JPH03151694A - Sealing method for electronic device housing - Google Patents

Abstract

PURPOSE:To eliminate deformation at a cover or the like by inserting a solder sheet to a junction and laser welding it. CONSTITUTION:When a cover made of the same iron alloy as that of a vessel is brought into contact with the vessel made of the alloy having a glass terminal and is hermetically sealed, a solder sheet is inserted to the junction of both, and welded by laser irradiation. That is, when a solder sheet 5 is inserted between the vessel 2 for forming a package 1 and a cover 3 and irradiated with a laser, the laser of the power of the degree for melting the solder is sufficient. Accordingly, the temperature rise of the parts of be welded may be low, and hence a stress is small. Thus, a deformation such as warpage of a package is eliminated, and an improper external appearance is eliminated.

Description

[Detailed Description of the Invention] [Summary] Regarding a method of sealing a housing containing an electronic device, the purpose is to perform laser welding without causing deformation of the housing, and the present invention relates to a container made of an iron-based alloy and equipped with a glass terminal. Electronic device casing [Industrial application field] characterized in that when a lid made of the same iron-based alloy is brought into contact with the casing and sealed, a solder sheet is inserted into the joint between the two, and the welding is performed by laser irradiation. The present invention relates to a method for sealing an electronic device housing.

Although a high degree of reliability is required, such as in optical transmission systems, electronic devices installed in environments where temperature and humidity change, such as outdoors, have a hermetic seal structure.

Since it is necessary to provide glass terminals for input and output on the casing (hereinafter referred to as the package), iron, which has a coefficient of thermal expansion close to that of glass, is used as a sealing material for the glass terminals and as a component of the package. alloys are used.

For example, iron-42% nickel (Pe-42% Ni),
Pe-52% Ni, iron-28% chromium (Fe-28%
Cr) +29% iron nickel-17% cobalt (Fe-
29%-17%Co, commonly known as Kovar) + Fe-42%N
Examples include i-6%Cr (commonly known as Sylvania).

Then, after mounting an electronic device in a container constituting the package and connecting input/output terminals to glass terminals provided on the container, the lid is aligned and welded to form a hermetically sealed package.

[Prior Art] Laser welding is used as a method for hermetically sealing packages.

Due to the need for compactness and light weight, the thickness of the package has become thinner, and the thickness of the package is about 0.5 mm, but when welding thin materials together, the materials lack rigidity. Deformation such as warping is likely to occur after laser welding.

In other words, warpage occurs because the stress caused by thermal contraction cannot be alleviated, and as the material itself becomes thinner, elastic deformation tends to occur more easily.

FIG. 2 shows this state. A welded part 4 is created by scanning a laser beam on the end surface where the container 2 and the lid 3 that make up the package l are joined. After welding, the lid 3 Warping occurs.

Conventionally, this problem has been dealt with by increasing the thickness of the member that easily deforms (in this case, the lid).

However, this method requires a large amount of welding energy to obtain a good penetration depth, and the welded portion 4
Since it is heated to a temperature above .degree. C., there is concern that it may affect the electronic devices stored in the package 1.

Therefore, soldering was considered as a countermeasure to this problem.

However, when soldering, it is necessary to heat the entire package to a soldering temperature, and in this case, as before, there is a concern that the electronic device may deteriorate due to heating.

Also, soldering requires the use of flux,
There is a problem of corrosion due to flux adhering to the inside of the package.

In addition, gold (Au) is applied to the bonding surface to improve solder wettability.
Surface treatment such as plating is required.

Although various methods have been tried as described above, countermeasures have been required since these go against the goals of cost reduction and weight reduction.

[Problem to be solved by the invention]

Laser sealing is used to hermetically seal electronic devices, and thin iron-based alloys are used to make them smaller and lighter.

However, the lid and other components of the package tend to deform due to heat shrinkage after laser welding, and countermeasures have been necessary.

[Means to solve the problem]

The problem mentioned above is that when a lid made of the same iron alloy is brought into contact with a container made of an iron alloy equipped with a glass terminal to form a hermetic seal, a solder sheet is inserted into the joint between the two and laser irradiation is performed. This problem can be solved by configuring a method for sealing an electronic device case using welding.

[Effect]

In the present invention, laser welding is performed by inserting a solder sheet into the joint, and FIG. 1 is a sectional view after welding.

That is, the solder sheet 5 is inserted between the container 2 and the lid 3 that constitute the package I, and laser irradiation is performed. Less rise is required and therefore less stress is generated.

In addition, lead (Pb)-based high melting point solder is suitable as the solder to be used, but since PB-based solder is a material with high elongation, stress caused by thermal contraction is absorbed by the plastic deformation of the solder itself. There is an advantage.

Therefore, as shown in FIG. 1, even if the container 2 and the lid 3 constituting the package 1 are made of materials with the same thickness, no deformation such as warpage will occur.

Next, in some cases, the joint surfaces are plated with Au, but in conventional welding, there is a problem that Fe gets mixed into the welded part made of ^U, causing solidification cracks and resulting in defects. When inserting a sheet, there is no such problem and it becomes possible to perform highly reliable welding.

〔Example〕

Using Fe-42%Ni as a package material, a container 2 with a thickness of 0.5 mm as shown in FIG.
and lid 3 was formed.

Next, as a solder sheet, the composition was Pbi, 0%5n-1,
A sample made of 5% Ag (melting point 309°C) and a thickness of 0.3M was prepared, and this was sandwiched between the container 2 and the lid 3, and laser welding was performed in the conventional manner.

In other words, as a laser, neodymium-yttrium
An aluminum garnet (Nd-vAG) laser was used, and the conditions were: Pulse width: 3 to 6 IIls, Defocus amount: On+
m average power output 50-150 W, pulse ray 1:
60ppS.

Welding speed: 150 mm 7 minutes.

Lens focal length: too mm, shielding gas: ^
r Gas pressure crab 1.5 kg/cm2 Gas flow rate:
30j! /minute.

As a result, it was possible to obtain a hermetically sealed package in which the lid 3 did not warp.

FIG. 3 is a graph showing the relationship between laser output and bond strength obtained by changing the pulse width from 3 to 6 ms, and shows that the bond strength of the welded part is maximum when the laser output is 100 W, and is approximately 2.5 ms. 5k
A value of g/mm2 can be obtained.

Note that if the laser output increases beyond that, not only the solder sheet but also the container 2 and lid 3 at the joint will melt, and in this case the joint strength will conversely decrease.

In the same figure, the broken line 6 indicates this state, and the pulse width is 3.
In the case of 11Is and 411Is, significant dissolution is already observed at a laser output of 150 W because the energy is large.

Next, airtightness was tested using a helium (He) leak detector, but no problems were found.

〔Effect of the invention〕

As described above, by carrying out the present invention, deformation such as warping of the package is eliminated, thereby eliminating appearance defects.

Furthermore, since metal plates of the same thickness can be used, weight reduction can be achieved at the same time.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a package according to the present invention after welding, FIG. 2 is a cross-sectional view showing the conventional state after welding, and FIG. 3 is a relationship between laser output and bonding strength. In the figure, 1 is the package, 2 is the container, 3 is the lid,
4 is a welded part, and 5 is a solder sheet.

Claims (1)

[Claims] When a container made of an iron-based alloy with a glass terminal is brought into contact with a lid made of the same iron-based alloy and sealed, a solder sheet is inserted into the joint between the two, and laser irradiation is performed to weld the two. A method for sealing an electronic device case.