JP3289963B2 - Electronic component sealing structure - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing structure of an electronic component which is suitably used as an acceleration sensor for detecting an impact at the time of a collision of an automobile body.

[0002]

2. Description of the Related Art An acceleration sensor is suitably used as a detecting means for detecting an impact at the time of a collision for operating an airbag device for protecting a driver from the impact. The acceleration sensor is an integrated circuit (IC)
And a hybrid integrated circuit (HIC) on which a plurality of electronic components such as a circuit is mounted. The control device for the airbag monitors, in the acceleration sensor, a change in the electric resistance value of the strain gauge due to the strain generated in the mass due to the deceleration at the time of the collision, and when the electric resistance value reaches a predetermined level. In addition, the explosive for inflating the airbag is ignited, and the inflated bag protects the driver from a collision impact.

FIG. 4 is a sectional view showing a sealing structure of a conventional electronic component 2 used as an acceleration sensor or the like. One surface 1a of wiring board 1 realized by ceramic
In this example, a conductor pattern 1c is formed by thick-film printing, and a terminal 3 of an electronic component 2 such as a strain gauge type acceleration sensor and its amplifier circuit and a lead 4 are soldered on the conductor pattern 1c. Is done. One surface 1a of wiring board 1
The lead 4 soldered to the substrate is inserted into an insertion hole 6 formed in a metal support substrate 5, and the other surface 1 b of the wiring substrate 1 is bonded to the support substrate 5 via an adhesive layer 7. You. A metal lid 8 is fixed to the support substrate 5 by welding so as to cover the wiring substrate 1 on which the electronic components 2 are mounted. When the lid 8 is fixed to the support substrate 5, the electronic component 2 is so-called hymetically sealed. That is, the lead 4
Is filled with nitrogen gas so that moisture does not enter the inside of the lid 8 from the insertion hole 6 into which the is inserted, and the insertion hole 6 is sealed with glass 9.

As a method of protecting the electronic component 2 from moisture, a so-called molding process of covering the entire wiring board 1 on which the electronic component 2 is mounted with a resin may be mentioned. In the case where a change in the electric resistance value due to the strain applied to the electronic component 2 is detected, or when it is necessary to communicate the inside of the lid 8 with the outside as in a pressure sensor or the like, the molding process can It is not suitable because it is no longer affected by.

[0005]

As described above, the airbag apparatus operates in response to a change in the electric resistance value of the strain gauge, which is the electronic component 2, so that the initial setting of the electric resistance value requires high precision. Need adjustment. Therefore, the wiring board 1
On one surface 1a, a trimming resistor for fine adjustment of the resistance value is formed by printing. Fine adjustment of the resistance value is performed after the wiring substrate 1 on which the electronic component 2 is fixed is adhered to the support substrate 5. However, the welding of the lid 8 performed after the trimming of the resistance value causes high heat to be applied to the electronic component 2, which causes distortion due to heat and changes the electric resistance value. Therefore, an offset occurs in which the electric resistance value deviates from the standard value, resulting in a problem that the yield is reduced.

In addition, since the soldering process of the electronic component 2 and the welding process of the lid 8 cannot be performed at once,
There is a problem that it takes time to assemble.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electronic component sealing structure in which the characteristics of electronic components have less variation and the number of assembly steps can be reduced.

[0008]

SUMMARY OF THE INVENTION The present invention provides an electronic component,
In the multilayer wiring board on which the electronic component is mounted, a lid is provided so as to hermetically cover the electronic component mounted on one surface of the wiring board, and a conductor pattern connected to a terminal of the electronic component is provided. Lead to the other surface of the wiring board,
An electronic component sealing structure, wherein an adjusting means for adjusting characteristics of the electronic component is connected to the conductor pattern led out to the other surface.

The lid of the present invention has a coefficient of thermal expansion substantially equal to that of the wiring board, and is connected to a conductor pattern formed around the electronic component by soldering separately from the conductor pattern. It is characterized by being performed.

[0010]

According to the present invention, a wiring board on which an electronic component is mounted comprises a multilayer wiring board in which a conductor pattern formed on one surface of the wiring board extends to the other surface, and the terminals of the electronic component are Are connected to a conductor pattern formed on one surface of the wiring board. Adjustment means for adjusting the characteristics of the electronic component is connected to the conductor pattern formed on the other surface of the wiring board, and a cover is provided so as to hermetically cover the electronic component connected to one surface of the wiring board. Can be

Therefore, even after the electronic component is sealed by the lid, the characteristics of the electronic component can be adjusted by the adjusting means, and the variation in the characteristics of the electronic component can be reduced. The yield can be improved. Further, the wiring board is formed of a multilayer wiring board, and therefore, the electronic component can be hermetically sealed by the lid.

Preferably, a lid having a thermal expansion coefficient substantially equal to that of the wiring board is connected to a conductor pattern formed around the electronic component separately from the conductor pattern in the same manner as the electronic component. That is, they are connected by soldering by the reflow method. Therefore, since the electronic component and the lid can be soldered simultaneously, the number of steps can be reduced.

[0013]

FIG. 1 shows an electronic component 1 according to an embodiment of the present invention.
4 is an exploded perspective view showing a sealing structure of FIG. Wiring board 10
Consists of a multilayer wiring board made of an electrically insulating material such as ceramic, and has a conductor pattern 11a for soldering a lid 16 on one surface 10a of the wiring board 10.
And a conductor pattern 1 for soldering a plurality of electronic components 14 such as a strain gauge type acceleration sensor and its amplifier circuit.
1b is formed by thick film printing. On the other surface 10b, lands 12 for soldering the plurality of leads 13 are formed by thick film printing. Conductor patterns 11a, 11b and land 1
The formation with 2 is performed by, for example, printing a printing ink called a paste in which a fine powder of gold, silver, palladium or the like is mixed with a vitreous binder in the form of a wiring pattern and baking it.

Conductor pattern 1 formed to surround electronic component 14 fixed to one surface 10a of wiring board 10
A cover 16 for hermetically covering the electronic component 14 mounted on the wiring board 10 is soldered to the conductor pattern 1a.
The terminal 15 of the electronic component 14 is soldered to 1b. Also, a lead 1 for connecting the electronic component 14 to be sealed to the wiring board of the air bag control device is provided on a land 12 formed on the other surface 10b of the wiring board 10.
The third end 13a is soldered.

The lid 16 includes a lid 17 for covering the electronic component 14 and an outer edge 18 formed at an end 17a of the lid 17, and the outer edge 18 has the sealed electronic component 14 attached thereto. An insertion hole 19 through which a screw for fixing to a support substrate or the like is inserted is formed. The lid 16 is used for the electronic component 1.
4 and the leads 13 are simultaneously soldered by a reflow method.

FIG. 2 is a sectional view showing a sealing structure of the electronic component 14 when the wiring board 10 has a two-layer structure, for example. The above-described wiring board 10 has a two-layer structure including a wiring board 20 and a wiring board 21. Wiring board 20
The conductor pattern 23a formed on the surface 20a on the opposite side to the wiring board 21 is passed through the inside of the wiring board 20 and is led out to the contact surface 22 between the wiring board 20 and the wiring board 21,
Further, the wiring board 21 extends along the wiring board 21 and is led out from the outer peripheral edge to a surface 21 a of the wiring board 21 on the side opposite to the wiring board 20. As described above, since the conductor pattern 23a is not led out from the surface 20a of the wiring board 20 to the surface 21a of the wiring board 21 by using a through-hole or the like but is led out using a two-layer structure, the electronic component 14 is sealed. At times, the tightness of the seal can be increased.

The terminal 15 of the electronic component 14 is soldered to the conductor pattern 23 a on the surface 20 a of the wiring board 20 by solder 24. Also, the surface 21a of the wiring board 21
The upper conductor pattern 23b has, for example, the electronic component 1
4, a trimming resistor 25 is formed as an adjusting means for finely adjusting the resistance value. On the surface 20a of the wiring board 20,
A conductor pattern 11a is formed so as to surround the electronic component 14, and the outer edge 18 of the lid 16 is soldered to the conductor pattern 11a with solder 24, whereby the lid 16 hermetically seals the electronic component 14.

FIG. 3 is a perspective view of the other surface 10b side of the wiring board 10 for explaining the trimming resistor 25.
On the conductor pattern 23b formed on the other surface 10b of the wiring board 10, for example, a trimming resistor 25 for adjusting the offset resistance value of the strain gauge is formed by printing. Therefore, the resistance value can be adjusted even after the electronic component 14 is sealed with the lid 16. The end 13a of the lead 13 is soldered to the land 12 formed on the other surface 10b of the wiring board 10.

Solder 24 is printed on conductor patterns 11a and 23a and lands 12 on one surface 10a and the other surface 10b of wiring substrate 10 composed of multilayer wiring substrates 20 and 21. Each of the lands 12 has a lead 1
3 are brought into contact with each other, and the conductor pattern 23
The terminal 15 of the electronic component 14 is in contact with a. Further, a conductor pattern 11a formed so as to surround the electronic component 14
, The outer edge 18 of the lid 16 is in contact.

When the respective parts come into contact, the solder 24
Heat is applied and cooled to a temperature at which is dissolved. By this operation, each component is soldered on the contacted conductor pattern, and the electronic component 14 is
Sealed. At this time, the inside of the lid 16 is filled with nitrogen gas and sealed so that the electronic component 14 is not affected by moisture.

Subsequently, fine adjustment of the resistance value of the trimming resistor 25 printed on the conductor pattern 23b formed on the other surface 10b of the wiring board 10 is performed. The trimming resistor 25 is formed to have a lower resistance value, and the resistance value is adjusted by trimming the trimming resistor 25 with a laser beam or the like at the time of adjustment.

As described above, according to this embodiment, the conductor pattern 23a formed on one surface 10a of the wiring board 10 is formed.
Is passed through the inside of the wiring board 10 composed of the multilayer wiring boards 20 and 21 and is led out to the other surface 10b of the board 10, so that the electronic component 14 can be hermetically sealed. Further, since the trimming resistor 25 is formed outside the electronic component 14 sealed with the lid 16 and the wiring board 10,
Even after the electronic component 14 is sealed, fine adjustment of the resistance value by the trimming resistor 25 can be performed. Therefore, variations in the characteristics of the electronic component 14 can be reduced, and the yield can be improved.

Further, according to the present embodiment, since the lid 16 can be soldered simultaneously with the soldering step of the electronic component 14, the number of assembling steps can be reduced.

The lid 16 used in this embodiment is
In order to prevent the soldering between the lid 16 and the wiring board 10 from being damaged by the influence of heat and to reduce the airtightness of the electronic component 14, a so-called 42 having a thermal expansion coefficient substantially equal to that of the wiring board 10 is used. Although an iron-based material such as an alloy or a 45 alloy is used, another material having a suitable soldering property having a suitable thermal expansion coefficient may be used.

In this embodiment, an example in which a two-layer multilayer wiring board is used as the wiring board 10 has been described.
The use of a multi-layer wiring board having more than two layers is also included in the scope of the present embodiment. Furthermore, the present invention can be applied to, for example, a pressure sensor and the like in addition to the acceleration sensor.

[0026]

As described above, according to the present invention, the electronic component sealed by the lid is connected to the adjusting means formed outside by using the wiring board composed of the multilayer wiring board.
Even after the electronic component is sealed, it is possible to perform the adjustment related to the electronic component by the adjusting means. Therefore, an offset or the like generated in the manufacturing process can be adjusted, and variation in characteristics can be suppressed, and the yield can be improved. Also, since the lid is preferably soldered to the wiring board, the lid can be connected at the same time as the electronic component soldering step, and the number of steps can be reduced.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing a sealing structure of an electronic component 14 according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a sealing structure of the electronic component 14 when the wiring board 10 has a two-layer structure.

FIG. 3 is a perspective view of the other surface 10b side of the wiring board 10 for explaining a trimming resistor 25;

FIG. 4 is a cross-sectional view showing a conventional electronic component 2 sealing structure.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Wiring board 11a, 11b, 23a, 23b Conductive pattern 14 Electronic component 16 Lid 25 Trimming resistance

Claims (2)

(57) [Claims] An electronic component and a multilayer wiring board on which the electronic component is mounted, wherein the electronic component mounted on one surface of the wiring board is:
Providing a lid that hermetically covers, leading a conductor pattern connected to the terminal of the electronic component to the other surface of the wiring board, and applying the characteristic of the electronic component to the conductor pattern led to the other surface. An electronic component sealing structure to which an adjusting means for adjusting is connected. 2. The method according to claim 1, wherein the lid has a thermal expansion coefficient substantially equal to that of the wiring board, and is connected to a conductor pattern formed around the electronic component by soldering separately from the conductor pattern. The electronic component sealing structure according to claim 1, wherein: