Semiconductor device manufacturing: process – Making device or circuit responsive to nonelectrical signal – Responsive to electromagnetic radiation
Reexamination Certificate
2000-03-24
2002-07-16
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making device or circuit responsive to nonelectrical signal
Responsive to electromagnetic radiation
C264S001250, C385S091000, C385S094000
Reexamination Certificate
active
06420205
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a package for housing a photosemiconductor element.
2. Description of the Related Art
A conventional package for housing a photosemiconductor element comprises: (a) a substrate made of a ceramics material such as sintered aluminum oxide in general, and having, on the top surface thereof, a recess for housing a photosemiconductor element; (b) a tubular fixing member attached by brazing to a through hole formed on a side of the substrate and the periphery of the substrate around the through hole, having therein a space for transmitting optical signals, and made of metallic material such as an iron-nickel alloy (iron: 50 wt %, nickel: 50 wt %); (c) a light-transmitting member attached to an inside of the tubular fixing member with glass to block the inside; (d) a plurality of wiring conductor layers which is made of tungsten, molybdenum, manganese or the like deposited and led out from the inside of the recess of the substrate to the periphery of the substrate, and to which electrodes of a photosemiconductor element are connected via electrically connecting means such as bonding wires; and (e) a lid attached to the top surface of the substrate to close the recess. A photosemiconductor device is completed as a product by adhering and fixing a photosemiconductor element into the recess of the substrate with an adhesion such as glass, a resin or a brazing material, while electrically connecting the individual electrodes of the photosemiconductor element to the wiring conductor layers via the electrically connecting means such as bonding wires, and thereafter joining he lid to the top surface of the substrate with a sealing material made of glass, a resin, a brazing material or the like to hermetically house the photosemiconductor element into a container composed of the substrate and the lid, while welding and connecting an optical-fiber member to the tubular fixing member by using laser light beams of YAG or the like.
Such a photosemiconductor device causes the photosemiconductor element to excite light in a predetermined manner on the basis of driving signals supplied from an external electric circuit, thereby causing the optical-fiber member to receive the excited light via the light-transmitting member and causing the optical-fiber member to transmit the excited light in a optical fiber thereof, so that the photosemiconductor device is used in high-speed communication and the like.
Further, in the package for housing a photosemiconductor element mentioned above, the tubular fixing member is brazed and attached to the substrate in the following way.
(1) At first, a nickel plating layer and a gold plating layer are deposited in succession on the surface of the tubular fixing member in order to braze and attach the tubular fixing member to the substrate reliably and firmly.
The nickel plating layer is an under member for firmly depositing the gold plating layer on the tubular fixing member, and is deposited on the periphery of the tubular fixing member to a thickness of approximately 0.5 &mgr;m to 5 &mgr;m by the electrolytic plating method or the electroless plating method.
Further, the gold plating layer has the function of enhancing the wettability of a brazing material to the tubular fixing member, and is deposited on the nickel plating layer to a thickness of approximately 1 &mgr;m to 3 &mgr;m by the electrolytic plating method or the electroless plating method.
(2) Next, the light-transmitting member is attached to an inside of the tubular fixing member with glass to block the inside.
The light-transmitting member is attached to the tubular fixing member by applying, for example, low-melting-point solder glass having a melting point lower than that of the light-transmitting member, to the inside of the tubular fixing member, placing the light-transmitting member on the coating low-melting-point solder glass, and thereafter heating them up to a temperature of approximately 450° C. in the air to melt the low-melting-point solder glass.
(3) Finally, the tubular fixing member is brazed and attached to the periphery of the substrate around the through hole with a low-melting-point brazing material comprising an gold-tin alloy or the like, whereby a package for housing a photosemiconductor element is completed as a product.
The tubular fixing member is brazed to the substrate by placing the tubular fixing member on the periphery of the substrate around the through hole so as to sandwich the low-melting-point brazing material made of a gold-tin alloy (gold: 80 wt %, tin: 20 wt %) or the like, and thereafter heating them up to a temperature of approximately 300° C. to melt the low-melting-point brazing material.
However, this conventional method for producing a package for housing a photosemiconductor element has a drawback of being incapable of firmly brazing and attaching the tubular fixing member to the substrate, because when the light-transmitting member is attached to the inside of the tubular fixing member with glass, part of the nickel plating layer deposited on the periphery of the tubular fixing member is, due to heat and atmosphere in glass attachment, diffused in the gold plating layer and exposed to the surface of the gold plating layer, which is oxidized to become a large amount of nickel oxide on the surface of the gold plating layer, with the result that the poor wettability of the nickel oxide to the brazing material largely decreases the joint strength of the brazing material to the tubular fixing member.
Then, in order to overcome the drawback described above, it may be considered to deposit the nickel plating layer and the gold plating layer in succession on the surface of the tubular fixing member after attaching the light-transmitting member to the inside of the tubular fixing member with glass.
However, this may induce another drawback. The glass attaching the light-transmitting member to the inside of the tubular fixing member is low-melting-point solder glass, and the low-melting-point solder glass has poor chemical resistance. Therefore, in the case of depositing the nickel plating layer and the gold plating layer on the surface of the tubular fixing member after attaching the light-transmitting member to the inside of the tubular fixing member with the glass, the glass is melted by a chemical of a plating solution, with the result that the light-transmitting member is detached from the tubular fixing member.
SUMMARY OF THE INVENTION
The present invention, which has been made in view of the drawbacks described above, is aimed at providing a method for producing a package for housing a photosemiconductor element made to have a considerably high reliability by firmly brazing and attaching a tubular fixing member to a substrate.
The invention provides a method for producing a package for housing a photosemiconductor element,
the package for housing a photosemiconductor element comprising a substrate having a recess for housing the photosemiconductor element on a top surface of the substrate, a through hole being formed in a side of the substrate; a tubular metallic fixing member which is brazed to an outer surface of the substrate around the through hole, an optical fiber member being connected to one end of the tubular metallic fixing member; a light-transmitting member attached to an inside of the tubular metallic fixing member to block the inside; and a lid attached to the top surface of the substrate to close the recess,
the method comprising:
(a) a first step of depositing a nickel plating layer on a surface of the tubular metallic fixing member and successively depositing a gold plating layer thereon without occurrence of diffusion of the nickel plating layer to the gold plating layer, and attaching the light-transmitting member to an inside of the metallic fixing member with glass without occurrence of damage to a surface of the light-transmitting member; and
(b) a second step of brazing and attaching the metallic fixing member to the outer surface of the substrate ar
Hogan & Hartson L.L.P.
Kyocera Corporation
Niebling John F.
Simkovic Viktor
LandOfFree
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