RU2670631C1 - Method of preparing microwires with glass shell for electrical connection - Google Patents

Abstract

FIELD: technological processes.SUBSTANCE: invention relates to the field of electroplating and can be used in microelectronics for the manufacture of high-quality electrical contacts on microwires with a diameter of up to 40 microns with a glass shell of up to 15 microns, including variable cross-section, used for the manufacture of HMI, stress-sensitive sensors and magnetic labels. Method includes the complete local removal of the glass shell in the places of electrical contact creation without damaging the microwire cores by etching the glass shell of microwires with an etching gel, followed by washing with running water and electrochemical deposition of a copper sublayer with a thickness of 0.3–1 mcm on the etched contact areas using a pyrophosphate electrolyte, the following composition CuSO⋅5HO 1.0–2.5 g/l, KRO80–100 g/l, at a temperature of 15–30 °C, cathode current density of 1–2 A/dm, of time of 0.5–2 minutes.EFFECT: microwires are prepared for subsequent soldering at a temperature of 190±5 °C POS61 soldering alloy, containing 39 % lead and 61 % tin, they have high wettability to molten solder alloy, adhesion, and provide reliable electrical contact with butt joints, lap joints and telescopic joints.1 cl, 3 dwg

Description

The invention relates to the field of materials processing for microelectronics and can be used for the manufacture of high-quality electrical contacts on microwires with a diameter of up to 40 microns with a glass shell of up to 15 microns, including variable cross-section used for the manufacture of GMI, stress-sensitive sensors and magnetic labels.

A known method of connecting microwires [US 8348137 B1]. The method consists in: 1) placing an elongated coil spring having first and second ends, and made of brazed material at the proximal end of the microwire, so that the proximal end of the microwire is connected to the first end of the coil spring; 2) the supply of molten solder to the proximal end of the microwire and to the first end of the spring, while the material of the solder should be effectively connected with the spring, the shell and the metal conductor of the microwire after cooling without affecting the shell of the microwire. As the solder cools, the microwire conductor connects to the first end of the spring through a solder cap extending along part of the length of the first end of the spring, while the microwire exits the second end of the spring. The disadvantages of the method are: insufficient adhesion of lead-tin solders to the conductors of microwires; the small contact area of solder to the core of the microwire is actually limited by the cross-sectional area of the microwire, which in the presence of a thin oxide film increases the ohmic component in the junction; a significant increase in the length of the microwire for sensors and magnetic labels due to the need to place contact springs on the end parts of the microwire, as well as restrictions on the use of microwires for sensitive sensors due to the influence of contact springs on the magnetic properties of the microwire-coil system used in sensors, for example in gmi scanners.

Also known is a method of connecting microwires [US 20150194236 A1]. The method consists in the use of special back washers of various designs, depending on the sizes of the attached electrical contacts. The disadvantages of the method are: 1) compression fixation of the microwire in the channel of the washer, which can lead to premature destruction of the glass shell of the microwire and as a result of the failure of the sensor based on it; 2) an increase in the weight and size characteristics of the sensors and magnetic tags on the basis of microwires due to the considerable size of the washers, which limits their use.

Creating reliable and durable electrical connections with thin wires, conductors and microwires of amorphous materials is a serious technical problem. The technical result when using the method is to prepare for high-quality electrical connection of the microwire with the conductor by the soldering method, for the following types of connections: a - butt; b - overlapping; c - telescopic, using solders containing lead (39-50%), tin (50-61%) and having a melting point not higher than 183 ° С.

The technical result is achieved after complete local removal of the glass shell at the points where the electrical contact is made without damaging the microwire core by etching the glass shell of the microwires with a pickling gel, followed by washing with water and electrochemical deposition of the copper sublayer on the etched contact areas using pyrophosphate electrolyte.

The invention is illustrated in the drawing, where: in FIG. 1 shows the types of electrical connections: a - butt; b - overlapping; in - telescopic, in FIG. 2 shows the complete local etching of the glass shell; in fig. 3 shows the result of electrochemical deposition of the copper sublayer on the bare portion of the microwire core after complete local etching of the glass envelope.

The result is achieved by performing successive stages: 1) complete local removal of the glass shell at the points of creating electrical contact without damaging the microwire core by etching the glass shell of the microwires using etching gel; 2) rinsing in running water; 3) electrochemical deposition of the copper sublayer on the etched contact areas using a pyrophosphate electrolyte.

To achieve the result, the following conditions must be met:

- the used composition of the etching gel must ensure complete removal of the glass shell without the formation of ulcers and uneven etching of the microwire core;

- electrolyte composition for deposition of CuSO ₄ ⋅5H ₂ 0 copper underlayer - 1.0-2.5 g / l, K ₄ P ₂ O ₇ - 80-100 g / l;

- mode of deposition of the copper sublayer - temperature (T) - 15-30 ° C, cathode current density 1-2 A / dm ² , time (t) 0.5-2 min.

The invention is intended for surface treatment of amorphous magnetically soft microwires with a diameter of up to 40 microns with a glass shell of up to 15 microns, including variable sections used for the manufacture of GMI, stress sensitive sensors and magnetic labels, in particular, to create reliable electrical contacts.

The principle of operation of the method consists in the delicate local removal of the glass shell of the microwire when using a gel for etching and subsequent deposition of a copper underlayer with a thickness of 0.3-1 μm.

The proposed method carried out the preparation of electrical contacts by local removal of glass shells from the surface of the microwires and the electrochemical deposition of the copper sublayer in the places of subsequent soldering:

Example 1. Microwire Co67Fe4Ni2Mo2B11Si14 with a core diameter of 16.04 microns and a glass shell thickness of 8.56 microns. Conducted successive operations for the complete local etching of the glass shell to the microwire cores in the etching gel for 15 hours 51 minutes, washing in water and air drying. After drying, electrochemical deposition of the copper sublayer from the CuSO ₄ ⋅ 5H ₂ O electrolyte - 1.75 g / l, K ₄ P ₂ O ₇ - 90 g / l was carried out according to the following mode: temperature (T) - 22.5 ° С, density cathode current 1.5 A / dm ² , time (t) 1 min 15 sec. As a result of deposition, a copper sublayer was obtained with a thickness from 370 to 810 nm.

Example 2. Microwire Co67Fe4Ni2Mo2B11Si14 with a core diameter of 11.62 microns and a glass shell thickness of 10.03 microns. Conducted successive operations for the complete local etching of the glass shell to the microwire cores in the etching gel for 18 hours and 34 minutes, washing in water and air drying. After drying, electrochemical deposition of the copper sublayer from the CuSO ₄ ⋅ 5H ₂ O electrolyte - 1 g / l, K ₄ P ₂ O ₇ - 80 g / l was carried out according to the following mode: temperature (T) - 15 ° C, cathode current density 1 A / dm ² , time (t) 2 min. As a result of deposition, a copper sublayer was obtained with a thickness from 430 to 580 nm.

Example 2. Microwire Co67Fe4Ni2Mo2B11Si14 with a core diameter of 16.61 microns and a glass shell thickness of 11.65 microns. Conducted successive operations for the complete local etching of the glass shell to the microwire cores in the etching gel for 21 hours and 34 minutes, washing in water and air drying. After drying, electrochemical deposition of the copper sublayer from the CuSO ₄ ⋅ 5H ₂ O electrolyte — 2.5 g / l, K ₄ P ₂ O ₇ — 100 g / l was carried out according to the following mode: temperature (T) —30 ° C, cathode current density 2 A / dm ² , time (t) 0.5 min. As a result of deposition, a copper sublayer was obtained with a thickness from 290 to 950 nm.

The cores of the microwires after complete local etching of the glass shell and deposition of the copper sublayer followed by soldering at a temperature of 190 ± 5 ° C with POS61 solder, containing 39% lead and 61% tin, have a high wettability to molten solder, adhesion and provide reliable electrical contact butt and overlap and telescopic connections.

Claims (1)

The method of preparing microwires with a glass shell for electrical connection, including complete local removal of the glass shell at the points of making electrical contact without damaging the microwire core by etching the glass shell of microwires with a pickling gel, subsequent washing with running water and electrochemical deposition of copper sublayer 0.3- 1.0 μm for pickled contact areas using a pyrophosphate electrolyte having the composition CuSO ₄ ⋅ 5H ₂ O - 1.0-2.5 g / l, K ₄ P ₂ O ₇ - 80-100 g / l, at a temperature of 15-30 ° C, a cathode current density of 1-2 A / dm ² , time 0.5-2.0 min.