DE2308041A1 - SOLDER ALLOY AND USE OF THE SAME - Google Patents

Description

23080A1

A-65
^A ^ February 19, 1973

ASAHI GLASS COi, LTD., Tokyo, Japan

Solder alloy and use of the same

The invention relates to a solder alloy and the use thereof. It has been difficult in the past to apply a solder alloy directly to an inorganic solid oxide body such as glass, ceramic or metal with an oxide surface, e.g. B. silicon, germanium, aluminum, titanium, zirconium, tantalum or the like. Apply. A solder alloy has now been proposed which adheres firmly to the aforementioned difficult-to-solder materials when using ultrasound. These solder alloys belong to the alloy groups Pb-Sn-Zn-Sb and Pb-Sn-Zn-Sb-Al. Such solder alloys and the use of the same are z. As described in U.S. Patent Application No. 91,208, filed November 19, 1970. These special solder alloys for soldering of ceramics or the like are applicable at temperatures ranging from 200 to 350 ⁰ O. These temperatures are relatively low. However, if these solder alloys are used to solder electrical or electronic components, the quality of the electrical or electronic components is lowered. If z. For example, a glass bulb of a vidicon is to be soldered to a front glass plate, it is necessary that this takes place at a temperature below about 180 ⁰ C.

Accordingly, it is the object of the present invention to provide the solder alloy, their application temperature below about 180 and which is suitable for soldering materials that are difficult to solder, as well as a use of the same.

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This object is achieved according to the invention by a solder alloy with 2 to 98.5 percent by weight of Pb; 1 to 97.5 percent by weight Sn; 0.5-60 percent by weight of Cd; 0.05-10 weight percent Zn; 0-5 weight percent Sb; 0-5 weight percent Bi and 0-15 percent by weight of at least one rare earth element dissolved.

According to the invention, these solder alloys are excellent for soldering difficult-to-solder materials by applying it to the difficult-to-solder material in a molten state and applying a vibration treatment in the contact area. An essential idea of the present invention is to use a solder alloy made of lead, tin, cadmium and zinc and to carry out a vibration treatment, preferably with ultrasound. The solder alloy is suitable for soldering of all hard solderable materials such as glass, ceramic, silicon or germanium at temperatures below about 180 ⁰ C.

The solder alloy according to the invention which is suitable for soldering ceramic materials or semiconductors or the like and is applicable at relatively low temperatures, is composed of mother alloys of Pb and Sn. Zn is added, to increase the solderability of oxides and Cd is added to lower the melting point. If required, Sb is added to increase weather resistance and water resistance. The rare ones Earths are optionally added to increase the bond strength and Bi is added to increase the bond strength To regulate melting point. The components Sb, Bi and the rare earth metals can be omitted.

In the specified solder composition, Pb is in the range from 2 to 98.5 percent by weight and Sn in the range from 1 to 97.5 Weight percent before. If the amount of lead in the solder

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is below 2 percent by weight, and if the amount of Sn is above 97.5 percent by weight, the range is the semi-molten state of the melting solder alloy, d. H. the temperature range within which a Mixture of liquid and mixed crystals is too tight, so that the molten alloy immediately from liquid state changes to the solid state, whereby the processability is significantly impaired.

On the other hand, if there is more than 98.5 weight percent Pb and less than 1 weight percent Sn in the solder alloy are, the melting point and viscosity of the solder alloy are too large, and the smoothness and airtightness are too large of the solder alloy are too small. Zn is added to the solder to give it a high bond strength to ceramic materials such as pottery and glass and semiconductors. If the amount of Zn in the solder exceeds 0.05 percent by weight, so this effect is exerted to a sufficient extent. On the other hand, if the amount of zinc in the solder is 30% by weight exceeds, it is difficult to come to a uniform structure in the manufacture of the solder. Preferably the amount of zinc is in the range from 1 to 10 percent by weight.

The rare earth metals are added in an amount preferably less than 15 percent by weight of the solder alloy. If the amount of the rare earth elements exceeds 15% by weight, a solder alloy with a uniform structure cannot be obtained. It is generally preferred to add the rare earths in the range of 1-10 percent by weight. The rare earth metals La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er ₁ Tm, Yb, Lu, Y and Sc are possible. From an economical point of view, it is preferable to use Ce and in particular a mixture of rare earth metals such as. B. Cermischmetall, consisting of 86.8 # Ce,

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3.0% La, 4.0 # Nd, 6.2% Sm and Pr with the main impurities of 3.2 10 Pe, 0.37% Mg, 0.27 1 ° Al and 0.73% Si (in percent by weight ).

Further, if more than 3 ½ weight percent Sb is added to the solder alloy, the water resistance and weather resistance of the solder alloy are improved. However, if the amount of Sb in the solder exceeds 5% by weight, the ductility is lowered. The melting point of the solder alloy can be lowered by adding Bi. However, if the amount of Bi in the solder exceeds 5% by weight, the adhesive strength is deteriorated.

Cd is an important component in the solder according to the invention. This component causes a lowering of the melting point of the Solder alloy. If no Cd is added, the melting temperature is very high and the temperature range of the semi-molten one Condition is too tight. Preference is given to adding more than 0.5 percent by weight of Cd. However, if the amount of Cd in the solder exceeds 60 percent by weight, the ductility is reduced.

A small amount of Al can help prevent slag can be added on the molten solder alloy. Furthermore, small amounts of one or more of the elements Si, Ti or Be are added to opacify the surface to prevent the solder alloy. It is preferred to have less than 0.1 weight percent Al and less than 0.5 weight percent to add a combined amount of Si, Ti or Be to the solder.

A particularly high bond strength can be achieved with a solder the following composition (in percent by weight) can be achieved.

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Pb 40 - 60%

Sn 20 - 40 %

Zn 1 - 5 Io

Gd 5-25 %

Bi ο - 3%

Sb 0 - 3%

In the method for producing the solder alloy, the metal components are melted and preferably mixed in a vacuum or under an inert gas atmosphere such as nitrogen or argon or under a reducing gas such as hydrogen. The solder alloy has a melting point of 70-180 ⁰ C and is at these low temperatures, a large adhesion. The solder alloy can be applied at remarkably low temperatures, so that it is very suitable for soldering electrical or electronic components which are destroyed at higher temperatures. The adhesive strength of the solder alloy according to the invention is not significantly superior to the adhesive strength of conventional solder alloys which are used at relatively high temperatures and which contain no Cd. A major advantage of the solder alloy according to the invention, however, is that such objects can be soldered excellently which require greater airtightness than adhesive strength.

The soldering according to the invention is not only suitable for Soldering of metal without an oxide skin, but also for soldering the following difficult-to-solder materials with an oxide surface. The solder according to the invention can be applied directly to a large number of materials that are difficult to solder, in particular on inorganic Estkörperoxde, such as oxide glass, z. B. silicate glass or quartz glass, glass ceramic, pottery or porcelain, sintered, melted or burned refractory oxides, such as aluminum oxide, magnesium oxide, spinel, thorium oxide,

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Beryllium oxide, zirconium oxide, ceramic materials, for electrical and electronic components such as barium titanate, ferrites, Steatite, forsterite, titanium oxide, natural or synthetic inorganic oxide crystals such as quartz crystals, ruby crystals or sapphire crystals and for cermets. Furthermore, the solder alloy can be used on difficult-to-solder semiconductor metals such as silicon or germanium can be applied directly, as well as on difficult-to-solder metals with oxide surfaces, such as aluminum, titanium, Zirconium, tantalum or silicon or germanium or the like. The solder according to the invention can be firmly attached to the surface of the material that is difficult to solder can be connected by applying a vibration treatment (preferably an ultrasonic vibration treatment) in a molten state brings up. To use the solder alloy according to the invention, the soldering surface of the difficult-to-solder material is used brought into contact with the molten or half-molten solder, and the solder is subjected to a vibration treatment. Suitable results are obtained when using ultrasound at a frequency of preferably 20-100 KHz in achieved in a direction parallel to the surface to be soldered.

In a special case, a soldering spatula is heated to around 200 250 ⁰ G and set in vibration in a direction parallel to the surface to be soldered. During this processing, the soldering spatula exerts a frictional force on the surface to be soldered, so that the activity of the oxide surface is increased. If a material is to be soldered with a relatively large heat capacity, so it is preferable to the surface of this material to approximately 100 - preheat 150 ⁰ C before the soldering operation begins, so that the bonding strength is improved between the solder layer and the Oxydoberfläche. The solder layer can usually have a thickness of 0.02 0.2 mm or up to several millimeters.

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In a further method for soldering a surface of a material that is difficult to solder with the one according to the invention The vibration treatment and preferably the ultrasonic vibration treatment is applied to a bath of the molten solder Solder applied and the difficult to solder material is immersed so that the solder on the surface of the with the molten solder that has come into contact with it. The difficult-to-solder material that comes with the solder is coated, is then with another solderable material, such as. B. brought into contact with a solderable metal, whereupon the contact area is heated to effect adhesive strength. On the other hand, you can also two difficult to solder materials are connected to each other by applying the solder according to the invention to both to be connected Applies surfaces and then brings the coated surfaces into contact with one another and the contact area heated to melt the solder. After cooling, it is found that good adhesive strength is achieved in this way will.

The solder according to the invention is particularly suitable as a base solder layer on which a conventional solder, which is in mainly consists of Pb and Sn, and which in itself is not suitable for soldering the difficult-to-solder material, is applied. In the latter case, the solder according to the invention is applied to the glass or ceramic surface or the like. whereupon the conventional solder is applied to this solder layer or whereupon a solderable material with the conventional Solder is attached to it.

In the following the invention is illustrated by means of embodiments explained in more detail.

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example 1

Solder alloys of various compositions are listed in the table below. They are used to solder a soda lime glass plate with the dimensions 77 mm 27 mm 0.9 mm. An ultrasonic vibration soldering spatula is used for this. This is brought into contact with a ^{solder heated to 180 °} C. on the glass surface, so that an ultrasonic oscillation with a frequency of 60 KHz and an amplitude of 5 M is emitted in a direction running parallel to the surface to be soldered, the solder with the Surface is connected.

Tabel

Pb Sn Sb Cd Zn Bi rare earth metals

30th 30th 30th 2 , 75 25.4 84 25th 47 45 45 63 50 2 20th 2 2 , 25 1 1 20th 20th 32 20th 10 52 3 3 3 2 0.5 3 2 20th 1 2.1 1.0

Solidus temperature

( ⁰ C) Liquidus temperature

( ⁰ C) 143 145 150 177 142 165

143 145 100 143 142 145

145 230

Bond strength excellent excellent weak excellent {*

excellent excellent,

Water resistance

Ductility

pretty the end weak the end pretty pretty lich signed pretty signed lich borrowed Well lich Well Well Well

from-from-from-from-from-badly signed. signed. borrowed signed.

Well

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The table two seven different solder compositions in percent by weight, as well as the solidus temperature and the liquidus temperature and the various properties, such as the bond strength, the water resistance and the ductility. In this table, the rare earth metal is a mixed cerium metal, consisting of 86.8% Ce; 3.0 % La; 4.0% Nd; 6.2 "A Sm and Pr as well as with 3.2 % Fe; 0.37 ° Mg; 0.27 $> Al and 0.73 ° Si (percent by weight).

Lot No. 3 in this table is outside the scope of the invention. To measure the bond strength, the edge of a razor blade is placed on the edge of the solder layer applied to the glass plate and moved along the glass plate in order to separate the solder layer. In the table, the term "excellent" means that more than half of the solder layer adheres. The term "weak" means that all of the solder is peeled off. To measure the water resistance, the solder applied to the glass plate is kept in an atmosphere of 100% relative humidity at 60 ^° C. for 10 days and the changes in the solder layer are observed from the opposite side of the glass plate. In the table, the term "excellent" means that no change was observed, and the term "fairly good" means that the peripheral areas of the solder layer are discolored. The term "weak" means that the solder is peeled from the glass plate.

To measure the ductility, a wire about 1 mm in diameter is formed from a block of solder. The expression "Excellent" means that the wire is easily formed and the term "fairly good" means that it is still succeeds in forming a wire, but this wire

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is interrupted every now and then. The term "bad" means that wire formation is not possible.

These tests show that a solder without Cd cannot be applied at relatively low temperatures, otherwise the bond strength is very low. On the other hand, shows a solder with a Cd content and in particular with a Cd content of 10-20 percent by weight provides excellent adhesive strength, weather resistance and ductility.

Example 2

In a clay crucible, 30 % Pb, 46 $ Sn, 1 $> Sb, 20 $> Cd and 3 % Zn (percent by weight) are ^{heated to 450 °} C. for 1 h under a nitrogen atmosphere as starting materials, the solder being formed. A vidicon tube is connected to a faceplate with solder. The tube is made of borosilicate glass and has the shape of a cylinder 20 mm in diameter and 1 mm in thickness. The faceplate is made from the same borosilicate. It has a thickness of 1 mm and a diameter of 20 mm. The faceplate is placed on the end of the tube and the solder is applied to the tip of the ultrasonic soldering spatula and melted. The interface between the tube and the faceplate is coated with the molten solder. The solder layer is kept ^{at about 170 ° C. with the heated spatula.} The airtightness of the soldered joint is measured with a helium leak tester. The volume of the helium gas penetrating through the soldered joint (normal conditions) at 1 atmosphere and per second (atmospheres cm / sec) is measured and calculated. The leak volume is less than 1 χ 10 atmospheres cnr / sec. Thus, the solder joint is suitable for practical use. The soldering temperature is about 170 ^° C. Such a low soldering temperature is excellently suited for soldering Vidicon tubes without any tension or other disturbances.

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uniformity and accuracy occur.

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Claims (5)

PATENT CLAIMS 1. Solder alloy characterized by 2 - 98.5 percent by weight Pb; 1-97.5 weight percent Sn; 0.5-60 percent by weight of Cd; 0.05-10 weight percent Zn; 0-5 percent by weight Sb; 0 - 5 percent by weight Bi and 0-15 percent by weight of at least one rare earth detail. 2. Use of the solder alloy according to claim 1, for soldering a material that is difficult to solder with an oxide surface surface by applying the molten solder using a vibration treatment to the point of contact between the difficult to solder material and the solder alloy. " 3. Use according to claim 2, characterized in that an ultrasonic vibration treatment is applied. 4. Use according to one of claims 2 or 3, characterized in that glass, ceramics, glass ceramics, pottery, Porcelain, refractory oxides, inorganic oxide crystals, Silicon or germanium can be soldered. 5. Use according to any one of claims 2 to 4, characterized in that on the difficult to solder Material applied solder layer a solderable metal or a material provided with a solder layer difficult to solder applying a vibration treatment to the point of contact. / 096?