JP3381602B2 - Electronic component manufacturing method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an electronic component having a bumped electronic component mounted on a substrate.

[0002]

2. Description of the Related Art BGA (B
It is known that an electronic component such as a flip chip is mounted on a substrate such as an all grid array and solder bumps are formed on other electrodes formed on the substrate. A conventional method of manufacturing an electronic component will be described below with reference to the drawings. FIG. 12 is a sectional view of a conventional electronic component. 12
In the above, copper electrodes 2A and 2B as circuit electrodes are formed on the upper surface and the lower surface of the substrate 1, respectively. Copper electrode 2
Nickel films 3A and 3B as barrier layers on A and 2B
The gold films 4A and 4B are formed through. The copper electrode 2A on the upper surface side and the copper electrode 2B on the lower surface side are connected by an internal wiring 5. The gold film 4A of the copper electrode 2A is electrically connected to the gold bumps 7 of the bumped electronic component 6 so that the bumped electronic component 6
The gap between the substrate 1 and the substrate 1 is sealed with the insulating resin 8, and the solder bumps 9 are formed on the gold film 4B of the other copper electrode 2B to assemble the electronic component.

Here, the gold films 4A, 4 on the copper electrodes 2A, 2B.
B will be described. The gold films 4A and 4B are generally formed by a plating method and are necessary for ensuring good electrical continuity with the gold bumps 7 of the electronic component 6 with bumps. The nickel films 3A and 3B function as a barrier layer that prevents copper, which is a material of the copper electrodes 2A and 2B, from diffusing into the gold films 4A and 4B.

[0004]

A metal compound layer such as a nickel compound is likely to be formed on the surfaces of the gold films 4A and 4B. These metal compounds are used for the gold bump 7 and the gold films 4A and 4B.
It is necessary to suppress the formation of these layers as much as possible because it is a conduction inhibitor that inhibits the conduction and bonding of the gold films. For this purpose, it is necessary to increase the thickness of the gold films 4A and 4B to a certain degree or more. It was However, thickening the gold films 4A and 4B has an adverse effect of deteriorating the bonding property of the solder bump 9. This is because the gold in the gold film 4B melts into the molten solder when the solder bumps are formed, and combines with the solder gap to form a brittle compound. As described above, in order to ensure good conduction with the gold bumps 7, the gold film 4A is thicker (0.3
It is desirable that the gold film 4B is thin in order to secure the bonding property of the solder bumps 9 on the other hand, and so to speak, if one of them is satisfied, there is a contradictory relationship that the other is not satisfied.

In order to solve this problem, a partial plating method is applied to separately perform the gold film 4A plating step and the gold film 4B plating step, so that the gold film 4A is thick and the gold film 4B is at the minimum necessary thickness. However, the partial plating method has a problem that the number of steps is increased and the cost is significantly increased.

[0006] Therefore, an object of the present invention is to provide a method of manufacturing an electronic component which can secure good electrical continuity with a gold bump of an electronic component with bumps and bondability of a solder bump.

[0007]

According to a first aspect of the present invention, there is provided a method of manufacturing an electronic component, wherein a substrate is provided with a first electrode for conducting the bump of the electronic component with bumps and a second electrode for forming a solder bump. A first step of forming, a second step of forming a barrier layer containing at least nickel on these electrodes, a third step of forming a gold film on the surface of these barrier layers, and the first step. A fourth step of removing a conduction blocker formed on the surface of the gold film on the electrode, and aligning the bump of the bumped electronic component with the first electrode to conduct electricity, and the bumped electronic component on the substrate. It includes a fifth step of fixing and a sixth step of forming solder bumps on the second electrodes.

An electronic part manufacturing method according to a second aspect is the electronic part manufacturing method according to the first aspect, wherein in the fourth step, the gold film is formed on the surface of the gold film by utilizing sputtering by plasma treatment. The conduction inhibitor was removed.

According to a third aspect of the present invention, there is provided an electronic component production method according to the first aspect, wherein the substrate is subjected to a heat treatment prior to the fourth step so that the electronic component is formed on the first electrode. By removing the conduction inhibitor after promoting the generation of the conduction inhibitor on the surface of the gold film, more metal impurities contained in the gold film were removed.

The electronic component manufacturing method according to claim 4 is the electronic component manufacturing method according to claim 1, wherein the upper limit of the thickness of the gold film is 0.1% by weight of gold dissolved in the solder bump.
The value is as follows, and the lower limit value is set to 0.01 μm.

According to the invention described in each of the claims, the gold bump is formed on one of the plurality of electrodes formed on the same substrate by removing the conduction inhibitor generated on the surface of the gold film on the electrode through which the gold bump is conducted. Can be well conducted, and a solder bump can be formed on the other electrode with good bondability.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (Embodiment 1) FIG. 1 is a side sectional view of an electronic component according to Embodiment 1 of the present invention, and FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. It is process explanatory drawing of an electronic component manufacturing method. First, the structure of the electronic component will be described with reference to FIG. In FIG. 1, a resist 11a is formed on the surface of the substrate 11, and a bumped electronic component 16 is bonded to the upper surface of the substrate 11. The electronic component 16 with bumps is fixed to the substrate 11 with an insulating resin 18, and the electronic component 16 with bumps is electrically connected to the electrodes 12 formed on the upper surface of the substrate 11 by the gold bumps 17. The electrode 12 is connected to an electrode 13 formed on the lower surface of the substrate 11 by an internal circuit 14, and a solder bump 15 is formed on the electrode 13.

Next, a method of manufacturing an electronic component will be described with reference to FIGS. 2 to 7 show an electronic component manufacturing method in the order of steps. In FIG. 2, a resist 11a is formed on the surface of the substrate 11. The electrode 12 on the upper surface of the substrate 11 is formed by forming a nickel film 23A as a barrier layer on the copper electrode 22A (first electrode) and further coating the nickel film 23A with a gold film 24A very thinly. . The gold film 24A is formed to ensure electrical continuity with the gold bumps 17 of the electronic component 16 with bumps bonded to the substrate 11. In addition, the electrode 1 on the lower surface of the substrate 11
Similarly, 3 is formed by forming a nickel film 23B on the copper electrode 22B (second electrode) and further coating a gold film 24B. The electrode 12 on the upper surface and the electrode 13 on the lower surface of the substrate 11 are formed by the same plating process. Therefore, the gold film 2
The thickness of 4B is the same as the thickness of the gold film 24A.

Next, a method of setting the thickness of these gold films 24A and 24B will be described. FIG. 11 shows the proportion (% by weight) of gold that melts into the solder bumps 15 and the bonding strength between the solder bumps 15 and the electrodes 13 when the most common eutectic solder is used (the solder bumps are left at 175 ° C. for 50 hours It is a graph showing the relationship with the subsequent bonding strength). As shown in FIG. 11, a load in the horizontal direction is applied to the solder bumps 15 formed on the gold film 24B of the electrode 13, and the bonding strength is defined as the load value when the bonding portion is broken.

As a practical criterion, the bonding strength (F) is 1 after the solder bump is formed.
The strength was set to 00, and 60 or more was determined to be a strength that causes no practical problem. According to the experiment, when the gold content exceeds 0.10%, the bonding strength of the solder bump is less than 60. This is because, as described above, as the proportion of gold that dissolves in the solder bumps increases, the amount of gold and tin compounds produced by the combination of tin and gold in the solder increases.

Therefore, the upper limit of the thickness of the gold film 24B needs to be a value such that the weight% of gold dissolved in the solder bumps does not exceed 0.10%. The upper limit value of the thickness of the gold film 24B for satisfying this requirement can be obtained by the formula (Equation 1).

[0017]

[Equation 1]

Incidentally, when a solder bump is formed on the circular electrode 13 having a diameter of 210 μm by using a solder ball having a diameter of 300 μm, the upper limit of the thickness of the gold film 24B is 0.20 μm. The lower limit of the thickness of the gold film 24B is the nickel film 2
It is 0.01 μm, which is the minimum required to prevent the oxidation of 3B. The thickness of the gold film 24B is set in the range between the upper limit value and the lower limit value thus determined. Therefore, the gold film 24
The thickness of A becomes the same as that of the gold film 24B as a result of plating in the same step. The gold electroplating method for the gold films 24A and 24B is preferably a substitution type electroless plating method which is advantageous in terms of cost.

On the surfaces of the gold film 24A and the gold film 24B thus formed by the plating method, a compound layer formed by the impurities such as nickel mixed in during the plating process being exposed to air and being oxidized on the surfaces. Is occurring. this house,
The compound layer formed on the surface of the gold film 24A is a conduction inhibitor 25 that inhibits good conduction between the electrode 12 and the gold bump 17.

Therefore, in order to remove the conduction block 25, plasma treatment of the surface of the substrate 11 is performed. Figure 3
The substrate 11 is placed on the electrode 31 in the vacuum chamber 30 with the electrode 12 facing upward, as shown in FIG. Then, after the vacuum suction means 32 suctions the inside of the vacuum chamber 30 by vacuum, a plasma generating gas such as argon gas is supplied into the vacuum chamber 30 by the plasma gas supply unit 33. By driving the high frequency power supply unit 34 in this state and applying a high frequency voltage to the electrode 31, plasma is generated in the vacuum chamber 30, and the resulting sputtering effect of argon ions and electrons causes the gold of the electrode 12 to grow. The conduction blocker 25 on the surface of the film 24A is removed. If the substrate 11 is heat-treated prior to the plasma treatment, generation of the conduction inhibitor 25 on the surface of the gold film 24A is promoted, and as a result, more metal impurities are removed from the gold film 24A to remove the gold film 24A. The purity can be increased.

Next, the electronic component 1 with bumps is provided on the substrate 11.
6 is bonded. As shown in FIG. 4, the conductive resin 40 is applied in advance to the lower end portion of the gold bump 17 of the bumped electronic component 16. The gold bumps 17 of the electronic component 16 with bumps are aligned with the electrodes 12 of the substrate 11 and then lowered with respect to the substrate 11. Then, the gold bumps 17 are heated while being pressed against the electrodes 12 to cure the conductive resin 40. As a result, the gold bump 17 is electrically connected to the electrode 12 via the conductive resin 40. At this time, the gold film 24A of the electrode 12
Since the above conduction inhibitor is removed in the previous step, good conduction (low electric resistance) and sufficient adhesive strength are secured.

Next, as shown in FIG. 5, the insulating resin 41 is filled in the gap between the electronic component with bumps 16 and the substrate 11, and the insulating resin 41 is cured by heat treatment, whereby the electronic component with bumps is cured. 16 is fixed to the substrate 11. At this time, since the surface roughness of the surface of the resist 11a of the substrate 11 is increased by the sputtering effect of the plasma treatment, the adhesion with the insulating resin 41 is improved, and good resin sealing can be performed. After this, as shown in FIG. 6, flux 42 is applied on the electrodes 13 of the substrate 11, and then solder balls 43 are mounted on the electrodes 13. Thereafter, the solder balls 43 are melted by heating the substrate 11 and then solidified to form the solder bumps 15 on the electrodes 13 as shown in FIG.

At this time, a metal compound such as nickel oxide is also formed on the gold film 24B of the electrode 13, but since these are reduced by the flux 42, the bondability of the solder bump 15 is affected. Does not reach. Further, since the thickness of the gold film 24B is set in the range that does not hinder the bonding strength after soldering as described above, the amount of gold melted in the solder bumps 15 does not become excessive, so that tin and gold are It is possible to suppress the formation of a brittle compound layer caused by compounding and form a solder bump having excellent bonding strength.

(Second Embodiment) FIG. 8 and FIG. 9 are process explanatory views of an electronic component manufacturing method according to a second embodiment of the present invention. The substrate 11 and the electrodes 12 and 13 shown in FIG. 8 are the same as those in the first embodiment. In the second embodiment, an anisotropic conductive material is used as a method for adhering the electronic component 16 with bumps to the substrate and at the same time electrically connecting the gold bumps 17 to the electrodes 12. First, the electrode 12 on the substrate 11
Anisotropic conductive material 44 is attached to the periphery of. The anisotropic conductive material 44 is a thermosetting insulating resin 45 containing conductive particles 46 (see FIG. 9).

Next, the gold bump 17 of the bumped electronic component 16
Is aligned with the electrode 12, and the bumped electronic component 16 is lowered by a heating tool (not shown) to press the gold bump 17 against the electrode 12. As a result, as shown in FIG. 9, the gold bumps 17 are formed on the gold film 24 of the electrode 12 via the conductive particles 45.
At the same time as conducting with A, the insulating resin 45 is thermally cured.
At this time, the gold film 24A is plasma-treated in the previous step and the conduction block 25 is removed, so that good conduction between the gold bump 17 and the electrode 12 can be secured. The subsequent steps are the same as those in the first embodiment.

(Third Embodiment) FIG. 10 is a process explanatory diagram of an electronic component manufacturing method according to a third embodiment of the present invention. Figure 10
The substrate 11 and the electrodes 12 and 13 shown in FIG.
The same as in. In the third embodiment, the electronic component 16 with bumps is bonded to the substrate 11 with an insulating resin so that the gold bumps 17 are directly connected to the electrodes 12. First, the insulating resin 4 is formed around the electrode 12 on the substrate 11.
7 is applied.

Next, the gold bump 17 of the bumped electronic component 16
Is aligned with the electrode 12, the electronic component 16 with bump is lowered, and the gold bump 17 is pressed against the electrode 12. As a result, as shown in FIG. 10, the gold bump 17 is brought into direct contact with the gold film 24A of the electrode 12 to be electrically connected. At this time, the gold film 24A
Since the plasma treatment was performed in the previous step to remove the conduction inhibitor, good conduction between the gold bump 17 and the electrode 12 can be ensured.

Thereafter, the bumped electronic component 16 is pressed against the substrate 11 for a predetermined period of time and held, whereby the insulating resin 4 is formed.
7 is cured and the bumped electronic component 16 is fixed to the substrate 11. The subsequent steps are the same as those in the first embodiment.

As described in each of the above embodiments, by plasma-treating the upper surface of the substrate 11 prior to bonding the electronic component 16 with bumps, a complicated process such as a partial plating method is not required, The gold bump 17 can be satisfactorily conducted to one electrode 12 of the plurality of electrodes formed on the same substrate, and the solder bump 15 can be satisfactorily formed on the other electrode 13. Also, electronic component with bump 1
Since the plasma treatment of the substrate 11 is performed prior to the mounting of 6, the electronic component 16 with bumps is not damaged by the plasma. Furthermore, since the gold film formed on the electrodes 12 and 13 is extremely thin, it is possible to reduce the amount of gold, which is an expensive material, to reduce the cost.

Although a typical example of the method of connecting the electronic component 16 with bumps to the electrodes has been described in the first, second and third embodiments, the present invention is not limited to this.

[0031]

According to the present invention, by removing the conduction inhibitor on the surface of the gold film on the electrode through which the gold bump conducts, the gold bump is formed on the same substrate without requiring a complicated process such as a partial plating method. In addition, the gold bump can be satisfactorily conducted to one of the plurality of electrodes, and the solder bump can be formed on the other electrode with good bondability. Furthermore, since the gold film formed on the electrode is extremely thin, it is possible to reduce the amount of gold, which is an expensive material, to reduce the cost.

[Brief description of drawings]

FIG. 1 is a side sectional view of an electronic component according to a first embodiment of the present invention.

FIG. 2 is a process explanatory view of the electronic component manufacturing method according to the first embodiment of the present invention.

FIG. 3 is a process explanatory diagram of the electronic component manufacturing method according to the first embodiment of the present invention.

FIG. 4 is a process explanatory view of the electronic component manufacturing method according to the first embodiment of the present invention.

FIG. 5 is a process explanatory diagram of the electronic component manufacturing method according to the first embodiment of the present invention.

FIG. 6 is a process explanatory view of the electronic component manufacturing method according to the first embodiment of the present invention.

FIG. 7 is a process explanatory view of the electronic component manufacturing method according to the first embodiment of the present invention.

FIG. 8 is a process explanatory diagram of an electronic component manufacturing method according to a second embodiment of the present invention.

FIG. 9 is a process explanatory diagram of the electronic component manufacturing method according to the second embodiment of the present invention.

FIG. 10 is a process explanatory diagram of an electronic component manufacturing method according to a third embodiment of the present invention.

FIG. 11 is a graph showing the relationship between the proportion of gold that dissolves in the solder bumps and the bonding strength of the solder bumps.

FIG. 12 is a sectional view of a conventional electronic component.

[Explanation of symbols]

11 board 12, 13 electrodes 15 Solder bump 16 Electronic components with bumps 17 gold bumps 22A, 22B Copper electrode 23A, 23B Nickel film 24A, 24B Gold film 25 conduction blocker 41, 45, 47 Insulating resin 43 Solder ball 44 anisotropic conductive material 46 Conductive particles

Continuation of front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 23/12 H01L 21/60

Claims (4)

(57) [Claims] 1. A first step of forming a first electrode for electrically connecting to a bump of an electronic component with bumps and a second electrode for forming a solder bump on a substrate, and at least nickel on these electrodes. A second step of forming a barrier layer containing Al, a third step of forming a gold film on the surface of these barrier layers, and removal of a conduction inhibitor generated on the surface of the gold film on the first electrode. And a fifth step of aligning the bumps of the electronic component with bumps with the first electrode to make them conductive and fixing the electronic component with bumps to the substrate, and the second electrode on the second electrode. And a sixth step of forming solder bumps. 2. The method of manufacturing an electronic component according to claim 1, wherein in the fourth step, the conduction inhibitor generated on the surface of the gold film is removed by utilizing sputtering by plasma treatment. 3. Prior to the fourth step, by subjecting the substrate to a heat treatment to promote generation of a conduction inhibitor on the surface of the gold film on the first electrode, the conduction inhibitor is removed. 2. The method of manufacturing an electronic component according to claim 1, further comprising removing more metal impurities contained in the gold film. 4. The upper limit of the thickness of the gold film is such that the weight% of gold dissolved in the solder bump is 0.1% or less, and the lower limit thereof is 0.01 μm. 1. A method for manufacturing an electronic component according to 1.