JPH0727615A - Manufacture of pyroelectric infrared detector and structure thereof - Google Patents

Abstract

PURPOSE:To improve the productivity and reliability by mounting a lead-out- electrode connecting parts through gold bumps on the electrodes on a circuit board, and bonding both parts. CONSTITUTION:A circuit board 6 is fixed and supported in a case 1 with lead pins 5a and 5b. Electrodes 7 and 9 on the board, wherein copper, gold or the like is plated on the surfaces, are formed. A FET 9 and a high resistor 10 are provided on the lower surface. Upper surface electrodes 12a and 12b and lower surface electrodes 13a and 13b are formed on the upper surface and the lower surface of a pyroelectric body 11. Lead-out electrode connecting parts d1 and d2 are formed on the outsides of lower surface electrode parts c1 and c2 corresponding to the electrodes 12a and 12b at the electrodes 13a and 13b. For example, a chromium thin film is deposited. Furthermore, the thin films of copper, gold or the like are overlapped. Gold bumps 14 are provided between the electrodes 7 and 8 and the connecting parts d1 and d2 and connect both parts. Since the thin films of the copper, gold or the like are formed on the surfaces of both parts, the bonding property is excellent. Therefore, defects such as migration do not occur, and the high reliability is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a pyroelectric infrared detector for spot-detecting infrared rays emitted from a human body and the structure thereof.

[0002]

2. Description of the Related Art In a conventional pyroelectric infrared detector,
When a pyroelectric body is supported on a circuit board equipped with a FET and a high resistance body, a metal such as Ag is attached to an adhesive such as an epoxy-based adhesive in order to join a predetermined electrode of the board and the electrode of the pyroelectric body. A metal paste in which a filler is dispersed or wire bonding is used. For example, Japanese Patent Application Laid-Open No. 61-193030 discloses an infrared detector having such a junction structure.

[0003]

However, it is not easy to precisely apply a small amount of metal paste, and it is difficult to mechanize it. Further, it may take a long time for heat curing, stains may adhere during that time, or perfect bonding may not be achieved. Furthermore, the yield is often reduced by attaching a metal paste to unnecessary portions of the pyroelectric body, and migration may occur in the long term, and it is not easy to obtain high reliability.

On the other hand, in wire bonding, there is a concern that the pyroelectric body may be damaged by the pressing of the head at the time of connection, and in some cases trouble such as disconnection of the connection portion during transportation or in the field may occur.

The present invention has been made in view of such circumstances.
An object of the present invention is to provide a manufacturing method and a structure thereof capable of improving the productivity and reliability of a pyroelectric infrared detector for spot-detecting infrared rays emitted from a human body.

[0006]

The present invention has means for solving the above-mentioned problems as follows. That is, in the first invention, at least a lower electrode of the pyroelectric body is formed by depositing a thin film made of chromium or the like by a vapor deposition method or a sputtering method, and a lead electrode connecting portion extended from the lower electrode portion of the lower electrode. On the thin film made of chromium or the like, a film of copper or gold is overlaid by plating or the like, while on the circuit board electrode connected to the lead-out electrode connection portion, a film of copper or gold is plated or the like. The lead-out electrode connecting portion is mounted on the electrode on the circuit board via the Au bump, and the both are joined together.

In the second invention, the pyroelectric body and the high resistance body housed in a closed container filled with an inert gas or dry air are connected in parallel, and one electrode of the pyroelectric body is made of a metal stem. It is connected to the ground lead pin fixedly supported by
The other electrode is connected to the gate terminal of the FET for impedance conversion, and the drain terminal and the source terminal of the FET are connected to the drain lead pin and the source lead pin, which are fixedly supported by the metal stem in an insulated state, respectively. In a structure of a pyroelectric infrared detector for detecting infrared rays emitted from a human body or the like spotwise through an infrared transmission window provided in the closed container, at least chromium is used as a lower surface electrode of the pyroelectric body. A thin film made of, for example, is deposited, and at the extraction electrode connecting portion of the lower surface electrode extending from the lower surface electrode portion, a coating film of copper or gold is superposedly formed on the thin film made of chromium or the like. It is characterized in that the lead-out electrode connecting portion is joined to an electrode on a circuit board on which a coating film of copper, gold or the like is adhered, via an Au bump. That.

[0008]

Since the extraction electrode connection portion of the lower surface electrode of the pyroelectric body is mounted on the circuit board upper electrode through the Au bump and the both are joined, the positioning of the both is easy and the joining does not require labor. In addition, a good joining state can be obtained.

When this joining method is used for the pyroelectric infrared detector, the time required for assembly is shortened, the production yield is improved, and a highly reliable detector can be obtained.

[0010]

Embodiments of the present invention will be described in detail below with reference to the drawings. FIG. 2 is a vertical sectional view of a dual type pyroelectric infrared detector, and FIG. 1 is an enlarged view of a portion A in FIG. In FIGS. 1 and 2, reference numeral 1 is a metal case, and an infrared transmission window 3 is provided in an opening 2 on the upper surface thereof. Reference numeral 4 is a disc-shaped stem that closes the lower opening of the case 1, and is a terminal (lead pin) 5a for grounding, source and drain.
.About.5c penetrate the stem 4 and are fixedly supported in an insulated state. The case 1, the infrared transmitting window 3 and the stem 4
To form a closed container, and the inside of the closed space is filled with an inert gas or dry air.

A circuit board 6 is fixedly supported in the case 1 by the lead pins 5a to 5c. A circuit pattern is formed on a board made of alumina, for example, and circuit board upper electrodes 7 and 8 are formed on the upper surface thereof. An FET 9 for impedance conversion and a high resistance element 10 are provided on the lower surface. A coating film of copper or gold is formed on the circuit board electrodes 7, 8 by plating or the like.

Reference numeral 11 denotes a pyroelectric body made of, for example, lead zirconate titanate-based oxide ceramics (PZT) or lithium tantalate, whose upper and lower surfaces are shown in FIG.
As shown in (B), upper surface electrodes 12a and 12b and lower surface electrodes 13a and 13b are formed, respectively.

The lower electrodes 13a and 13b are the upper electrodes 12
Lead-out electrode connecting portions d ₁ and d ₂ are formed so as to extend outside the lower surface electrode portions c ₁ and c ₂ corresponding to a and 12b. For example, chromium is formed by the sputtering method or the vapor deposition method.
13a, is deposited as a thin film of about several hundreds number 1000Å on the surface of the 13b, the lead electrode connecting portion d _1, the d ₂ sputtering coating further such as copper or gold on top of the thin film or a vapor deposition method or the like They are superposed. The top electrode
A thin film of chromium is formed on the surfaces of 12a and 12b by the same method.

Numerals 14 and 14 (see FIGS. 1 and 2) are Au bumps for connecting the electrodes 7 and 8 on the circuit board to the lead-out electrode connecting portions d ₁ and d ₂ , respectively. Since a thin film of copper or gold is formed on the surfaces of the electrode connection parts d ₁ and d ₂ , the bondability between the two is extremely good, and defects such as migration do not occur and high reliability can be obtained. Moreover, as will be described later, by using the Au bumps 14, highly workable and highly accurate joining work can be performed, and the product cost can be reduced.

Explaining the equivalent circuit, as shown in FIG. 4, the pyroelectric body 11 and the high resistance body 10 are connected in parallel, and one lower surface electrode 13b of the pyroelectric body 11 is connected to the ground lead pin 5a.
The other lower surface electrode 13a is connected to the gate terminal of the FET 9, and the drain terminal and the source terminal of the FET 9 are connected to the drain lead pin 5c and the source lead pin 5b, respectively.

In such a circuit structure, the electrodes 13a and 13b of the pyroelectric body 11 are connected to the electrodes 7 and 8 on the circuit board via the Au bumps 14 and 14, respectively.
The circuit board 6 and the pyroelectric body 11, which are separately formed, can be assembled very easily, reliably and accurately.

At the time of assembly, the circuit board 6 in which the coating film of copper or gold or the like is formed on the circuit board upper electrodes 7 and 8 in advance is fixedly supported on the stem 4 via the lead pins 5a to 5c, and Au bumps 1 on the electrodes 7 and 8 on each circuit board
4 and 14 are placed, and the pyroelectric body 11 on which the copper or gold coating is already formed on the lower surface electrodes 13a and 13b is placed thereon, and the Au bumps 14 and 14 on the circuit board upper electrodes 7 and 8 and the lower surface electrodes 13a and 13b can be joined and integrated with good workability, and the time required for assembly can be greatly reduced.

The Au bumps 14 are bonded to each other by forming a coating film of copper or gold on both objects, so that the bonding is very good and the electrical connection is ensured.
Moreover, unlike the case of using a conventional metal paste, it does not require the troublesome consideration that a minute amount must be applied with high accuracy, and it enables a clean connection, improves product quality, and migrates over the long term. High reliability can be obtained without worrying about the occurrence of.

Further, the circuit board 6 and the pyroelectric body 11 have different coefficients of thermal expansion, and in the case of the conventional metal paste, since they are bonded with high rigidity, there is a concern that residual stress may occur. Since there is a good joint between ductility and ductility, there is no concern about residual stress.

Further, the Au bump 14 has a diameter of several hundreds to several tens of μ.
Since it is miniaturized to m, the lower surface electrode 13 of the pyroelectric body 11
a, 13b and the electrodes 7, 8 on the circuit board can be made finer, and it is also possible to improve the integration degree of the detector by applying it to an array type, etc., and greatly improve the productivity and reliability. You can

[0021]

As described above, according to the present invention,
The electrode on the circuit board, which has a coating of copper or gold formed on the surface in advance, and the lead-out electrode connection part are joined via Au bumps, so a pyroelectric infrared detector can be assembled with good workability, and the yield is improved. In addition, in the assembled state, a good joined state between the electrodes can be obtained, and the product quality can be stably improved at low cost.

[Brief description of drawings]

FIG. 1 is an enlarged sectional view of an essential part showing an embodiment of a pyroelectric infrared detector of the present invention.

FIG. 2 is a vertical sectional view of the same.

3A is a plan view of the same pyroelectric body, and FIG. 3B is a bottom view thereof.

FIG. 4 is an equivalent circuit diagram of the same.

[Explanation of symbols]

1, 3, 4 ... Airtight container, 5a ... Ground lead pin, 5b ... Source lead pin, 5c ... Drain lead pin, 6 ... Circuit board, 7, 8 ... Circuit board upper electrode, 9 ... FET, 10 ... High resistance body, 11 ... pyroelectric, 13a, 13b ... lower electrode, c _1, c ₂ ...
Lower surface electrode portion, d ₁ , d ₂ ... Lead-out electrode connecting portion, 14 ... Au bump.

Claims (2)

[Claims] 1. A thin film made of chromium or the like is deposited on at least a lower surface electrode of a pyroelectric material by a vapor deposition method or a sputtering method, and the extraction electrode connecting portion extending from the lower surface electrode portion of the lower surface electrode is provided with the thin film. While forming a coating of copper or gold on a thin film made of chrome etc. by plating, etc., deposit a coating of copper or gold etc. on the electrode on the circuit board connected to the extraction electrode connecting part by plating etc. A method for manufacturing a pyroelectric infrared detector, which is characterized in that the extraction electrode connecting portion is formed on the electrode on the circuit board via an Au bump and the both are joined. 2. A pyroelectric body and a high resistance body housed in a closed container filled with an inert gas or dry air are connected in parallel, and one electrode of the pyroelectric body is fixedly supported by a metal stem. Is connected to the earth lead pin, the other electrode is connected to the gate terminal of the FET for impedance conversion, and the drain terminal and source terminal of the FET are
Connected to the drain lead pin and the source lead pin, which are fixedly supported in an insulating state on the metal stem, respectively, so that infrared rays emitted from the human body or the like can be spot-wise detected through an infrared transmission window provided in the closed container. In the structure of the pyroelectric infrared detector, a thin film made of chromium or the like is deposited on at least the lower surface electrode of the pyroelectric body, and the extraction electrode connection portion extended from the lower surface electrode portion of the lower surface electrode is formed. Is formed by superimposing a coating film of copper or gold on the thin film made of chromium or the like, and its lead-out electrode connection portion is formed through the Au bump and the circuit board electrode on which the coating film of copper or gold is deposited. Pyroelectric infrared detector structure characterized by being joined.