DE2308041B2 - USE OF A SOLDER ALLOY - Google Patents

Description

The invention relates to the use of a solder alloy.

It has been difficult in the past to solid a solder alloy directly onto an inorganic one Oxide bodies such as glass, ceramic or metal with an oxide surface, e.g. B. silicon, germanium, aluminum, To apply titanium, zirconium, tantalum or the like. There are now solder alloys known which when used from ultrasound to adhere firmly to the difficult-to-solder materials mentioned. These solder alloys are among the Alloy groups Pb - Sn-Zn - Sb and Pb — Sn - Zn -Sb-Al (DT-OS 21 04 625).

These special solder alloys for soldering ceramic or the like. Are at temperatures in the range applicable from 200 to 350 ° C. These temperatures are relatively low. If you have these solder alloys, however used to solder electrical or electronic components, so at these temperatures the quality the electrical or electronic.! Components reduced. If z. B. a glass flask of a Vidicon to a Front glass plate is to be soldered on, it is necessary that this is done at a temperature below about 180 ° C happens.

From DT-PS 7 29 875 and US-PS 19 46 609 solder alloys of the type Pb — Sn — Cd — Zn are known. The usability of these alloys for soldering oxide bodies is not from these publications, however known.

Accordingly, it is the object of the present invention to provide a solder alloy for soldering oxide bodies to be used at an application temperature below about! 80 "C. M

This object is achieved according to the invention by using a solder alloy with 2 to 98.5% Pb; 1 to 97.5% Sn: 0.5 to 60% Cd; 0.05 to 10% Zn; 0 to 5% Sb; 0-1 cig! "-" -.. · These solder alloys soldering difficult solderable materials, α m applying it to the hard solderable material in Lolzenem condition and subjects the Kontaktbe-S emer sThwingungsbehandlung The solder alloy e.gnet become the solders Aher Mater.al.en difficult to solder, such as glass, ceramic, silicon or germanium at temperatures below Se solder alloy is from mother-Dieerniiu ₅ t manufactured. Zn is

lf ^gierU Sen m dieTötbarkeit ⁸ _V oxides on to H ^to H ^g en and Cd is added to reduce the melting-Ik. If necessary, Sb is added to increase the weather resistance and the hmzugegeo. Rare earth metals

wide gThS given around the bond strength too increase and Bi is added to the melting point to regulate. The components Sb, B, and the See earth metals can be omitted if the amount of lead in the solder is below 2% H Ik sets the amount of Sn above 97.5%, so .st B eth of the molten state * of Melting solder alloy, i.e. the temperature range within which is a mixture of liquid and mixed crystals is too narrow, so that _ d.e Molten alloy immediately from the liquid State changes to the solid state, whereby d.e Processability is significantly impaired.

If, on the other hand, there is more than 98.5% Pb and less than 1% Sn in the solder alloy, the melting point and viscosity of the solder alloy are too low, and the smoothness and airtightness of the solder alloy are too low. Zn is added to the solder in order that a high bonding strength with respect to Kera SmTterialien such as pottery, glass and Halble.tern Z ENEU case, "the amount of Zn in the solder exceeds 005%, so this effect is atgeüb sufficiently? Other hand, if the When the amount of zinc in the solder exceeds S. It is difficult to obtain a uniform structure in the preparation of the solder, and it is preferable that the amount of zinc is in the range of 1 to

The rare earth metals are used in an amount preferably less than 15% of the solder alloy added. If the amount of rare earth metals exceeds 15%, no solder alloy can with a uniform structure can be achieved. It is generally preferred to use the rare earths in the area of 1 - 10% to be added. The rare earth metals La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Y and Sc in question. From the economic point of view, it is preferable to use Ce and especially a mixture of rare earth metals such. B. Cermix metal, consisting of 86.8% Ce, 3.0% La, 4.0% Nd, 6.2% Sm and Pr with the main impurities of 3.2% Fe, 0.37% Mg, 0.2 /% Al and 0.73% Si (in percent by weight).

Further, if more than 0.05% Sb is added to the solder alloy, the water resistance becomes and the weather resistance of the solder alloy is improved. However, if the amount of Sb in the solder exceeds 5%, so the ductility is reduced. The melting point of the solder alloy can be lowered by adding Bi will. However, if the amount of bi in the lot is 5%

exceeds, the adhesive strength is impaired.

Cd is an important component in the solder according to the invention. This component causes a decrease 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 state is too narrow. It is preferable to use more than 0.5% Cd too. However, if the amount of Cd in the solder exceeds 60%, the ductility is lowered.

A small amount of Al can be added to prevent ι ο slag on the molten solder alloy. Furthermore, small amounts of one or more of the elements Si ₁ Ti or Be can be added in order to prevent clouding of the surface of the solder alloy. It is preferable to add less than 0.1% Al and η less than 0.5% of a combined amount of Si, Ti or Be to the solder.

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

Sn 20-40% Pb 40-60% Zn 1- 5% CD 5-25% Bi 0-3% Sb 0-3%

In the process for preparing the solder alloy, the metal components are melted and m is preferably in vacuum or under an inert gas atmosphere, such as under nitrogen or argon, or under a reducing gas such as hydrogen is mixed. The solder alloy has a melting point of 70-180 ⁰ C and is at these low i "> temperatures a large adhesion. The solder alloy can be applied at remarkably low temperatures, so that they are very well suited for soldering of electric or electronic components, 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 do not contain Cd which require great airtightness rather than adhesive strength.

The solder alloy according to the invention is suitable not only for soldering 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 difficult-to-solder materials, in particular to inorganic solid-state oxides such as oxide glass, e.g. B. silicate glass or quartz glass, glass ceramics, pottery or porcelain, sintered, melted or fired refractory oxides such as aluminum oxide, magnesium oxide, spinel, thorium oxide, beryllium oxide, zirconium oxide, t> o 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 applied directly to difficult-to-solder semiconductor metals, such as silicon or germanium, and to 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 connected to the surface of the difficult-to-solder material by applying it in a molten state using a vibration treatment (preferably an ultrasonic vibration treatment). To use the solder alloy according to the present invention, the soldering surface of the difficult-to-solder material is brought into contact with the molten or semi-molten solder, and the solder is subjected to a vibration treatment. Suitable results are achieved when using ultrasound with a frequency of preferably 20-100 kHz in a direction parallel to the surface to be soldered.

In a special case, a soldering spatula is heated to around 200-250 ° C and vibrated 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 pre-heat the surface of this material to approximately 100-15O 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 even up to several millimeters.

In another method of soldering a surface of a difficult-to-solder material to the The solder according to the invention is the vibration treatment and preferably the ultrasonic vibration treatment applied to a bath of the molten solder, and the difficult-to-solder material becomes immersed so that the solder is brought into contact with the surface of the molten solder Material adheres firmly. The difficult to solder material, which is covered with the solder, is then with another solderable material, such as B. brought into contact with a solderable metal, whereupon the Contact area is heated to effect an adhesive strength. On the other hand, two can also Difficult-to-solder materials are connected to one another by applying the solder according to the invention to both Applying surfaces to be joined and then the coated surfaces in contact with one another brings and heats the contact area to melt the solder. After cooling down you can see that on in this way a good adhesive strength is achieved.

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

In the following, the invention is explained in more detail with the aid of exemplary embodiments.

example 1

Solder alloys of various compositions are listed in the table below. They are used to hold a soda lime glass plate with the dimensions 77 mm 27 mm 0.9 mm

to solder. An ultrasonic vibration soldering spatula is used for this. This gets in touch with you Brought to 180 ° C heated solder aui the glass surface, so that an ultrasonic vibration with a

Tabel

Frequency of 6OkHz and an amplitude of 5 μ in a direction running parallel to the surface to be soldered is exerted, the solder with the Surface is connected.

1 30th 2 30th 3 30th 4th 2 5 25.4 6th 84 7th 25th Pb 47 45 45 63.75 50 2 20th Sn 2 2 1 I. Sb 20th 20th 32.25 20th 10 52 CD 3 3 3 2 0.5 3 2 Zn 20th 1 Bi 2.1 1.0 Rare earth metals 143 145 100 143 142 145 145 Solidus temperature ( ⁰ C) 143 145 150 177 142 165 230 Liquidus temperature (° C) excellent excellent weak excellent excellent excellent excellent Bond strength quite excellent weak quite excellent quite ■ pretty Water resistance Well Well Well Well excellent excellent excellent quite excellent excellent bad Ductility Well

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

Lot No. 3 in this table is outside the scope of the invention. To measure the bond strength, the cutting 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 expression "excellent" means that more than half of the solder layer will adhere. 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 means; 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 layer is peeled off the glass plate.

To measure the ductility, a wire about 1 mm in diameter is formed from a block of solder. The term "excellent" means that the wire is easily formed, and the term "fairly good" means that it is still possible to form a wire, but this wire now and then is interrupted. The term "bad" means that wire formation is not possible.

These experiments show that a solder without Cd with

relatively low temperatures can not be applied, otherwise the bond strength is very high is low. On the other hand, shows a LoI with a Cd content and in particular with a Cd content from 10-20% excellent adhesive strength, weather resistance and ductility.

B e i s ρ i e 1 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 hour under a nitrogen atmosphere, 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 ³ / sec) is measured and calculated. The leak volume is less than 1 x 10- '° atmospheres cmVsec. Thus, the solder joint is suitable for practical use. The soldering temperature is about 170 ° C. Such a low soldering temperature is excellent for soldering Vidicon tubes without any stresses or other disturbances in terms of uniformity and accuracy.

Claims (4)

Claims: "ho to 15% of at least one rare Ü for soldering a material that is difficult to solder, 1. Use a solder alloy with 2 to 98.5% Pb; 1 to 97.5% Sn; 0.5 to 60% Cd; 0.05 to 10% Zn; 0 to 5% Sb; 0 to 5% Bi and 0 to 15% of at least one rare earth metal for soldering a difficult solderable material with an oxide surface. 2. Use of a Loilegierung with the composition according to claim 1 for the im Claim 1 mentioned purpose, wherein the point of contact between the difficult to oil Material and the molten soldering of a vibration treatment, in particular an ultrasound treatment, undergoes. ι ■ "> 3. Use of a solder alloy with the composition of claim 1 for the im Claim 1 mentioned purpose, where glass, ceramic, glass ceramic, Pottery, porcelain, refractory oxides, inorganic oxide crystals, silicon or germanium can be used. 4. Use of a solder alloy with the composition according to claim 1, for the im Claim 1 mentioned purpose, wherein one applied to the difficult to solder material solder layer a solderable metal or a hard-solderable material provided with a solder layer under vibration treatment the point of contact. 30th