JPH10303334A - Plastic wiring board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To hardly move moisture in a plastic wiring board between a semiconductor element and an adhesive material layer even in the case that the plastic wiring board is heated, and to prevent the generation of a so-called popcorn phenomenon that the moisture present between the semiconductor element and the adhesive material layer is suddenly expanded to turn inner moisture to steam and pushes up the semiconductor element by using the plastic wiring board. SOLUTION: A wiring board 10 is provided with a chip loading conductor layer or the like formed by executing an etching processing to metal foil adhered to both surfaces of a plastic substrate 11. In this case, a solid pattern conductor layer 17 is formed by providing the formation area of plural pads 15b for a solder ball on a mother board connection surface 22, and an opening part 17a for discharging the moisture is formed at the peripheral part of the solid pattern conductor layer 17.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plastic wiring board, and more particularly, to a BGA (Ball Grid Array) or PGA.
The present invention relates to a plastic wiring board constituting a GA (Pin Grid Array) or the like.

[0002]

2. Description of the Related Art In order to protect a semiconductor device and at the same time to connect with a wiring formed on a motherboard, the semiconductor device is mounted on various packages. Conventionally, ceramics, metals, and the like have been used as materials for forming the package, and plastics have been mainly used as sealing materials for semiconductor devices. Recently, plastics have been used as materials for wiring boards. I have.

[0003] As the plastic package, B
GA, PGA and the like can be mentioned. For example, a plastic wiring board constituting BGA is manufactured by the following method. In the following, a plastic wiring board is a wiring board for mounting a semiconductor element,
It excludes wires (solder balls) for connecting a sealing member or a semiconductor element to a wiring on a wiring board.

[0004] First, a large-area plastic substrate for preparing a plurality of plastic wiring substrates is prepared.
After bonding a metal foil (copper foil) to both sides of the plastic substrate, a through hole for a through hole is formed. A conductor layer is formed on the wall surface of the through-hole by a method such as electroless plating using a catalyst to form a through-hole. Next, a photo-resist layer having a predetermined pattern is formed on the metal foil by using a photolithography technique, and then a conductive layer having a predetermined pattern is formed by performing an etching process. Next, after the photoresist layer is once removed, a photolithography technique is again used to expose the entire plastic substrate so that only predetermined portions (bonding pads, solder ball pads, etc.) of the conductor layer are exposed. A resist layer is formed to cover a portion including another conductor layer.
Next, plating (Ni plating and Au plating) is performed on the exposed conductor layer portion, cut into a predetermined wiring board shape, and then solder balls are fixed to the solder ball pads. The process for manufacturing the plastic wiring board is completed.

FIGS. 4A and 4B are plan views schematically showing one unit of the plastic wiring board. FIG. 4A shows a chip mounting surface, and FIG. 4B shows a motherboard connection surface. In FIG. 4, the photoresist layer covering almost the entire plastic substrate and the solder balls are omitted. As shown in FIG.
A chip mounting conductor layer 16 having a shape obtained by combining a line extending radially from the center and a large and small square is formed substantially at the center of the chip mounting surface 21.
Bonding pad 1 for wire bonding around
2 are formed. Also, this bonding pad 1
A plating lead 14 extending around the plastic substrate 11 is connected to 2, and a through hole 13 is formed in the middle of the plating lead 14. Note that the chip mounting conductor layer 16 has a shape in which a line extending radially from the center and a large and small rectangle are combined, because the semiconductor chip 19 (FIG. 5) is formed on the plastic substrate 11.
Semiconductor chip 19 and plastic substrate 1 when bonded to
This is for reducing the warpage due to the difference in thermal expansion from the number 1.

On the motherboard connection surface 22, a solid pattern conductor layer 57 for heat dissipation and grounding is formed at a portion facing the chip mounting conductor layer 16, and is formed in a region excluding the solid pattern conductor layer 57. A large number of solder ball pads 15a are formed at predetermined intervals, and the solder ball pads 15a and the through holes 13 are
a. Also, the solid pattern conductor layer 5
7, a solder ball pad 15b is also formed. A plating film (not shown) is formed on the bonding pad 12 and the solder ball pads 15a and 15b. Although the number of bonding pads 12 and solder ball pads 15a and 15b shown in FIG. 4 is not so large, actually, a larger number of bonding pads 12 and solder ball pads 15a and 15b are formed. I have.

FIG. 5 is a sectional view showing a plastic wiring board 50 (FIG. 4) on which a semiconductor chip is mounted.
-Corresponds to a cross section taken along line A

As shown in FIG. 5, a photoresist layer 23 is formed on substantially the entire surface of both surfaces of the plastic substrate 11 except for the bonding pad 12 and the solder ball pads 15a and 15b. At the center of the chip mounting surface 21, a semiconductor chip 19 is bonded onto the chip mounting conductor layer 16 via a photoresist layer 23 and an adhesive layer 18, and the pad portion 19a and the bonding pad 12 on the semiconductor chip 19 are bonded to each other. Are connected by a wire 20.
Solder balls 24a, which are external connection terminals, are fixed to the solder ball pads 15a on the mother board connection surface 22 via eutectic solder 25, and the central portion of the solid pattern conductor layer 57 is also used for heat dissipation and grounding. A plurality of solder balls 24b serving also as a utility are fixed. The other parts of the plastic wiring board 50 have been described with reference to FIG. 4, and the description thereof is omitted here.

When the plastic wiring board 50 shown in FIGS. 4 and 5 is mounted on a motherboard, the solder balls 24a and 24b fixed to the solder ball pads 15a and 15b of the plastic wiring board 50 are formed on the motherboard. The motherboard to which the plastic wiring board 50 is temporarily fixed is carried into a reflow furnace after being temporarily fixed via cream solder or the like, and then reflowed to connect the solder balls 24a and 24b to the wiring on the motherboard. Was.

[0010]

However, when the above-mentioned reflow process is performed, a phenomenon called a so-called popcorn may occur, and the semiconductor chip 1 mounted on the plastic wiring board 50 is caused by the popcorn phenomenon.
9 is peeled off from the adhesive layer 18 and the semiconductor chip 19 is removed.
There is a problem that the adhesive strength between the adhesive layer 18 and the adhesive layer 18 is greatly reduced.

In the popcorn phenomenon, as the temperature of the plastic wiring substrate 50 rises during reflow, the moisture existing between the semiconductor chip 19 and the adhesive layer 18 becomes steam and expands rapidly, causing the semiconductor chip 19 to expand. It is thought to be caused by pushing up.

The present inventors have studied the cause of the popcorn phenomenon and found that the semiconductor chip 1
Most of the water existing between the semiconductor chip 9 and the adhesive layer 18 is removed from the plastic substrate 11 below the semiconductor chip 19 during the reflow step. I found it to be something. That is, since the solid pattern conductor layer 57 is formed in a portion facing the chip mounting conductor layer 16, the moisture cannot pass through the solid pattern conductor layer 57, while Since the opening 16a is formed, the water moves between the semiconductor chip 19 and the adhesive layer 18 through the opening 16a as shown by an arrow B in the figure, and the popcorn phenomenon occurs. It happens.

[0013]

Means for Solving the Problems and Effects Thereof The present inventors have further studied for the purpose of preventing the occurrence of the popcorn phenomenon based on the result of the examination of the cause of the occurrence of the popcorn phenomenon, and Mounting conductor layer 16
By forming an opening for releasing moisture in the solid pattern conductor layer 57 formed in a portion opposed to the above, or by partially removing the solid pattern conductor layer 57, in the reflow process, It has been found that moisture escapes from the motherboard mounting surface 22 side through the opening and the removed portion formed in the solid pattern conductor layer 57, and as a result, it is possible to prevent the popcorn phenomenon from occurring, thus completing the present invention. I came to.

That is, a plastic wiring board (1) according to the present invention is a plastic wiring board comprising a conductor layer formed by performing an etching process on a metal foil adhered to both surfaces of a plastic substrate.
A solid pattern conductor layer including a region for connecting a plurality of heat radiation external connection terminals is formed on a surface facing the semiconductor element mounting surface, and an opening for releasing moisture is formed in a peripheral portion of the solid pattern conductor layer. It is characterized by being.

According to the plastic wiring board (1), since the opening for releasing moisture is formed in a peripheral portion of the solid pattern conductor layer, the plastic wiring board on which the semiconductor element is mounted is mounted on a motherboard. Even when the plastic wiring substrate is heated during mounting or the like, moisture in the plastic substrate moves to the outside of the solid pattern conductor layer through the opening and diffuses as vapor into the surroundings. Therefore, by using the plastic wiring board (1), even when the plastic wiring board is heated, moisture in the plastic wiring board almost moves between the semiconductor element and the adhesive layer. In addition, since the water existing between the semiconductor element and the adhesive layer becomes water vapor, it is possible to prevent the so-called popcorn phenomenon, which is caused by rapid expansion and pushing up the semiconductor element.

Further, the plastic wiring board (2) according to the present invention is the plastic wiring board (1) described above,
The ratio of the area of the opening to the total area of the solid pattern conductor layer and the opening is 50% or more.

According to the plastic wiring board (2), since the ratio of the area of the opening to the total area of the solid pattern conductor layer and the opening is 50% or more, the plastic wiring board is heated. Also in this case, the moisture in the plastic substrate is smoothly discharged to the outside through the opening, so that the popcorn phenomenon can be effectively prevented from occurring.

The plastic wiring board (3) according to the present invention is the plastic wiring board (1) described above,
The solid pattern conductor layer is removed except for a portion near the heat-radiating external connection terminal.

According to the plastic wiring board (3), since the solid pattern conductor layer is removed except for a portion near the heat-radiating external connection terminals, even when the plastic wiring board is heated. In addition, the moisture in the plastic substrate is smoothly discharged to the outside through the portion where the solid pattern conductor layer is removed, so that the popcorn phenomenon can be effectively prevented from occurring.

A plastic wiring board (4) according to the present invention is a plastic wiring board comprising a conductor layer formed by subjecting a metal foil adhered to both surfaces of a plastic substrate to an etching treatment, wherein A conductor layer pattern is formed at a connection portion of the plurality of heat radiation external connection terminals on a surface facing the element mounting surface.

According to the plastic wiring board (4), only the connecting portions of the plurality of heat-radiating external connection terminals form the conductor layer pattern, and the other portions have no conductor layer. Moisture in the plastic substrate is smoothly discharged to the outside through the portion where the conductor layer pattern is not formed, so that the popcorn phenomenon can be effectively prevented from occurring.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the plastic wiring board according to the present invention will be described below with reference to the drawings.

The type of the plastic wiring board according to the embodiment is not particularly limited, but specific examples thereof include a plastic wiring board constituting BGA, PGA, or the like. In the following, a plastic wiring board constituting a BGA will be described as an example.

FIG. 1 is a plan view schematically showing the motherboard connection surface of the plastic wiring board according to the embodiment (1). In FIG. 1, the plastic substrate 1
1 omits a photoresist layer covering almost the entirety and solder balls.

The other parts except the solid pattern conductor layer 17 formed in the central part of the motherboard connection surface 22 are configured in the same manner as the conventional plastic wiring board 50 shown in FIGS. Only the solid pattern conductor layer 17 will be described.

The solid pattern conductor layer 17 is formed so as to include a region where a plurality of solder ball pads (radiation external connection terminals) 15b are formed. Opening 17a is formed. In FIG. 1, a rectangular opening 17a is formed. However, the shape of the opening 17a is not limited to a rectangle, and may be a triangle or the like, a circle, an ellipse, or the like. Is also good. Also, the size of the opening 17a is not limited to the size shown in FIG. 1 and may be smaller, but it is preferable that the opening is evenly distributed around the solid pattern conductor layer 17 as much as possible. Is desirable. The ratio of the area of the opening 17a to the area of the solid pattern conductor layer 17 including the opening 17a is 50%.
% Or more is preferable. Although nine solder ball pads 15b are shown in FIG. 1, a larger number of solder ball pads 15b are actually formed.

Since the opening 17a is formed in the solid pattern conductor layer 17 as described above, a semiconductor chip (not shown) is mounted on the plastic wiring substrate 10 on which the solid pattern conductor layer 17 is formed. When the wafer is carried into a reflow furnace to connect the wiring on the motherboard and the solder balls fixed to the plastic wiring board 10,
As the temperature of the plastic substrate 11 rises, moisture contained in the plastic substrate 11 below the semiconductor chip moves outward through the opening 17a, and only the photoresist layer exists outside the opening 17a. It diffuses into the surroundings as vapor. As a result, the water in the plastic substrate 11 hardly moves to the interface between the semiconductor chip and the adhesive layer (not shown), and the so-called water caused by the water moving to the interface between the semiconductor chip and the adhesive layer. The occurrence of the popcorn phenomenon can be prevented.

FIG. 2 is a plan view schematically showing a motherboard connection surface of the plastic wiring board according to the embodiment (2). In FIG. 2 also, a photoresist layer covering almost the entire plastic substrate 11, and Solder balls are omitted.

This plastic wiring board 30 is configured similarly to the plastic wiring board 10 shown in FIG. 1 except for the conductor layer 37 at the center, so that only the conductor layer 37 will be described here.

In this plastic wiring board 30, the solid pattern conductor layer 17 is removed except for the central portion where the solder ball pad 15b is formed. That is, the solder ball pad 15b
The conductor layer 37 is formed only in the vicinity of the region where is formed.

Therefore, after the semiconductor chip is mounted on the plastic wiring board 30, when the semiconductor chip is carried into a reflow furnace for connecting the wiring on the mother board and the solder balls fixed to the plastic wiring board 30, the plastic wiring board 30 As the temperature rises, the moisture in the plastic substrate 11 below the semiconductor chip easily moves toward the motherboard connection surface 22 and becomes vapor and diffuses around. As a result, it is possible to prevent a so-called popcorn phenomenon caused by moisture moving to the interface between the semiconductor chip and the adhesive layer.

FIG. 3 is a plan view schematically showing a motherboard connection surface of the plastic wiring board according to the embodiment (3). In FIG. 3 as well, a photoresist layer covering almost the entire plastic substrate 11, and Solder balls are omitted.

This plastic wiring board 40 has the same configuration as the plastic wiring board 10 shown in FIG. 1 except for the solder ball pad 15b at the center, so that only the solder ball pad 15b will be described here. I do.

In this plastic wiring board 40, the solid pattern conductor layer 17 is removed except for the solder ball pad 15b at the center, and only the solder ball pad 15b is formed.

Therefore, after the semiconductor chip is mounted on the plastic wiring board 40, the semiconductor chip is carried into a reflow furnace to connect the wiring on the motherboard and the solder balls fixed to the plastic wiring board 40. As the temperature rises, the moisture in the plastic substrate 11 below the semiconductor chip easily moves toward the motherboard connection surface 22 and becomes vapor and diffuses around. As a result, it is possible to prevent a so-called popcorn phenomenon caused by moisture moving to the interface between the semiconductor chip and the adhesive layer.

[0036]

Examples and Comparative Examples Hereinafter, examples of a plastic wiring board according to the present invention will be described with reference to the drawings. As a comparative example, a conventional plastic wiring board 50 (FIG.
FIG. 5) was produced. Then, after mounting the semiconductor chips on the plastic wiring boards 10, 30, 40, and 50 according to the examples and the comparative examples, the semiconductor chips are left in an atmosphere of high humidity, and then the plastic wiring board 1 on which the semiconductor chips are mounted.
0, 30, 40, and 50 were carried into a reflow furnace, and whether or not a popcorn phenomenon occurred was observed. The conditions and results of the above Examples and Comparative Examples are described below.

<Conditions Common to Examples and Comparative Examples> Plastic Wiring Board Used Example 1—Plastic Wiring Board 10 (FIG. 1) Example 2—Plastic Wiring Board 30 (FIG. 2) Example 3 ... Plastic wiring board 40 (Fig. 3) Comparative example 1 ... Plastic wiring board 50 (Figs. 4 and 5) Plastic substrate 11 Dimensions: 27mm x 27mm x 0.2mm Constituent material: BT (bismaleimide triazine) Metal constituting the resin conductor layer: Cu (However, the bonding pad 12 and the solder ball pads 15a and 15b are Cu
A Ni plating film and an Au plating film were formed thereon. Thickness of Cu conductor layer: 30 μm Photoresist layer 23 Material: UV-curable acrylate resin, thickness: 5
0 μm leaving conditions in a high humidity atmosphere Relative humidity: 60%, leaving days: 9 days, temperature: 30 ° C. Reflow furnace conditions Atmosphere: nitrogen, maximum temperature: 240 ° C., transit time: 5 minutes <in the case of Example 1 Conditions> Outer shape of solid pattern conductor layer 17: 10 mm × 10 mm Length of one side of opening 17 a: 2 mm (12 pieces) <Condition in case of second embodiment> Outer shape of conductor layer 37: 5 mm × 5 mm <third embodiment Condition> Case of Solder Ball Pad 15b: 0.5 mm Number of Solder Ball Pads 15b: 16 <Condition of Comparative Example 1> Outer Shape of Solid Pattern Conductive Layer 57: 10 mm × 10 mm Example 1 Tables 1 to 3 show the results in the case of Comparative Example 1 and Comparative Example 1.

[0038]

[Table 1]

As is clear from the results shown in Table 1 above, in the case of the plastic wiring board 50 according to Comparative Example 1, the popcorn phenomenon occurred with a probability of 30% (3/10). In the plastic wiring boards 10, 30, and 40 according to the first to third embodiments, no popcorn phenomenon occurred, and the opening 17 a was formed in the solid pattern conductor layer 17 in the center of the motherboard connection surface 22. By partially removing the solid pattern conductor layer 17, when the plastic wiring substrates 10, 30, and 40 are heated, the plastic substrate 11 below the semiconductor chip 19 is heated.
It is possible to prevent the water present in the semiconductor chip 19 from moving to the interface between the adhesive layer 18 and the semiconductor chip 19 and the adhesive layer 18. Can be prevented.

[Brief description of the drawings]

FIG. 1 is a plan view schematically showing a motherboard connection surface of a plastic wiring board according to Embodiment (1) of the present invention.

FIG. 2 is a plan view schematically showing a motherboard connection surface of a plastic wiring board according to Embodiment (2).

FIG. 3 is a plan view schematically showing a motherboard connection surface of a plastic wiring board according to a third embodiment.

FIG. 4 is a plan view schematically showing one unit of a conventional plastic wiring board, where (a) shows a chip mounting surface;
(B) has shown the motherboard connection surface, respectively.

FIG. 5 is a cross-sectional view schematically showing a conventional plastic wiring board on which a semiconductor chip is mounted.

[Description of Signs] 10, 30, 40 Plastic wiring substrate 11 Plastic substrate 15b Solder ball pad 16 Chip mounting conductor layer 17 Solid pattern conductor layer 17a Opening 22 Motherboard connection surface 37 Conductor layer

Claims (4)

[Claims] 1. A plastic wiring board comprising a conductor layer formed by subjecting a metal foil adhered to both sides of a plastic substrate to an etching process,
A solid pattern conductor layer including a region for connecting a plurality of heat radiation external connection terminals is formed on a surface facing the semiconductor element mounting surface, and an opening for releasing moisture is formed in a peripheral portion of the solid pattern conductor layer. A plastic wiring board characterized by being made. 2. A ratio of the area of the opening to the total area of the solid pattern conductor layer and the opening is 50%.
The plastic wiring board according to claim 1, wherein: 3. The plastic wiring board according to claim 1, wherein the solid pattern conductor layer is removed except for a portion near the heat radiation external connection terminal. 4. A plastic wiring board comprising a conductor layer formed by subjecting a metal foil adhered to both sides of a plastic substrate to an etching treatment,
A plastic wiring board, wherein a conductor layer pattern is formed at a connection portion of a plurality of heat-radiating external connection terminals on a surface facing a semiconductor element mounting surface.