JP7205470B2 - Window materials, optical packages - Google Patents

Description

The present invention relates to window materials and optical packages.

Conventionally, after placing an optical element such as a light emitting diode in a concave portion of a circuit board, the opening of the concave portion is sometimes sealed with a window material having a transparent resin base material or the like, and used as an optical package.

In this case, the window material is bonded to the circuit board with a resin adhesive or the like, but depending on the type of the optical element, etc., there has been a demand for improved airtightness. For this reason, it has been studied to join the circuit board and the window material with a metal material instead of using a resin adhesive.

For example, Patent Document 1 discloses a mounting substrate, an ultraviolet light emitting element mounted on the mounting substrate, a spacer provided on the mounting substrate and having a through hole for exposing the ultraviolet light emitting element, and and a cover arranged on the spacer so as to close the through hole. a second bonding metal layer facing the first bonding metal layer and formed along the entire circumference of the outer peripheral edge of the facing surface, wherein the through hole is formed in the spacer main body; The opening area of the through hole gradually increases as the distance from the mounting substrate increases, the cover is formed of glass that transmits ultraviolet rays emitted from the ultraviolet light emitting element, and the spacer and the cover are directly connected to each other. wherein the second bonding metal layer of the spacer and the first bonding metal layer of the mounting substrate are bonded by AuSn over the entire circumference of the second bonding metal layer; Disclosed is a light emitting device characterized by

Japanese Patent No. 5877487

However, the cover used in the light-emitting device disclosed in Patent Document 1 is bonded to the mounting substrate with AuSn via a spacer, and a large amount of gold (Au) is used, which poses a problem from the viewpoint of cost. .

SUMMARY OF THE INVENTION In view of the above problems of the prior art, it is an object of one aspect of the present invention to provide a window material at a reduced cost.

In order to solve the above problems, in one aspect of the present invention, there is provided a window material for an optical package having an optical element, comprising:
a substrate of inorganic material;
a bonding layer disposed on one surface of the substrate of the inorganic material;
The bonding layer has a base metal layer and a solder layer,
The volume ratio of gold in the bonding layer is 10% or less,
The average value of the thickness of the solder layer is 5 μm or more and 50 μm or less,
The Young's modulus of the solder constituting the solder layer is 50 GPa or less,
The solder constituting the solder layer contains tin, germanium, and nickel,
The germanium content is 10% by mass or less,
A window in which the germanium content and the nickel content satisfy the following formula (1), and the total of the germanium content and the nickel content is more than 1.2% by mass provide materials.
[Ni]≦2.8×[Ge] ^0.3 (1)
(However, [Ni] indicates the content of nickel in terms of mass%, and [Ge] indicates the content of germanium in terms of mass%.)

According to one aspect of the present invention, it is possible to provide a window material with reduced cost.

FIG. 2 is an explanatory diagram of the configuration of the window member of the embodiment; Explanatory drawing of the structural example of the side surface of the base|substrate of an inorganic material. FIG. 4 is an explanatory view of positions of thickness measurement points of the solder layer of the window material; FIG. 2 is an explanatory diagram of the configuration of the optical package according to the embodiment; FIG. 4 is an explanatory diagram of a material before cutting of an inorganic material substrate before singulation in an example. FIG. 4 is an explanatory diagram of a temperature profile of a reflow test in Example 1; The temperature profile of the joining process in Example 2. FIG. 10 is an explanatory diagram of a linear pattern formed on the side surface of the inorganic material substrate after singulation in Example 4;

Hereinafter, the embodiments for carrying out the present invention will be described with reference to the drawings. Various modifications and substitutions can be made to.
[Window material]
A configuration example of the window material of the present embodiment will be described.

The window material of the present embodiment relates to a window material for an optical package provided with an optical element, and has an inorganic material substrate and a bonding layer disposed on one surface of the inorganic material substrate. The volume ratio of gold in is 10% or less.

A configuration example of the window material of the present embodiment will be specifically described below with reference to FIGS. 1(A) and 1(B). FIG. 1A schematically shows a cross-sectional view of the inorganic material substrate 11 and the bonding layer 12 of the window material 10 of the present embodiment along a plane parallel to the stacking direction. 1(B) shows the structure of the window material 10 shown in FIG. 1(A) along the block arrow A shown in FIG. 1(A). That is, the bottom view of the window member 10 shown in FIG. 1(A) is shown.

The window material 10 of this embodiment has a substrate 11 made of an inorganic material and a bonding layer 12 . The bonding layer 12 can be arranged on one surface 11a of the substrate 11 made of inorganic material.

Here, the one surface 11a of the substrate 11 made of an inorganic material corresponds to the surface to be bonded to the circuit board having the optical element when manufacturing the optical package. That is, the one surface 11a of the inorganic material substrate 11 can also be said to be the surface facing the optical element.

One surface 11a of the substrate 11 made of inorganic material and the other surface 11b opposite to the other surface 11b are exposed to the outside in the case of an optical package.

Although FIG. 1 shows an example in which the substrate 11 made of an inorganic material has a plate-like shape, the shape is not limited to such a shape.

Here, each member included in the window material of this embodiment will be described.
(Inorganic material substrate)
The substrate 11 made of an inorganic material is not particularly limited, and can be made of any material and have any shape.

However, when the substrate 11 made of an inorganic material is used as an optical package, light in a wavelength region that is particularly required to be transmitted (hereinafter referred to as “light in a desired wavelength region”) among light related to optical elements provided on a circuit board. described), it is preferable to select the material, thickness, etc. so that the transmittance is sufficiently high. For example, for light in a desired wavelength range, the transmittance is preferably 50% or higher, more preferably 70% or higher, still more preferably 80% or higher, and particularly preferably 90% or higher.

The substrate 11 made of inorganic material preferably has a transmittance of 50% or more, more preferably 70% or more, for light in a wavelength range of 0.7 μm or more and 1 mm or less, for example, when light in a desired wavelength region is infrared light. More preferably, 80% or more is even more preferable, and 90% or more is particularly preferable.

Further, when the light in the desired wavelength region is light in the visible region (blue to green to red), the substrate 11 made of an inorganic material has a transmittance of 50% or more for light having a wavelength in the range of 380 nm to 800 nm, for example. It is preferably 70% or more, more preferably 80% or more, and particularly preferably 90% or more.

The substrate 11 made of an inorganic material preferably has a transmittance of 50% or more, more preferably 70% or more, for light having a wavelength of 200 nm or more and 380 nm or less, when the light in the desired wavelength region is light in the ultraviolet region. 80% or more is more preferable, and 90% or more is particularly preferable.

When the light in the desired wavelength region is UV-A light in the ultraviolet region, for example, the transmittance of the inorganic material substrate 11 is preferably 50% or more, and preferably 70% or more, for light with a wavelength of 315 nm or more and 380 nm or less. is more preferable, 80% or more is more preferable, and 90% or more is particularly preferable.

When the light in the desired wavelength region is UV-B light in the ultraviolet region, for example, the transmittance of the substrate 11 made of inorganic material is preferably 50% or more, and preferably 70% or more, for light with a wavelength of 280 nm or more and 315 nm or less. is more preferable, 80% or more is more preferable, and 90% or more is particularly preferable.

When the light in the desired wavelength region is UV-C light in the ultraviolet region, for example, the transmittance of the substrate 11 made of an inorganic material is preferably 50% or more, and preferably 70% or more, for light with a wavelength in the range of 200 nm or more and 280 nm or less. is more preferable, 80% or more is more preferable, and 90% or more is particularly preferable.

The transmittance of the substrate 11 made of an inorganic material can be measured according to JIS K 7361-1 (1997).

The material of the substrate 11 made of an inorganic material can be arbitrarily selected as described above, and is not particularly limited. Glass or the like can be preferably used. Quartz includes quartz glass and those containing 90% by mass or more of SiO ₂ . Examples of glass include soda lime glass, aluminosilicate glass, borosilicate glass, alkali-free glass, crystallized glass, and high refractive index glass (nd≧1.5). The material of the inorganic substrate is not limited to one type, and two or more types of materials can be used in combination. For this reason, for example, the material of the substrate 11 made of an inorganic material is selected from, for example, quartz, soda lime glass, aluminosilicate glass, borosilicate glass, alkali-free glass, crystallized glass, and high refractive index glass (nd≧1.5). One or more materials described above can preferably be used.

When glass is used as the material of the substrate 11 of inorganic material, the substrate 11 of inorganic material may be chemically strengthened.

The thickness of the inorganic material substrate 11 is also not particularly limited, but is preferably 0.03 mm or more, more preferably 0.05 mm or more, and even more preferably 0.1 mm or more. , 0.3 mm or more.

By setting the thickness of the inorganic material substrate 11 to 0.03 mm or more, the strength required for the optical package is sufficiently exhibited, and moisture or the like penetrates the optical element through the surface of the inorganic material substrate 11 of the window material. It is particularly possible to suppress transmission to the arranged side. By setting the thickness of the inorganic material substrate 11 to 0.3 mm or more as described above, the strength of the optical package can be particularly increased, which is preferable.

The upper limit of the thickness of the substrate 11 made of inorganic material is also not particularly limited, but is preferably 5 mm or less, more preferably 3 mm or less, and even more preferably 1 mm or less. This is because the transmittance of light in a desired wavelength region can be sufficiently increased by setting the thickness of the inorganic material substrate 11 to 5 mm or less. It is more preferable to set the thickness of the substrate 11 made of inorganic material to 1 mm or less, because it is possible to reduce the height of the optical package.

The shape of the inorganic substrate 11 is not particularly limited, and the thickness need not be uniform. Therefore, when the thickness of the inorganic material substrate is not uniform, the thickness of at least the portion of the inorganic material substrate on the optical path of the optical element in the optical package is preferably within the above range. It is more preferable that the thickness of the substrate of the inorganic material is within the above range at any portion.

The shape of the substrate 11 made of inorganic material is not particularly limited as described above. For example, a plate-like shape or a shape in which a lens is integrated, that is, a shape including concave portions and convex portions derived from the lens can be used. Specifically, for example, one surface 11a of the substrate 11 made of an inorganic material is a flat surface, and the other surface 11b has a convex portion or a concave portion. A form in which is reversed from the form in which . In addition, one surface 11a of the inorganic material substrate 11 has convex portions and the other surface 11b has concave portions. form. Furthermore, there is a form in which each of the one surface 11a and the other surface 11b of the inorganic material base 11 has a convex portion or a concave portion.

Even if the one surface 11a of the inorganic material substrate 11 has a convex portion or a concave portion, the portion of the one surface 11a of the inorganic material substrate 11 where the bonding layer 12 is arranged may be formed by, for example, a plurality of window materials. It is preferable that the bonding layer 12 be flat in order to suppress variations in the shape of the bonding layer 12 between the window materials 10 when the window material 10 is manufactured.

The side surface of the inorganic material substrate 11 can have a linear pattern along the outer periphery of one surface 11a.

The window material of the present embodiment can be arranged, for example, on a circuit board on which optical elements are arranged to form an optical package. Therefore, depending on the form of the optical package, the size of the window material may be very small. Therefore, it is preferable to adopt a cutting method using a laser beam when cutting the pre-cut material of the substrate 11 of inorganic material into a desired size.

In such a cutting method using a laser beam, for example, the focal position of the laser beam is set to an arbitrary position in the thickness direction of the inorganic material substrate before cutting, and the irradiation position of the laser beam is on the cutting line. Along the line, the irradiation position of the laser beam and/or the pre-cut material of the inorganic material substrate is moved. After that, by applying a force so that the cutting line serves as a fulcrum, or by applying a natural force, the pre-cut material of the inorganic material substrate can be cut into an arbitrary shape along the cutting line.

In the above cutting method, the focal position of the laser beam is set at an arbitrary position in the thickness direction of the material before cutting the inorganic material substrate, and by moving the irradiation position of the laser beam, etc., the inorganic material substrate is cut. It is thought that the bonding state of the inorganic material changes at the location through which the laser beam focal position of the material passes. For this reason, it is presumed that the pre-cut material of the inorganic material base can be easily cut starting from the portion where the bonding state of the inorganic material has changed due to the subsequent application of force.

Depending on the thickness of the material of the inorganic material substrate before cutting, it is possible to change the focal position of the laser beam in the thickness direction of the material of the inorganic material substrate before cutting, and irradiate the laser beam multiple times along the cutting line. can also In this way, when the focal position of the laser beam is changed and the laser beam is irradiated multiple times along the cutting line, the laser is It is preferable to change the focal position of the laser light from a position far from the light incident surface to a position close to it.

The number of times of laser light irradiation is preferably 2 or more, more preferably 3 or more, and even more preferably 5 or more, since the occurrence of defects such as chipping, cracking, and chipping of the cut surface can be suppressed. Although the upper limit of the number of times of laser light irradiation is not particularly limited, if it exceeds 10 times, the cost increases, so 10 times or less is preferable.

When the material is cut by such a cutting method, a linear pattern, which is thought to be caused by a change in the bonding state of the inorganic material, remains at the position through which the focal position of the laser beam passes. Since the focal position of the laser beam is set to an arbitrary position in the thickness direction of the inorganic material substrate before cutting, for example, as shown in FIG. A linear pattern 111 along the outer circumference of the surface 11a or the other surface 11b can be used. From the viewpoint of suppressing defects such as chipping, cracking, and chipping during cutting, the linear pattern 111 is a linear pattern parallel to one surface 11a and the other surface 11b of the substrate 11 made of an inorganic material. It is preferable to have them, but they do not necessarily have to be parallel.

As described above, when the laser beam is irradiated a plurality of times along the cutting line, the same number of linear patterns as the number of times of irradiation remain on the side surface, that is, the cut surface of the substrate of the obtained inorganic material. Further, it is preferable that the intervals between the plural linear patterns are substantially the same from the viewpoint of suppressing the occurrence of defects such as chipping of the cut surface. Specifically, for example, it is preferable that the width between the linear patterns included in the side surface of the inorganic material substrate obtained after cutting is within 20% of the median value. Since the linear pattern is generated at a position corresponding to the focal position of the laser beam, the interval between the linear patterns can be controlled by the focal position of the laser beam.

The method for cutting the substrate 11 of inorganic material is not limited to the above example, and any method can be used for cutting. When cutting is performed by a method other than the cutting method described above, the side surface of the substrate 11 of inorganic material, that is, the cut surface may have a cross-sectional shape different from that in the above case. Other cutting methods include, for example, a dicing saw and a wire saw. These cutting methods are effective when the thickness of the inorganic material substrate before cutting is 1 mm or more.

An antireflection film may be arranged on the surface of the substrate 11 made of an inorganic material. By arranging the antireflection film, when an optical package is formed, light from the optical element or the outside is suppressed from being reflected on the surface of the substrate 11 made of an inorganic material, and light from the optical element or the outside is suppressed. It is preferable because it can increase the transmittance. Although the _{antireflection film} is not particularly limited _, for example, a _multilayer film can be used. ) and the like and a second layer of silica (silicon oxide, SiO ₂ ) alternately laminated. The number of layers constituting the multilayer film is not particularly limited. It is preferable to have at least one pair, and more preferably to have two or more pairs. This is because the multilayer film having one or more sets of the first layer and the second layer can particularly suppress reflection of light on the surface of the substrate 11 made of an inorganic material.

Although the upper limit of the number of layers constituting the multilayer film is not particularly limited, it is preferable to have four or less pairs of the first layer and the second layer, for example, from the viewpoint of productivity.

When an antireflection film is provided, the antireflection film is preferably arranged on at least one surface 11a of the substrate 11 made of inorganic material, and more preferably on both the one surface 11a and the other surface 11b. When the antireflection films are arranged on both the one surface 11a and the other surface 11b, the structures of the two antireflection films may be different, but from the viewpoint of productivity, etc., the antireflection films with the same structure should be provided. is preferred.

When the above multilayer film is used as the antireflection film, it is preferable that the second layer of silica is positioned on the outermost surface. Since the second layer of silica is positioned on the outermost surface of the antireflection film, the surface of the antireflection film has a composition similar to that of the surface of the glass substrate, and the durability and adhesion to the bonding layer 12 are particularly high. This is because it is preferable.
(bonding layer)
The bonding layer 12 corresponds to a member for bonding the substrate 11 made of an inorganic material and a circuit board having an optical element in the case of an optical package. For this reason, the bonding layer 12 is not particularly limited as long as it is a member capable of bonding the substrate 11 made of inorganic material and the circuit board provided with the optical element. However, the bonding layer 12 is preferably made of a metal material from the viewpoint of improving the airtightness of the optical package. Also, the bonding layer 12 preferably has a gold volume ratio of 10% or less. By setting the volume ratio of gold in the bonding layer 12 to 10% or less, the ratio of gold contained in the bonding layer can be sufficiently suppressed, and the cost of the window material can be suppressed. The volume ratio of gold in the bonding layer 12 is more preferably 8% or less, and even more preferably 6% or less.

Since the bonding layer 12 may not contain gold, the volume ratio of gold in the bonding layer 12 may be 0 or more.

In the bonding layer 12, each layer such as a solder layer, which will be described later, can have a substantially uniform thickness. Therefore, for example, when a layer containing gold is present as a gold layer made of gold in the bonding layer 12 , the volume ratio of gold is defined as the ratio of the thickness of the gold layer to the thickness of the bonding layer 12 . can also Further, when the layer containing gold also contains components other than gold, the volume content ratio of gold in the layer containing gold to the ratio of the thickness of the layer containing gold to the thickness of the bonding layer 12 can also be a value obtained by multiplying

When the volume ratio of gold in the bonding layer is calculated using the thickness of each layer as described above, an average value of simple averages can be used as the thickness of the solder layer, which will be described later.

The bonding layer 12 preferably has an underlying metal layer 121 and a solder layer 122, as shown in FIG. 1A, for example.

The base metal layer 121 can have a function of enhancing adhesion between the inorganic material base 11 and the solder layer 122 . Although the structure of the base metal layer 121 is not particularly limited, it is preferably composed of a plurality of layers as shown in FIG. 1(A).

Although the configuration of the underlying metal layer 121 is not particularly limited, it can be composed of, for example, two layers or three layers. Specifically, for example, it can have a first base metal layer 121A and a second base metal layer 121B in order from the substrate 11 side of the inorganic material. Further, a third base metal layer (not shown) can be arranged between the second base metal layer 121B and the solder layer 122. FIG.

The first base metal layer 121A can have a function of enhancing adhesion between the base 11 made of inorganic material and other layers. The material of the first base metal layer 121A is preferably a material capable of enhancing adhesion between the substrate 11 made of an inorganic material and another layer, and more preferably a material capable of enhancing airtightness. The first base metal layer 121A is preferably a layer containing one or more selected from, for example, chromium (Cr), titanium (Ti), tungsten (W), and palladium (Pd). The first base metal layer 121A can also be a layer made of one or more materials selected from, for example, chromium (Cr), titanium (Ti), tungsten (W), and palladium (Pd). Even in this case, it is not excluded that the first base metal layer 121A contains unavoidable impurities.

More preferably, the first base metal layer 121A is a metal film or a metal oxide film of one or more metals selected from chromium (Cr), titanium (Ti), tungsten (W), and palladium (Pd). preferable.

The second base metal layer 121B has a function of enhancing adhesion between the solder layer and other layers, and is selected from, for example, nickel (Ni), copper (Cu), platinum (Pt), and silver (Ag). It is preferable to use a layer containing one or more kinds of metals. From the viewpoint of particularly reducing costs, the second base metal layer 121B is more preferably a layer containing one or more metals selected from nickel (Ni) and copper (Cu).

The second base metal layer 121B can also be a layer made of one or more metals selected from, for example, nickel (Ni), copper (Cu), platinum (Pt), and silver (Ag). Also in this case, from the viewpoint of cost, the second base metal layer 121B is preferably a layer made of one or more metals selected from nickel (Ni) and copper (Cu). In any of the above cases, the inclusion of unavoidable impurities in the second base metal layer 121B is not excluded.

Further, when a third base metal layer is further provided, the third base metal layer preferably contains one or more selected from, for example, nickel (Ni) and gold (Au). In particular, when the third base metal layer is a layer containing nickel (Ni), a layer containing a nickel-boron alloy (Ni--B) or a layer made of Ni--B is used to improve solder wettability. preferably. By providing the third base metal layer, for example, reaction between the base metal layer 121 and the solder layer 122 can be particularly suppressed. The third base metal layer can also be a layer made of one or more metals selected from nickel (Ni) and gold (Au). Even in this case, it is not excluded that the third base metal layer contains unavoidable impurities.

The thickness of each layer constituting the base metal layer 121 is not particularly limited and can be arbitrarily selected.

For example, the thickness of the first base metal layer 121A is preferably 0.03 μm or more from the viewpoint of particularly enhancing the adhesion of the inorganic material to the substrate 11 . Although the upper limit of the thickness of the first base metal layer 121A is not particularly limited, it is preferably 0.2 μm or less from the viewpoint of sufficiently reducing the cost.

The thickness of the second base metal layer 121B is preferably 0.1 μm or more from the viewpoint of particularly enhancing the adhesion to the solder layer 122 . Although the upper limit of the thickness of the second base metal layer 121B is not particularly limited, it is preferably 2.0 μm or less from the viewpoint of sufficiently reducing the cost.

When the third base metal layer is also provided, its thickness is not particularly limited, but from the viewpoint of particularly suppressing the reaction between the base metal layer 121 and the solder layer 122, it is preferably 0.05 μm or more, for example. Although the upper limit of the thickness of the third base metal layer is not particularly limited, it is preferably 1.0 μm or less from the viewpoint of sufficiently reducing the cost.

Next, the solder layer 122 will be explained.

The solder layer 122 has a function of joining the substrate 11 made of inorganic material and the circuit board having the optical element when manufacturing the optical package, and its configuration is not particularly limited.

However, the average thickness of the solder layer 122 is preferably 5 μm or more, more preferably 15 μm or more. By setting the average thickness of the solder layer 122 to 5 μm or more, for example, even if the bonding surface of the circuit board to be bonded with the bonding layer 12 includes unevenness, the unevenness is filled with the material of the solder layer. This is because the airtightness can be particularly improved.

Note that the average value here means a value of a simple average (sometimes called an arithmetic average or an arithmetic average). Hereinafter, when simply referred to as "average", it means a simple average.

The upper limit of the average thickness of the solder layer 122 is also not particularly limited, but is preferably 50 μm or less, more preferably 30 μm or less. This is because even if the average thickness of the solder layer 122 exceeds 50 μm and becomes excessively thick, the airtight sealing effect does not change significantly.

The average value of the thickness of the solder layer 122 is obtained by measuring the thickness of the solder layer 122 of the window material 10 at a plurality of arbitrary measurement points with a laser microscope (manufactured by Keyence Corporation, model VK-8510) and obtaining the average value. can be calculated by The number of measurement points for measuring the thickness of the solder layer 122 to calculate the average value is not particularly limited, but is preferably two or more, more preferably four or more. Although the upper limit of the number of measurement points is not particularly limited, it is preferably 10 points or less, more preferably 8 points or less, from the viewpoint of efficiency.

When calculating the average value of the thickness of the solder layer 122, it is more preferable to measure the thickness at measurement points Z1 to Z8 shown in FIG. 3, for example, and calculate the average value.

FIG. 3 is a diagram showing an example of measurement points, and corresponds to FIG. 1(B). FIG. 3 and FIG. 1B are views of the window material 10 viewed from the side where the bonding layer 12 is formed, that is, bottom views. It has a shape arranged along the outer circumference. The bonding layer 12 including the solder layer 122 has an opening in the center, and the base 11 made of the inorganic material can be seen through the opening.

As shown in FIG. 3, when the solder layer 122 has a square opening in the center and has a square outer shape, measurement points Z1, Z3, The thickness, which is the maximum height of the solder layer, is measured at Z5, Z7 and the measurement points Z2, Z4, Z6, and Z8 at the center positions of the side portions 32A to 32D, and the average value thereof is the average value of the thickness of the solder layer 122. It is preferable to

The shape of the bottom surface of the solder layer is not limited to those shown in FIGS. 1(B) and 3, and may be any shape. , the opening may also have a corresponding shape. Also in this case, for example, the thickness can be measured at the corners of each side and at each central position of the side, and the average value of the measured thicknesses can be used as the thickness of the solder layer. Corners and sides will be described later.

The thickness deviation of the solder layer 122, that is, the deviation from the simple average thickness is preferably within ±20 μm, more preferably within ±10 μm.

By setting the deviation of the thickness of the solder layer 122 within ±20 μm, it is possible to particularly improve the hermetic sealing between the window material and the circuit board on which the optical element is arranged when manufacturing the optical package. Because it is possible and desirable.

The thickness deviation of the solder layer 122 within ±20 μm means that the deviation is distributed in the range of −20 μm or more and +20 μm or less.

The deviation of the thickness of the solder layer 122 can be calculated from the average value of the thickness of the solder layer described above and the measured value used when calculating the average value.

In addition, the thickness of the solder layer 122 may vary, albeit minutely, between the corners and sides of the solder layer depending on the method of forming the solder layer. Therefore, a weighted average of the thickness of the solder layer 122 may also be calculated and used as an evaluation index. When calculating the weighted average of the thickness of the solder layer 122 , the weighted average of the thickness of each side included in the solder layer is calculated, and the average (simple average) of the weighted averages of the thicknesses of all the sides is the thickness of the solder layer 122 . It can be a weighted average.

The weighted average of the thickness of each side is obtained by measuring the thickness at the corner and the center position of the side included in each side, and when the measurement point is the corner, the weighted average of the corner is calculated. Depending on the length in the longitudinal direction, when the measurement point is a side portion, the weight can be added by the longitudinal length of the side for calculating the weighted average of the side portion.

In addition, the corner refers to the portion where the sides of the solder layer overlap, and the side refers to the other portion. For example, in the case of the solder layer 122 shown in FIG. 3, the solder layer 122 has a square opening in the center, has a square outer shape, and has four sides 301 to 304 . Solder layer 122 shown in FIG. 3 has corners 31A to 31D where sides 301 to 304 overlap each other.

Specifically, the corner portion 31A is an area surrounded by straight lines A1, A2, B1, and B2 where the side 301 and the side 304 overlap. The corner portion 31B is an area surrounded by straight lines A3, A4, B1, and B2 where the side 301 and the side 302 overlap. The corner 31C is an area surrounded by straight lines A3, A4, B3, and B4 where the sides 302 and 303 overlap. The corner 31D is an area surrounded by straight lines A1, A2, B3, and B4 where the sides 303 and 304 overlap.

Also, the solder layer 122 shown in FIG. 3 has side portions 32A to 32D. Specifically, the side portion 32A is a region surrounded by straight lines A2, A3, B1, and B2. Also, the side portion 32B is a region surrounded by straight lines A3, A4, B2, and B3. The side portion 32C is a region surrounded by straight lines A2, A3, B3, and B4. The side portion 32D is a region surrounded by straight lines A1, A2, B2, and B3.

When the weighted average is obtained for the side 301, the thicknesses at the corners 31A, 31B, and the side 32A can be calculated by weighting the length of the side 301 of each region in the longitudinal direction according to the following procedure. can. The thickness TZ1 measured at the measurement point _Z1 at the center position of the corner 31A is weighted by the longitudinal length W1 of the side 301 of the corner 31A. The thickness TZ2 measured at the measuring point _Z2 at the center position of the side portion 32A is weighted by the length L1 of the side 301 in the side portion 32A in the longitudinal direction. The thickness TZ3 measured at the measuring point _Z3 at the center position of the corner 31B is weighted by the longitudinal length W2 of the side 301 of the corner 31B. Then, the weighted average of the side 301 can be calculated by dividing the sum of the calculation results by the sum of W1, L1, and W2 used for weighting.

Similarly, the weighted average is calculated for the other sides, and the weighted average of the solder layers can be obtained by calculating the average value.

In the case of the solder layer 122 shown in FIG. 4, it can be calculated by the following formula (1).
Weighted average value = [(W1 x T _Z1 + L1 x T _Z2 + W2 x T _Z3 ) / (W1 + L1 + W2) + (W3 x T _Z3 + L2 x T _Z4 + W4 x T _Z5 ) / (W3 + L2 + W4) + (W2 x T _Z5 + L1 x T _Z6 + W1 x T _Z7 )/(W1 + L1 + W2) + (W4 x T _Z7 + L2 x T _Z8 + W3 x T _Z1 )/(W3 + L2 + W4)]/4 (1)
Note that T _Zx in the above formula (1) means the thickness of the solder layer measured at each measurement point Zx (where x is any one of 1 to 8), and is similarly expressed hereinafter. L1 and L2 in the above formula (1) are the lengths of the sides of the opening provided in the center of the solder layer 122, as shown in FIG. Although L1 and L2 can be lengths measured at arbitrary positions, it is preferable to use average values measured at a plurality of positions. For example, L1 is preferably the average value of the length of one side of the opening measured at both ends and the center of the opening, that is, measured along straight lines B2, B3, and B5, for example. Similarly, L2 is preferably the average value of the length of one side of the opening measured at both ends and the center of the opening, that is, measured along straight lines A2, A3, and A5, for example.

The line widths W1 to W4 of the solder layer 122 may also be lengths measured at arbitrary positions, but it is preferable to use average values measured at a plurality of positions. For example, in the case of the line width W1, the value measured along the straight line B5 passing through the longitudinal center of the side 304 and the value measured along the straight lines B2 and B3 passing through both ends of the opening are measured at three points. It is preferred to use the mean value of the values.

Depending on the method of forming the solder layer, for example, the thickness may be bilaterally symmetrical. For example, when a solder layer is formed by a dipping method and the dipping direction is known, the thickness of the solder layer is symmetrical with respect to the dipping direction. For example, when dipping is performed along the straight line B5 in FIG. 3, the thickness of the solder layer 122 becomes symmetrical with respect to the straight line B5. Therefore, in this case, the thickness of the solder layer 122 at the measurement points Z7, Z6, and Z5 is the same as the thickness of the solder layer 122 at the measurement points Z1, Z2, and Z3, respectively. need not be measured. For example, the thickness is measured at five measurement points Z1 to Z4 and Z8, and the weighted average of the thickness of the solder layer 122 can be calculated with T _Z1 =T _Z7 , T _Z2 =T _Z6 and T _Z3 =T _Z5 . . In the case of simple averaging, the average value can also be obtained from the values of the same measurement points only.

Although the weighted average value of the solder layer is not particularly limited, it is preferably 4 μm or more, more preferably 13 μm or more. The upper limit of the weighted average value of the solder layer is also not particularly limited, but is preferably 70 μm or less, more preferably 60 μm or less.

Moreover, the deviation from the weighted average value of the solder layer, that is, the difference between the thickness at each measurement point and the calculated weighted average value is preferably within ±30 μm.

The reason why the weighted average value and the deviation of the weighted average value are preferable is the same as in the case of the average value, so the description thereof will be omitted.

The shape of the bottom surface of the solder layer is not limited to those shown in FIGS. can also be Also in this case, for example, the thickness is measured at the center position of the corners and sides included in each side, and the weighted average of each area is calculated. Then, the weighted average of the solder layers can be calculated by finding the average of the weighted averages of the thicknesses of all the sides.

The window material of this embodiment can be used by bonding to a circuit board having an optical element, and the solder layer 122 can bond the circuit board and the window material.

In general, an oxide film is present on the surface of the solder layer 122. However, in order to facilitate bonding with the circuit board, the lower surface of the solder layer 122, that is, the surface of the side facing the circuit board, may be oxidized. It is preferable that the existing oxide film melts into the solder layer 122 melted by heating and is thin enough to allow the melted solder layer 122 to come into contact with the upper surface of the circuit board. Although the thickness of the oxide film on the surface of the solder layer is not specifically limited, the thickness of the oxide film is preferably 10 nm or less, more preferably 5 nm or less.

Since it is preferable that the oxide film is small, the thickness of the oxide film can be set to 0 or more.

The solder layer 122 can be composed of various solders (composition for bonding).

The solder used for the solder layer 122 is not particularly limited, but for example, a material with a Young's modulus of 50 GPa or less is preferable, a material with a Young's modulus of 40 GPa or less is more preferable, and a material with 30 GPa or less is even more preferable.

As described above, the window material of the present embodiment can be used as a member of an optical package. However, after the optical package is formed, for example, when the optical element is turned on or off, temperature changes occur in the solder layer. Sometimes. Further, by setting the Young's modulus of the solder used for the solder layer to 50 GPa or less, even if the solder layer portion undergoes a temperature change and expands or contracts, damage to other members can be particularly suppressed, which is preferable. It is from.

Further, when the Young's modulus of solder is 50 GPa or less, the stress generated by the difference in thermal expansion between the substrate 11 made of an inorganic material and the circuit board provided with the optical element is applied to the solder layer that joins both members when an optical package is formed. This is because it can be absorbed within 122, which is preferable.

The lower limit of the preferred range of the Young's modulus of the solder used for the solder layer 122 is not particularly limited.

The Young's modulus of solder can be calculated from the results of a tensile test performed on the solder.

Also, the melting point of the solder used for the solder layer 122 is preferably 200° C. or higher, more preferably 230° C. or higher. This is because when the melting point of the solder is 200° C. or higher, the heat resistance of the optical package can be sufficiently improved. However, the melting point of the solder used for the solder layer 122 is preferably 280° C. or less. This means that at least a portion of the solder layer 122 is melted by performing heat treatment when manufacturing the optical package. This is because it is possible to particularly suppress the occurrence of damage to, for example.

The solder used for the solder layer 122 preferably has a density of 6.0 g/cm ³ or more, more preferably 7.0 g/cm ³ or more. This is because by setting the density of the solder used for the solder layer 122 to 6.0 g/cm ³ or more, it is possible to particularly improve airtightness. Although the upper limit of the density of the solder used for the solder layer 122 is not particularly limited, it is preferably 10 g/cm ³ or less, for example.

The thermal expansion coefficient of the solder used for the solder layer 122 is preferably 30 ppm or less, more preferably 25 ppm or less. This is because when the thermal expansion coefficient of the solder is 30 ppm or less, it is used as an optical package, and shape change due to heat generated when the optical element emits light is suppressed, and damage to the optical package can be more reliably prevented. . Although the lower limit of the thermal expansion coefficient of the solder used for the solder layer 122 is not particularly limited, it is preferably 0.5 ppm or more, for example.

The copper erosion resistance of the solder used for the solder layer 122 is preferably 15% or less, more preferably 10% or less. This is because when the solder used for the solder layer 122 has a copper corrosion resistance of 15% or less, the reaction with the base metal layer 121 and the like can be suppressed, which is preferable. Although the lower limit of the copper erosion resistance of the solder used for the solder layer 122 is not particularly limited, it is preferably 0 or more. The copper erosion resistance of the solder can be evaluated by evaluating the copper erosion resistance.

Copper erosion resistance can be evaluated, for example, by the following procedure.

Two copper wires with a diameter of 0.5 mm are cut to a length of about 3 mm, and the surfaces of the two copper wires are immersed in RMA (Rosin Midly activated) type flux to remove the oxide film. .

The first copper wire from which the oxide film has been removed is washed with ethanol, and the cross-sectional area S1 of the _first copper wire is measured. In addition, the cross-sectional area of a copper wire means the cross-sectional area in the surface perpendicular|vertical to the longitudinal direction of a copper wire.

Next, the second copper wire from which the oxide film has been removed is dipped in a solder bath heated to 400° C. for 60 seconds with solder to be evaluated. At this time, in order to prevent re-generation of the oxide film on the copper wire, the copper wire is immersed in a solder bath within 60 seconds after removing the oxide film with the flux. After being immersed in the solder bath, pull up the copper wire, polish the copper wire from the end of the side immersed in the solder bath, and measure the cross _- sectional area S2 of the copper wire at a position where the copper cross section can be confirmed.

The cross _- sectional area S2 of the copper wire after being immersed in the solder bath is compared with the cross _- sectional area S1 of the copper wire before being immersed in the solder bath, and the ratio of reduction in the cross-sectional area is calculated. Specifically, it can be calculated by the following formula.
(Copper erosion resistance) = (S ₁ - S ₂ )/S ₁ × 100
The solder constituting the solder layer is not particularly limited as described above, but for example, it contains tin, germanium, and nickel, the germanium content is 10% by mass or less, and the germanium content and the nickel content are The amount preferably satisfies the following formula (1).

[Ni]≦2.8×[Ge] ^0.3 (1)
(However, [Ni] indicates the content of nickel in terms of mass%, and [Ge] indicates the content of germanium in terms of mass%.)
This is because the solder described above can be easily joined to the object to be joined without removing the oxide film after the solder is placed on the member to be joined.

Components contained in the solder that can be preferably used in the solder layer are described below.
(tin)
The solder mentioned above contains tin (Sn).

Tin can reduce the difference in thermal expansion between solder and members to be joined such as a circuit board and a base metal layer. Furthermore, by containing tin as a main component of the solder, the melting point temperature of the solder can be set to about 230° C., which is the melting point temperature of tin.

The solder described above may contain tin as a main component. Containing as a main component means, for example, a component contained in the solder in the largest amount, and a component contained in the solder in an amount of 60% by mass or more is preferable.

In particular, the content of tin in the solder is, for example, more preferably 85.9% by mass or more, still more preferably 87.0% by mass or more, and particularly preferably 88.0% by mass or more.

This is because when the content of tin in the solder is 85.9% by mass or more, it exhibits a particularly high effect of mitigating the difference in thermal expansion between the member to be joined and the solder and lowering the melting temperature of the solder. .

The upper limit of the tin content in the solder is not particularly limited.

In addition to tin, the solders mentioned also contain germanium and nickel. By containing these components, it is possible to suppress the formation of an oxide film on the surface of the solder when it is applied to the members to be joined. In addition to germanium and nickel, the above-mentioned solder can also contain arbitrary components described later. Therefore, in order to ensure a sufficient content of these components other than tin, the tin content is preferably 99.9% by mass or less, as described above.

As will be described later, depending on the content of germanium or the like, it is possible to particularly improve the hermetic sealing between the members to be joined. From the viewpoint of improving hermetic sealing properties, it is preferable that the content of components other than tin, such as germanium, in the solder is at least a certain amount. Therefore, when it is required to particularly improve airtightness, it is particularly preferable that the upper limit of the tin content is 98.8% by mass or less.
(germanium)
The solder mentioned above contains germanium.

Germanium can suppress the formation of an oxide film on the solder surface when the solder is applied to the joint surfaces of the members to be joined. This is because when the solder is melted for application, germanium contained in the solder is preferentially oxidized, and oxidation of nickel in the solder can be suppressed.

Although the content of germanium in the above solder is not particularly limited, it is preferably 10% by mass or less, more preferably 8% by mass or less.

This is because if the germanium content of the solder exceeds 10% by mass, the germanium itself will excessively form an oxide, which may rather interfere with the joining to the member to be joined.

Although the lower limit of the content of germanium is not particularly limited, it is preferably more than 0.5% by mass, more preferably 0.7% by mass or more.

When the solder is melted, excess oxygen gasifies to form voids in the solder. In particular, when solder is melted for bonding in a vacuum environment, the gas such as oxygen expands and tends to form voids in the solder. The air gap may reduce the airtightness between the members to be joined.

On the other hand, by increasing the content of germanium in the solder to more than 0.5% by mass, the generation of voids in the solder due to excess oxygen as described above is suppressed, and the members to be joined are hermetically sealed. It is preferable because it can particularly improve the stopping property.
(nickel)
The above solder contains nickel (Ni) as described above.

Nickel contained in the solder has a strong tendency to become an oxide when the solder is melted. Therefore, when an oxide is contained in a joint portion of a member to be joined, for example, a joint surface of a circuit board, the oxide of the joint portion and the solder are easily combined, and the solder and the oxide-containing oxide are easily combined. This is because the wettability with the joint portion is improved, and high joint strength can be exhibited.

Although the content of nickel in the above solder is not particularly limited, it is preferable to have a certain relationship with the content of germanium.

Specifically, the nickel content [Ni] in terms of mass % and the germanium content [Ge] in terms of mass % preferably satisfy the following formula (1).

[Ni]≦2.8×[Ge] ^0.3 (1)
This is because when the nickel content [Ni] in terms of mass % of the solder exceeds 2.8×[Ge] ^0.3 , when the solder is melted to apply it to the joint surface of the member to be joined, This is because part of the solder may remain undissolved in the form of particles, making it impossible to join.

In particular, the nickel content [Ni] in terms of mass% and the germanium content [Ge] in terms of mass% satisfy [Ni] ≤ 2.4 × [Ge] ^0.3 . Preferably, [Ni]≦2.0×[Ge] ^0.3 is more preferably satisfied.

The lower limit of the content of nickel in the solder is not particularly limited, and should be greater than 0% by mass.

Also, the value obtained by dividing the nickel content [Ni] in terms of mass % by the germanium content [Ge] in terms of mass % is preferably less than 2.0, more preferably less than 1.5. That is, [Ni]/[Ge]<2.0 is preferable, and [Ni]/[Ge]<1.5 is more preferable.

This is because when [Ni]/[Ge] is 2.0 or more, a nickel oxide film may occur on the surface of the solder melted for application to the bonding surface of the member to be bonded. This is because there is a risk of hindering Note that the nickel oxide film means an oxide film containing a relatively large amount of nickel among the metal components.

Further, the value obtained by dividing the nickel content [Ni] in terms of mass % by the germanium content [Ge] in terms of mass % is preferably 0.005 or more, more preferably 0.01 or more. That is, 0.005≦[Ni]/[Ge] is preferable, and 0.01≦[Ni]/[Ge] is more preferable.

This is because when [Ni]/[Ge] is less than 0.005, the solder cannot retain sufficient oxygen, and when the joint portion of the member to be joined contains oxides, the joint portion is oxidized. This is because the wettability with respect to objects may decrease, and the hermetic sealing between members to be joined may be impaired.

Furthermore, the sum of the germanium content and the nickel content is preferably greater than 1.2% by mass. This is because when the total content of germanium and nickel in the solder is more than 1.2% by mass, the hermetic sealing between the members to be joined can be particularly enhanced.
(iridium)
The solder described above may also contain iridium (Ir).

By containing iridium in the solder described above, it is possible to reduce the occurrence of voids in the solder when the solder is melted. It is not clear why the presence of iridium in the solder suppresses the formation of voids when the solder is melted.

By reducing the occurrence of air gaps when the solder is melted in this way, it is possible to secure a sufficient bonding area with the member to be bonded, so that the bonding strength can be increased. In addition, since it is possible to suppress the occurrence of leak paths, it is possible to improve the airtightness between the members to be joined.

In addition, the coarsening of the eutectic crystals in the solder reduces the elongation and strength of the joint when the solder is melted and solidified to form a joint for joining the members to be joined. It may cause cracks in the part. However, by containing iridium in the solder, it is possible to suppress the coarsening of the eutectic crystals, thereby suppressing the occurrence of cracks that cause a decrease in airtightness.

Solder is generally processed into a linear shape and used as linear solder, but linear solder containing coarse crystals is fragile and difficult to use. On the other hand, by containing iridium in the above solder, it is possible to suppress coarsening of eutectic crystals in the solder. For this reason, the above-mentioned solder containing iridium can suppress deterioration in handleability even when formed into a linear solder.

The eutectic contained in the solder mentioned here is, for example, a Ge—Ni eutectic formed of germanium and nickel.

Although the content of iridium in the solder is not particularly limited, it is preferably 0.1% by mass or less, more preferably 0.025% by mass or less, and even more preferably 0.005% by mass or less.

This is because if the iridium content in the solder exceeds 0.1% by mass, when the solder is melted, an oxide film may be generated on the surface, which may interfere with the joining of the members to be joined. It's for.

Moreover, when the content of iridium in the solder is 0.025% by mass or less, the hermetic sealing property between the members to be joined can be particularly enhanced, which is more preferable.

The lower limit of the iridium content is also not particularly limited, and can be, for example, 0% by mass or more, preferably 0.0005% by mass or more.
(zinc)
The solder described above may also contain zinc (Zn).

When solder contains zinc, zinc has a strong tendency to become an oxide when the solder is melted. Therefore, when the joint portion of the member to be joined contains an oxide, the oxide of the joint portion and the solder are easily combined, and the wettability between the solder and the joint portion containing the oxide is improved. It becomes possible to improve and exhibit high joint strength.

Although the content of zinc in the above solder is not particularly limited, it is preferably 0.5% by mass or less.

This is because if the zinc content in the solder exceeds 0.5% by mass, when the solder is melted, an oxide film may be generated on the surface, which may hinder the joining of the members to be joined. It's for.

The lower limit of the content of zinc is also not particularly limited, and can be, for example, 0% by mass or more.
(oxygen)
And the above solder can further contain oxygen.

Oxygen in the solder is a component that promotes bonding between the solder and the joint portion containing the oxide when the joint portion of the member to be joined contains an oxide.

Although the state of oxygen contained in the solder is not particularly limited, oxygen is preferably contained in a molten form in the metallic material of the solder, for example. This is because at the interface between the solder and the member to be joined, the gradient of oxygen concentration between the oxide of the jointed part of the member to be joined and the metal material in the solder becomes smooth, and the joint interface becomes strong. is.

The method of adding oxygen to the solder is not particularly limited, but for example, a method of melting and manufacturing solder in an oxygen-containing atmosphere, and/or a bonding operation with a member to be joined in an oxygen-containing atmosphere. There is a method of performing

In addition, it is preferable that the solder before joining the member to be joined satisfies the content of oxygen in the solder, which will be described later. Therefore, it is preferable to adjust the oxygen concentration by a method of melting and manufacturing solder in an oxygen-containing atmosphere.

In particular, it is more preferable that the oxygen content in the solder, which will be described later, is satisfied in both the state of the solder before joining the members to be joined and the state of the solder after joining.

Although the content of oxygen in the solder is not particularly limited, it can be, for example, 0.0001% by mass or more, preferably 0.0007% by mass or more.

This is because the oxygen content of 0.0001% by mass or more can sufficiently exhibit the effect of increasing the bonding strength.

Although the upper limit of the oxygen content in the solder is not particularly limited, it can be, for example, 2% by mass or less, preferably 1% by mass or less.

This is because if the amount of oxygen contained in the solder becomes too large, oxides are likely to precipitate inside the solder, which may rather reduce the bonding strength. Therefore, as described above, the oxygen content in the solder is preferably 2% by mass or less.

The content of oxygen in the solder referred to here means the content of oxygen contained inside the solder. That is, when an oxide film is formed on the solder surface, it indicates the oxygen content in the solder after removing the oxide film.

When measuring the amount of oxygen in the solder, the method of removing the oxide film is not particularly limited, and the oxide film can be removed, for example, by treating the surface of the solder with acid or the like.

The oxygen content in solder can be measured, for example, by the following procedures (1) to (3).
(1) Prepare 0.5 g of a small piece of the produced solder as a sample for analysis.
(2) Chemical etching is performed to eliminate the influence of the oxide film contained on the surface of the solder pieces prepared in (1).

Specifically, a beaker containing a small piece of solder and twice-diluted hydrochloric acid is set in a water bath and heated at 80° C. for 12 minutes. After that, decantation is performed with degassed water, followed by decantation with ethanol.
(3) Measure the oxygen concentration of the solder sample from which the oxide film was removed in (2). The oxygen concentration can be measured using, for example, an oxygen/hydrogen analyzer.

So far, each component that can be contained in the above-described solder has been described, but the material is not limited to such materials. Moreover, the above-mentioned solder may contain unavoidable components that are generated, for example, when preparing the solder. The inevitable component is not particularly limited. However, when containing one or more elements selected from the group consisting of Fe, Co, Cr, V, Mn, Sb, Pb, Bi, Zn, As, and Cd as inevitable components, the content of the above elements is The total content is preferably 1% by mass or less, more preferably 500 ppm or less in total.

This is because the above elements have the function of reducing the wettability of the solder to the member to be joined, and by setting the total content of the above elements to 1% by mass or less, the wettability of the solder to the member to be joined is reduced. can be suppressed.

And since Ga, P, and B cause void generation, when one or more elements selected from the group consisting of Ga, P, and B are contained as inevitable components, the total content is 500 ppm or less. Preferably, 100 ppm or less in total is more preferable.

Also, the above solder preferably does not contain silver (Ag).

This is because silver forms an intermetallic compound (Ag ₃ Sn) with tin. Also, since Ag ₃ Sn has a high melting point, if it exists on the solder surface, it may slightly reduce the wettability with the member to be joined.

The phenomenon of decreased wettability with the member to be joined does not pose a problem if the solder is joined while removing the oxide film using a conventional ultrasonic soldering iron or the like. However, if the bonding is performed in an environment in which an ultrasonic soldering iron or the like is not used and the action of removing the oxide film does not work, the bonding may be hindered.

It should be noted that the fact that the solder does not contain silver means that it is below the detection limit when the solder is dissolved in acid and analyzed by ICP emission spectrometry.

Then, the above-mentioned solder is a circle of the minimum size in which the eutectic exists within a region having an area of 1.0×10 ⁶ μm ² at an arbitrary position in the cross section of the solder. is formed for each eutectic, the number of circles having a diameter of 220 μm or more is preferably two or less, or the number of circles having a diameter of 350 μm or more is preferably one or less.

Further, in the above-mentioned solder, the eutectic existing in a region having an area of 1.0×10 ⁶ μm ² at any position in the cross section of the solder has two or less eutectic having an area of 2000 μm ² or more. , or one or less eutectic having a size of 4000 μm ² or more is preferable.

The above-mentioned solder preferably satisfies either or both of the above-mentioned regulations regarding the eutectic in a predetermined region of the cross section of the solder, at least before joining the members to be joined. In particular, the solder described above has any or both of the above provisions for eutectic within a given region of the cross-section of the solder both before joining the members to be joined and after joining the members to be joined. is more preferably satisfied. That is, it is more preferable that the above solder satisfies either or both of the above provisions when the eutectic within a predetermined region of the cross section of the solder is evaluated at an arbitrary timing. .

The shape of the region having an area of 1.0×10 ⁶ μm ² at any position described above is not particularly limited, and can be any shape. Examples of the shape of the area include a square, rectangle, polygon, and the like. In the case of a square area, the length of one side can be set to 1.0×10 ³ μm, for example. In the case of a rectangular region, the length of each side can be selected so as to secure the above area. Even in the case of a polygonal region, the length of each side can be selected so as to secure the above area, and the length of each side constituting the polygon is not limited.

The eutectic contained in the above-described solder includes, for example, a Ge—Ni eutectic formed of germanium and nickel.

As described above, the coarsening of the eutectic crystals in the solder reduces the elongation and strength of the joint when the solder is melted and solidified to form a joint that joins the members to be joined. can cause cracks to occur in joints. However, when the eutectic in the cross section of the solder satisfies the above conditions, it can be said that the coarsening of the eutectic crystal can be suppressed, and the occurrence of cracks that cause a decrease in airtightness can be suppressed.

In addition, solder can be processed into a linear shape and used as linear solder, but if the eutectic in the cross section of the solder satisfies the above conditions, coarsening of eutectic crystals in the solder is suppressed. It is possible to have sufficient handleability when it is made into linear solder.

Solders that can be suitably used for the solder layer 122 include, for example, tin (Sn)-antimony (Sb)-based solders, etc., in addition to the solders described above.

Although the content of each component in the tin-antimony solder is not particularly limited, it is preferable that the content of antimony is, for example, 1% by mass or more. This is because antimony has the function of increasing the solidus temperature in the tin-antimony solder, and when the content of antimony is 1% by mass or more, such an effect can be particularly exhibited, which is preferable.

Although the upper limit of the content of antimony is not particularly limited, it is preferably 40% by mass or less, for example. This is because an antimony content of 40% by mass or less prevents the solidus temperature from becoming excessively high, making it possible to obtain a solder suitable for mounting electronic components.

Tin-antimony based solders may contain tin. Tin can reduce the difference in thermal expansion between solder and members to be joined such as a circuit board and a base metal layer. Furthermore, by containing tin as a main component of the solder, the melting point temperature of the solder can be set to about 230° C., which is the melting point temperature of tin.

The tin-antimony solder can also be composed of antimony and tin, and in this case, the remainder excluding antimony can be composed of tin.

The tin-antimony-based solder can contain arbitrary additive components other than antimony and tin, and can contain, for example, one or more selected from silver (Ag), copper (Cu), and the like. Silver and copper have the function of increasing the solidus temperature of the solder, like antimony. In this case, the balance other than antimony and optional additive components can be made up of tin.

Although a configuration example of solder that can be suitably used for the solder layer 122 has been described, the solder used for the solder layer 122 of the window member 10 of the present embodiment is not limited to such solder as described above. be.

Although the shape of the bonding layer 12 is not particularly limited, for example, as shown in FIG. The bonding layer 12 including 122 can be arranged along the outer periphery of the inorganic material substrate 11 . The bonding layer 12 including the solder layer 122 has an opening in the center, and the base 11 made of the inorganic material can be seen through the opening. In FIG. 1B, the substrate 11 made of inorganic material is larger than the bonding layer 12 including the solder layer 122, but the configuration is not limited to this. For example, the outer periphery of the base material 11 made of an inorganic material and the outer periphery of the bonding layer 12 including the solder layer 122 may be configured to coincide with each other.

Although FIG. 1B shows the solder layer 122 positioned on the outermost surface of the bonding layer 12, the surface perpendicular to the stacking direction of each layer of the bonding layer 12 (vertical direction in FIG. 1A) is shown. The cross-sectional shape of the bonding layer 12 in 3 is preferably the same regardless of the layer.

The method for manufacturing the window material of the present embodiment is not particularly limited, but may include, for example, the following steps.

A substrate preparation step of preparing a substrate of an inorganic material.
a bonding layer forming step of forming a bonding layer on one surface of the inorganic material substrate;
Although the specific operation of the substrate preparation step is not particularly limited, for example, the inorganic material substrate can be cut to a desired size, or the inorganic material substrate can be processed to have a desired shape. . In addition, when an antireflection film is arranged on the surface of a substrate made of an inorganic material, the antireflection film can also be formed in this step. The method for forming the antireflection film is not particularly limited, and for example, it can be formed by a dry method or a wet method. In the case of a dry method, a vapor deposition method, a sputtering method, an ion plating method, or the like can be used. The film can be formed by one or more methods selected from. In the case of the wet method, the film can be formed by one or more methods selected from immersion methods, spray coating methods, and the like.

The bonding layer forming process can have, for example, a base metal layer forming step for forming a base metal layer and a solder layer forming step.

The base metal layer forming step can form a base metal layer on one surface of the inorganic material base. The method for forming the underlying metal layer is not particularly limited, and can be arbitrarily selected according to the type of the underlying metal layer to be formed. For example, a film can be formed by a dry method or a wet method. In the case of a dry method, the film can be formed by one or more methods selected from a vapor deposition method, a sputtering method, an ion plating method, and the like. . In the case of the wet method, the film can be formed by one or more methods selected from electrolytic plating, electroless plating, printing, and the like.

As described above, the base metal layer can also be composed of a plurality of layers, and each layer can be formed by an arbitrary method.

In the solder layer forming step, a solder layer can be formed on one surface of the substrate of inorganic material or on the base metal layer. The method of forming the solder layer is not particularly limited, and examples thereof include one or more selected from dipping, coating using a dispenser, printing, laser metal deposition, and soldering wire. .

In the dipping method, the solder, which is the raw material of the solder layer, is melted in a solder melting tank, and the part of the member that forms the solder layer, for example, the base of an inorganic material on which the base metal layer is arranged, is melted. It is a method of forming a solder layer by dipping in molten solder in a melting tank.

In the coating method using a dispenser, for example, molten solder is supplied from a dispenser connected to a syringe to a portion of a member forming a solder layer, such as a base made of an inorganic material on which a base metal layer is arranged, where the solder layer is to be formed, A method of forming a solder layer.

The printing method is a method of forming a solder layer by printing paste-like solder on a portion of a member on which a solder layer is to be formed, for example, a base made of an inorganic material on which a base metal layer is arranged, where the solder layer is to be formed. In addition, after printing, heat treatment can be performed as necessary.

In the laser metal deposition method, powdery solder is supplied to the part of the base metal base on which the solder layer is to be formed, for example, the part of the base made of an inorganic material on which the underlying metal layer is to be formed. , is a method of forming a solder layer by cooling.

The method using a solder wire uses solder processed into a wire shape, that is, a linear shape, and for example, an automatic soldering robot or the like is used to form a member that forms a solder layer, for example, a solder layer of an inorganic material substrate on which a base metal layer is arranged. In this method, a solder layer is formed by supplying melted solder to the portion where the is to be formed.

The method for manufacturing the window material of the present embodiment may further have optional steps as required.

As described with reference to FIGS. 1A and 1B, the bonding layer can be formed in a desired shape on one surface 11a of the substrate 11 made of an inorganic material.

For this reason, in the method for manufacturing a window material of the present embodiment, for example, after forming a bonding layer by a base metal layer forming step and a solder layer forming step, the bonding layer is patterned into a desired shape. It can also have a transformation step. In the patterning step, for example, a resist corresponding to a pattern to be formed is placed on the exposed surface of the solder layer, and portions of the solder layer and underlying metal layer not covered with the resist are removed by etching or the like. Can be patterned. A resist removal step can also be performed after the patterning step to remove the resist.

In the case where the base metal layer includes a plurality of layers, after forming a part of the layer included in the base metal layer, a patterning step is performed, and the part of the layer included in the deposited base metal layer is formed. can also be patterned. After the patterning step, a resist removing step for removing the resist may be performed, and then a remaining underlying metal layer may be formed on the patterned underlying metal layer.

Further, for example, in the method for manufacturing a window material of the present embodiment, before performing the base metal layer forming step and the solder layer forming step, a resist arrangement is performed in which a resist is arranged in a portion where the base metal layer and the solder layer are not formed. It can also have steps. By forming the underlying metal layer and the solder layer after forming the resist, it is possible to form the underlying metal layer and the solder layer only on the portions corresponding to the patterns to be formed. In this case, it is also possible to have a resist removing step for removing the resist after the solder layer forming step.

In addition, in order to simultaneously manufacture a plurality of window materials, when a plurality of bonding layers corresponding to each window material are formed on a substrate (material before cutting) of an inorganic material having a size corresponding to a plurality of pieces, it is possible to manufacture a plurality of window materials at the same time. It can also have a cutting step for cutting the substrate. The cutting method is not particularly limited, and a cutting method suitable for the base of the inorganic material, such as the cutting method using the laser beam described above, can be employed. When the bonding layer is continuously formed on adjacent window materials, that is, when the bonding layer is arranged on the cutting line, the bonding layer can also be cut together in the cutting step.

It should be noted that after forming the optical package, it is also possible to cut the substrate of the inorganic material together with the circuit board to separate it into individual pieces.

According to the window material of the present embodiment described above, since the volume ratio of gold in the bonding layer is suppressed, the window material can be manufactured at a reduced cost.
[Optical package]
Next, a configuration example of the optical package of this embodiment will be described.

The optical package of this embodiment can have the aforementioned window material and a circuit board having an optical element.

A configuration example of the optical package of this embodiment will be described with reference to FIG.

FIG. 4 schematically shows a cross-sectional view of the window material of the optical package of the present embodiment and the circuit board having the optical element on a plane parallel to the lamination direction. Although the window member 10 and the circuit board 41 are shown separately in FIG. 4 so as to be distinguished from each other, both members are joined and integrated in the optical package 40 .

As described above, the optical package 40 of this embodiment has the window member 10 described above and the circuit board 41 having the optical element 42 .

Since the window material 10 has already been described, the same numbers as in FIG. 1 are given and the description is omitted.

The circuit board 41 is not particularly limited, and various circuit boards having an insulating base material 411 and wiring (not shown) for supplying power to the optical element 42 can be used.

However, when the window material 10 is joined, the circuit board 41 must have an insulating base material 411 made of ceramics in order to improve the airtightness of the space surrounded by the window material 10 and the circuit board 41. is preferred.

Here _, the ceramic material used for the insulating base material ₄₁₁ of the circuit board 41 is not particularly limited. ) and the like.

The shape of the insulating base material 411 of the circuit board 41 is not particularly limited, but in the case of the optical package 40, the optical element 42 is arranged by the inorganic material base 11, the insulating base material 411, and the joint portion described later. It is preferable to be configured so that a closed space can be formed in the portion to be closed. For this reason, it is preferable that the insulating base material 411 has an opening in the central portion of its upper surface 411a and has a concave portion 411A that is a non-through hole including the opening. The upper surface of the insulating base material 411 is the surface facing the window material 10 when used as an optical package, and can be said to be the surface on the side that is joined to the window material 10 .

The wall portion 411B surrounding the concave portion 411A supports both the bonding layer 12 of the window member 10 and a base metal layer for a circuit board, which will be described later, in the case of an optical package. It can have a shape corresponding to the underlying metal layer.

Further, the circuit board 41 can have a circuit board base metal layer 412 on the upper surface 411a of the insulating base material 411 and on the upper surface of the wall portion 411B.

The circuit board base metal layer 412 can function to increase the adhesion between the insulating base material 411 of the circuit board 41 and the window member 10 . The specific configuration of the circuit board base metal layer 412 is not particularly limited. , and the base metal layer 412C for the third circuit board. Although an example in which the circuit board base metal layer 412 is composed of three layers is shown here, it is not limited to such a configuration, and may be composed of one layer, two layers, or four or more layers.

When the circuit board base metal layer 412 is composed of three layers as described above, for example, the first circuit board base metal layer 412A is made of the same metal as the metal used to form the wiring (circuit) on the circuit board 41. preferably configured. For example, the first circuit board base metal layer 412A can be a layer containing one or more metals selected from copper (Cu), silver (Ag), and tungsten (W). The first circuit board base metal layer 412A can also be a layer made of one or more metals selected from copper (Cu), silver (Ag), and tungsten (W). Even in this case, it is not excluded that the underlying metal layer 412A for the first circuit board contains unavoidable impurities.

The second circuit board base metal layer 412B can be a layer that prevents the third circuit board base metal layer 412C and the first circuit board base metal layer 412A, which will be described later, from being alloyed. It can be a layer containing (Ni). The base metal layer 412B for the second circuit board can also be a layer made of nickel (Ni). Even in this case, it is not excluded that the underlying metal layer 412B for the second circuit board contains unavoidable impurities.

The base metal layer 412C for the third circuit board can be a layer for preventing the base metal layer 412B for the second circuit board from being oxidized, and can be a layer containing gold (Au), for example. The base metal layer 412C for the third circuit board can also be a layer made of gold (Au). Even in this case, it is not excluded that the base metal layer 412C for the third circuit board contains unavoidable impurities.

The thickness of each layer constituting the circuit board underlying metal layer 412 is not particularly limited and can be selected arbitrarily.

The thickness of the base metal layer 412A for the first circuit board is preferably 1 μm or more, for example. The upper limit of the thickness of the base metal layer 412A for the first circuit board is also not particularly limited, but from the viewpoint of sufficiently reducing the cost, it is preferably 20 μm or less.

The thickness of the second circuit board base metal layer 412B is preferably 1 μm or more from the viewpoint of particularly suppressing alloying between the first circuit board base metal layer 412A and the third circuit board base metal layer 412C. The upper limit of the thickness of the base metal layer 412B for the second circuit board is also not particularly limited, but from the viewpoint of sufficiently reducing the cost, it is preferably 20 μm or less.

The thickness of the third circuit board base metal layer 412C is preferably 0.03 μm or more from the viewpoint of particularly preventing oxidation of other circuit board base metal layers. Although the upper limit of the thickness of the base metal layer 412C for the third circuit board is not particularly limited, it is preferably 2.0 μm or less, more preferably 0.5 μm or less, from the viewpoint of sufficiently reducing the cost.

The shape of the circuit board base metal layer 412 is also not particularly limited. It is preferred to have a corresponding shape. Specifically, the bonding layer 12 of the window member 10 and the base metal layer 412 for the circuit board have a cross-sectional shape in a plane perpendicular to the lamination direction (vertical direction in FIG. 4) of both members when forming an optical package. The same shape is preferred.

The method for forming the circuit board base metal layer 412 is not particularly limited, and can be arbitrarily selected according to, for example, the type of the circuit board base metal layer 412 to be formed. For example, a film can be formed by a dry method or a wet method. In the case of a dry method, the film can be formed by one or more methods selected from a vapor deposition method, a sputtering method, an ion plating method, and the like. . In the case of the wet method, the film can be formed by one or more methods selected from electrolytic plating, electroless plating, printing, and the like.

As described above, the underlying metal layer for a circuit board can be composed of a plurality of layers, and each layer can be formed by an arbitrary method.

The optical element 42 arranged on the circuit board 41 is not particularly limited, and for example, a light-emitting element such as a light-emitting diode, or a light-receiving element or the like can be used.

In addition, when the optical element 42 is a light emitting element, the wavelength region of the light emitted by the light emitting element is not particularly limited. For this reason, for example, a light emitting element that emits light in an arbitrary wavelength range selected from the range of ultraviolet light to infrared light, that is, light in an arbitrary wavelength range selected from the wavelength range of 200 nm or more and 1 mm or less is used. can be used.

However, according to the optical package of the present embodiment, the base of the window member, which is a member for transmitting light from the light emitting element, is not the base of transparent resin but the base 11 of inorganic material. Therefore, as compared with the case where a transparent resin substrate is used as the substrate of the window material, the hermetic sealing performance can be improved, and deterioration of the window material due to the light from the light emitting element can be suppressed. Therefore, when the optical element is a light-emitting element, the optical package of the present embodiment is particularly effective when using a light-emitting element that particularly requires airtightness or a light-emitting element that emits light whose resin is likely to deteriorate. It is preferable because it can demonstrate A light-emitting element that particularly requires airtightness includes, for example, a light-emitting element that emits UV-C, which is light in a wavelength range of 200 nm or more and 280 nm or less. Further, light-emitting elements that emit high-output light, such as lasers, can be used as light-emitting elements that cause deterioration of the resin to progress easily. Therefore, when the optical element 42 is a light-emitting element, a light-emitting element that emits UV-C, a laser, or the like can be preferably used as the light-emitting element from the viewpoint of exhibiting a particularly high effect.

The base 11 of the inorganic material of the window member 10 and the insulating base 411 of the circuit board 41 can be joined together by the joining portion 43 . As shown in FIG. 4 , the joint portion 43 can have the joint layer 12 of the window member 10 and the circuit board underlying metal layer 412 of the circuit board 41 . The bonding portion 43 can also be composed of the bonding layer 12 and the base metal layer 412 for the circuit board.

The structure of the joint portion 43 is not particularly limited, but from the viewpoint of cost, the volume ratio of gold in the joint portion is preferably 5% or less, more preferably 4% or less.

Since the joint 43 may not contain gold, the volume ratio of gold in the joint may be 0 or more.

Each layer such as the already-described solder layer and base metal layer included in the joint portion 43 can be formed with a substantially uniform thickness. Therefore, for example, when a layer containing gold exists as a gold layer made of gold in the joint portion 43, the volume ratio of gold is defined as the ratio of the thickness of the gold layer to the thickness of the joint portion 43. can also Further, when the layer containing gold also contains components other than gold, the volume content ratio of gold in the layer containing gold to the ratio of the thickness of the layer containing gold to the thickness of the joint portion 43 can also be a value obtained by multiplying

When the volume ratio of gold in the joint is calculated using the thickness of each layer as described above, an average value of simple averages can be used as the thickness of the solder layer.

According to the optical package of this embodiment described above, since the above-described window material is used, the optical package can be made at a reduced cost.

The method for manufacturing the optical package of this embodiment is not particularly limited, and the optical package can be manufactured by any method.

The method for manufacturing the optical package of this embodiment can have, for example, the following steps.

A circuit board preparation step of preparing a circuit board having an optical element.

A joining step of placing a window material on a circuit board and joining the window material and the circuit board.

In the circuit board preparation step, an optical element can be arranged on a circuit board manufactured by a conventional method, and a circuit board provided with the optical element can be prepared. In addition, in the case of separating into individual pieces after the joining step is finished, in the circuit board preparation step, a circuit board before cutting, in which a plurality of circuit boards are integrated, can be prepared.

Then, in the bonding step, the window material can be placed on the circuit board and the window material and the circuit board can be bonded. Although the specific bonding method is not particularly limited, for example, in the optical package 40 shown in FIG. They can be superimposed so as to be in contact. Then, for example, the window material 10 is heated from the other surface 11b of the substrate 11 made of an inorganic material toward the circuit board 41 side, that is, while being pressed along the block arrow B in the drawing, thereby forming the solder layer 122. is melted and then cooled, the window material 10 and the circuit board 41 can be joined.

In the bonding process, the oxide film present on the lower surface 12a of the bonding layer 12 melts into the melted solder layer 122 due to heating, and the melted solder layer 122 adheres to the upper surface 412a of the circuit board base metal layer 412. It is preferably thin enough to be in contact with. Although the thickness of the oxide film is not specifically limited, the thickness of the oxide film is preferably 10 nm or less, more preferably 5 nm or less.

The method of pressing the inorganic material substrate 11 is not particularly limited. A method using a weight and the like can be mentioned.

In the optical package obtained after the bonding step, when the region sealed by the window material 10 and the circuit board 41 is to be in a predetermined atmosphere, the atmosphere in performing the heat treatment may be set to the predetermined atmosphere. preferable. For example, an atmosphere selected from an air atmosphere, a vacuum atmosphere, an inert atmosphere, and the like can be used. The inert atmosphere can be an atmosphere containing one or more gases selected from nitrogen, helium, argon, and the like.

In the bonding step, the conditions for the heat treatment are not particularly limited, and, for example, it is preferable to heat the solder layer to a temperature higher than the melting temperature of the solder. However, if the heating is performed rapidly, thermal stress may be applied to the substrate of the inorganic material, and cracks may occur. , the temperature of the first heat treatment is preferably maintained for a certain period of time. The holding time at the first heat treatment temperature is not particularly limited, but is preferably 30 seconds or longer, more preferably 60 seconds or longer. However, from the viewpoint of productivity, the retention time at the first heat treatment temperature is preferably 600 seconds or less.

After the first heat treatment temperature is maintained for a certain period of time, the temperature is preferably further increased to the second heat treatment temperature, which is a temperature equal to or higher than the melting point of the solder of the solder layer. The temperature of the second heat treatment is preferably the melting point of the solder plus 20° C. or higher in order to sufficiently bond the window material 10 and the circuit board 41. If the temperature of the second heat treatment is too high, the second heat treatment temperature is set on the circuit board. The temperature of the second heat treatment is preferably 300° C. or less, for example, because the optical element may be damaged by heat. The time for holding at the second heat treatment temperature is not particularly limited, but is preferably 20 seconds or more in order to sufficiently bond the window material 10 and the circuit board 41 . However, in order to more reliably suppress the adverse effects of heat on the optical element, the holding time at the second heat treatment temperature is preferably 1 minute or less.

After heat treatment at the second heat treatment temperature, the bonding process can be completed by cooling to room temperature, for example, 23°C.

The method for manufacturing the optical package of this embodiment can have arbitrary steps as required. For example, when a circuit board in which a plurality of circuit boards are integrated and not singulated is subjected to the joining process, a cutting process may be included. The cutting method used in the cutting step is not particularly limited, and any method can be used. It is also possible to simultaneously cut the circuit board and the window material into individual pieces by the cutting method using a laser beam described in the description of the window material. Also, a plurality of cutting methods can be combined.

Although specific examples will be given below, the present invention is not limited to these examples.

First, methods for evaluating window materials and optical packages manufactured in the following examples will be described.
(Airtightness test)
An airtightness test was conducted on the optical packages using the window materials produced in the following examples, immediately after production, or after reflow treatment or heat cycle testing under predetermined conditions, to evaluate the hermetic sealing characteristics. .

The airtightness test was carried out in accordance with JIS Z 2331:2006, specifically in the following procedure.

First, the optical package to be evaluated was placed in a pressurized container and held for 2 hours under the condition that helium (He) was pressurized to 5.1 atm in the pressurized container (pressurization step ).
After the pressurization step, the optical package to be evaluated was taken out from the pressurized container, and the leak amount of helium (He) was measured in the vacuum container within one hour after taking it out (helium leak amount measurement step).
When the helium leak rate (He leak rate) measured in the helium leak amount measurement step was 4.9×10 ⁻⁹ Pa·m ³ /s or less, it was determined to be acceptable (determination step). In the judging step, if the He leak rate is greater than 4.9×10 ⁻⁹ Pa·m ³ /s, it is judged to be unacceptable.
[Example 1]
(Window material)
A window material shown in FIGS. 1A and 1B was produced.

Specifically, a disk-shaped plate made of quartz having a diameter of 100 mm and a thickness of 0.5 mm was prepared as a pre-cutting material for the substrate of inorganic material (substrate preparation step).

Then, a bonding layer was formed on one surface of the material before cutting of the inorganic substrate by the following procedure (bonding layer forming step).

First, by ion beam vapor deposition, a first base metal layer and a second base metal layer are formed in order from the side of the inorganic material base before cutting on the entire surface of the inorganic material base before cutting. A film was formed (underlying metal layer forming step).

A chromium (Cr) layer with a thickness of 0.03 μm was formed as the first base metal layer, and a copper (Cu) layer with a thickness of 0.2 μm was formed as the second base metal layer.

Next, after applying a resist to the surface of the second metal underlayer opposite to the surface facing the first metal underlayer, that is, the entire exposed surface, the resist is exposed using ultraviolet rays, and then developed. By doing so, the patterned resist was arranged (resist arrangement step). The patterned resist had a quadrangular cross section in a plane parallel to one side of the inorganic material substrate before cutting, and had a quadrangular opening in the center.

Then, portions of the first base metal layer and the second base metal layer, which were not covered with the resist, were etched with an etchant, patterned, and then the resist was removed (resist removing step).

Next, a nickel (Ni) layer having a thickness of 0.8 μm was formed as a third base metal layer by electroless Ni plating on the patterned first base metal layer and second base metal layer. This formed a patterned underlying metal layer including a first underlying metal layer, a second underlying metal layer, and a third underlying metal layer.

Next, a solder layer was formed on the base metal layer. The solder used for the solder layer was prepared in advance by the following procedure.

The components contained in the solder are weighed so that Sn is 97.499% by mass, Ge is 1.5% by mass, Ni is 1.0% by mass, and Ir is 0.001% by mass, mixed and melted. to create a raw material alloy. After the raw material alloy was melted, it was poured into a mold to prepare solder.

Then, the solder, which is the raw material of the solder layer, is melted in the solder melting tank, and the portion of the inorganic material substrate on which the base metal layer is arranged, which forms the solder layer, is melted in the solder melting tank. After dipping, the solder layer was formed by cooling (solder layer forming step).

The solder used to form the solder layer had a melting point of 230° C., a density of 7.3 g/cm ³ , and a coefficient of thermal expansion of 22.9 ppm. Also, the copper erosion resistance was 7.47%.

The melting point was measured by using a DSC (manufactured by Shimadzu Corporation, model: DSC-60) by raising the temperature at 10°C/min. The density was measured by the Archimedes method.

The coefficient of thermal expansion was measured using a vertical thermal expansion meter (manufactured by Shinku Riko, model: DL-7000). In the measurement, the temperature was raised at a rate of 5°C/min within the temperature range from 23°C to 200°C in an argon atmosphere.

Copper erosion resistance was evaluated by the following procedure.

Two copper wires with a diameter of 0.5 mm are cut to a length of about 3 mm, and the two copper wires are immersed in RMA (Rosin Midly activated) type flux to remove the surface oxide film. .

The first copper wire from which the oxide film has been removed is washed with ethanol, and the cross-sectional area S1 of the _first copper wire is measured. In addition, the cross-sectional area of a copper wire means the cross-sectional area in the surface perpendicular|vertical to the longitudinal direction of a copper wire.

Next, the second copper wire from which the oxide film has been removed is immersed in a solder bath heated to 400° C. for 60 seconds. At this time, in order to prevent re-generation of the oxide film on the copper wire, the copper wire is immersed in a solder bath within 60 seconds after removing the oxide film with the flux. After being immersed in the solder bath, pull up the copper wire, polish the copper wire from the end of the side immersed in the solder bath, and measure the cross _- sectional area S2 of the copper wire at a position where the copper cross section can be confirmed.

The cross _- sectional area S2 of the copper wire after being immersed in the solder bath is compared with the cross _- sectional area S1 of the copper wire before being immersed in the solder bath, and the ratio of reduction in the cross-sectional area is calculated. Specifically, it was calculated by the following formula.
(Copper erosion resistance) = (S ₁ - S ₂ )/S ₁ × 100
When evaluating copper erosion resistance, a digital microscope (manufactured by Keyence Corporation, model: VHX-900) and image processing software attached to the digital microscope were used to measure the cross-sectional area of the copper wire.

Moreover, when the Young's modulus of the obtained solder was calculated from the results of the tensile test, it was confirmed to be 20 GPa. For the tensile test, a tensile tester (Autograph AGX-100 kN manufactured by Shimadzu Corporation) was used, and a test piece of JIS No. 14A was tested at a tensile speed of 3 mm/min.

A method for calculating the average value of the thickness of the solder layer and the weighted average value will be described with reference to FIG. FIG. 3 is a diagram for explaining the measurement points, and corresponds to FIG. 1(B). In this embodiment, as described above, a bonding layer including a solder layer is formed on one surface of the inorganic material substrate before cutting so as to correspond to a plurality of window materials. Therefore, the thickness of the solder layer was evaluated by arbitrarily selecting the solder layer included in one window material by cutting and dividing into individual pieces. Therefore, FIG. 3 shows the solder layer 122 and the inorganic material substrate 11 included in one window material after being separated into pieces used for the measurement.

When separated into individual pieces, the solder layer 122 has a belt-like shape along the outer circumference of the inorganic material substrate 11 in a cross section perpendicular to the lamination direction of the inorganic material substrate 11 and the solder layer 122 .

The solder layer was formed by the dipping method as described above, and was formed by introducing it into the solder melting bath along the straight line B5 in FIG. Therefore, the thickness of the solder layer is symmetrical with respect to the straight line B5.

For this reason, the thickness of the solder layer is measured at five measurement points Z1, Z2, Z3, Z4, and Z8 in FIG. Regarding the thickness T _Zx at Z7, T _Z1 =T _Z7 , T _Z2 =T _Z6 and T _Z3 =T _Z5 . Then, when the average value of the thickness of the eight measurement points Z1 to Z8 was calculated, the simple average was 29.31 μm.

Also, the weighted average value of the solder layer 122 was calculated by the above-described formula (1) using the measured values at the thicknesses T _Z1 to T _Z4 and T _Z8 at the measurement points Z1, Z2, Z3, Z4, and Z8. By the way, it was confirmed that the weighted average was 20.14 μm.

As described above, since the thickness of the solder layer is bilaterally symmetrical about the straight line B5, T _Z1 =T _Z7 , T _Z2 =T _Z6 ,T _Z3 =T Calculation is performed as _Z5 . Since formula (1) has already been explained, the explanation is omitted here.

As for the length L1 of one side of the opening, the average of the lengths of one side of the opening measured along the straight lines B2, B3, and B5 was used. Similarly, the length L2 of one side of the opening was measured at both ends and the center of the opening, that is, the average value of the lengths of one side of the opening measured along the straight lines A2, A3, and A5 was used.

The average value of the line widths measured at a plurality of points was also used for each line width W1 to W4 of the solder layer. In the case of the line widths W1 and W2, the values measured along the straight line B5 passing through the longitudinal center of the sides 304 and 302 and the values measured along the straight lines B2 and B3 passing through both ends of the opening are three points. The average value of the measured values at was used. In the case of the line widths W3 and W4, the values measured along the straight line A5 passing through the longitudinal centers of the sides 301 and 303 and the values measured along the straight lines A2 and A3 passing through both ends of the opening are measured at three points. The average value of the measured values at was used.

As a result of the above calculations, it was confirmed that the maximum deviation of the thickness of the solder layer from the simple average was 10 μm, and the maximum deviation from the weighted average was 19 μm. rice field.

After the solder layer 122 is formed, as shown in FIG. 5, a patterned bonding layer 52 is formed on one surface of the pre-cut material 51 of the inorganic material substrate so as to correspond to the plurality of window materials. A substrate 50 was obtained. Then, the laser beam is focused on an arbitrary position in the thickness direction of the pre-cutting material 51 of the substrate of inorganic material, and after scanning the irradiation position of the laser beam along the contour of the patterned bonding layer 52, the laser beam The pre-cutting material 51 of the substrate of inorganic material was cut by applying a force so that the place where the focal position of . The laser beam was scanned once along the planned cutting line. Therefore, as shown in FIG. 2, the side surfaces of the individualized inorganic material substrate 11 had a linear pattern 111 along the outer peripheries of one surface 11a and the other surface 11b.

As a result of the above steps, as shown in FIG. 1B, the solder layer 122 is formed along the outer circumference of the base 11 made of inorganic material in a bottom view of the window material 10 when viewed from the side on which the bonding layer 12 is formed. , and has a rectangular opening in the center, through which the substrate 11 made of an inorganic material can be seen. Although FIG. 1B shows the solder layer 122 located on the outermost surface, the cross-sectional shape of the bonding layer 12 in a plane parallel to one surface 11a of the substrate 11 made of inorganic material is shown in FIG. ) has the same shape as the solder layer 122 shown in FIG.

The bonding layer 12 composed of the base metal layer 121 and the solder layer 122 is formed along the outer periphery of the inorganic material substrate 11 as described above, and has an outer shape of 5 mm square and a line width of the same value all around. , and the line widths W1 to W4 (see FIG. 3) are all 0.65 mm.

A window material was manufactured by the above steps.

Since the window material 10 does not include a layer containing gold, the volume ratio of gold in the bonding layer is zero. For this reason, it was confirmed that the bonding material cost could be significantly reduced to about 25% compared to the conventional window material using an AuSn alloy.

Further, when the thickness of the oxide film on the surface of the solder layer 122 of the window member 10 was measured using an XPS measuring device (Quantera SXM (manufactured by Ulvac-Phi)), the thickness of the oxide film was found to be 5 nm. It could be confirmed.
(optical package)
The optical package 40 shown in FIG. 4 was manufactured using the window material and the circuit board 41 having the optical element 42 .

As the circuit board 41, the insulating base material 411 is made of alumina (aluminum oxide) and has a rectangular parallelepiped shape of 5.8 mm square and 1.28 mm in height, and has wiring (not shown). was used. The insulating base material 411 of the circuit board 41 has an opening formed in the central portion of its upper surface 411a, and has a concave portion 411A which is a non-through hole including the opening. The recess 411A is configured so that the optical element 42 can be placed on its bottom. The upper surface 411a of the insulating base material 411 is the surface facing the window material 10 when the optical package 40 is formed. The opening is square, and the recess 411A is a square columnar cavity (square tube) surrounded by walls 411B.

The circuit board 41 has a circuit board base metal layer 412 on the upper surface 411a of the insulating base material 411 so as to surround the opening and along the outer circumference of the upper surface 411a of the insulating base material 411. ing.

As the circuit board base metal layer 412, a first circuit board base metal layer 412A, a second circuit board base metal layer 412B, and a third circuit board base metal layer 412C are laminated in this order from the insulating substrate 411 side. layered structure.

A silver (Ag) layer with a thickness of 10 μm as the base metal layer 412A for the first circuit board, a nickel (Ni) layer with a thickness of 5 μm as the base metal layer 412B for the second circuit board, and a base for the third circuit board. A gold (Au) layer having a thickness of 0.4 μm was formed as the metal layer 412C.

The base metal layer 412 for circuit board has a shape corresponding to the bonding layer 12 of the window member 10 . Specifically, the cross-sectional shape of the bonding layer 12 of the window material 10 and the base metal layer 412 for the circuit board in a plane perpendicular to the lamination direction (vertical direction in FIG. 4) is It was configured to have the same shape as the metal layer 412 . Therefore, the base metal layer 412 for the circuit board had an outer shape of 5 mm square and a line width of 0.65 mm.

An optical element (manufactured by OptoSupply, model: OSBL1608C1A) was placed on the bottom of the recess 411A and connected to wiring (not shown).

Then, the window member 10 and the circuit board 41 having the optical element 42 were joined together according to the following procedure to manufacture the optical package 40 (joining step).

First, the upper surface 412a of the circuit board base metal layer 412 of the circuit board 41 provided with the optical element 42 and the lower surface 12a of the bonding layer 12 of the window material 10 on the solder layer 122 side are arranged to face each other and be in contact with each other. bottom.

Then, from the other surface 11b of the inorganic material substrate 11 of the window member 10, a pressing means having a pressing member in contact with the inorganic material substrate 11 and a spring for applying pressure to the pressing member is applied along the block arrow B. It was placed in a heat treatment furnace while being pressurized.

Next, the atmosphere in the heat treatment furnace was changed to a vacuum atmosphere, and the temperature was raised from 23° C. to 80° C., which is the first heat treatment temperature, and then held for 300 seconds. Next, the temperature was raised to 280°C, which is the second heat treatment temperature, and after holding for 30 seconds, the heater was turned off and the temperature was cooled to 23°C.

An optical package was manufactured by the above procedure.

The joint portion 43 of the obtained optical package only has the third circuit board base metal layer 412C as a layer containing gold. The volume ratio of gold in the joint portion 43 calculated from the thickness was 0.87%.

Seven optical packages were manufactured under the same conditions in order to conduct the following reflow test and heat cycle test.
(evaluation)
(1) Airtightness test without heat treatment One optical package was passed the airtightness test described above after manufacturing.
(2) Airtightness test after reflow test Further, the following reflow tests 1 to 3 were performed for each of the three optical packages.

As reflow test 1, one optical package was placed in a reflow oven and heated once with the temperature profile shown in FIG.

As reflow test 2, one optical package was placed in a reflow oven and heated three times repeatedly with the temperature profile shown in FIG.

As reflow test 3, one optical package was placed in a reflow oven and heated repeatedly five times with the temperature profile shown in FIG.

An airtightness test was conducted on each of the optical packages after reflow tests 1 to 3, and all optical packages passed.
(3) Airtightness test after heat cycle test The following heat cycle tests 1 to 3 were performed for each of the three optical packages.

As heat cycle test 1, one optical package was subjected to 100 cycles of heat cycles in which it was held at −40° C. for 30 minutes and then at 85° C. for 30 minutes.

As a heat cycle test 2, one optical package was subjected to 500 heat cycles of holding at −40° C. for 30 minutes and then holding at 85° C. for 30 minutes.

As a heat cycle test 3, one optical package was subjected to 200 heat cycles of holding at −40° C. for 30 minutes and then holding at 100° C. for 30 minutes.

An airtightness test was conducted on each of the optical packages after the above heat cycle tests 1 to 3, and all of the optical packages passed.

According to the optical package of this embodiment, since the proportion of gold in the joint portion is suppressed, the optical package can be manufactured at a reduced cost.

Moreover, as described above, it was confirmed that high airtightness was maintained not only immediately after manufacturing, but also when a reflow test and a heat cycle test were performed. This is because the solder used for the solder layer of the window material has a low Young's modulus of 20 GPa, so that cracks in the inorganic material base 11 and separation between the inorganic material base 11 and the circuit board 41 do not occur. Conceivable.
[Example 2]
(Window material)
The window materials shown in FIGS. 1A and 1B were produced and evaluated according to the following procedure.

Also in this example, as in the case of Example 1, a disk-shaped plate made of quartz was prepared as a pre-cutting material for the substrate of inorganic material (substrate preparation step).

Next, a bonding layer was formed on one surface of the material before cutting of the inorganic material substrate by the following procedure (bonding layer forming step).

An underlying metal layer having a lattice pattern was formed on one surface of the inorganic material substrate before cutting by ion beam vapor deposition or electroless plating (underlying metal layer forming step).

Specifically, first, a chromium (Cr) layer having a thickness of 0.2 μm as the first base metal layer 121A and a copper (Cu) layer having a thickness of 0.2 μm as the second base metal layer 121B are sequentially formed from the base 11 side of the inorganic material. ) layer was formed by ion beam evaporation.

Next, after applying a resist to the surface of the second metal underlayer opposite to the surface facing the first metal underlayer, that is, the entire exposed surface, the resist is exposed using ultraviolet rays, and then developed. By doing so, the patterned resist was arranged (resist arrangement step). The patterned resist had a quadrangular cross section in a plane parallel to one side of the inorganic material substrate before cutting, and had a quadrangular opening in the center.

Then, portions of the first base metal layer and the second base metal layer, which were not covered with the resist, were etched with an etchant, patterned, and then the resist was removed (resist removing step).

Next, a nickel-boron alloy (Ni—B alloy) having a thickness of 0.8 μm is formed as a third base metal layer by electroless nickel-boron alloy plating on the patterned first base metal layer and the second base metal layer. ) formed a layer.

Next, in the same manner as in Example 1, a solder layer 122 was formed on the underlying metal layer 121 . The solder layer 122 uses the same solder as in the first embodiment.

Then, in the same manner as in Example 1, the pre-cut material 51 (see FIG. 5) of the inorganic material substrate was cut into individual pieces. As a result, a window material having an inorganic substrate of 5 mm square was obtained.

Since the obtained window material does not contain a gold-containing layer, the volume ratio of gold in the bonding layer is zero. As shown in FIG. 2, the side surface of the inorganic material substrate after singulation had a linear pattern 111 parallel to one surface 11a and the other surface 11b of the inorganic material substrate 11. .

The line width and the length of one side of the solder layer 122 of the window material 10 were measured using an optical microscope (BX51TRF manufactured by Olympus). L2 was 3.0 mm.

Since the line widths W1 to W4 and the lengths L1 and L2 of the sides of the openings were measured and calculated in the same manner as in Example 1, description thereof is omitted here.

Using a laser microscope (manufactured by Keyence Corporation, model: VK-8510), the thickness of the solder layer was cut out from the same inorganic material substrate before cutting. Eight measurement points Z1 to Z8 shown in FIG. Then, using the obtained measured values, the average value (simple average value) of the thickness of the solder layer for each sample and the weighted average value using the above-described formula (1) were obtained. Table 1 shows the results.

（光学パッケージ）
上記窓材を用いて図４に示した光学パッケージを作製した。

(optical package)
An optical package shown in FIG. 4 was produced using the above window material.

As the circuit board 41, the insulating base material 411 is made of alumina (aluminum oxide) having a rectangular parallelepiped shape with an outer shape of 5.8 mm square and a height of 1.28 mm, and has wiring (not shown). was used. The insulating base material 411 of the circuit board 41 has an opening formed in the central portion of its upper surface 411a, and has a concave portion 411A which is a non-through hole including the opening. The recess 411A is configured so that the optical element 42 can be placed on its bottom. The upper surface 411a of the insulating base material 411 is the surface facing the window material 10 when the optical package 40 is formed. The opening is square, and the recess 411A is a square columnar cavity (square cylinder) surrounded by walls 411B.

The circuit board 41 has a circuit board base metal layer 412 on the upper surface 411a of the insulating base material 411 so as to surround the opening and along the outer circumference of the upper surface 411a of the insulating base material 411. ing.

As the circuit board base metal layer 412, a first circuit board base metal layer 412A, a second circuit board base metal layer 412B, and a third circuit board base metal layer 412C are laminated in this order from the insulating substrate 411 side. layered structure.

A tungsten (W) layer having a thickness of 10 μm as the first circuit board base metal layer 412A, a nickel (Ni) layer having a thickness of 3 μm as the second circuit board base metal layer 412B, and a third circuit board base metal layer 412B. A gold (Au) layer having a thickness of 2 μm was formed as the metal layer 412C.

The base metal layer 412 for circuit board has a shape corresponding to the bonding layer 12 of the window member 10 . Specifically, the cross-sectional shape of the bonding layer 12 of the window material 10 and the base metal layer 412 for the circuit board in a plane perpendicular to the lamination direction (vertical direction in FIG. 4) is It was configured to have the same shape as the metal layer 412 . For this reason, the base metal layer 412 for circuit board had an outer shape of 3.6 mm square and a line width of 0.3 mm.

An optical element (manufactured by OptoSupply, model: OSBL1608C1A) was placed on the bottom of the recess 411A and connected to wiring (not shown).

Then, the window member 10 and the circuit board 41 having the optical element 42 were joined together according to the following procedure to manufacture the optical package 40 (joining step).

First, the upper surface 412a of the circuit board base metal layer 412 of the circuit board 41 provided with the optical element 42 and the lower surface 12a of the bonding layer 12 of the window material 10 on the solder layer 122 side are arranged to face each other and be in contact with each other. bottom.

Then, from the other surface 11b of the inorganic material substrate 11 of the window member 10, a pressing means having a pressing member in contact with the inorganic material substrate 11 and a spring for applying pressure to the pressing member is applied along the block arrow B. It was placed in a heat treatment furnace (under _N2 atmosphere) while applying pressure (200 g). Then, the window material 10 and the circuit board 41 are fusion-bonded with the temperature profile shown in FIG. 7 to form an optical package.

Specifically, the temperature was raised from 23° C. to 80° C., which is the first heat treatment temperature, and then held for 300 seconds. Next, the temperature was raised to 280°C, which is the second heat treatment temperature, and after holding for 60 seconds, the heater was turned off and cooled to 23°C.

The joint portion 43 of the obtained optical package only has the third circuit board base metal layer 412C as a layer containing gold. The volume ratio of gold in the joint portion 43 calculated from the thickness was 3.0% to 3.4%.
(evaluation)
The obtained optical package passed an airtightness test.
[Example 3]
An optical package was fabricated in the same manner as in Example ₂ , except that the atmosphere in the heat treatment furnace was changed to an air atmosphere (air atmosphere) when the window material 10 and the circuit board 41 were joined.

The obtained optical package passed an airtightness test.
[Example 4]
A window material and an optical package were manufactured in the same manner as in Example 2, except that when the window material was manufactured, the laser beam was scanned twice after the solder layer 122 was formed and then the individual pieces were separated. bottom.

Specifically, in the first irradiation of the laser beam, in the thickness direction of the material before cutting of the substrate of the inorganic material, the laser beam is set at a position far from the laser beam incident surface and along the planned cutting line. The irradiation position of was moved. Then, in the second irradiation of the laser beam, the focal position of the laser beam is changed to a position closer to the incident surface of the laser beam than in the first irradiation, and the irradiation position of the laser beam is similarly along the planned cutting line. was moved.

After the second irradiation with the laser beam, a force was applied so that the place where the focal position of the laser beam passed was a fulcrum, thereby cutting the pre-cutting material of the inorganic material substrate.

As a result, as shown in FIG. 8, two linear patterns 811 and 812 are formed on the side surfaces of the individualized inorganic material substrate 11, which are considered to be caused by changes in the bonding state of the inorganic material. It was confirmed that The two linear patterns 811 and 812 had shapes along the outer peripheries of the one surface 11a and the other surface 11b.

It was also confirmed that patterns of similar shapes were obtained on the cut surface even when the output of the laser was changed.

In this case also, the substrate 11 made of the inorganic material could be singulated without defects such as chipping, cracking, and chipping.

When the surface roughness of the linear patterns 811 and 812 generated at this time was measured using a laser microscope (manufactured by Keyence Corporation, model: VK-8510), the surface roughness Ra was 0.3 μm. When the surface roughness of the region 82 between the pattern 811 and the surface 11a was measured, the surface roughness Ra was 1.1 μm. From the evaluation result of the surface roughness, it was confirmed that the bonding state of the inorganic material changed between the linear pattern 811 and the other portions.

An optical package was produced in the same manner as in Example 2, except that the obtained window material was used.

An airtightness test was conducted on the obtained optical package, and it passed.

Although the window material and the optical package have been described above with the embodiments and examples, the present invention is not limited to the above-described embodiments and examples. Various modifications and changes are possible within the scope of the present invention described in the claims.

This application claims priority based on Japanese Patent Application No. 2017-122542 filed with the Japan Patent Office on June 22, 2017. invoke.

REFERENCE SIGNS LIST 10 window material 11 inorganic material substrate 111, 811, 812 linear pattern 12, 52 bonding layer 121 underlying metal layer 122 solder layer 40 optical package 41 circuit board 411 insulating substrate 42 optical element 43 bonding portion

Claims (6)

A window material for an optical package having an optical element,
a substrate of inorganic material;
a bonding layer disposed on one surface of the substrate of the inorganic material;
The bonding layer has a base metal layer and a solder layer,
The volume ratio of gold in the bonding layer is 10% or less,
The average value of the thickness of the solder layer is 5 μm or more and 50 μm or less,
The Young's modulus of the solder constituting the solder layer is 50 GPa or less,
The solder constituting the solder layer contains tin, germanium, and nickel,
The germanium content is 10% by mass or less,
A window in which the germanium content and the nickel content satisfy the following formula (1), and the total of the germanium content and the nickel content is more than 1.2% by mass material.
[Ni]≦2.8×[Ge] ^0.3 (1)
(However, [Ni] indicates the content of nickel in terms of mass%, and [Ge] indicates the content of germanium in terms of mass%.) 2. The window material according to claim 1, wherein the thickness deviation of said solder layer is within ±20 μm. 3. The window material according to claim 1, wherein the side surface of the substrate of the inorganic material has a linear pattern along the outer periphery of the one surface. An optical package comprising the window material according to any one of claims 1 to 3 and a circuit board provided with an optical element. 5. The optical package according to claim 4, wherein said circuit board has an insulating substrate made of ceramics. the base of the inorganic material of the window material and the insulating base of the circuit board are bonded by a bonding portion including at least the bonding layer,
6. The optical package according to claim 4 or 5, wherein the volume fraction of gold in said joint is 5% or less.

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