3M 9703 Conductive Adhesive Transfer Tape is an anisotropic conductive adhesive designed to conduct electricity primarily through its thickness, or Z-axis, while providing electrical isolation laterally across the X-Y plane.
This makes it useful for creating thin, low-profile electrical connections without conventional soldering.
So, how can an adhesive tape conduct electricity in one direction while helping prevent electrical connections between adjacent conductors?
The answer is in the tape’s construction and the way it forms electrical contact.
How 3M 9703 Works
3M 9703 consists of an adhesive matrix containing conductive particles distributed throughout the adhesive.
When the tape is positioned between two opposing conductive surfaces and the assembly is subjected to appropriate pressure, the conductive particles establish electrical contact between those surfaces.
The result is a conductive path through the thickness of the tape.
At the same time, the particles are not intended to create a continuous conductive path across the surface of the adhesive. This directional behavior is what makes the tape anisotropically conductive.
In simple terms, you can think of it as creating an electrical connection from one conductive surface to the other, while helping electrically isolate neighboring connections.
The adhesive also provides the mechanical bond that holds the components together.
Why Use an Anisotropic Conductive Adhesive?
As electronic assemblies become smaller and more flexible, traditional soldering and mechanical connection methods aren’t always practical.
An anisotropic conductive adhesive can provide several advantages in applications where a thin, flexible and low-profile electrical connection is needed.
Because the connection does not require conventional solder reflow, it can also be useful for certain assemblies involving heat-sensitive or flexible components.
However, reliable performance depends on proper surface preparation, alignment, pressure and assembly conditions.
Typical Applications
3M 9703 can be considered for applications such as:
- Flexible printed circuit connections
- Membrane switches
- Flex-to-board interconnections
- EMI shielding and grounding
- Low-profile electronic assemblies
- Wearable and other flexible electronics
- Certain sensor and LED applications
The specific suitability of the tape depends on the electrical and mechanical requirements of the application and the materials being bonded.
Surface Preparation
As with most adhesive applications, surface preparation is important.
Surfaces should be clean and free of oils, dust and other contaminants that could interfere with electrical or adhesive contact.
The conductive surfaces also need to be compatible with the application. Depending on the design, conductive materials can include metals such as copper, gold or silver-based conductive inks.
Oxidized, contaminated or otherwise unsuitable surfaces can affect both electrical contact and adhesive performance.
Pad Design and Alignment
The design of the conductive pads is another important consideration.
The pads need to provide sufficient contact area for the intended connection, while maintaining the spacing necessary to take advantage of the tape’s anisotropic conductivity.
Proper alignment is particularly important in fine-pitch applications.
The goal is to establish consistent contact between the intended conductive surfaces without creating unintended electrical connections between adjacent conductors.
Pressure and Assembly Conditions
Application pressure is also important because the conductive particles must establish reliable contact with the opposing conductive surfaces.
Too little pressure may result in inadequate electrical contact or increased resistance.
At the same time, excessive pressure or an inappropriate assembly process can potentially damage delicate components or substrates.
For production applications, the pressure, temperature, dwell time and other assembly conditions should be established according to the tape manufacturer’s recommendations and validated for the specific materials and design.
Key Considerations
The primary benefit of 3M 9703 is its directional electrical conductivity combined with adhesive bonding.
It can provide a very thin electrical interconnection while eliminating the need for a conventional soldered connection in applications where the tape’s electrical and mechanical performance is appropriate.
But it isn’t a universal replacement for solder or other electrical interconnection methods.
When evaluating 3M 9703, consider:
- Required electrical resistance
- Current and voltage requirements
- Conductor and substrate materials
- Pad size and spacing
- Surface condition
- Required bonding pressure
- Temperature and environmental conditions
- Mechanical stresses such as flexing and vibration
- Long-term reliability requirements
For applications involving significant current, demanding environmental conditions or critical electrical performance, the application should be tested and validated rather than relying solely on general tape specifications.
The Bottom Line
3M 9703 is different from a conventional conductive tape because it is designed for anisotropic, or directional, conductivity.
It can establish an electrical connection through the thickness of the adhesive while helping maintain electrical isolation between adjacent conductors.
That combination of electrical connectivity, adhesive bonding and a very low-profile construction makes anisotropic conductive adhesive useful for certain electronic assemblies where conventional soldering or mechanical connections may not be practical.
As with any specialized electrical adhesive, successful results depend on selecting the right materials and controlling the assembly process.
If you’re considering 3M 9703 for a particular application, the key questions aren’t simply “Is it conductive?” but rather: What materials are being connected, what electrical performance is required, and how will the assembly be manufactured?
Those factors will determine whether an anisotropic conductive adhesive is the right solution for the application.