JP3976018B2 - Optical hermetic package - Google Patents

Description

  The present invention relates to an optical hermetic package in which an optical member is provided on a part of a cap and has airtightness, for example, an optical hermetic package that hermetically seals an optical sensor or the like that requires airtight control with controlled atmosphere. The present invention relates to an optical hermetic package used for mounting an optical element in which a fragile optical material must be used for an optical member such as an infrared image sensor.

  In a far-infrared image sensor such as a thermopile type that detects incident energy of far-infrared light as heat, the optical sensor is sealed with a gas such as Xe having a low thermal conductivity or exhausted to a high vacuum in order to improve sensitivity. It is housed in an optical hermetic package. In this case, in order to be established as a far-infrared image sensor, it is essential that an optical member such as a window material or a lens made of a material capable of transmitting far-infrared light is hermetically sealed on the front surface of the sensor light-receiving surface. It is a condition. As this optical member, undoped Ge, Si, ZnSe, ZnS, KBr, or the like is used. When Ge or Si is used, as shown in Patent Document 1, a metal film that gets wet with solder by vapor deposition or the like is formed on the lower surface of the peripheral portion of the optical member, and the optical member and the cap are soldered together. It is joined.

JP-A-10-170337 JP-A-11-212555

  However, when an optical member made of a fragile material such as ZnSe, ZnS, or KBr is used in such an optical hermetic package, the optical member is broken by the force applied from the package member to which the optical member is joined, and the airtight Destruction can occur.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide an optical hermetic package that can prevent hermetic failure.

In order to achieve this object, in the present invention, a metal film made of Fe-Ni alloy is formed on the upper, lower and side surfaces of the peripheral part of the optical member made of ZnS , and the optical member is interposed through the metal film. Join the cap.

  In the optical hermetic package according to the present invention, since a stress from the outside can be received by the metal film, the stress acting on the optical member can be dispersed and the destruction can be prevented, thereby preventing the occurrence of the hermetic failure. can do.

(First embodiment)
1 is a sectional view showing an optical hermetic package according to the present invention, that is, a sensor with a lens (camera) in which an infrared image sensor chip is vacuum-mounted, and FIG. 2 is a sectional view showing a lens portion of the optical hermetic package shown in FIG. It is. As shown in the figure, the disc-shaped stem 1 has an insulated connection terminal 2 called TO-8, and a far-infrared image sensor chip 3 is die-bonded on the surface of the stem 1 so that the sensor chip 3 and the connection terminal 2 are connected. Are electrically connected by wire bonding using the wire 4. Further, the mounting side of the sensor chip 3 of the stem 1 is covered with a metal cap 6, and the metal cap 6 is made of a 50Ni—Fe alloy having a Ni content of 50% called 50 alloy, and has a thickness of 0.3 mm. A circular opening 7 is formed on the upper surface of the metal cap 6 facing the surface of the sensor chip 3, and a zinc sulfide (ZnS) lens 9 is formed in the opening 7 through a bonding layer 10 made of solder. A metal film 8 made of 42Ni—Fe alloy having a Ni content of 42% and having a thickness of 150 μm is formed on the upper surface, the lower surface, and the side surfaces of the peripheral portion 11 of the lens 9. That is, the metal film 8 having the same thermal expansion coefficient as that of the lens 9 is formed on the upper surface, the lower surface, and the side surface of the peripheral portion 11 of the lens 9, and the lens 9 is bonded to the metal cap 6 through the metal film 8. Has been. The metal film 8 is formed by electroplating, that is, electrolytic alloy plating. For example, the composition of NiSO ₄ · 6H ₂ O 0.95 mol / L (250 g / L), NiCl ₂ · 6H ₂ O 0.17 mol / L (40 g / L), boric acid 0.49 mol / L (30 g / L) In a watt Ni plating bath, 0.05 mol / L of malonic acid, 0.008 mol / L (2 g / L) of C ₇ H ₄ NNaO ₃ S · 2H ₂ O (sodium saccharin) and 0.35 mol of FeSO ₄ · 7H ₂ O / L or less (0 to 97 g / L or less) is added to prepare a Ni—Fe alloy plating bath, the alloy plating bath is used at pH 2.5 and 50 ° C., and the current density is set to 1 to 9 A / dm ^2. A metal film 8 is formed. In addition, as an example of the publicly known technique related to the electrolytic alloy plating method, there is a research report by Mr. Nagayama, Kyoto City Industrial Experiment Station, etc. at the 7th Techno Research Conference of the Kinki Regional Industrial Technology Cooperation Promotion Conference.

  In the optical hermetic package shown in FIG. 1, the metal film 8 is formed on the upper surface, the lower surface, and the side surface of the peripheral portion 11 of the lens 9, so external stress can be received by the metal film 8. For this reason, stress acting on the lens 9 can be dispersed to prevent breakage, so that airtight breakage can be reliably prevented. Further, as shown in FIG. 3, even if a crack 12 is generated in the peripheral portion 11, the place where the crack 12 may be generated is near the joint portion between the upper surface or the lower surface and the side surface of the peripheral portion 11 where stress is concentrated. Yes, even if a crack 12 occurs, it is covered with the metal film 8 and thus does not lead to hermetic failure, so that it is possible to reliably prevent the hermetic failure from occurring. In addition, zinc sulfide (ZnS), which is the material of the lens 9, is a sintered product and has a thermal expansion coefficient of about 7.5 ppm / k. Since the metal film 8 having the above is formed, tensile stress does not act on the lens 9. Therefore, as described above, the tensile stress, which is generally known as a characteristic of the ceramic material, is about several times smaller than the strength against the compressive force. By adopting a structure that does not act, it is possible to more reliably prevent the occurrence of airtight destruction. Further, particularly when the lens 9 is not large enough with respect to the dimensions of the sensor chip 3, a phenomenon occurs in which the S / N ratio of the image is lowered due to wrinkles near the periphery of the imaging area of the sensor chip 3. However, this phenomenon is caused by the fact that light incident on the peripheral portion 11 is transmitted to the sensor chip 3 side as it is, and the metal film 8 on the upper surface, the lower surface and the side surface of the peripheral portion 11 is formed. In some cases, the metal film 8 blocks the transmission of light in the peripheral portion 11, so that even when the lens 9 is small, the S / N ratio is improved and a clear image can be obtained.

  The metal film 8 is formed by electrolytic alloy plating, and the as-plated 42Ni-Fe alloy has a coefficient of thermal expansion of 8.5 ppm / k, but tensile stress remains in the metal film 8. Since this applies a compressive stress to the lens 9, for example, when the temperature is slowly raised to 350 ° C., the heat of the 42Ni—Fe alloy remains as shown in FIG. When the expansion coefficient is reduced to about 7 ppm / k and then cooled, the lens 9 is lightly clamped to the metal film 8 without changing from the initial state, and the lens 9 is protected by the metal film 8. Since a 50Ni—Fe alloy is selected as the material of the metal cap 6 and the thickness of the metal cap 6 is 0.3 mm, a compressive stress is generated in the metal film 8 at the time of solder bonding by the subsequent bonding layer 10. If the thickness of the metal film 8 is matched to the stress of the metal material of the metal cap 6, a compressive stress can be generated in the lens 9. In this case, even if a tensile force acts on the lens 9, When the tensile force is smaller than a predetermined value, no tensile stress acts on the lens 9, and in the case of a non-metallic material such as zinc sulfide, as described above, generally, the tensile stress is less than the tensile stress. Since the strength is about several times higher, the lens 9 is protected from external force and is not damaged.

  In addition, since electrolytic plating basically leaves a tensile stress inside, some reversal of the thermal expansion coefficient is absorbed by its own stress. In addition, the stress can be adjusted by heat treatment conditions, and variations of the stress adjusting means are further widened.

  In addition, since the Fe—Ni alloy is used as the material of the metal film 8 and the metal film 8 is formed by the electrolytic alloy plating method, the composition of the material of the metal film 8 can be set by the plating conditions. Since the integer of thermal expansion can be easily adjusted from the composition of the material of the metal film 8, the development period and cost can be greatly reduced at the same time.

(Second Embodiment)
FIG. 5 is a cross-sectional view showing a lens portion of another optical hermetic package according to the present invention. As shown in the figure, a metal vapor deposition layer 13 is provided on the upper surface of the peripheral portion 11 of the lens 9, and the vapor deposition layer 13 is composed of a 20 nm Ti layer and a 100 nm Ni layer thereon.

  In the optical hermetic package having the lens portion shown in FIG. 5, since the metal vapor deposition layer 13 is provided on the upper surface of the peripheral portion 11 of the lens 9, the reliability can be improved. In other words, in electroplating, in recent years, the elimination of defects has progressed due to demands for eliminating errors in recording media such as compact disks. However, there are probabilistic defects, and in the manufacture of far-infrared image sensors, one of the application fields of the present invention, it is necessary to thoroughly eliminate gas leaks that impair airtightness because the parts used are relatively expensive. is there. When this gas leak occurs, when thick plating (metal film 8) is used as in the present invention, there are few paths through the metal film 8, and the interface between the lens 9 and the metal film 8 is not satisfactory. Often due to continuity. Accordingly, it is sufficient that the path can be blocked by any one of the paths from the front side to the back side of the lens 9, and after the metal deposition layer 13 serving as the plating base layer is formed on the upper surface of the peripheral portion 11 of the lens 9 by the deposition method. If the metal film 8 is formed by plating, it is possible to prevent the airtightness from being deteriorated by a slight defect at the interface between the lens 9 and the metal film 8 and to improve the reliability.

  Each drawing is deformed for easy explanation of the process, and there is a portion that does not show an accurate dimensional ratio. The numerical values in the embodiments are examples for explaining the present embodiment, and are not limited to these, and naturally change due to variations in design conditions.

  In the above-described embodiment, the case where the optical member is the lens 9 has been described. However, the present invention can also be applied to the case where the optical member is a window member or the like. In the above-described embodiment, the metal vapor deposition layer 13 is provided on the upper surface of the peripheral portion 11 of the lens 9. However, the vapor deposition layer is provided between at least one of the upper and lower surfaces of the peripheral portion of the optical member and the metal film. What is necessary is just to provide.

It is sectional drawing which shows the airtight package for optics which concerns on this invention. It is sectional drawing which shows the lens part of the airtight package for optics shown in FIG. It is sectional drawing for demonstrating the effect in the airtight package for optics shown in FIG. It is a graph for demonstrating the heat processing method in 1st Example which concerns on this invention. It is sectional drawing which shows the lens part of the other airtight package for optics which concerns on this invention.

Explanation of symbols

6 ... Metal cap 8 ... Metal film 9 ... Lens 11 ... Peripheral part 13 ... Deposition layer

Claims (3)

In an optical hermetic package in which an optical member is provided in a part of a cap and has airtightness,
Forming a metal film made of Fe-Ni alloy on the upper surface, the lower surface and the side surface of the peripheral portion of the optical member made of ZnS ;
An optical hermetic package, wherein the optical member is bonded to the cap via the metal film.   2. The optical hermetic package according to claim 1, wherein the metal film is formed by electroplating. The optical hermetic package according to claim 2, wherein a vapor deposition layer is provided between at least one of an upper surface and a lower surface of the peripheral portion of the optical member and the metal film.

Images