JP3929178B2 - IC mounting structure - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an IC chip mounting structure, and more particularly to a flip chip mounting structure having protruding electrodes.
[0002]
[Prior art]
2. Description of the Related Art In recent years, flip chip bonding has been developed in which a bare chip is directly mounted face-down on a substrate as semiconductor packages become smaller and higher in density. With the advent of camera-integrated VTRs, mobile phones, and the like, mobile devices on which small packages of approximately the same dimensions as bare chips, so-called CSP (chip size / scale packages), have appeared one after another. Recently, the development of CSP is progressing rapidly, and the market demand is in full swing.
[0003]
FIG. 5 shows a process of manufacturing the protruding electrode on the IC wafer. In the IC wafer manufacturing process of FIG. 5A, an electric circuit is formed on the IC wafer 8, and a bonding pad 9 is formed for external connection.
[0004]
In the UBM (UnderBumpMetal) deposition process shown in FIG. 5B, the UBM 10 which is a metal for connecting the common electrode for electrolytic bump deposition and the bump to the bonding pad 9 is sputtered on the bonding pad 9 side of the IC wafer 8. It precipitates by etc.
[0005]
In the plating resist forming process shown in FIG. 5C, a plating resist 11 for electrolytic bump deposition is formed on the UBM 10 by a photolithography process.
[0006]
In the solder plating process shown in FIG. 5D, the solder 12 is electrolytically deposited on the opening of the plating resist 11 by electroplating.
[0007]
In the resist stripping step shown in FIG. 5E, the plating resist 11 is stripped with a resist stripping solution.
[0008]
In the UBM etching process shown in FIG. 5F, the UBM 10 under the solder 12 is left and the UBM 10 on the IC wafer 8 is removed by etching.
[0009]
In the reflow process shown in FIG. 5G, a solder bump 13 is formed by applying a flux to the solder 12 and performing reflow. Thereafter, the flux is washed to complete the IC wafer 14 with protruding electrodes.
[0010]
FIG. 6 shows the IC mounting process. 6A is a manufacturing process shown in FIG. 5, and the IC wafer 14 with protruding electrodes is manufactured.
[0011]
In the dicing process shown in FIG. 6B, the IC wafer 14 with protruding electrodes is cut into individual IC chips 15 with protruding electrodes using a dicing saw.
[0012]
In the flux application process shown in FIG. 6C, the IC chip 15 with protruding electrodes 15 is immersed in a flux tank, and the flux 16 is applied onto the solder bumps 13 of the IC chip 15.
[0013]
In the placement step shown in FIG. 6D, the IC chip 15 and the bonding pattern 2 on the circuit board 5 are recognized, and the solder bumps 13 of the IC chip 15 are placed on the bonding pattern 2.
[0014]
In the reflow process shown in FIG. 6 (e), the IC chip 15 is connected to the circuit board 5 by reflowing the solder bumps 13.
[0015]
In the sealing step shown in FIG. 6 (f), the gap between the IC chip 15 and the circuit board 5 is sealed with the sealing resin 4. Thus, the IC mounting substrate 17 is completed.
[0016]
FIG. 7 shows an X-ray transmission diagram of the conventional IC mounting substrate 17. Solder bumps 13 are arranged symmetrically on the IC chip 1 and bonded.
[0017]
[Problems to be solved by the invention]
However, the above-described IC mounting structure has the following problems. That is, after the IC is mounted, in order to inspect whether the IC is oriented in the normal direction and placed in the correct position, the IC chip cannot be distinguished from the appearance because the back surface is exposed. Bumps and bonding patterns can be discriminated by transmitting X-rays through the substrate on which the IC is placed. However, if the solder bumps are arranged symmetrically, the directionality of the IC chip cannot be discriminated. For this reason, since it is necessary to conduct an electrical inspection for the determination, the productivity is low, and there are problems such as an increase in cost.
[0018]
The present invention has been made in view of the above-described conventional problems, and an object of the present invention is to provide an IC mounting having an easy placement discrimination method in flip chip mounting excellent in reliability and productivity mounted on a small portable device or the like. Provide structure.
[0019]
[Means for Solving the Problems]
In order to achieve the above object, an IC mounting structure according to the present invention is an IC mounting structure in which an IC chip having a protruding electrode for connection for connecting to a bonding pattern on a circuit board is flip-chip mounted on the circuit board. A directional protruding electrode indicating the direction of the IC chip is provided in the connecting protruding electrode forming surface of the chip, and the height of the directional protruding electrode is set so as not to contact the circuit board. It is characterized by being formed lower than this.
[0020]
Further, the directional protruding electrode showing the directionality is not in electrical contact with the IC chip.
[0021]
Further, the directional protruding electrode exhibiting the directivity is characterized in that its root shape is different from that of the other connecting protruding electrodes.
[0023]
Further, the material of the connecting protruding electrode and the directional protruding electrode is formed of solder.
[0024]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an IC mounting structure according to the present invention will be described with reference to the drawings. FIG. 1 is an embodiment of the present invention, in which FIG. 1A is an X-ray projection of a mounting circuit board, and FIG. 1B is a cross-sectional view taken along line AA ′ of FIG. FIG. 2 is an explanatory view showing the shape of a directional bump in the embodiment of the present invention. FIGS. 3A and 3B and FIGS. 4A and 4B are cross-sectional views of directional bumps and are explanatory views showing bump heights. The same members as those in the prior art are denoted by the same reference numerals.
[0025]
FIG. 1A shows an X-ray transmission diagram of a mounted circuit board. Among the bumps mounted on the circuit board 5, the direction bump 3 has a planar shape different from that of the other solder bumps 13, so that the directionality of the chip can be easily determined. Further, since no connection is made to the circuit board 5, there is no corresponding bonding pattern on the circuit board 5.
[0026]
FIG.1 (b) is AA 'sectional drawing of Fig.1 (a). Since the height of the directional bump 3 is lower than that of the other solder bumps 13, it does not contact the circuit board 5 even after reflow. Therefore, when the IC chip 1 is placed on the circuit board 5, the directional bump 3 becomes higher than the other solder bumps 13, and the problem that the solder bumps 13 cannot be connected to the bonding pattern does not occur. Furthermore, since the directional bump 3 is electrically independent from the IC chip and also electrically independent from the circuit board 5, it is reliably insulated even after sealing, and no reliability problem occurs. .
[0027]
FIG. 2 shows the root shape of the directional bump and a top view when the solder bump is formed. By making the bump base shape 6 into a cross shape, the solder bump shape is different from the circular shape. Since the solder bumps are usually circular, it can be easily determined which bump is the directional bump 3 in the X-ray transmission diagram, and it can be easily determined whether or not the placement is normal on the circuit board.
[0028]
FIG. 3 shows a method of changing the bump height of the general bump and the directional bump in the electrolytic solder plating bump. By setting the plating resist opening diameter in electroplating to the relationship of “general bump resist opening diameter (R)”> “directional bump resist opening diameter (r)”, the amount of directional bump plating after electroplating is reduced. . The height of the solder bump formed by reflowing the solder has a relationship of “general bump height (H)”> “directional bump height (h)”. The bump height can be easily changed by using solder as the bump material.
[0029]
FIG. 4 shows a method of changing the bump height of the general bump and the directional bump in the electroless solder bump. When a single solder ball supply method is considered for the electroless bump formation method, the supplied solder amount is the same. The resist bump diameter is in the relationship of “general bump diameter (R)” <“directional bump diameter (r)”, and the solder bump height formed by reflow is “general bump height (H)”> “direction” Bump height (h) ". The bump height can be easily changed by using solder as the bump material.
[0030]
【The invention's effect】
As described above, according to the IC mounting structure of the present invention, the directional protrusion electrode is formed in the formation surface of the general bump which is the protruding electrode for connecting the IC chip, so that the directionality can be easily determined at the time of bonding. You can In addition, the directional bumps, which are directional protrusion electrodes, can be freely arranged in the IC chip by not electrically contacting the IC. In addition, the directionality can be easily determined by changing the shape of the directional bumps with other bumps. Further, since the directional bumps do not come into contact with the fixed substrate, the mounting can be facilitated and the reliability can be improved. Moreover, the height can be easily changed by using solder for the directional bump material and the general bump material .
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing an IC mounting structure according to an embodiment of the present invention.
FIG. 2 is an explanatory view showing the shape of a directional bump according to an embodiment of the present invention.
FIG. 3 is an explanatory view showing a method of changing the height of the electrolytic bump according to the embodiment of the present invention.
FIG. 4 is an explanatory diagram showing a method for changing the height of an electroless bump according to an embodiment of the present invention.
FIG. 5 is an explanatory view showing a method for manufacturing a bump electrode on a wafer.
FIG. 6 is an explanatory diagram showing a method of mounting a protruding electrode on a circuit board.
FIG. 7 is an X-ray transmission diagram of a conventional IC mounting substrate.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 IC chip 2 Bonding pattern 3 Directional bump 4 Sealing resin 5 Circuit board 6 Bump root shape 7 Bump shape 8 Wafer 9 Bonding pad 10 UBM
11 Plating resist 12 Solder 13 Solder bump 14 IC wafer 15 with protruding electrodes IC chip 16 Flux 17 IC mounting substrate

Claims (4)

In an IC mounting structure in which an IC chip having a connection protruding electrode for connection with a bonding pattern on a circuit board is flip-chip mounted on the circuit board, the directionality of the IC chip is within the connection protrusion electrode forming surface of the IC chip. IC mounting structure characterized with, that the height of the directional protruding electrodes so as not to contact the circuit board and formed lower than the height of the connection protruding electrodes having a directional projection electrodes showing a. 2. The IC mounting structure according to claim 1, wherein the directional protruding electrode indicating the directionality is not in electrical contact with the IC chip. 3. The IC mounting structure according to claim 1, wherein the directional protruding electrode showing the directionality has a root shape different from that of another connecting protruding electrode. Wherein the material of the connection protruding electrodes and the directional projection electrodes, IC mounting structure according to any one of claims 1 to 3, characterized in that formed by soldering.

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