JPH11135905A - Printed wiring board and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen a contact resistance between a circuit formed on the surface of a hole-filling member and a through connection hole. SOLUTION: A through connection hole 4 is provided to a base material 1, the through connection hole 4 is filled up with a hole-filling member 5, and the surface of the hole filling member 5 is set flush with that of the through connection hole 4. A conductor 6 is formed on the surface of the hole filling member 5 through electroless copper plating. A large amount of electroless copper plating metal catalyst Pd is attached to granular alumina oxide, and the electroless copper plating metal catalyst Pd is added to the hole-filling member 5 through the intermediary of the alumina oxide.

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 a resin is buried in a through-hole and a circuit is formed by depositing a conductor on the surface of the buried resin by electroless plating, and a method of manufacturing the same.

[0002]

2. Description of the Related Art Generally, after a through connection hole is formed,
In order to protect the conductor deposited on the wall surface of the through-hole or to mount an electronic component or form a circuit on the through-hole, the through-hole is filled with ink as a filling material and solidified. It is buried in this way, so-called hole filling is performed. When a circuit is formed on the through-hole, the through-hole is filled, and the surface of the solidified filling member is flattened so as to be flush with the surface of the through-hole. A circuit is formed by depositing copper on the surface of the filling member formed on a flat surface by copper plating or the like. In this case, since the filling material itself does not have a catalytic action to precipitate copper by electroless copper plating,
After filling, a Pd catalyst is applied to the surface of the filling material,
Copper was deposited using this Pd catalyst as a core of plating.

[0003]

In the above-described conventional printed wiring board, Pd applied to the surface of the filling member is not used.
A metal bond is formed between the catalyst and copper deposited by electroless copper plating, and high adhesion is obtained. However, a strong bonding force cannot be obtained between the Pd catalyst and the filling member only because only intermolecular bonding occurs due to surface tension or Van der Waals force. Therefore,
The adhesive force between the filling member and the deposited copper is weak and easily peeled. For this reason, the filling material sealed by the deposited copper causes thermal expansion in the heating / cooling process in the process of manufacturing or using the printed wiring board, and accordingly, the deposited copper covering the filling material also becomes circular. Arc-shaped bending occurs. Due to the bending of the copper, stress due to the bending is concentrated on the connection portion between the copper and the land portion of the through connection hole, the copper and the land portion of the through connection hole are separated, the contact resistance increases, and the contact failure increases. There was a problem that occurred.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and has as its object to reduce the contact resistance between a circuit formed on the surface of a filling member and a through connection hole. It is to provide a wiring board and a manufacturing method thereof.

[0005]

In order to achieve this object, a printed wiring board according to the present invention comprises a through connection hole formed in a base material, and a through hole having the same height as the surface of the through connection hole. In a printed wiring board provided with a filling member buried so as to have a thickness and a circuit deposited by electroless plating on the surface of the filling member, a metal catalyst for electroless plating is added to the filling member. . Therefore, since metal bonding is performed between the electroless plating metal catalyst and the electroless metal fixed in the filling member, the adhesion between the filling member and the conductor deposited by the electroless plating is high. Become.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram illustrating a method for manufacturing a printed wiring board according to the present invention. In FIG.
Reference numeral 1 denotes a copper-clad laminate as a substrate having copper foils 2 and 2 formed on both sides, and the copper-clad laminate 1
, A through hole 3 is formed by a drill. Thereafter, a seeder process is performed, and a first electroless copper plating is performed to form a through connection hole 4.

As shown in FIG. 1B, a liquid filling member 5 is injected into the through-hole 4 and solidified by buffing so that the surface is flush with the surface of the through-hole 4. It is processed flat by polishing to form blind vias. Here, the filling member 5 is made of an epoxy resin, an inorganic filler, a curing agent, and the like, and Pd is added as a metal catalyst for copper plating. Next, the filling member 5
The second electroless copper plating is performed on the surface of the hole and the land portion 4 a of the through-hole 4, and the conductor 6 is deposited on the surface of the filling member 5. At this time, since the metal catalyst Pd for copper plating is added to the filling member 5 and the Pd is fixed in the solidified filling member 5, the Pd is deposited on the fixed Pd by electroless copper plating. Conductor 6 is metal-bonded. For this reason, Pd, which is a nucleus of plating, acts as a so-called anchor in the filling member 5, so that the conductor 6 is formed with high adhesion to the filling member 5.

As shown in FIG. 1C, two-layer and three-layer inner circuits 6a, 6a are formed by etching, and an interlayer insulating resin layer 7, 6 is formed on these inner circuits 6a, 6a.
7 are formed, and the adhesive layers 8, 8 are formed on the interlayer insulating resin layers 7, 7. As shown in FIG. 3D, a non-through hole 9 reaching the surface of the inner circuit 6a by the laser beam is formed in the adhesive layer 8 and the interlayer insulating resin layer 7. next,
After performing a desmear process to remove the smear residue in the non-through hole 9 and perform a seeder process, a plating resist 10 is formed on the adhesive layer 8, roughened, and a third electroless copper plating is performed. By doing so, the non-through connection holes 11 and the outer layer circuits 12 and 12 which are one layer and four layers are formed.

In the printed wiring board thus formed, as described above, the deposited conductor 6 is metal-bonded to the Pd fixed in the filling member 5, so that the conductor 6 is attached to the filling member 5. Close contact with high bonding strength. Therefore, the back surface of the conductor 6 having a smaller coefficient of thermal expansion and a higher rigidity than the filling member 5 maintains a close contact state with the surface of the filling member 5 with a high bonding force, thereby preventing the filling member 5 from expanding due to heat. Is done. Therefore,
Conventionally, the surface of the filling member 5 and the back surface of the conductor 6 are separated from each other by the expansion of the filling member 5, and the conductor 6 is not deformed into an arc-shaped cross section. Is prevented from peeling off.

Table 1 shows the filling members (5-1, 5) of the present invention.
3 shows the composition of -2) and the composition of the conventional filling member (5-3). In the case of the plugging member 5 of the present invention, the metal catalyst Pd for copper plating is added as it is (5-1).
(5-2) shows a case where a large number of copper plating metal catalysts Pd are once adhered to granular alumina oxide called a carrier, and the copper plating metal catalyst is added to the filling member 5 via the carrier. That is, the alumina oxide of this example has an outer size of about 0.3 to 3 μm, and has a particle size of 10 to 1000 mm as a metal catalyst for copper plating on its surface.
In this state, a large number of Pd are adhered and added to the filling member 5.

Thus, a large number of metal catalysts for copper plating P
It has been experimentally confirmed that adding d to the filling member 5 after attaching d to the carrier increases the metal bond with the conductor 6. This is because, compared to the case where the metal catalyst for copper plating is added as it is to make it uniform (5-1), the metal catalyst for copper plating Pd is formed by the carrier.
It is presumed that the metal bonding with the conductor 6 becomes high because the density of the metal becomes high. Further, by setting the particle size of the metal catalyst for copper plating to 10 ° or more, the particle size can be made large enough to obtain a necessary metal binding force with the conductor 6. Further, by setting the particle size of the metal catalyst for copper plating to 1000 ° or less, the number of metal catalysts for copper plating sufficient to obtain the required metal binding force with the conductor 6, that is, the required surface area of the metal catalyst for copper plating Is obtained.

[0012]

[Table 1] The additive reduces bubbles generated when the filling member 5 is buried in the through connection hole 4.

Table 2 shows the reliability of the multilayer printed wiring board manufactured according to the composition shown in Table 1 by MIL-STD.
This is a comparison obtained by performing 1000 cycles of a thermal shock test of -202E and 107D. The standard is the quality standard M
IL-P-551. Samples in which the connection resistance after 1000 cycles exceeded ± 10% of the initial value are N
G. As is clear from this table, the number of samples was 10
Compared to 0, 39 defects occurred in the conventional product (5-3), whereas defects occurred in the products (5-1, 5-2) of the present invention in which Pd was added to the filling material. Did not. The cause of the defect of the conventional product is caused by peeling generated at the boundary between the inner layer circuit 6a and the hole filling member 5,
In the present invention, by adding Pd to the filling member 5, the adhesion between the inner layer circuit 6a and the filling member 5 is improved,
It is considered that peeling was prevented.

[0014]

[Table 2] * 1: JIS C5012 Attached Figure 1.1 Composite test pattern for double-sided printed board (front), Attached Figure 1.2 (back), sample D was formed in one layer, four layers, and two layers and three layers in land ( Land diameter φ 0.7 mm), and blind vias (hole diameter φ 0.3 mm) for connecting one and two layers and three and four layers, buried vias (hole diameter φ 0) for connecting two and three layers. .3 mm) so that these three connection holes were coaxially arranged to form a multilayer printed wiring board connecting one to four layers. However, the thickness of the substrate is 0.4 mm, the insulation thickness between the first and second layers and the third and fourth layers is 80 μm, the thickness of the one-layer circuit is 30 μm, and the thickness of the two-layer circuit is 40 μm ( The thickness of the copper foil of the base material is 18 μm, the thickness of the second plating is 12 μm + the thickness of the second plating is 10 μm, and the thickness of the three layers is 40 μm (the thickness of the copper foil of the base material is 18 μm + the thickness of the first plating is 12 μm + 2). The thickness of the fourth plating was 10 μm), and the thickness of the four-layer circuit was 30 μm. * 2: The number of samples whose conduction resistance after 1000 cycles exceeded 10% of the initial value for 100 samples.

[0015]

EXAMPLE Desmear treatment was carried out using chromic anhydride 95 at 38 ° C.
Performed with 0 g / l for 18 minutes. Roughening is performed using NaF: 1.
_{0g / l, CrO 3: 15} / l, H 2 SO 4: 400ml /
This was performed for 5 minutes with a 36 ° C. mixture of 1 l.

In this embodiment, the conductor 6 deposited on the surface of the filling member 5 is made of copper. However, the conductor 6 is not limited to copper, and is deposited when a potential difference is applied, such as nickel, tin, gold, and platinum. Any metal can be used as long as it is a metal that is easily ionized, that is, a metal having a large ionization tendency. Further, the example in which the metal catalyst for electroless plating is added to the filling member 5 has been described. However, it may be added to the interlayer insulating resin layer 7, and in this case, the adhesion of the outer layer circuit 12 to the interlayer insulating resin layer 7 is reduced. improves. In the present embodiment, the outer layer circuit 12 is formed outside the inner layer circuit 6a to form a four-layer multilayer printed wiring board. However, the inner layer circuits 6a, 6a Formed
It may be a so-called double-sided board. Further, an example in which Pt is used as the metal catalyst for electroless plating has been described. However, the present invention is not limited to this, and Au, Pd, Ag, and Cu may be used. May be used.

[0017]

As described above, according to the present invention, the addition of the metal catalyst for electroless plating to the filling member improves the adhesion between the circuit deposited on the filling member and the through connection hole. As a result, the contact resistance is reduced, so that poor conduction can be prevented.

Further, the metal catalyst for electroless plating was adhered to the granular alumina oxide, and the metal catalyst for electroless plating was added to the filling material via the alumina oxide, so that the metal was deposited on the filling material and the filling material. The metal bonding with the conductor is higher, and the contact resistance is further reduced.

[Brief description of the drawings]

1A and 1B are diagrams illustrating a method for manufacturing a printed wiring board according to the present invention, wherein FIG. 1A shows a state in which a through connection hole is formed, FIG. 1B shows a state in which a hole filling member is buried, and FIG.
Shows a state in which an interlayer insulating layer is formed, and (d) shows a state in which a non-through connection hole is formed.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Base material, 4 ... Through connection hole, 5 ... Filling member, 6 ... Precipitated conductor, 6a ... Inner layer circuit (2 layers, 3 layers), 7 ... Interlayer insulating resin layer, 11 ... Non-through connection hole, 12 ... Outer layer Circuit (1 layer, 4 layers
layer).

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Yasuhiro Iwasaki 413 Kushida, Ninomiya-cho, Haga-gun, Tochigi Prefecture Inside Hitachi AIC Co., Ltd. Inside the corporation

Claims (4)

[Claims] 1. A through-hole formed in a base material, a hole-filling member embedded in the through-hole so as to be flush with the surface of the through-hole, and a surface of the hole-filling member formed by electroless plating. A printed wiring board provided with a deposited conductor, wherein the filling member is made of a material to which a metal catalyst for electroless plating is added. 2. The printed wiring board according to claim 1, wherein the metal catalyst for electroless plating has a particle size of 10 to 1000.
A printed wiring board characterized in that one or a mixture of two or more of Au, Pt, Pd, Ag, and Cu is used. 3. A through-hole is formed in a base material, and a filling member to which a metal catalyst for electroless plating is added is buried in the through-hole, and the surface of the filling member is flush with the surface of the through-hole. Wherein a conductor is deposited on the surface of the filling member by electroless plating. 4. The method for manufacturing a printed wiring board according to claim 3, wherein the metal catalyst for electroless plating is adhered to granular alumina oxide and added via the alumina oxide. Production method.