Electrically conductive adhesives have been around for many decades. In fact it was the advent of the American/Russian space race in the 1960’s that really propelled conductive adhesive technology to the forefront in electronic design. At the time NASA was looking for an alternative system that would replace or reduce wiring, traditional electronic devices and indeed die bonding on early PCB’s in their rockets and capsules. Driven by a need to reduce the weight of the spacecraft and the inherent dangers of astronauts trying to solder a repair to a wiring loom or electrical system inside a space capsule, conductive adhesives were high on NASA’s R&D program.
From as early as 1972 with the showcasing of the worlds first electronic hand held calculator with a conductive epoxy adhesive used to bond in the LCD module, electronics design has rapidly changed and conductive adhesive technology has had to stay one step ahead.
Nowadays of course the trend for ever smaller consumer electronic devices such as mobile phones, iPads, MP3 players and of course wearable clothing with electronic sensors and data recorders has meant that designers have had to look to alternative methods of conductive joining or conductive pathways. Mechanical electrical connectors are bulky and limit the size of a product. Conductive adhesives can replace these making space for more electronic features or ultimately reducing the size and weight of the finished product.
With increasing legislation comes the need for technologists to design new products to replace outdated methods of joining substrates. In recent years, the law was changed to ban lead solder being used in electronic applications. Conductive adhesives for surface mount device applications were now a significant option for electronic design engineers. It was really this sea-change in electronic/electrical manufacturing processes that brought the benefits of using conductive adhesives back into the limelight.
There are significant benefits in using electrically conductive adhesives and these include.
- Faster processing times.
- Fewer inventory items needed.
- Can be used on heat sensitive substrates.
- Large range of chemistries to suit almost any substrate.
- Can be used on flexible materials and foils.
- No toxic metals used.
Today of course, the range of conductive adhesives and their applications is vast and varied. Conductive adhesives are tailored to suit almost any application. When selecting the right adhesive for your specific application then it is important to consider the following points. The type of conductive filler used ie Silver, Copper Nickel or Graphite and whether your application would suit a paste or a liquid adhesive, be air cured or thermally cured. Typically conductive adhesives fall into two main categories.
- Single component, thermally curing. This type of adhesive material is very sensitive to temperature when stored. Typically these will need to be either deep frozen or stored below +5ºC and brought to room temperature just prior to use. This obviously has an impact on pot life and waste material. Elecolit 3653 is a highly flexible, silver filled conductive adhesive.
- Two component, chemical/room temperature curing. These are typically much slower curing adhesives and may take up to 24hrs to fully cure. However, cure speeds can dramatically reduce with the application of heat. They are mixed in either a 1:1 or 2:1 ratio by weight or volume and have a much shorter pot life than single component adhesives. However, wastage is kept to a minimum as you only mix what you need. Elecolit 325 is an extremely good silver-filled, 2-part conductive adhesive. Elecolit 336 has a lower filler content and as such has a higher resistance, but lower price tag.
Some typical applications include applying or repairing conductive paths in heated car windscreens and mirrors, RFID shielding applications, bonding batteries to flexible foil/film, SMD mounting, bonding flexible film LCD’s to hard FR4 boards, circuit track repairs, bonding ground wire, populating PCB’s the list is almost endless.
Eurobond Adhesives Ltd has been supplying high performance electrically conductive adhesives for over three decades. As well as our own products we are a distributor of Panacol conductive adhesives. We offer a comprehensive range of products and a wealth of experience to draw on. If you would like to discuss your current application or a future project then please contact our technical team. We would be happy to help.
Call us on 01795 427888 or Email: firstname.lastname@example.org