SU1745475A1 - Composite solder - Google Patents

Abstract

Usage: in electrical engineering, electrical engineering and other industries, mainly for soldering copper and its alloys. Composite solder contains matrix - powder of low-melting solder and filler - powders of refractory metal and medium-melting solder with low-temperature flux in the following ratio of components, wt.%: Low-melting solder Sn-Pb 70.1.85; medium fusible solder Cu-R 7-12; refractory metal C 3 ... 8; low-temperature flux 5..10. 1 tab.

Description

The invention relates to the field of soldering, in particular to compositions of composite solder for low-temperature soldering, and can be used in the electrical, electrical engineering and other industries of the industry primarily for soldering copper and its alloys.

Solder 1 is known, containing a refractory component in the form of copper powder in an amount of 20 ... 80%, which ensures optimal properties of copper compounds during subsequent soldering with tin-lead solders.

The disadvantages of this mixture are that a relatively high superheat is required to obtain a strong solder joint, which causes the copper particles to dissolve in the tin, resulting in the intense dissolution of the hot metal in the melt (erosion), and an increase in the porosity of the weld and reduction of mechanical properties of the solder joint.

Metal-ceramic solder 2 is known for soldering a semiconductor crystal and a substrate containing wt.%:

Fusible Powder

metal (173.,. 350 ° C) 40-70

Refractory powder

metal (900 ... 1100 ° С) 30-60

However, this solder, when low-temperature soldering, has a lower stretchability over the surface of copper, copper alloys and plasticity, an increased porosity of the solder joints and does not provide the required quality of solder joints, so the strength at low-temperature soldering of copper with composite solder 2 does not exceed 60 MPa.

The purpose of the invention is to increase the strength of soldered joints.

This is achieved by the fact that composite solder contains a matrix — a powder of low-melting solder and a filler — powder of a refractory metal and medium-melting solder with low-temperature flux.

cl

WITH

%

s

01

in the following ratio, wt.%:

Fusible solder

Sn-Pb (183-300 ° C) 70 ... 85

Medium melting Cu-P solder (720 ° C) 7 ... 12

Refractory metal C (1100 ° C) 3 ... 8

Low-temperature flux5 ... 10

A comparable analysis allows us to conclude that composite solder is different in that the medium melting point component (Cu-P), which has a lower melting point (720 ° C), provides a strong solder joint at lower soldering temperatures than the prototype in question. 2, which significantly expands their technological capabilities.

In the process of melting, the matrix is doped with copper phosphide (CisP) and copper (Cu), the concentration of which in the alloy is determined by the heating temperature and the duration of its holding at a given temperature.

The introduction of a filler in the amount of lower values of the lower limits is inefficient and does not significantly affect the quality of the soldered joints. The limitations on the upper limit are explained by the sharp deterioration in the technological and mechanical characteristics of composite solder and solder joints. This is due to the fact that with the introduction of more than 20% of the matrix melt into the powder solder is saturated with alloying elements and filler powder, the amount of oxides increases, as a result, the melting point and viscosity of Sn-Pb-solder and porosity increase dramatically. This all leads to a decrease in the ability of Sn-Pb-solder to spreading and tensile strength of solder joints.

The proposed solder is characterized by high flowability, the wetting angle is in the range of 10 ... 15 ° and provides higher mechanical performance (130 MPa) of the paired compounds due to alloying of the melt with copper phosphide and copper, the interaction of particles introduced into the powder tin-lead solder SizR, C with metal metal.

The introduction of powder filler in the specified amounts of Cu-P, Cu gives new technological properties to powdered Sn-Pb-solder and physicomechanical properties of soldered compounds.

For an experimental verification of the technological properties of the proposed composition and the physicomechanical properties of the steam compounds, mixtures were prepared by mixing Sn-Pb, Cu, Cu-P powders. Water was used as a flux.

zinc chloride solution, which was introduced into the powder mixture immediately before soldering. This amount of flux produces solder in the form of

paste and keep well in the powder mixture.

Samples of size 40x 40x2 mm were made from the studied materials by five samples for each experiment, the surfaces of the samples were cleaned and degreased with ethyl alcohol, the amount of the solid mixture was weighed, corresponding to a volume of 64 mm3, placed on a substrate that was heated in a furnace or using induction or flame heating.

The sample with solder was installed strictly horizontally using various devices, the temperature was controlled by a chromel-alumel thermocouple. The experiments were carried out with overheating over the Sn-Pb-solder liquidus at 50 ° C with a holding time of 0.2 min. The spreading area of the solders was measured with PC-2 planimeter.

5 The soldering processes of samples from copper and brass overlap, butt and kosostik (a 30.45 °) were performed as follows.

After the machining of the cutter, the soldered surfaces before soldering were degreased with acetone to remove grease and dirt. The cleaned samples were placed in a clamp, the composite solder was placed in the joint, and then the assembly was compressed, after which the soldering was performed with the application of pressure of 3 ... 5 MPa.

For soldering wide gaps, the samples were placed in special assembly devices, installed with the necessary lap and gap.

0 portion of the freshly prepared mixture (150%) of the volume of the gap (GOST 20485-75) was placed at the gap of the sample being fed. The soldering was carried out by the gas-flame method according to the mode: Tm 230 ... 250 ° C; soldering time 20 s;

5 gap size 0.05 ... 0.3 mm; heating rate 50 ... 100 ° C / s. The soldering temperature was controlled by a chromel-aluminum thermocouple mounted on the sample near the gap.

0 After soldering and cooling, the joints were cleaned with a metal brush, washed in water and dried in a drying cabinet.

The resulting solder joints were subjected to mechanical tests.

5 The ultimate strength was determined on a UME-10-TM testing machine, the impact viscosity on an upgraded copra BKM-5-2. The electrical resistance was determined by the potentiometric method according to OST 1-13564-79.

Examples of the performance of solder and the results of studies of technological and physico-mechanical properties of solder joints are given in the table.

The use of this solder in comparison with the prototype will allow to increase the strength of soldered joints and expand technological capabilities.

Claims (1)

Claims of composite solder for brazing of copper and its alloys, containing powder low-melting point solder, a filler powder of a refractory metal and a low-temperature flux, characterized in that. In order to increase the strength of solder joints, the filler additionally contains medium-melting solder powder in the following ratio, wt.%: Powder of low-melting solder 70 ... 85 Powder of medium-melting solder 7 ... 12 Powder of refractory metal 3 ... 8 Low-temperature flux5 ... 10 Note. In all cases, the soldering temperature was 230 ... 260 ° C, the gap between the welded surfaces 0.1 ... 0.2 mm.