JP2000269372A - Bga package and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize high density of a wiring pattern and improve adherence between ball pads and a resin board, by specifying the thicknesses of a first conducting layer for forming a wiring pattern and a second conducting layer for forming ball pads, and the surface roughness of the surfaces of the first and second conducting layers. SOLUTION: Copper foils 4, 5 are laminated on both surfaces of a prepreg 1, and a base board 6 is formed by vacuum press. Through holes 2 are formed on the base board 6 and filled with conductive resin 3. After that, the copper foils 4, 5 are etched, a wiring pattern 7 is formed on a chip component mounting surface 1a side, and ball pads 8 are formed on a mother board bonding surface 1b side. A copper foil having a thickness of d1 less than thickness d2 of the copper foil 5 laminated on the mother board bonding surface 1b and/or a copper foil having surface roughness of a sticking surface 4a smaller than that of a sticking surface 5a of the copper foil 5 are used as the copper foil 4 laminated on the chip component mounting surface 1a.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a BGA package, and more particularly to a BGA package, which is mainly used as a package for mounting an IC chip. BG with a ball pad on the motherboard bonding surface opposite to
A package and a method of manufacturing the A package.

[0002]

2. Description of the Related Art In response to demands for higher density and higher speed in semiconductor devices, a BGA (Ball Grid Arra) capable of increasing the number of terminals has been developed.
y) has recently attracted attention. The BGA is most suitable for mounting an IC such as a microprocessor or an ASIC which requires multiple terminals.

Until recently, ceramic BGAs have attracted attention among BGAs from the viewpoint of reliability, but the focus has shifted to plastic packages from the viewpoint of cost reduction.

[0004] A plastic BGA has a BT (Bismal) having a conductor layer formed by patterning copper foil on both sides.
eimide Triazine) 1 consisting of resin, polyimide resin, etc.
A resin substrate made of a layer or a multi-layered high heat-resistant resin is used, and a cavity down type in which a heat slug is joined to the resin substrate to enhance heat dissipation, or the heat slug is not joined, There is a cavity-up type or the like in which a chip component is mounted on a surface opposite to a surface on which external connection terminals are arranged.

FIG. 10A shows an example of the cavity-up type BGA. IC chip 21 of resin substrate 22
The wiring pattern 23 is provided on the mounting surface (chip component mounting surface 30).
Are formed on the motherboard bonding surface 31 on the side opposite to the surface on which the wiring patterns 23 are arranged, and a large number of ball pads 24 are formed. These ball pads 24 and the wiring patterns 23 are connected via wiring through holes 26, The lower surface of the IC chip 21 is connected to ball pads 24 via through holes 27 for heat radiation, and solder balls 25 are welded on these ball pads 24. The wiring pattern 23 is connected to pads (not shown) formed on the IC chip 21 via bonding pads 23a and bonding wires 28. And IC chip 2
1, a portion including the bonding wire 28 and most of the wiring pattern 23 is covered with a mold resin 29.

The BGA wiring pattern 23 and the ball pad 24 shown in FIG. 10A have the same thickness adhered to both main surfaces of the resin substrate 22 as shown in FIG. 10B. In addition, it is formed by performing an etching process or the like on the copper foils 33 and 34 having the same surface roughness of the bonding surface with the resin substrate 22.

[0007]

In recent years, the performance and miniaturization of electronic equipment have been rapidly progressing, and ICs have been
Chips have also become highly integrated, and demands for higher density wiring patterns 23 on chip component mounting surface 30 have been increasing.

The increase in the density of the wiring pattern 23 is largely related to the thickness of the copper foil 33 which is a conductor layer for forming the wiring pattern 23 and the surface roughness of the surface of the copper foil 33 to be bonded to the resin substrate 22. As the thickness is reduced and the surface roughness is reduced, the wiring pattern 23
Density can be increased.

On the other hand, on the mother board bonding surface 31 side having the ball pad 24, the adhesion between the copper foil 34, which is a conductor layer for forming the ball pad 24, and the resin substrate 22 is emphasized. Contrary to the 30 side, the thickness of the copper foil 34 is preferably large, and the surface roughness of the surface of the copper foil 34 to be bonded to the resin substrate 22 is preferably large. As described above, the requirements for the thickness and surface roughness of the copper foil on the chip component mounting surface 30 side and the motherboard bonding surface 31 side are contradictory.

However, in the prior art, FIG.
, Copper foils 33 and 34 adhered to the chip component mounting surface 30 side and the motherboard bonding surface 31 side, respectively.
Are the same, and the surface roughness of the bonding surface with the resin substrate 22 is the same. Therefore, the density of the wiring patterns 23 on the chip component mounting surface 30 is increased, and the motherboard bonding surface 3
1, it was difficult to simultaneously achieve high adhesion between the ball pad 24 and the resin substrate 22.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and aims at simultaneously increasing the density of a wiring pattern on a chip component mounting surface and improving the adhesion between a ball pad and a resin substrate on a mother board joint surface. BG that can be
A package is intended to be provided.

[0012]

Means for Solving the Problems and Their Effects To achieve the above object, a BGA package according to the present invention (1)
A first pattern for forming the wiring pattern in a BGA package having a wiring pattern on a chip component mounting surface of a resin substrate and a ball pad on a motherboard bonding surface opposite to the wiring pattern placement surface; The thickness of the conductor layer is smaller than the thickness of the second conductor layer for forming the ball pad, and / or the surface roughness of the surface of the first conductor layer to be adhered to the resin substrate is reduced. The surface roughness of the second conductor layer is smaller than the surface roughness of the surface to be adhered to the resin substrate.

According to the BGA package (1), the thickness of the first conductor layer and the thickness of the second conductor layer, and / or the surface roughness of the first conductor layer and the second conductor The surface roughness of the layer is suitable for each of the chip component mounting surface side and the motherboard bonding surface side, and the density of the wiring pattern is increased, and the adhesion between the ball pad and the resin substrate is improved. Improvement can be achieved at the same time.

The BGA package (2) according to the present invention is characterized in that, in the BGA package (1), the thickness of the first conductor layer is in the range of 5 to 18 μm.

According to the BGA package (2), the thickness of the first conductor layer for forming the wiring pattern is in the range of 5 to 18 μm, and the density of the wiring pattern is further increased. The thickness is suitable for realizing.

In the BGA package (3) according to the present invention, in the BGA package (1) or (2), the surface roughness (R _Z) of the surface of the first conductor layer to be adhered to the resin substrate is provided. ) Is in the range of 2.5 to 5.0 μm.

According to the BGA package (3), the surface roughness (R _Z ) of the first conductor layer for forming the wiring pattern is in the range of 2.5 to 5.0 μm. The density of the wiring pattern can be further increased.

Further, in the BGA package (4) according to the present invention, in any one of the BGA packages (1) to (3), the thickness of the second conductor layer is 12 to 35.
It is characterized by being within the range of μm.

According to the BGA package (4), the thickness of the second conductor layer for forming the ball pad is in the range of 12 to 35 μm, and the thickness of the second conductor layer is further increased. The thickness is suitable for improving the adhesion to the resin substrate.

In the BGA package (5) according to the present invention, in any one of the BGA packages (1) to (4), the surface roughness of the bonding surface of the second conductor layer to the resin substrate is provided. (R _Z ) is 5.0 to 10.0 μm
m.

According to the BGA package (5), the surface roughness (R _Z ) of the second conductor layer for forming the ball pad is in the range of 5.0 to 10.0 μm. Thus, the adhesion to the resin substrate can be further improved.

Further, the method (1) for manufacturing a BGA package according to the present invention comprises the steps of: adhering a first copper foil for forming a wiring pattern on a chip component mounting surface of a resin substrate;
Adhering a second copper foil for forming a ball pad to the motherboard bonding surface opposite to the wiring pattern arrangement surface, wherein the step of attaching the second copper foil forms a ball pad. The thickness of the copper foil is smaller than the thickness of the second copper foil, and / or the surface roughness of the bonding surface of the first copper foil with the resin substrate is the second copper foil. The first copper foil and / or the second copper foil are subjected to a thickness adjustment process and / or a surface treatment process so as to be finer than the surface roughness of the bonding surface of the copper foil to the resin substrate. It is characterized by including a process.

According to the BGA package manufacturing method (1), the thickness of the first conductor layer and the thickness of the second conductor layer, and / or the surface roughness of the first conductor layer and the second 2, the surface roughness of the conductor layer can be set to a value suitable for each of the chip component mounting surface side and the mother board bonding surface side. A BGA package that can simultaneously improve the adhesion to the BGA can be manufactured.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a BGA package according to the present invention and a method for manufacturing the same will be described with reference to the drawings.

FIG. 1 is a schematic sectional view showing a part of the manufacturing process of the BGA package according to the embodiment (1).
1 in the figure shows a prepreg made of BT resin,
The prepreg 1 is a sheet-like material in which a base material such as a glass cloth is impregnated with a resin and semi-cured.

First, copper foils 4 and 5 are laminated on both main surfaces of the prepreg 1 and are vacuum-pressed to produce a base substrate 6 (FIGS. 1A and 1B). Next, the through hole 2 is formed in the base substrate 6. Generally, a drill is used, but it is also possible to process with a laser beam depending on the material. After the through holes 2 are formed, the holes are filled with the conductive resin 3 (FIG. 1C). Then, copper foil 4,
5, the chip component mounting surface 1a is etched.
Wiring pattern 7 is formed on the
The ball pad 8 is formed on the b side (FIG. 1D).

At this time, the copper foil 4 laminated on the chip component mounting surface 1a has a thickness d ₁ smaller than the thickness d _{2 of the} copper foil 5 laminated on the motherboard bonding surface 1b; The copper foil 5 has a surface roughness smaller than the surface roughness of the bonding surface 5a.

The copper foil 4 has a thickness d ₁ of 3
１８18 μm, the surface roughness of the sticking surface 4 a is desirably in the range of 2.5-7.0 μm, and more preferably, the thickness d ₁ is in the range of 5-18 μm. The surface roughness of the sticking surface 4a is in the range of 2.5 to 5.0 μm.

The copper foil 5 has a thickness d ₂ of 1
It is preferably in the range of 0 to 35 μm, and the surface roughness of the sticking surface 5 a is preferably in the range of 5.0 to 12.0 μm,
More preferably, there thickness d ₂ is in the range of 12～35Myuemu, surface roughness of the bonded face 5a is with the scope of 5.0～10.0Myuemu.

According to the BGA package according to the embodiment (1), the thickness d ₁ of the copper foil 4 and the thickness d _{2 of} the copper foil 5,
And / or the surface roughness of the bonding surface 4a of the copper foil 4 and the surface roughness of the bonding surface 5a of the copper foil 5 are suitable for the chip component mounting surface 1a and the motherboard bonding surface 1b, respectively. Thus, the density of the wiring pattern 7 can be increased, and the adhesion between the ball pad 8 and the prepreg 1 can be improved at the same time.

In the above embodiment (1), a two-layer structure in which copper foils 4 and 5 are adhered to both main surfaces of prepreg 1 has been described as an example.
Of course, it is also possible to form a three-layer structure or a four-layer structure by stacking three or three sheets.

FIG. 2 is a schematic sectional view showing a part of the manufacturing process of the BGA package according to the embodiment (2).
In the drawing, reference numeral 9 denotes a resin core material on which a conductive circuit layer 10 made of copper is formed. Copper foils 13 and 14 are laminated on both main surfaces of the core material 9 via prepregs 11 and 12, respectively, and are vacuum-pressed to produce a base substrate 15.

After the base substrate 15 is formed, the copper foils 13 and 14 are etched in the same manner as shown in FIG. 1 to form a wiring pattern 16 on the chip component mounting surface 11a side, and the mother board bonding surface 12a A ball pad 17 is formed on the side.

At this time, the copper foil 13 laminated on the chip component mounting surface 11a has a thickness d ₃ smaller than the thickness d _{4 of the} copper foil 14 laminated on the motherboard bonding surface 12a, and The surface roughness of the bonding surface 13a is smaller than the surface roughness of the bonding surface 14a of the copper foil 14.

Desirable ranges of the thickness d ₃ , the surface roughness of the sticking surface 13a, the thickness d ₄ , and the surface roughness of the sticking surface 14a are the same as the ranges described in the above embodiment (1). Is the same.

The method of producing the copper foils 13 and 14 corresponding to the chip component mounting surface 1a and the motherboard bonding surface 1b will be described.

The copper foil 13 having a small thickness d _{3 and a} small surface roughness of the sticking surface 13a is obtained by adding fine particles to the original foil deposited by electrolytic copper plating so as to have a granular crystal structure. It is produced by attaching. Therefore, there is only a surface roughness of the size of a ball.

FIG. 3 is a photomicrograph of the surface of the copper foil produced by the above-described production method, which was observed with an optical microscope.
Ultra-fine roughened particles are uniformly formed, and the surface roughness R
_Z is 2.5 μm. 3A is 1600 times, and FIG. 3B is 3200 times. FIG. 4 is a schematic sectional view showing the surface structure of the copper foil.

The copper foil 14 having a large thickness d _{4 and a} large surface roughness of the sticking surface 14 a is obtained by depositing fine particles on the original foil deposited by electrolytic copper plating so as to have a columnar crystal structure. It is produced by attaching. Therefore, the thickness d
_The thicker ₄ is, the greater the surface roughness.

FIG. 5 is a photomicrograph of the surface of the copper foil produced by the above-described production method, which was observed with an optical microscope.
Roughened particles are formed on the top of the base mountain, and the surface roughness R _Z
Is 5.1 μm. Note that FIG. 5A is 1600 times and FIG. 5B is 3200 times. FIG. 6 is a schematic sectional view showing the surface structure of the copper foil.

[0041]

EXAMPLES and COMPARATIVE EXAMPLES The four-layered BGA shown in FIG. 7 was produced by the method shown in FIG. Specific manufacturing conditions are shown below.

Size of prepregs 11 and 12: 200 mm × 300 mm × thickness 0.2 mm Material of prepregs 11 and 12: BT resin Thickness of copper foil 13 for forming wiring pattern 16: 9 μm Pasting copper foil 13 Surface roughness R _Z of the attaching surface 13a: 2.5 μm Thickness of the copper foil 14 for forming the ball pad 17: 12 μm Surface roughness R _Z of the attaching surface 14a of the copper foil 14: 6.3 μm Solder ball 18 Diameter of 0.76 mm Conditions when vacuum pressing copper foils 13 and 14 Temperature: 190 ° C., 2 hours Pressure: 25 kg / cm ² Vacuum evacuation: 100 torr or less 50 minutes Copper foil 13 bonded to chip component mounting surface 11a The conductor width / interval is 100/100 μm, 70/70 μm, 50
Three types of / 50 μm patterning were performed using a test film. As a result, a fine pattern of 50/50 μm could be formed.

The adhesion between the ball pad 17 and the resin substrate (prepreg) 12 was examined by pulling the solder ball 18 welded on the ball pad 17 in the direction of arrow T as shown in FIG. As a result, when the average strength is 1.5 kg, the solder ball 18 is
Peeled from 7.

When the adhesion between the ball pad 17 and the resin substrate 12 is high, only the solder ball 18 is peeled off from the ball pad 17 as shown in FIG. When the adhesion was low, the ball pad 17 was separated from the resin substrate (prepreg) 12 as shown in FIG.

Table 1 shows the thickness of the copper foil 13 and the bonding surface 13
The results obtained when the above three types of patterning were performed while changing the surface roughness (R _Z ) of a.

[0046]

[Table 1] As is clear from Table 1, the thickness of the copper foil 13 is 5 to 18 μm.
m, and the surface roughness R _Z of the bonding surface 13a of the copper foil 13 is in the range of 2.5 to 5.0 μm.
A fine pattern of 50 μm could be formed.

Table 2 shows the thickness of the copper foil 14 and the bonding surface 14
The results obtained when the adhesion was examined by changing the surface roughness (R _Z ) of a.

[0048]

[Table 2] As is clear from Table 2, the thickness of the copper foil 14 is 12 to 35.
in the range of [mu] m, when the surface roughness of the bonding surface 14a of the copper foil 14 (R _Z) is in the range of 5.0～10.0Myuemu, high adhesion.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a part of a manufacturing process of a BGA package according to Embodiment (1) of the present invention.

FIG. 2 is a schematic cross-sectional view showing a part of the manufacturing process of the BGA package according to the embodiment (2).

FIG. 3 is a micrograph of the surface of a copper foil observed with an optical microscope.

FIG. 4 is a schematic sectional view showing a surface structure of a copper foil.

FIG. 5 is a micrograph of the surface of a copper foil observed with an optical microscope.

FIG. 6 is a schematic sectional view showing a surface structure of a copper foil.

FIG. 7 is a schematic cross-sectional view showing an example of a BGA manufactured by the method shown in FIG.

FIG. 8 is an enlarged schematic sectional view showing the vicinity of a ball pad.

FIG. 9 is an enlarged schematic cross-sectional view showing the vicinity of a ball pad.

FIG. 10 is a schematic sectional view showing an example of a conventional cavity-up type BGA.

[Explanation of symbols]

 1, 11, 12 Pre-preg 1a, 11a Chip component mounting surface 1b, 12a Motherboard joint surface 4, 5, 13, 14 Copper foil 7, 16 Wiring pattern 8, 17 Ball pad

Claims (6)

[Claims] 1. A BGA package having a wiring pattern on a chip component mounting surface of a resin substrate and having a ball pad on a motherboard bonding surface opposite to a surface on which the wiring pattern is arranged, for forming the wiring pattern. Thickness of the first conductor layer is smaller than thickness of the second conductor layer for forming the ball pad, and / or the surface of the first conductor layer to which the resin substrate is adhered. A BGA package, wherein the roughness is smaller than the surface roughness of the surface of the second conductor layer to be bonded to the resin substrate. 2. The method according to claim 1, wherein the thickness of the first conductor layer is 5 to 18 μm.
2. The BG according to claim 1, wherein the BG is within a range of m.
A package. 3. A surface roughness (R _Z ) of a surface of the first conductor layer to be adhered to the resin substrate is 2.5 to 5.0 μm.
3. The method according to claim 1, wherein
The BGA package as described. 4. The thickness of the second conductor layer is 12 to 35.
The BGA package according to claim 1, wherein the BGA package is in a range of μm. 5. The surface roughness (R _Z ) of the surface of the second conductor layer to be bonded to the resin substrate is 5.0 to 10.0 μm.
The BGA package according to claim 1, wherein the BGA package is within a range of m. 6. A step of adhering a first copper foil for forming a wiring pattern on a chip component mounting surface of a resin substrate, and a step of attaching a ball pad to a motherboard bonding surface opposite to the wiring pattern placement surface. A step of attaching a second copper foil for forming the BGA package, the thickness of the first copper foil being greater than the thickness of the second copper foil before these steps. Thin and / or the first
The surface roughness of the bonding surface of the copper foil with the resin substrate,
Thickness adjustment processing and / or surface treatment on the first copper foil and / or the second copper foil so as to be smaller than the surface roughness of the bonding surface of the second copper foil with the resin substrate. A method for manufacturing a BGA package, comprising a step of performing processing.