Electricity: measuring and testing – Magnetic – Magnetic field detection devices
Reexamination Certificate
2001-10-12
2003-05-13
Oda, Christine (Department: 2858)
Electricity: measuring and testing
Magnetic
Magnetic field detection devices
C324S525000
Reexamination Certificate
active
06563313
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electronic device and a manufacturing method thereof. Particularly, the invention is useful in inspecting a bonding connection state when a circuit element such as a magnetic sensor built-in chip is connected onto a circuit wiring board by bonding.
2. Description of the Prior Art
As an electronic device, an electronic compass having a magnetic sensor circuit therein will be described hereinbelow. The case where a Pch MOS transistor and an Nch MOS transistor are used as switching devices or switching elements will be explained (the phrases “switching elements” and “switching devices” are used interchangeably herein).
FIG. 8
is a schematic diagram of wiring patterns on the surface of a circuit wiring board, on which a conventional magnetic sensor circuit is formed. On the circuit wiring board, in a Pch MOS transistor mounting portion and an Nch MOS transistor mounting portion, wiring patterns Pa
1
and Pa
2
for connecting lead terminals of the respective MOS transistors are formed.
The wiring pattern Pa
1
is a pattern for connecting two terminals, which are connected in parallel with each other, to drain terminals in the respective MOS transistors and for connecting them to +FL terminals of X-axis [sensors] sensor
10
and Y-axis sensor
20
. The wiring pattern Pa
2
is a pattern for connecting two terminals, which are connected in parallel with each other, to the drain terminals in the respective MOS transistors and for connecting them to −FL terminals of the X-axis sensor
10
and Y-axis sensor
20
.
That is, the wiring pattern Pa
1
is the wiring pattern for connecting the +FL terminal of the X-axis sensor
10
and the +FL terminal of a Y-axis sensor
20
to the drain terminals formed in the respective MOS transistors. The wiring pattern Pa
2
is the wiring pattern for connecting the −FL terminal of the X-axis sensor
10
and the −FL terminal of the Y-axis sensor
20
to the drain terminals formed in the respective MOS transistors. Consequently, the portion between the terminals (+FL) and (−FL) of the X-axis sensor
10
and the portion between the terminals (+FL) and (−FL) of the Y-axis sensor
20
are connected in parallel with each other.
FIG. 9
shows the detail circuit of FIG.
8
and the configuration of a circuit for measuring a flip coil resistance. The X-axis sensor
10
and the Y-axis sensor
20
are magnetic sensors. The sensor
10
comprises a flip coil (FL)
11
and resistors
12
,
13
,
14
, and
15
, in which magnetic resistor elements are connected as a Wheatstone bridge. The sensor
20
comprises an FL
21
and resistors
22
,
23
,
24
, and
25
, in which magnetic resistor elements are connected as a Wheatstone bridge. An earth terminal
16
is connected between the resistors
14
and
15
. An earth terminal
26
is connected between the resistors
24
and
25
.
A voltage obtained by detecting a magnetic field in the X-axial direction is outputted from CHxH derived between the resistors
13
and
15
and CHxL derived between the resistors
12
and
14
and is then converted into a digital value by an A/D converter
30
in a subsequent step. On the other hand, a voltage obtained by detecting a magnetic field in the Y-axial direction is outputted from CHyH derived between the resistors
23
and
25
and CHyL derived between the resistors
22
and
24
and is then converted into a digital value by the A/D converter
30
in the subsequent step.
The A/D converter
30
comprises: Nch MOS transistors
31
and
32
as switching elements for operating the X-axis sensor
10
and the Y-axis sensor
20
; a constant-current power supply
33
connected to the Nch MOS transistors
31
and
32
; and an earth terminal
34
connected to the other terminal of the constant-current power supply
33
. The Nch MOS transistor
31
is connected between the resistors
12
and
13
and the Nch MOS transistor
32
is connected between the resistors
22
and
23
.
Furthermore, on the circuit wiring board, Nch MOS transistor mounting patterns (hereinbelow, referred to as “mounting patterns”)
41
,
42
, . . . ,
48
and Pch MOS transistor mounting patterns (hereinbelow, referred to as “mounting patterns”)
51
,
51
, . . . ,
58
are formed. Particularly, the mounting patterns
47
and
48
are connected to the patterns
53
and
54
, respectively, and they are connected to the +FL terminals of the X-axis sensor
10
and the Y-axis sensor
20
. Namely, it is the wiring pattern Pa
1
described in FIG.
8
. The mounting patterns
45
and
46
are connected to the patterns
51
and
52
, respectively, and they are connected to the −FL terminals of the X-axis sensor
10
and the Y-axis sensor
20
. That is, it is the wiring pattern Pa
2
explained in FIG.
8
. Thus, the flip coil
11
is connected in parallel to the flip coil
12
.
The mounting patterns
41
and
43
are connected to an earth terminal
49
. A signal N
2
is supplied to the mounting pattern
42
. A signal N
1
is supplied to the mounting pattern
44
. The mounting patterns
55
and
57
are connected in parallel to a moiety comprising a capacitor
71
connected to an earth terminal
70
and a direct-current power supply
73
connected to a resistor
72
. The direct-current power supply
73
is connected to an earth terminal
74
.
A signal P
2
is supplied to the mounting pattern
56
and a signal P
1
is supplied to the mounting pattern
58
. The signals P
1
and P
2
drive transistors in a Pch MOS transistor
80
, which will be described later. The signals N
1
and N
2
drive transistors in an Nch MOS transistor
90
, which will be described later.
In a case where the resistance of each of the flip coils
11
and
12
is measured, since the resistance of each of the flip coils
11
and
12
is as small as several ohms, contact resistances
60
and
62
with connect pins of jigs and wiring resistances
61
and
63
between the connect pins of the jigs and a measuring device cannot be ignored. In consideration of them, the contact resistance
60
, wiring resistance
61
, contact resistance
62
, wiring resistance
63
, and constant-current power supply
64
are connected in series. A voltmeter
65
is connected in parallel with the constant-current power supply
64
. The contact resistances
60
and
62
are connected to the mounting patterns
46
and
54
, respectively. The resistances of the flip coils
11
and
20
are obtained on the basis of measurement by the voltmeter
65
. Thus, the bonding connection state is inspected.
FIG. 10
shows a case where MOS transistors are mounted on the circuit constructional diagram shown in FIG.
9
. As shown in the diagram, the package of the Pch MOS transistor
80
is SSOT. Lead terminals of the transistor are connected to the mounting patterns
51
to
58
by soldering, so that the transistor is mounted on the circuit wiring board. Lead terminals of the Nch MOS transistor
90
are connected to the mounting patterns
41
to
48
by soldering, so that the transistor is mounted on the circuit wiring board.
Lead terminals
81
and
82
of the Pch MOS transistor
80
are connected in parallel to a drain terminal of a switching element
80
a
. Terminals
83
and
84
of the Pch MOS transistor
80
are connected in parallel to a drain terminal of a switching element
80
b
. Terminal
91
and
92
of the Nch MOS transistor
90
are connected in parallel to a drain terminal of a switching element
90
a
. Terminals
93
and
94
of the Nch MOS transistor
90
are connected in parallel to a drain terminal of the switching element
90
b.
The operation of the magnetic sensor circuit with the above-mentioned configuration will now be described.
FIG. 11
is an explanatory diagram of the operation of the magnetic sensor circuit.
FIG. 11A
is a timing chart.
FIG. 11B
is a V-B graph. First, a control unit (not shown) sets the signal P
1
to a low level L and sets the signal N
2
to a high level H to operate the flip coils
11
an
Adams & Wilks
Lair Donald M
Oda Christine
Seiko Instruments Inc.
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