Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Ball or nail head type contact – lead – or bond
Reexamination Certificate
1999-10-29
2002-10-08
Smith, Matthew (Department: 2825)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Ball or nail head type contact, lead, or bond
C257S781000, C257S795000
Reexamination Certificate
active
06462425
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a semiconductor device mounted on an insulated circuit board and a manufacturing method thereof. And more particularly the present invention relates to a semiconductor device having a connecting conductor with a shape limited in a joint portion in view of favorable insulation characteristics and a manufacturing method thereof.
2. Description of the Background Art
FIG. 18
shows a typical example of a conventional semiconductor device mounted on an insulated circuit board. Among processes for forming the semiconductor device as shown in
FIG. 18
by mounting a semiconductor substrate on the insulated circuit board, the following process is known. First, a semiconductor substrate
101
with a connecting underlying metal film
105
on an electrode pad
102
is prepared. Then the semiconductor substrate is aligned with an insulated circuit board
111
having a solder resist
131
and a connecting conductor
113
connected on to a terminal electrode
112
, and the connecting underlying metal film is joined with the connecting conductor. At the mounting of the semiconductor substrate to the insulated circuit board, a gap between insulated circuit board
111
and semiconductor substrate
101
is filled and sealed with resin
114
, after the connecting conductor is fused and joined with the connecting underlying metal film. A surface of the connecting underlying metal film of the semiconductor device mounted according to the above described process is completely covered with connecting conductor
113
that expands in a horizontal direction at the fusion due to its wettability. In other words, there is no region of the connecting underlying metal film not covered by the fused connecting conductor.
An interval between electrode pads has been shrinking with the progress in semiconductor device integration. In the semiconductor device with the above described structure, a favorable insulation characteristic is hard to secure because the connecting conductor is fused and expands onto the surface of the connecting underlying metal film due to its wettability and increases its diameter as shown in
FIG. 18
, thereby reducing the interval between connecting conductors. Even if the connecting conductor does not fuse nor expand as in the case of solid-state welding, the connecting conductor is compressed in the process and increases its diameter, possibly narrowing the interval between the electrode pads, thereby leading to the degradation of insulation characteristic.
SUMMARY OF THE INVENTION
An object of the present invention is, therefore, to provide a semiconductor device having a structure allowing mounting of a semiconductor substrate with a narrow electrode pad interval on an insulated circuit board while securely maintaining a favorable insulation characteristic and a manufacturing method thereof
A semiconductor device according to the present invention includes: an electrode pad formed on a main surface of a semiconductor substrate; a protective insulation film covering the electrode pad and the main surface of the semiconductor substrate; a connecting underlying metal film connected to the electrode pad to cover an opening of the protective insulation film formed in a region corresponding to the electrode pad; a connecting conductor connecting an insulated circuit board and the semiconductor substrate to establish electrical conduction between a terminal electrode formed on the insulated circuit board and the connecting underlying metal film; and non-conductive resin surrounding the connecting conductor and filling a gap between the insulated circuit board and the semiconductor substrate; and the connecting underlying metal film is not covered by the connecting conductor at least in a region of a peripheral portion including an outer peripheral portion.
With the above structure, even when the interval between electrode pads decreases along with the advance of semiconductor device integration, the connecting conductor does not expand in a horizontal direction onto the connecting underlying metal film regardless of wettability.: Thus, the gap between the connecting conductors is securely filled by non-conductive resin. In addition, in the case of solid-state welding, where the connecting conductor does not fuse, the connecting conductor hardly increases its diameter due to the constraint by the non-conductive resin, even when a stress is applied in such a direction that the connecting conductor is compressed in a longitudinal direction thereof. Thus, a favorable insulation characteristic can be maintained. To be specific, both in the case of fusion and the solid-state welding, as the connecting conductor does not cover the peripheral portion of the connecting underlying metal film, it is impossible to increase the diameter of the connecting conductor above a certain level at an end portion thereof. When the diameter of the connecting conductor is decreased only in a portion in contact with the connecting underlying metal film, the shape described above cannot be obtained. The diameter of the connecting conductor must be smaller than a predetermined size along its entire length. In other words, the connecting conductor cannot be joined with the connecting underlying metal film without covering the peripheral portion of the connecting underlying metal film unless the diameter of the connecting conductor is decreased to become smaller than the predetermined size, along its entire length. The above described effect can be obtained as far as an area of the connecting underlying metal film is larger than a sectional area of the end portion of the connecting conductor, for example, when the area of the connecting underlying metal film is made larger so that it contains the diameter of the end portion of the connecting conductor with a sufficient margin to accommodate the shift in alignment of the connecting conductor and the connecting underlying metal film, or when the size of the connecting conductor and the connecting underlying metal film bear different relations.
Therefore even in a highly integrated semiconductor device, insulation failure will not occur in the joint portion mentioned above, whereby improved production yield and reduced manufacturing cost can be obtained. Here, the above described connecting underlying metal film is formed only for the purpose of electrical conduction (joining, or connection prior to the joining) with the connecting conductor, and is not intended for wiring, test pads or the like.
In the semiconductor device described above, preferably a portion of the connecting underlying metal film covered by the connecting conductor is limited to a portion in a region corresponding to the opening formed in the protective insulation film, and a portion surrounding the portion is not covered by the connecting conductor.
With the above described structure, as the joint portion is limited to a portion in a region corresponding to the opening, the semiconductor substrate can be mounted while securely maintaining a favorable insulation characteristic, even in a still more highly integrated semiconductor device.
In addition, in some cases, in the semiconductor device described above, desirably the portion of the connecting underlying metal film covered by the connecting conductor is limited to a portion of the connecting underlying metal film including the region corresponding to the opening formed in the protective insulation film, and a portion surrounding the portion is not covered by the connecting conductor.
Depending on the use of the semiconductor device, in some cases a large joint portion is preferable. In such case, with the above described structure of joint portion, the area of joint portion can be made larger while securely maintaining a favorable insulation characteristic.
In the semiconductor device described above, desirably the region of the connecting underlying metal film corresponding to the opening is depressed to a side of the semiconductor substrate, and a step is
Harada Kozo
Iwasaki Toshihiro
Kimura Michitaka
Yamada Satoshi
Yasunaga Masatoshi
Malsawma Lex H.
McDermott & Will & Emery
Mitsubishi Denki & Kabushiki Kaisha
Smith Matthew
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