You are viewing this site in staging mode. Click in this bar to return to normal site.

Guide to Insulation Piercing Connectors

13 December 2018 09:00

Guide To Insulation Piercing Connectors

An insulation-piercing connector is a type of electrical connector that utilises a connection process to pierce or displace the insulation of a wire or cable to make a conductive path with the conductor inside.  They are also commonly known as insulation piercing clips, insulation displacement connectors and wire taps. Using an insulation piercing connector bypasses the need to strip a conductor of insulation before making a connection.  

Insulation Piercing connectors are purpose built for diagnosing, testing or connecting to wires in circuit quickly, with a minimum of fuss, where the terminal connection is in hard to reach area or its unsuitable to disconnect. They are available in various sizes, contact types and connection forms and using them during electrical testing is fast, efficient and dependable, as it doesn’t involve any wire stripping or twisting. The fast installation and minimum clean up combined with dependable performance have made insulation piercing connectors popular in many industries. Example electrical testing applications include; vehicle wiring looms, electronic locks, alarms, network and telecoms cables. These low voltage circuits are ideal for insulation piercing connectors. 

Below we explain the common types available and offer the advantages and disadvantages of using such insulation piercing connectors.

Performance and Reliability Factors

Connectors with insulation piercing technology are designed to create a semi-permanent metal to metal connection between the wire conductor and the insulation piercing connector.  There are a nunber of factors that affect their performance and the reliability of the connection.  These include:

  • The type of contact;
  • Method of connection;
  • Connector tip design.

Type of Contact

The connection reliability directly affects the insulation piercing connector performance during electrical testing. The most common contacts in use include a single needle or a set of multiple needles often known as a 'bed of nails'.  The number or size of these sharpened needles that pierce the insulation directly impacts on the connection quality.    The correct type of contact for your application is pivotal. Too small and the needle(s) will struggle to breach the insulation making the connection weak or intermittent meaning misleading results are likely. Too large and the hole made by the needle(s) won’t self-heal and conductor damage through corrosion or dirt bypassing the insulation is likely. Example contact types:  

Single Needle                                                          Bed of Nails

XEL Piercing Test Connector                 WIPT-2-S Wire Insulation Small Piercing Tap

XEL Insulation Piercing Connector Blue Insulation Piercing Probes with Bed of Nails


Connection Methods

Another important factor affecting the reliability of an insulation piercing clip is the connection method. Sufficient force to hold the contact interface in place is critical to ensure a strong and reliable connection for electrical testing. Connection methods typically suit different applications and those available include screw down, spring loaded and hand force. Some will combine two of the methods to maximise the likelihood of a good first time connection.  Below we explore the different methods and explain their advantages and disadvantages.

Screw down Connection

Screw down insulation piercing clips are slower to install than both spring-loaded and hand force piercing connectors.  Although the connection is stronger and more reliable for electrical testing at longer durations. Reasonable access around the wire is needed to ensure the technician can tighten the piercing connector to make a good connection.


  • Hands-free testing;
  • Personal assurance the connector is tight;
  • Very reliable connection;
  • Robust.


  • Slower installation;
  • Limited to applications where wires are accessible enough for the connection to be screwed down.


             E Z Hook XEP Micro Size               WIPT-2-S Small Piercing Tap           6405 Insulation Piercing Connector 

 XEP Micro Insulation Piercing Probes WTS Small Piercing Probe SetPair of Vehicle Piercing Probe Connectors


Spring Loaded Connection

Spring loaded insulation piercing connections are fast to install and provide a reliable connection for fast electrical testing and simple diagnostics. Many technicians use a spring-loaded piercing test clip when access is awkward and it prevents hand force or screw connections. Spring loaded connections are solely reliant on the quality, strength and condition of the spring. The spring has to be able to overcome the conductor insulation and frequent use and age may result in poor connection reliability as the spring weakens and its holding force of the contact interface reduces.


  • Fast installation;
  • Hands-free testing;
  • Reliable connection.


  • Shortened performance life cycle;
  • Strength of spring needs to overcome insulation strength.


    Fluke AC89 HD Probe                           Electro-PJP 6003                             Pomona 6483

 Fluke AC89 HD Probe Red/Yellow Electro-PJP 6003 Red Probe Pomona 6483 Black Assembled Lead

Hand Force Connections

Insulation piercing connectors with hand force connections rely on manually pulling a plunger that sinks the needle into the insulation to create a contact. The connection is dependent on the force from the technician. The hand-held nature of these probes often limits the maximum voltage capacity.


  • Reliable connection;
  • Durable;
  • Long product life;
  • Costs effective.


  • Slower installation;
  • Limited to applications where wires are easily accessible.


     E-Z Hook XJ Piercing Hook                    Fluke TP88

E-Z Hook XJ Red Hook TP88 Pair Black/Red


Connector tip

Insulation piercing connectors will have some kind of shape to the tip of the connector which is designed to assist with the positioning of the wire that is being connected to.  This usually takes the form of a 'V' or 'U' shape at a radius suitable to allow wires that the connector is designed for to sit central under the needle(s).  It is also possible to find tips that have extending hooks with an embedded needle to capture wires in a jaw.

It is import to choose the insulation piercing connector that is designed for the range of wire diameters that you with to use them with.  It is ideal for the wire to sit central in the tip so that the needle(s) pierce the exact centre of the wire.  If the tip is too large with a small diameter wire it is possible that the wire incorrectly seats in the tip and the needle(s) misses the conductor or makes a poor connection.  If the connector tip is too small for a large diameter wire it is possible for the needle to push the insulation off to the side and again miss the conductor.  This is especially important if the point of connection is difficult to view whilst making the connection. 

'V' shaped tips are the most forgiving for a wider range of wires and the technician can assist the connection process by slightly pulling the connector onto the wire to help it centralise at the bottom of the 'V'.

pierced Wire Issues & Solutions  

There has been debate that wires that have been pierced can corrode internally over time as the insulation has been damaged by the needle(s) from the insulation piercing connector. This can allow air and moisture to make contact with the internal conductor allowing the natural oxidation and corrosion process to occur.   There is evidence to show that this can be true however there are also a number of techniques to mitigate against this possibility:

Use an insulation piercing connector that is the most suitable for the wire it is being used on.  Use a connector that minimises the size of piercing that is required to gain a reliable connection.  A large single needle is best for larger diameter wires with thick insulation.  A bed of nails is more suited to small diameter wires or those with thin insulation. 

Cover the piercing holes so that they become hermetically sealed.   Use electrical tape, waterproof varnish, such as a nail varnish or heatshrink. All of which are easy to apply and cost effective. 

Conclusion & Recommendations

Insulation piercing connectors are useful in many applications, most commonly; automotive diagnostics; telecoms, security alarms, and decoders.  There are a number of purpose-built connectors available on the market using different contact types, sizes and connection types along with differing designs of the tip to assist with wire positioning.  To choose the right insulation piercing connector for your application it is recommended to use a ‘work backwards’ approach and assess what wires you plan to test.  From there, identify your exact insulation piercing connector requirements by wire diameter capabilities, contact type, and connection method. Many insulation piercing connectors are serviceable in different applications, however using the right tool for the job, usually makes the task faster, safer and accurate.

Please fell free to contact us if you require further assistance.

Find an insulation piercing connector to suit your application by clicking the button below.

Discover Related Newsletters

Click any of the images below and discover specific information based on the following topics;

Guide to Automotive Diag Accessories Guide to Current Drain Testing Guide to Fused Test Probes

 News & Blog Homepage