Glow Wire Testing for PCB Connectors

Ultra-reliable connectors don’t just need to withstand vibrations and high voltage, they also need to withstand high heat buildup along conductors running through the connector body. Connectors designed for power systems, appliances, and many consumer products undergo glow wire testing to assess flammability of components, including connectors. These tests are important parts of safety qualification for consumer products, and they are given in multiple industry standards.

In particular, glow wire testing provides safety qualification in the event a component heats up so hot that it ignites. This is something that could occur in power electronics connectors that must provide significant current and plug into mains outlets. This article will examine the basic procedures for glow wire testing, as well as the types of equipment that require glow wire testing for subcomponents, including connectors.

Ensure Safety With Glow Wire Testing

Glow wire testing refers to a safety test standard used to simulate the effects of a fire source or overheated component within an electrical product. It is designed to assess how likely a product is to ignite and spread fire to the rest of the system, as well as how long a product might continue to burn after the initial ignition.

This is particularly important for electronic connectors in power systems. These connectors can carry high current, and sometimes at high DC or AC voltages, which can lead to excessive heat generation. With excess heat brings the potential for a fire to begin in the component, which can then spread throughout the rest of the product.

How Glow Wire Tests Are Performed

A glow wire test involves heating a loop of wire to a specified temperature; this will be between 550 °C and 960 °C, depending on the standard being used. The test is performed by applying the glow wire to a sample component for a specified period of time. The wire's temperature is intended to simulate an overheated conductor, which is then in contact with the component body. The test checks for the following:

• Whether the component catches fire
• How long the component burns
• Whether it releases burning fragments that spread fire

This test allows a component manufacturer to do two things: determine at what temperature their component might ignite, and determine whether any flame retardants in the component are effective.

Glow wire test in action

Glow Wire Test Standards

Glow wire testing is part of multiple safety standards used to evaluate components and products intended for use in environments where fire safety is a concern. The main standards used to qualify glow wire performance are defined in the International Electrotechnical Commission (IEC) 60695-2 series. There are four relevant standards covering different products and materials:

The IEC standards are widely used in Europe, while the Underwriters Laboratories (UL) standards are followed in the US. The main US standard for glow wire testing is UL 746A, which is often used for products intended specifically for the U.S. market. The qualification standards are similar to those found in IEC.

Who Ensures Glow Wire Compliance For Connectors?

Connector manufacturers are responsible for ensuring compliance with glow wire standards and testing methodologies. They are also responsible for ensuring connector body materials and any flame retardants can meet any required glow wire performance target so that safety is assured in the end product. However, products also have to be tested at an overall product level, which means glow wire testing typically goes beyond just examining connectors.

At the product level, the OEM or CM is responsible for ensuring passage of glow wire testing. Some products where this applies includes:

• Household appliances: Products like microwaves, toasters, washing machines, and other household appliances often undergo glow wire testing.
• IT equipment: Computers, servers, routers, and other IT equipment are often subject to glow wire testing due to the significant heat they can generate and their continuous operation.
• Lighting equipment: Light fixtures, especially those using high-intensity lamps, or power connectors for high-power LED arrays, are often subject to glow wire testing.
• Other electronic devices: In general, any device that carries a risk of overheating may be subject to glow wire testing. This can include TVs, audio equipment, power tools, and some electronic toys.

To ensure safety with selected connectors, make sure your connector manufacturer has products that can provide reliability in PCB mounting and in panel mounting, both for board-to-board or board-to-wire connectors. They should also be able to provide technical data illustrating compliance with glow wire testing requirements and safety standards.

No matter what you need to procure and manufacture, make sure you first build and qualify your designs using the complete set of system analysis tools from Cadence. Only Cadence offers a comprehensive set of circuit, IC, and PCB design tools for any application and any level of complexity. Cadence PCB design products also integrate with a multiphysics field solver for thermal analysis, including verification of thermally sensitive chip and package designs.

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