Metal working – Method of mechanical manufacture – Electrical device making
Reexamination Certificate
1999-05-13
2001-04-10
Young, Lee (Department: 3729)
Metal working
Method of mechanical manufacture
Electrical device making
C029S740000, C029S840000, C156S073600, C257S778000, C257S780000, C257S781000, C257S782000, C257S783000
Reexamination Certificate
active
06212768
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a flip chip mounting method and apparatus therefor for mounting a semiconductor element, such as LSI or so forth on a circuit board.
2. Description of the Related Art
As a method for mounting a bare chip, there has been proposed a pressure welding method. The pressure welding method does not require a supply of a bonding material, such as solder or conductive resin or the like. Electrical connection of an electrode of an LSI and a pad on a circuit board is established only by mechanical contact by shrinking force of a seal resin filled between the LSI and the circuit board.
Process steps of pressure welding are as follow. At first, a seal resin is supplied to a mounting position on the circuit board, where the LSI is to be mounted. Next, on the mounting portion, the LSI is mounted and pressurized. Subsequently, under this condition, heat or light is applied to cure the sealing resin to connect the electrode of the LSI and the pad on the circuit board.
A fabrication process of the semiconductor device disclosed in Japanese Unexamined Patent Publication No. Showa 63-151033 is shown in FIG.
4
.
At first, as shown in
FIG. 4A
, a thermosetting resin
13
is applied on a surface having a conductor wiring
12
of a wiring board
11
.
Next, as shown in
FIG. 4B
, an LSI chip
14
is pressurized onto a wiring board
11
by a pulse heating tool
16
so that a projection electrode
15
on LSI chip
14
and a conductor wire
12
, on wiring board
11
match with each other. Upon pressurizing the LSI chip
14
, the thermosetting resin
13
on the conductive wiring
12
are pushed out to the circumference. Then, the projection electrode
15
and the conductive wire
12
are electrically contacted. In this condition, by supplying power to the pulse heating tool
16
, the pulse heating tool
16
is heated to cure the thermosetting resin
13
.
Subsequently, as shown in
FIG. 4C
, after a while upon termination of heating of the pulse heating tool
16
, pressurizing force is released when the temperature is lowered to be lower than or equal to a predetermined value to fix the LSI chip
14
on the wiring board
11
and thus to establish electrical connection between the projection electrode
15
of the LSI chip
14
and the conductive wire
12
.
In Japanese Unexamined Patent Publication No. Heisei 5-152359, there has been disclosed a potting apparatus which applies micro vibration to a protective resin during sealing or after sealing to get bubbles generated in the protective resin out or to prevent generation of bubbles initially and thus penetrates the protective resin into a fine gap.
In Japanese Unexamined Patent Publication No. Heisei 8-153752, there has been disclosed a following flip chip mounting method. At first, in a group of an insulation layer provided with a mounting pad of the circuit board, a sealing resin is filled. Next, in this condition, bubble in the circumference of the mounting pas is removed by heating and vacuum defoaming or application of ultrasonic vibration. Subsequently, an amount of the sealing resin is supplied in overlapping manner, and the semiconductor element is mounted.
In the pressure welding method set forth above, since the seal resin is filled between the LSI and the circuit board with flaring by the LSI, the protective resin is difficult to penetrate into the via hole or recessed portion of a solder resist formed on the circumference of the mounting pad. Namely, when flaring speed of the sealing resin is high or when the via hole or the recessed portion is small, the sealing resin flows out without filing into the via or recessed portion to permit residual air within the via or the recessed portion. In the pressure welding method, after flaring the seal resin, the seal resin is heated and cured. The residual air may expand during the process steps set forth above, a gap (hereinafter referred to as “void”) is formed between the LSI and the circuit board. The void can cause lower reliability of electrical connection of the LSI and the circuit board due to lowering of fitting force of the LSi and the circuit board and lowering of shrinking force of the sealing resin and so forth. Therefore, it is required to completely avoid the void.
In the potting apparatus disclosed in Japanese Unexamined Patent Publication No. Heisei 5-152359, admixing of the bubble in the protective resin supplied from the nozzle is avoided. Avoiding the bubble residing in the fine groove of the electrode portion of the circuit board is difficult. On the other hand, upon mounting of the LSI on the circuit board, bubble penetrating into the protective resin from a bump can be avoided.
In the flip chip mounting method disclosed in Japanese Unexamined Patent Publication No. Heisei 8-153752, a vacuum drawing process is required to take a long period in operation. On the other hand, when the semiconductor element is mounted on the circuit board, penetration of bubble into the seal resin cannot be avoided.
SUMMARY OF THE INVENTION
The present invention has been worked out for improving the conventional technical problem set forth above. Therefore, it is an object of the present invention to provide a flip chip mounting method and the apparatus therefor having high reliability in electrical connection between a semiconductor and a circuit board so as to avoid voids in a via formed in a circuit board or in a recessed portion of a solder resist formed in a circumference of a mounding pad.
According to the first aspect of the present invention, a flip chip mounting method for connecting a semiconductor element and a circuit board, comprises:
a step of supplying a thermosetting type resin to a mounting portion on the circuit board;
a step of mounting an electrode of the semiconductor element on an electrode of the circuit board under a condition where the semiconductor element is heated by a heating tool;
a step of applying a high frequency vibration on the heating tool or the circuit board in the condition where the electrode of the semiconductor element is mounted on the electrode of the circuit board; and
a step of heating and pressurizing the thermosetting type resin by the heating tool.
In the preferred process, connection between the electrode of the semiconductor element and the electrode of the circuit board may be performed by metal diffusion. The thermosetting type resin may be a quick set type resin. The bump electrode formed in the semiconductor element may have a cone shaped tail.
According to the second aspect of the present invention, a flip chip mounting apparatus for connecting a semiconductor element and a circuit board, comprising:
means for supplying a thermosetting type resin to a mounting portion on the circuit board;
means for mounting an electrode of the semiconductor element on an electrode of the circuit board under a condition where the semiconductor element is heated by a heating tool;
means for applying a high frequency vibration on the heating tool or the circuit board in the condition where the electrode of the semiconductor element is mounted on the electrode of the circuit board; and
means for heating and pressurizing the thermosetting type resin by the heating tool.
REFERENCES:
patent: 5814890 (1998-09-01), Iwasaki
patent: 5821625 (1998-10-01), Yoshida
patent: 5821627 (1998-10-01), Mori et al.
patent: 5829125 (1998-11-01), Fujimoto et al.
patent: 5850677 (1998-12-01), Ryoichi
patent: 5861678 (1999-01-01), Schrock
patent: 5866950 (1999-02-01), Iwasaki et al.
patent: 57-4223 (1955-06-01), None
patent: 63-151033 (1988-06-01), None
patent: 5-152359 (1993-06-01), None
patent: 8-153752 (1996-06-01), None
Hutchins, Wheeler & Dittmar
Kim Paul D.
NEC Corporation
Young Lee
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