JP3582111B2 - Manufacturing method of printed wiring board - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method for manufacturing a printed wiring board having a through hole penetrating an insulating substrate, and more particularly to a method for filling a through hole with a filler.
[0002]
[Prior art]
For example, in a ball grid type printed wiring board, through holes are provided for achieving electrical continuity of each pattern circuit provided on the front surface and the back surface, or for dissipating heat.
As shown in FIG. 16, the through holes 90 are provided through the insulating substrate 9 constituting the printed wiring board. A metal plating film 93 is provided on the inner wall of the through hole 90.
[0003]
The through hole 90 is filled with a filler 91 using an epoxy resin. The filler material 91 prevents the flux, the solder cleaning liquid and the like from seeping out through the through-holes 90 when the printed wiring board is soldered to the motherboard, and prevents the pattern circuit 961 or the semiconductor chip 5 provided on the front surface of the insulating substrate 9. Alternatively, it serves to prevent contamination of the die pad 963 on which it is mounted.
[0004]
[Problem to be solved]
However, in the printed wiring board, a peeled portion 991 may be generated between the metal plating film 93 in the through hole 90 and the filler 91 depending on the temperature at which the printed wiring board is soldered on the motherboard ( (FIG. 16). When the printed wiring board is used, moisture may enter from the peeled portion 991 and accumulate as moisture 995 between the insulating substrate 9 and the adhesive 990. The moisture 995 may corrode the pattern circuit 961, the semiconductor chip 5, or the die pad 963 provided on the front surface of the insulating substrate 9.
[0005]
Further, when the printed wiring board is soldered to the motherboard as described above, the heat causes the water 995 to be rapidly heated, and as shown in FIG. 17, a peeling portion is formed between the insulating substrate 9 and the semiconductor chip 5. 992. Further, the pattern circuit 961, the semiconductor chip 5, and the die pad 963 may be damaged.
[0006]
In view of the conventional problems, the present invention does not cause separation between the metal plating film in the through-hole and the filler filled in the through-hole, thereby preventing moisture from entering. An object of the present invention is to provide a method for manufacturing a printed wiring board.
[0007]
[Means for solving the problem]
According to the present invention, a through-hole penetrating the insulating substrate is formed in an insulating substrate coated with copper foil on both sides .
Next, a metal plating film is applied to the surface of the insulating substrate and the inner wall of the through hole.
Next, a roughened surface layer is formed on the surface of the metal plating film by a chemical surface treatment,
Next, a filler is supplied to the inside of the through hole and the periphery of the opening so as to protrude from the surface of the insulating substrate, and is cured.
Next, the filler protruding from the surface of the insulating substrate and the roughened surface layer are polished and removed.
Thereafter, there is provided a method of manufacturing a printed wiring board, wherein a pattern circuit is formed on the surface of the insulating substrate by an etching resist method .
[0008]
The most remarkable point in the present invention is that a roughened surface layer is formed by chemical surface treatment on the surface of the insulating substrate and the surface of the metal plating film provided on the inner wall of the through hole. After supplying and curing the filler, the filler and the roughened surface layer protruding from the surface of the insulating substrate are polished and removed.
[0009]
The surface of the metal plating film is subjected to a chemical surface treatment to form a roughened surface layer. Examples of the chemical surface treatment include a method of performing only the blackening treatment, a method of sequentially performing the blackening treatment and the blackening reduction treatment, and a method of sequentially performing the blackening treatment, the blackening reduction treatment, and the acid treatment.
[0010]
As a method of performing only the blackening treatment, for example, the method is performed by immersing the insulating substrate in a blackening treatment solution in which sodium chlorite, trisodium phosphate, sodium hydroxide, or the like is dissolved in water. Thereby, the needle-like crystals are generated on the surface of the metal plating film. This crystal forms a roughened surface layer in the through hole and on the surface of the insulating substrate.
[0011]
As a method of sequentially performing the above-described blackening treatment and blackening reduction treatment, for example, the above-mentioned insulating substrate is immersed in the above-mentioned blackening treatment liquid, and then the first reduction is performed by dissolving sodium borohydride, sodium hydroxide or the like in water. The insulating substrate is immersed in the treatment liquid. Further, this is immersed in a second reduction treatment solution in which sodium hydroxide, formaldehyde, methanol and the like are dissolved in water. As a result, the needle-like crystals are formed on the surface of the metal plating film, and the crystals are reduced.
[0012]
As a method of sequentially performing the blackening treatment, the blackening reduction treatment, and the acid treatment, for example, the insulating substrate is immersed in the blackening treatment solution and the reduction treatment solution in this order, and then the sulfuric acid for acid treatment is used. Dipped in an acid treatment liquid. As a result, the needle-like crystals are formed on the surface of the metal plating film, and the crystals are once reduced and then oxidized.
[0013]
Next, a filler is filled into the inside of the through hole forming the roughened surface layer and the periphery of the opening, and is cured. Next, the filler projecting from the surface of the insulating substrate is polished and removed together with the roughened surface layer of the metal plating film on the surface of the insulating substrate using a buff, a brush or the like. Thereby, the surfaces of the metal plating film and the filler become smooth, and the entire surface of the insulating substrate becomes smooth. Next, a pattern circuit is formed on the surface of the smooth insulating substrate.
[0014]
The filler is an electrically insulating material or a conductive material. The electric insulating material is, for example, one or more synthetic resins selected from epoxy resins and polyimide resins. The metal plating film is made of one or more selected from copper, nickel, and gold. On the other hand, as the conductive material, there is carbon paste or the like. As the insulating substrate, for example, a glass epoxy substrate, a glass polyimide substrate, a glass maleimide triazine substrate, or the like is used.
[0015]
The through holes are used to electrically connect the pattern circuits provided on the front surface and the back surface of the insulating substrate. Further, the through hole can be used as a heat dissipation hole for dissipating heat from the semiconductor chip or the pattern circuit.
For example, a semiconductor chip can be mounted on the printed wiring board. The printed wiring board is mounted on a separate motherboard.
The printed wiring board is, for example, a ball grid array or a pin grid array.
[0016]
[Action and effect]
In the method for manufacturing a printed wiring board according to the present invention, a metal plating film is formed on the inner wall of the through hole, and the surface of the metal plating film is subjected to a chemical surface treatment to form a roughened surface layer. The inside of the through hole is filled with a filler. The filler comes into close contact with the inner wall of the through hole due to the unevenness of the roughened surface layer. Therefore, even if it receives a thermal shock, the filler does not peel off from the inner wall of the through hole. Therefore, it is possible to prevent moisture from entering through the through holes.
[0017]
In the present invention, the filler is supplied not only inside the through hole but also around the opening. Therefore, even if the filler shrinks when the filler is hardened, the entire inside of the through hole can be filled with the filler.
[0018]
In the metal plating on the surface of the insulating substrate, the surface becomes a roughened surface layer, which is then polished and removed to obtain a uniform smooth surface. Therefore, even when the metal plating surface is further covered with a plating film, a plating film having a uniform thickness can be formed. For this reason, a pattern circuit having a smooth and uniform layer thickness can be formed on the surface of the insulating substrate.
[0019]
Therefore, even when the pattern circuit is used as a die pad and an electronic component such as a semiconductor chip is mounted on the die pad using an adhesive, the pattern circuit and the adhesive can be brought into close contact with each other. Therefore, even when subjected to a thermal shock, the adhesive does not peel off from the circuit pattern, and there is no intrusion of moisture. As a result, damage to the electronic components and the pattern circuit can be suppressed.
[0020]
ADVANTAGE OF THE INVENTION According to this invention, the peeling does not generate | occur | produce between the metal plating film in a through-hole, and the filler filled inside the through-hole, and can prevent invasion of moisture, and can manufacture a printed wiring board. It seeks to provide a way.
[0021]
【Example】
Example 1
A method for manufacturing a printed wiring board according to an embodiment of the present invention will be described with reference to FIGS.
As shown in FIGS. 1 and 2, the printed wiring board 10 manufactured according to the present embodiment has a through hole 90 penetrating the insulating substrate 9. The inner wall of the through hole 90 is covered with the metal plating film 3 having the roughened surface layer 30. The inside of the through hole 90 is filled with the electric insulating material 1 as a filler.
[0022]
On the front surface of the insulating substrate 9, a pattern circuit 61 and a die pad 63 for mounting a semiconductor chip are provided. On the back side surface of the insulating substrate 9, a pattern circuit 62 and a heat radiation pad 64 are provided.
The die pad 63 and the heat radiating pad 64 are connected by the through hole 90 provided substantially in the center of the insulating substrate 9. As shown in FIG. 2, the pattern circuits 61 and 62 on the front side and the back side are connected by the through holes 90 provided in the periphery of the insulating substrate 9.
[0023]
The semiconductor chip 5 is mounted on the die pad 63 by the adhesive 59. The semiconductor chip 5 is connected to the bonding pad 610 at the tip of the pattern circuit 61 by a wire 50. The semiconductor chip 5 and the wire 50 are sealed with a resin 55. The adhesive 59 is a die attach resin, an epoxy resin, an epoxy resin containing a filler, or the like.
The printed wiring board 10 of this example is of a type in which the semiconductor chip 5 and the pattern circuit 61 are connected by wires 50.
[0024]
Further, a pattern circuit 62 and a heat radiation pad 64 are provided on the back side surface of the insulating substrate 9. On the pattern circuit 62, a plurality of pads 620 for bonding with the pads 82 of the motherboard 8 by the solder 81 are provided.
[0025]
Next, a method for manufacturing the printed wiring board will be described with reference to FIGS.
First, as shown in FIG. 3, an insulating substrate 9 having a front surface and a rear surface covered with a copper foil 2 is prepared. Next, as shown in FIG. 4, a through hole 90 penetrating the insulating substrate 9 is formed. Next, as shown in FIG. 5, the metal plating film 3 is applied to the surface of the insulating substrate 9 and the inner wall of the through hole 90. The metal plating film 3 is copper.
[0026]
Next, as shown in FIG. 6, a roughened surface layer 30 is formed on the surface of the metal plating film 3 by a chemical surface treatment. The chemical surface treatment is performed by a blackening treatment.
The blackening treatment is performed by immersing the insulating substrate 9 in the following blackening treatment liquid for 0.3 to 15 minutes. By this blackening treatment, acicular crystals of copper are formed on the surface of the metal plating film 3.
[0027]
(1) Blackening treatment liquid / component (concentration in water)
Sodium chlorite. . . . . . . 20-70 g / liter,
Trisodium phosphate 12 water. . . . 10-30 g / l,
Sodium hydroxide. . . . . . . . 10-30 g / l,
·temperature. . . . . . . . 70-98 ° C,
[0028]
Next, as shown in FIG. 7, the electrical insulating material 1 made of epoxy resin is supplied into the through hole 90 and the periphery of the opening by means such as screen printing. At this time, the electric insulating material 1 is made to protrude from the surface of the insulating substrate 9. Next, the electrically insulating material 1 is heated to 150 ° C. and cured.
Next, as shown in FIG. 8, the electrical insulating material 1 and the roughened surface layer 30 protruding from the surface of the insulating substrate 9 are polished and removed by a buff to obtain a smooth surface.
[0029]
Next, as shown in FIGS. 9 to 13, a pattern circuit, a die pad, and a heat radiation pad are formed on the surface of the insulating substrate 9 by an etching resist method.
That is, first, as shown in FIG. 9, the front and back surfaces of the insulating substrate 9 are coated with a resist film 71 having a desired pattern. Next, unnecessary portions of the copper foil 2 and the metal plating film 3 are removed from the insulating substrate 9 by etching. Next, the resist film 71 is peeled off.
[0030]
Thus, as shown in FIG. 10, the pattern circuit 61, the bonding pads 610, and the die pads 63 are formed on the front surface of the insulating substrate 9. In addition, a pattern circuit 62 and a heat radiation pad 64 are formed on the back side surface of the insulating substrate 9.
[0031]
Next, as shown in FIG. 11, a solder resist film 72 is coated on the front and back surfaces of the insulating substrate 9 so as to partially expose the metal plating film 3 in the pattern forming portion. Next, as shown in FIG. 12, the Ni / Au plating film 4 is partially coated on the surface of the metal plating film 3 by plating.
[0032]
Thus, the die pad 63 and the bonding pad 610 are covered with the Ni / Au plating film 4 as shown in FIG. Further, pads 620 for bonding to the motherboard are formed on the back side surface of the insulating substrate 9. Thereby, the printed wiring board 10 is obtained.
[0033]
As shown in FIG. 14, the semiconductor chip 5 is mounted on the die pad 63 of the printed wiring board 10 using an adhesive 59. The semiconductor chip 5 is electrically connected to the bonding pads 610 by the wires 50. The semiconductor chip 5 and the wire 50 are sealed with a resin 55.
[0034]
As shown in FIG. 1, the pads 620 on the back side of the printed wiring board 10 are arranged on the pads 82 of the motherboard 8 via the ball-shaped solder 81. This is heated to solder the pads 620 of the printed wiring board and the pads 82 of the motherboard 8.
[0035]
Next, the operation and effect of this example will be described.
In the method of manufacturing a printed wiring board according to the present embodiment, as shown in FIGS. 6 and 7, the surface of the metal plating film 3 formed on the inner wall of the through hole 90 is subjected to a chemical surface treatment to form a roughened surface layer. 30 are formed. Therefore, the electrically insulating material 1 comes into close contact with the inner wall of the through hole 90 due to the unevenness of the roughened surface layer 30.
Therefore, even if it receives a thermal shock, the electric insulating material 1 does not peel off from the inner wall of the through hole 90. Therefore, it is possible to prevent moisture from entering through hole 90.
[0036]
Therefore, even when the printed wiring board is mounted on the motherboard by soldering, no separation occurs between the metal plating film in the through hole and the electrical insulating material due to the melting temperature of the solder.
[0037]
The electric insulating material 1 is supplied not only inside the through hole 90 but also around the opening. Therefore, even if the electrical insulating material 1 contracts when the electrical insulating material 1 is cured, the entire inside of the through hole 90 can be filled with the electrical insulating material 1.
[0038]
Further, a roughened surface layer is formed on the metal plating 3 on the surface of the insulating substrate 9 and then polished to obtain a uniform smooth surface. Therefore, even when the surface of the metal plating 3 is further covered with a plating film, a plating film having a uniform thickness can be formed.
For this reason, the pattern circuit 61 and the die pad 63 having a smooth and uniform layer thickness can be formed on the surface of the insulating substrate 9.
[0039]
Therefore, when the semiconductor chip 5 is mounted on the die pad 63 using the adhesive 59, the die pad 63 and the adhesive 59 can be brought into close contact. Therefore, even when subjected to a thermal shock, the adhesive 59 does not peel off from the die pad 63 and there is no intrusion of moisture. As a result, damage to the semiconductor chip 5, die pad 63, and pattern circuit 61 can be suppressed.
[0040]
In the above description, the connection between the semiconductor chip 5 and the wiring pattern 61 on the insulating substrate 9 is performed by the wire 50 via the bonding pad 610. However, as shown in FIG. 15, the connection between the semiconductor chip 5 and the wiring pattern 61 can be made by providing a solder bump 500 on the bonding pad 610 of the wiring pattern 61 and connecting to the semiconductor chip 5.
[0041]
Example 2
In the present example, a blackening treatment and a blackening reduction treatment were sequentially performed as a chemical surface treatment to form a roughened surface layer on the surface of the metal plating film.
That is, first, the blackening process described in the first embodiment was performed. Next, the insulating substrate was immersed in the following first reduction treatment liquid and second reduction treatment liquid in order to perform a blackening reduction treatment. The immersion time in the first reduction treatment liquid and the immersion time in the second reduction treatment liquid are 0.1 to 15 minutes.
[0042]
{Circle around (1)} First reduction treatment solution / component sodium hydrogen borohydride. . . . . 0.1-5.0 g / liter,
Sodium hydroxide. . . . . . . 0.1-5.0 g / liter,
·temperature. . . . . . . . . . . . . 30-60 ° C,
[0043]
{Circle around (2)} Second reduction treatment liquid / component sodium hydroxide. . . . . . . 1.0 to 10 g / liter,
Formaldehyde. . . . . . . 1.0-20g / liter,
methanol. . . . . . . . . . 1.0-30g / liter,
·temperature. . . . . . . . . . . . . 30-60 ° C,
[0044]
By the above-mentioned blackening reduction treatment, needle-like crystals of reduced copper are formed on the surface of the metal plating film.
Others are the same as the first embodiment. In the present embodiment, since the above treatment is performed, it is superior to the case of the first embodiment in the point of further improving the acid resistance. In addition, in this embodiment, the same effects as in the first embodiment can be obtained.
[0045]
Example 3
In this example, as a chemical surface treatment, a blackening treatment, a blackening reduction, and an acid treatment were sequentially performed to form a roughened surface layer on the surface of the metal plating film.
That is, in performing the processing of this example, first, the blackening processing described in the first embodiment was performed, and then the blackening reduction processing described in the second embodiment was performed. Next, the insulating substrate was immersed in an acid treatment solution containing the following components. The immersion time in the acid treatment liquid is 0.1 to 10 minutes.
[0046]
(1) Acid treatment liquid / sulfuric acid component. . . . . 30-300 g / l,
·temperature. . . . . . 5-40 ° C,
[0047]
By the chemical surface treatment, needle-like crystals of oxidized copper were formed on the surface of the metal plating film.
Others are the same as the second embodiment. In this embodiment, the same effect as that of the second embodiment can be obtained.
[Brief description of the drawings]
FIG. 1 is a sectional view of a state in which a printed wiring board according to a first embodiment is mounted on a motherboard.
FIG. 2 is an explanatory view showing the front side of the printed wiring board according to the first embodiment.
FIG. 3 is a sectional view of an insulating substrate having a surface coated with copper foil in the method for manufacturing a printed wiring board according to the first embodiment.
FIG. 4 is a cross-sectional view of the insulating substrate having a through hole, following FIG. 3;
FIG. 5 is a sectional view of the insulating substrate provided with the metal plating film, following FIG. 4;
FIG. 6 is a sectional view of the insulating substrate on which the roughened surface layer is formed, following FIG. 5;
FIG. 7 is a sectional view of the insulating substrate following FIG. 6 in which an electric insulating material is filled in a through hole;
FIG. 8 is a sectional view of the insulating substrate whose surface is polished, following FIG. 7;
FIG. 9 is a sectional view of the insulating substrate covered with the resist film, following FIG. 8;
FIG. 10 is a sectional view of the insulating substrate on which the pattern has been formed, following FIG. 9;
FIG. 11 is a sectional view of the insulating substrate covered with the solder resist film, following FIG. 10;
FIG. 12 is a sectional view of the insulating substrate provided with the Ni / Au plating film, following FIG. 11;
FIG. 13 is a sectional view of the insulating substrate following FIG. 12 from which a solder resist film has been removed;
FIG. 14 is a sectional view of a printed wiring board on which a semiconductor chip is mounted.
FIG. 15 is a cross-sectional view of the printed wiring board according to the first embodiment, which is electrically connected to a semiconductor chip using bumps.
FIG. 16 is an explanatory diagram showing an internal state of a through hole in a conventional example.
FIG. 17 is an explanatory view showing an internal state of a through hole when a thermal shock is applied in a conventional example.
[Explanation of symbols]
1. . . Electrical insulating material,
10. . . Printed wiring board,
2. . . Copper foil,
3. . . Metal plating film,
30. . . Roughened surface layer,
4. . . Ni / Au plating film,
5. . . Semiconductor chip,
61, 62. . . Pattern circuit,
63. . . Die pad,
64. . . Heat radiation pad,
8. . . Motherboard,
9. . . Insulating substrate,
90. . . Through hole,

Claims (6)

Drill a through-hole through the insulating substrate on the insulating substrate covered with copper foil on both sides .
Next, a metal plating film is applied to the surface of the insulating substrate and the inner wall of the through hole.
Next, a roughened surface layer is formed on the surface of the metal plating film by a chemical surface treatment,
Next, a filler is supplied to the inside of the through hole and the periphery of the opening so as to protrude from the surface of the insulating substrate, and is cured.
Next, the filler protruding from the surface of the insulating substrate and the roughened surface layer are polished and removed.
Thereafter, a pattern circuit is formed on the surface of the insulating substrate by an etching resist method. 2. The method according to claim 1, wherein the chemical surface treatment is a blackening treatment. 2. The method according to claim 1, wherein the chemical surface treatment includes a blackening treatment and a blackening reduction treatment sequentially. 2. The method according to claim 1, wherein the chemical surface treatment includes a blackening treatment, a blackening reduction treatment, and an acid treatment in that order. 5. The method according to claim 1, wherein the roughened surface layer has a needle-like surface. 6. The method for manufacturing a printed wiring board according to claim 1, wherein the polishing of the roughened surface layer is performed with a buff or a brush.

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