JP2778744B2 - IC electrode forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial application field) The present invention relates to a method for forming an electrode of an IC having a bump electrode (bump).

(Prior Art) In mounting IC components, face-down bonding has come to be used in accordance with a demand for miniaturization and low cost. For this face-down bonding, an IC provided with a bump electrode called a bump is generally used.

FIG. 2 shows an example of an IC. This IC1 is an IC
Au is placed on the electrode portion 3 made of Al (aluminum) of the main body 2.
(Protruded electrode 4) formed by raising (gold) by 15 to 30 μm by wet plating method.
(Gold), an adhesion reinforcing layer 5 of Cr (chromium), Ti (titanium), etc. and Cu (copper), Pb (lead), Pt (platinum)
Is formed by a sputtering method.

Then, as shown in FIG. 3 (a), the IC1 is placed on a wiring board 8 having good flatness, such as glass or ceramic, on which a wiring pattern 7 having connection electrodes with the IC1 is formed. As shown in FIG.
And pressing each of the bump electrodes 4 with the adhesive 9
Alternatively, they are fixed by mechanical means and face-down bonding is performed.

In the face-down bonding as described above, it is important that each protruding electrode of the IC and the connection electrode are electrically and mechanically connected, and that the IC can be quickly replaced at the time of repair.

However, the height of each protruding electrode of the IC varies somewhat during its formation, which reduces the reliability of connection.
In addition, there is a problem that both the bonding method and the mechanical fixing method have poor repairability.

Therefore, as a method of solving these problems, a soft low-melting metal is fused on each protruding electrode of the IC by immersion and then face-down bonded (LMC
Law) has been proposed. According to this LMC method, the low melting point metal absorbs the variation in the height of each protruding electrode, and checks the electrical characteristics before fixing the IC and the wiring board. It has the advantage that it can be replaced.

However, also in the above-mentioned LMC method, when the electrode pitch becomes fine, variation in the amount of the low melting point metal fused to each protruding electrode becomes a problem. That is, if the amount of the low melting point metal is large,
When the IC and the wiring board are pressed against each other, the low-melting-point metal protrudes, causing a short circuit between adjacent electrodes, and if the amount is too small, the connection becomes unstable.

(Problems to be Solved by the Invention) As described above, in the LMC method, it is important to stably attach an appropriate amount of a low melting point metal to each protruding electrode.

An object of the present invention is to stably bond an appropriate amount of a low-melting-point metal to each protruding electrode of an IC.

[Configuration of the invention]

(Means for Solving the Problems) The present invention is a method for forming an electrode of an IC in which a low-melting-point metal is bonded on a protruding electrode provided on the IC, and uses a plated electrode plate. This plated electrode plate is formed by forming a conductive film on an insulating plate, forming an insulating film on the conductive film, and placing the conductive film in a position of the insulating film corresponding to the projecting electrode of the IC. It is exposed as. Then, the low-melting point metal is plated on the exposed electrode portion of the plated electrode plate to form a plated piece, and the protruding electrode of the IC is joined to the plated piece by pressing.

(Function) In the present invention, by forming a plating piece by plating a low melting point metal on each electrode portion of the plating electrode plate, the plating piece can be formed stably in a fixed state, and this plating piece can be The low-melting-point metal in each of the projecting electrodes can be made uniform by being pressed against the projecting electrodes and joining the low-melting-point metal to each of the projecting electrodes.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

As shown in FIGS. 1 (a ₁ ) and (a ₂ ), a conductive film 12 of Cr (chromium), ITO, or the like is formed on an insulating plate 11 made of glass or the like by a sputtering method, evaporation, or the like. Si on
An insulating film 13 such as N (silicon nitride) is formed by a CVD method, a sputtering method, or the like. Then, the insulating film 13 is subjected to an etching process of resist application, exposure, etching, and resist stripping to partially remove the insulating film 13 at a predetermined position corresponding to each of the bump electrodes 4 of the IC 1. The conductive film 12 in this portion is exposed and formed as an electrode portion 14, and a plated electrode plate 15 is formed.

Next, the plated electrode plate 15 was coated with In (indium), Sn
Each of the exposed electrode portions 14 of the plated electrode plate 15 is immersed in a plating solution of a soft low-melting metal such as (tin), Pb (lead), solder, or the like, as shown in FIG. Only a few μ on top
A low-melting metal having a thickness of, for example, 5 to 10 μm is plated with a thick film to form a plating piece 16.

In this case, the metal of the conductive film 12 on the insulating plate 11 and the plated piece 16 of the low melting point metal are formed using a combination of materials that can be easily separated. For example, when Cr is used as the metal of the conductive film 12, In is used as the low melting point metal. Then, Sn electrolytic plating is further plated on the In plating piece 16 to an appropriate thickness, for example, 3 μm. This is because the alloy becomes an In / Sn alloy when the face-down bonding is finally performed by heating, and the reliability of the bonding force is improved. Each plating piece 16 obtained in this manner is separated for each electrode portion 14, and has a stable shape and dimensions.

Next, as shown in FIG.
IC1 is arranged on a plating electrode plate 15 provided with a plating piece 16 thereon. As described above, this IC1 is obtained by forming each protruding electrode 4 by a plating method. At the same time, align each protruding electrode 4 of IC1
Each protruding electrode 4 is pressed on each plating piece 16. in this case,
Align each plated piece 16 with each protruding electrode 4 at the same time
It may be heated to about 200 ° C. and pressed.

Then, as shown in FIG. 1 (d), the plating pieces 16 are transferred to the respective projecting electrodes 4 of the IC 1 and, thereby, a low melting point metal is joined onto the respective projecting electrodes 4. In this manner, the low-melting-point metal can be stably fused to each protruding electrode 4 of the IC 1 without variation. That is, the effect is far greater than that of the method of fusing a low melting point metal by the immersion method. As a result, it is possible to stably perform face-down bonding such as chip-on-glass, and to further reduce the distance (pitch) between electrodes.

In practicing the present invention, as shown in FIG. 1 (a ₂ ), by forming electrode portions 14 corresponding to a large number of ICs 1 on one plated electrode plate 15, several tens of I c
The plating piece 16 can be transferred to each of the projecting electrodes 4.

In the above embodiment, the insulating film 13 of the plated electrode plate 15
Although SiN or the like is used, the insulating film 13 may be basically any type, and may be the resist itself.

Further, the present invention can be applied not only to face-down bonding to a wiring board but also to inner lead bonding in tape automated bonding (TAB).

That is, bonding at a low temperature can be stably performed, and as a result, the tape itself can use inexpensive polyester.

〔The invention's effect〕

According to the present invention, a low-melting-point metal can be stably bonded to each projecting electrode of an IC in an appropriate amount without variation, and reliable connection can be performed even when the electrode pitch is fine.

[Brief description of the drawings]

Explanatory view showing an embodiment of a method of Figure 1 _{(a 1) (a 2)} (b) (c) (d) the present invention, FIG. 2 cross-sectional view of part of IC,
FIGS. 3A and 3B are explanatory views showing a face-down bonding state. DESCRIPTION OF SYMBOLS 1 ... IC, 4 ... Protrusion electrode, 11 ... Insulating plate, 12 ... Conducting film, 13 ... Insulating film, 14 ... Electrode part, 15 ... Plating electrode plate, 16 ... Plating piece.

Claims (1)

(57) [Claims] 1. A method for forming an electrode of an IC, comprising joining a low-melting metal to a protruding electrode provided on the IC, comprising: forming a conductive film on an insulating plate; and forming an insulating film on the conductive film. And using a plated electrode plate having the conductive film exposed as an electrode portion at a position corresponding to the projecting electrode of the IC on the insulating film, and plating the low melting point metal on the exposed electrode portion of the plated electrode plate. A method for forming an electrode of an IC, comprising: forming a plated piece by pressing the projecting electrode of the IC;