Y of filling material filling hardened large diameter through hole A method for manufacturing a printed wiring board, characterized by being small. 6. The value of Y is 0.4 to 1.3, and the value of Y of the filling material that fills and hardens the small-diameter through-hole in the range is that the hardening fills the large-diameter through-hole. 6. The method according to claim 5, wherein the value of Y of the filling material is smaller than the value of Y.
A method for manufacturing the printed wiring board according to the above. 7. The method for manufacturing a printed wiring board according to claim 5, wherein the value of Y of the filling material that fills and hardens the large-diameter through-hole is 0.7 or more and 1.3 or less. 8. The method for manufacturing a printed wiring board according to claim 5, wherein the value of Y of the filling material that fills and hardens the small-diameter through hole is 0.4 or more and less than 0.7. . 9. A method for manufacturing a printed wiring board, comprising a plurality of through holes, and filling and curing a filling material in the through holes, wherein at least two through holes having different hole diameters are provided.
Manufacturing a printed wiring board characterized in that the standard deviation of the particle size of the filler in the filling material to be filled in the large-diameter through hole is smaller than the standard deviation of the particle size of the filler in the filling material to be filled in the small-diameter through hole. Method.