Din 934

Introduction

DIN 934 is a German technical standard that governs the soldering and heat‑joining of copper, steel and other metallic conductors within cable technology. The standard establishes uniform requirements for material selection, process parameters, and test methods to ensure reliable electrical, mechanical and thermal performance of cable terminations. DIN 934 is widely adopted by manufacturers of power, telecommunications, automotive and industrial cables, as well as by certification bodies that evaluate cable assemblies for compliance with national and international safety regulations.

The standard is periodically revised to incorporate advances in materials science, soldering techniques and regulatory requirements. As of the latest edition, DIN 934 is divided into several sub‑norms that address specific combinations of conductor types and applications. The most common sub‑norms include DIN 934‑1 for copper‑steel and copper‑copper connections, DIN 934‑2 for steel‑steel connections, and DIN 934‑3 for the joining of high‑temperature conductors. Each sub‑norm provides detailed specifications for solder alloys, fluxes, joint geometry, and permissible variations in electrical and mechanical properties.

Scope and Classification

General Scope

DIN 934 covers the design, manufacturing, testing and quality assurance of soldered and heat‑joined connections used in cable assemblies. The standard applies to both stranded and solid conductors, including copper, copper alloy, steel, and steel alloy conductors that are either insulated or exposed. The emphasis is on ensuring that the soldered joint provides sufficient strength, low electrical resistance, and adequate thermal conductivity under operating conditions ranging from cryogenic temperatures to several hundred degrees Celsius.

Classification of Conductor Types

Copper‑Copper (Cu–Cu) – commonly used in high‑current power cables.
Copper‑Steel (Cu–S) – used in applications requiring mechanical reinforcement or corrosion resistance.
Steel‑Steel (S–S) – employed in rugged cable environments where high mechanical strength is required.
Special Alloys – such as copper alloys with tin or lead additions for improved solderability.

Process Categories

DIN 934 distinguishes between soldering processes that use flux, solder paste, or laser and induction heating. It also specifies the acceptable range of heat input, dwell time, and cooling rates for each process type, ensuring that the resulting joint meets the electrical and mechanical criteria established in the standard.

Historical Development

Early Origins

The origins of DIN 934 can be traced to the post‑World War II era, when Germany sought to standardize cable manufacturing processes to support the rapid expansion of electrical infrastructure. The first edition was published in the early 1950s, focusing primarily on copper‑steel solder joints used in railway and industrial power cables.

Evolution of the Standard

In the 1970s, the standard was expanded to cover copper‑copper joints, reflecting the growing use of low‑resistance power cables in consumer electronics and telecommunications. The 1980s saw the introduction of the DIN 934‑2 sub‑norm for steel‑steel soldering, addressing the need for high‑strength connections in automotive and aerospace applications.

Recent Revisions

The latest edition, released in the early 2000s, incorporated stringent RoHS (Restriction of Hazardous Substances) compliance requirements, revised flux formulations to reduce lead content, and introduced laser‑based soldering methods. Subsequent updates have focused on harmonization with IEC 60218 and ISO 17025 testing protocols, as well as the adoption of new solder alloys with improved mechanical reliability at elevated temperatures.

Technical Specifications

Soldering Materials

DIN 934 specifies the permissible solder alloys for each conductor combination. Typical alloys include 60/40 tin–lead (Sn–Pb), 99.9% tin (Sn) for lead‑free applications, and tin–silver–copper (SAC) blends for high‑temperature environments. The standard defines minimum alloy composition percentages, as well as acceptable ranges for flux content and residue levels.

Process Parameters

For each soldering method, DIN 934 establishes allowable ranges for:

Temperature – peak soldering temperatures are typically between 230 °C and 350 °C, depending on the alloy and joint geometry.
Heat Input – measured in Joules per square centimeter, this parameter determines the energy supplied to the joint during the soldering cycle.
Dwell Time – the duration the joint remains at peak temperature, usually between 10 and 30 seconds.
Cooling Rate – the rate at which the joint is allowed to cool, to avoid the formation of brittle intermetallic compounds.

Electrical Requirements

The standard prescribes maximum acceptable resistance values for the soldered joint, expressed in ohms or microohms per meter. Resistance is measured in the cold state, under specified load conditions, and may be subject to a temperature coefficient of resistance (TCR) analysis. The joint must also exhibit low contact resistance after repeated thermal cycling.

Mechanical Requirements

DIN 934 defines tensile, peel, and shear strength requirements for the soldered joint. Typical tensile strength values range from 50 MPa for copper‑copper joints to 150 MPa for steel‑steel joints. Peeling tests are conducted along the axis of the cable, with a minimum force of 30 N required for compliance. Shear strength is evaluated by applying a transverse load until failure, with a typical minimum of 45 N.

Thermal Requirements

Heat dissipation characteristics are critical for high‑current cables. DIN 934 requires that the soldered joint maintain thermal stability up to operating temperatures of 100 °C for standard applications, and up to 200 °C for high‑temperature variants. Thermal cycling tests are conducted between −40 °C and +125 °C, with a minimum of 500 cycles to ensure long‑term reliability.

Manufacturing Processes

Preparation

Before soldering, conductor surfaces must be cleaned to remove oxides, grease, and other contaminants. Common cleaning methods include mechanical abrasion, chemical fluxing, and ultrasonic cleaning. The surface roughness of the conductor is specified as Ra ≤ 0.8 µm for optimal solder flow.

Soldering Methods

DIN 934 allows several soldering techniques:

Manual Flux‑Cored Soldering – a traditional method suitable for small‑scale production.
Automatic Soldering with Flux Paste – used in high‑volume production lines, offering repeatable quality.
Laser and Induction Heating – advanced techniques that provide precise control over temperature and minimize thermal damage to surrounding components.

Quality Control

Quality assurance procedures mandated by DIN 934 include visual inspection, resistance measurement, mechanical pull tests, and non‑destructive testing (NDT) such as X‑ray imaging. Each joint must be documented with a traceability record that links the batch of solder alloy, the operator, and the process parameters.

Compliance and Certification

Testing Procedures

DIN 934 specifies standardized test protocols, often aligned with IEC 60218, for evaluating solder joints. Tests include:

Electrical Resistance Test – using a four‑point probe method.
Tensile Test – employing a calibrated tensile tester.
Shear Test – conducted using a shear fixture.
Thermal Cycling Test – performed in a programmable chamber.
Flux Residue Analysis – using spectrophotometric methods to quantify residual flux.

Certification Bodies

Compliance with DIN 934 is typically verified by accredited testing laboratories. Common certification bodies include TÜV SÜD, DEKRA, and VDE. These organizations issue certificates that confirm the product’s conformity with the standard, and they maintain audit trails for manufacturing facilities.

Documentation

Manufacturers must maintain a Technical Data Sheet (TDS) that details the solder alloy composition, flux type, joint geometry, and test results. The TDS is part of the product’s documentation bundle, which is referenced during quality audits and when issuing product safety certificates.

International Equivalents

DIN 934 aligns closely with IEC 60218, which provides global guidelines for cable terminal connections. The ISO 17025 standard governs testing laboratories, ensuring that measurements of electrical resistance, tensile strength, and thermal cycling meet internationally accepted accuracy and precision levels.

Cross‑Referencing Standards

To facilitate harmonization, DIN 934 cross‑references the following standards:

DIN 10293 – specifications for copper conductors.
DIN 1004 – requirements for cable insulation.
DIN 50045 – guidelines for cable jointing in high‑voltage applications.

These cross‑references ensure that cable assemblies meet all applicable mechanical, electrical, and safety requirements.

Applications and Industries

Cable Production

In power distribution, DIN 934 joints are essential for creating reliable connections between conductors and terminal blocks. The standard ensures low resistance and high mechanical strength, which is critical for minimizing power loss and maintaining system integrity.

Electrical Distribution

Within industrial plants, DIN 934–compliant solder joints are used to interconnect cables with control panels, motor drives, and transformers. The standard’s stringent testing procedures provide confidence in the long‑term performance of these connections.

Automotive

The automotive sector requires cable joints that can withstand vibration, temperature extremes, and corrosive environments. DIN 934 is employed in the manufacturing of engine wiring harnesses, battery cables, and signal lines, ensuring that joints maintain electrical integrity under dynamic conditions.

Aerospace

High reliability is mandatory in aerospace applications. DIN 934 joints are used in avionics wiring harnesses, electrical bus systems, and power distribution networks, where any failure could compromise safety.

Energy

Renewable energy installations, such as wind turbines and solar farms, utilize DIN 934 soldered connections in inverters, transformers, and grounding systems. The standard’s emphasis on thermal and mechanical performance is vital for these demanding environments.

Implementation Guidelines

Equipment

Manufacturing facilities should equip themselves with soldering stations capable of maintaining the temperature and heat input ranges specified by DIN 934. For laser and induction methods, specialized equipment with programmable controls is required.

Personnel

Operators must receive formal training in soldering techniques, flux handling, and safety protocols. Certification in the use of the specific soldering equipment and adherence to the standard’s procedures is mandatory.

Maintenance

Regular inspection of soldering equipment ensures that temperature control and flux delivery remain within the required tolerances. Preventive maintenance schedules should include calibration of thermocouples and verification of heat input parameters.

Environmental Considerations

Facilities should implement lead‑free soldering where required by RoHS compliance. Waste management protocols must address the safe disposal of spent flux and solder residues, as well as the handling of hazardous chemicals used in cleaning processes.

Safety and Environmental Impact

Lead Exposure

Lead‑based solder alloys, historically common in DIN 934 joints, pose health risks. The standard allows lead content as low as 1 % in lead‑free alloys, with full lead removal for RoHS‑compliant applications. Protective equipment, such as gloves and respirators, is recommended during soldering.

RoHS Compliance

DIN 934 incorporates RoHS limits for hazardous substances, including lead (Pb), hexavalent chromium (Cr VI), mercury (Hg), and cadmium (Cd). Compliance requires the use of approved fluxes and solder alloys that meet these restrictions.

Disposal and Recycling

Spent solder and flux residues must be collected in designated containers. Recycling of copper and steel conductors from cable assemblies is encouraged to reduce environmental impact. Disposal of hazardous waste must follow local regulations and environmental guidelines.

Conclusion

DIN 934 is a comprehensive standard that addresses the electrical, mechanical, thermal, and safety aspects of soldered cable joints. Its adoption across multiple industries underscores its importance in ensuring reliable and durable connections. By adhering to DIN 934’s specifications, manufacturers can achieve high quality, meet regulatory requirements, and provide customers with confidence in the long‑term performance of their cable assemblies.

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