Semiconductor device manufacturing: process – Making passive device – Resistor
Reexamination Certificate
1999-01-11
2001-05-29
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making passive device
Resistor
C338S203000, C338S307000, C338S308000
Reexamination Certificate
active
06238992
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a method for manufacturing resistors generally used in electronic circuits.
BACKGROUND OF THE INVENTION
There is an increasing demand for rectangular chip resistors with highly accurate resistance to eliminate adjustment for electronic circuits as the size of electronic equipment continues to shrink. In particular, since the allowance required for the resistance of rectangular chip resistors is in the range of ±0.5% to ±0.1%, the demand for rectangular chip resistors made of thin metal film resistance, in which precise resistance is achieved more easily, is overtaking demand for conventional rectangular chip resistors which are constituted of thick film resistance made of grazed material.
Furthermore, the demand for multiple chip resistors, which are packages of two or more rectangular chip resistors, is increasing as a result of the need to increase the mounting density of electronic components on circuit boards. In the field of multiple chip resistors, the demand for thin film multiple chip resistors with a thin metal resistance (hereafter referred to as “resistors”) is also overtaking demand for conventional multiple chip resistors with thick film resistance.
A conventional method for manufacturing resistors is explained below with reference to FIG.
4
.
First, a substrate
21
made of 96% aluminum is supplied (Process A). The substrate
21
has an a surface a horizontal division groove (slit)
22
and vertical division grooves (slit)
23
at constant intervals so as to configure two or more resistance elements. Through holes
24
are provided in the horizontal division groove
22
. A thin film top electrode layer
25
, typically of Au, is formed on the top face of the substrate
21
across the horizontal division grooves
22
and at both sides of the through holes
24
(Process B).
Then, a thin film bottom electrode layer (not illustrated), typically of Au, is formed on the bottom face of the substrate
21
at a position corresponding to the top electrode layer
25
(Process C).
A thin film resistance layer
26
typically of NiCr is formed over the entire top face of the substrate
21
(Process D).
The thin film resistance layer
26
is then etched using photolithography, so as to leave a portion of the thin film resistance layer
26
connected to the top electrode layer
25
to form a pattern of a resistance
27
(Process E).
The resistance is corrected, by means such as a YAG laser, to adjust the resistance
27
to a specified value (Process F).
A resin paste, made typically of epoxy resin, is printed to completely cover an adjusted resistance
28
, and then cured to form a protective layer
29
(Process G).
The substrate
21
is then primarily cut along the horizontal division groove
22
(Process H). A thin film side electrode layer
31
made of Ni system is formed on a cut face of the primary divided substrate
30
by means such as sputtering (Process I). Here, the side electrode layer
31
is formed only on the cut face of the primary divided substrate
30
. It is not necessary to form the side electrode layer
31
on a side face of the through hole
24
, which separates adjacent electrodes. Accordingly, a resist is applied to the side face of the through holes
24
before forming the side electrode layer
31
, and the resist is removed after sputtering a thin Ni film by means such as the lift-off method in order to form the side electrode layer
31
only on the cut face.
Next, the substrate, after the side electrode layer is formed, is cut along the vertical division grooves
23
(secondary division) to make substrate pieces (Process J).
Lastly, an electrode plating layer
33
is formed on the entire face of the top electrode layer
25
, bottom electrode layer, and side electrode layer
31
of a substrate piece
32
(Process K).
In the process of applying resist to the through holes
24
in the prior art, however, the resist may not be fully applied to the side face of the through holes
24
due to deviations. As a result, electrode material may attach to a part of the side face of the through holes
24
when forming a side electrode layer
31
, as shown in
FIG. 5
, creating an electrode material spill
38
. This causes short circuits between electrodes or solder bridges during soldering.
SUMMARY OF THE INVENTION
A method for manufacturing resistors of the present invention comprises the steps of forming more than one top electrode layer on a top face of a rectangular substrate, forming at least one resistance layer so as to electrically connect with said more than one top electrode layer, forming a protective layer so as to cover at least said resistance layer, forming a side electrode layer on a side face of said substrate so as to electrically connect with said top electrode layer, and separating said adjacent top electrode layers by removing a part of said side electrode layer and said substrate.
In this manufacturing method, a part of the substrate is removed after forming the side electrode layer so as to create a concavity, which separates the top electrode layers, between adjacent electrodes. Accordingly, the resistor manufacturing method of the present invention eliminates the possibility of attachment of an electrode material to the concavity, enabling to prevent short circuits between adjacent electrode terminals and the occurrence of solder bridges during soldering.
REFERENCES:
patent: 5334968 (1994-08-01), Negoro
patent: 5379190 (1995-01-01), Hanamura et al.
patent: 5850171 (1998-12-01), Lin et al.
patent: 6023217 (2000-02-01), Yamada et al.
patent: 4-357801 (1992-12-01), None
Matsushita Electric - Industrial Co., Ltd.
Niebling John F.
Ratner & Prestia
Simkovlc Viktor
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