Connector main test items and performance parameters

A connector, also known as a plug and socket, is an electronic engineering component that connects parts, usually referring to the electrical connector. This component enables the connection of two active devices for the transmission of current or signals. Connectors are mainly used in circuits and the connection between them. They are essential components in the electrical system’s core for establishing the necessary electrical connections.

Currently the most popular connectors
Currently the most popular connectors

The main application areas of connectors are smart homes, automotive industries, communications, computers, peripherals, industrial, military, and aerospace. With the development of technology, the usage of connectors in various industries is becoming more and more extensive. In the production and manufacturing industries, connectors play an irreplaceable role. Their performance directly affects the proper functioning of the entire system. Therefore, performance testing is particularly critical. Today, we will discuss connector test items and their performance parameters.

Connector test items can be divided into electrical performance testing, mechanical performance testing, and environmental performance testing, corresponding to the main test specifications as follows:

International specifications:

1-1-1MIL-STD-1344A

1-1-2mil-std-202f

1-1-3EIA-364C (American Institute of Electronics Industries)

1-1-4IEC-512 (International Electrotechnical Commission)

Product or Industry Specifications:

1-2-1MIL-STD-24308C For D-SUB CONN

1-2-2 PCIEISA Standard

1-2-3 IEEE 1394

1-2-4 PCMCIA

Electrical Performance Tests

The main test items and descriptions are as follows:

Contact Resistance

Purpose: To maintain the contact impedance of the connector during its service life to minimize the loss or attenuation of signals and energy during transmission.  

Test Method Reference: EIA-364-23 (EIA-364-06) or MIL-STD-1344A.  

Test Points:

a. Test current/voltage 100mA@20mV with no load on the connector (connecting system) under test.                  

b. Test current is low to avoid contact impedance being affected by thermoelectric effects on the terminals (conductors).                      

c. The test voltage is low to avoid breakdown and melting of the insulation film at the contact interface between the terminals (conductors).  

Specification requirements: generally required 50m (initial); 100m (final), that is, after the life test or environmental testing. 

Definition of contact impedance this parameter reduces the loss or attenuation of signals and energy in the transmission process, the current is like the flow of water, the lower the resistance, the less energy loss and attenuation.

In terms of the connector contact, the factors that affect the size of its impedance are the positive force (for elastic contact structure), the contact environment, such as the surface roughness of the terminals (conductors), the surface treatment (such as plating of the metal properties and densities), the terminals and terminals (or other conductors) bonding method (is the weld or riveted or elastic contact, etc.).

From the point of view of electrical theory, the contact impedance for the C point of the green circle contact at the impedance; in the guest use point of view, the connector provides A point to B point of conduction (connection), so the guests want the impedance should be included in the point from A point to B point of all the conductors themselves and the impedance of the contact (including soldering, riveting, and other contact modes) as shown in the figure below.

Definition of contact impedance
Definition of contact impedance

Withstanding Voltage

Purpose: To confirm that the two conductors (or two circuits) between the insulating medium (including gas) and its spacing are suitable and sufficient to ensure that the connector in the switching shock voltage or accidental overload (a certain period over-voltage) state can maintain the normal function, to ensure safety.  

Test Method: EIA-364-20 or MIL-STD-1344A.  

Test points:

a. Generally, the measurement point is placed between the two conductors (or two circuits) nearest to each other, or two conductors (or two circuits) are designated, and every two conductors (or two circuits) are measured if necessary.    

b. The test voltage can be AC (60Hz; sine wave; RMS = * peak) or DC.       

c. Load speed: 500V/second; duration: 60second.       

d. Breakdown (sparking) or leakage current greater than 5mA at the required test voltage is considered bad.  

Specification requirements: cell phone connectors are generally 100VAC Min./minute.  

Definition of withstand voltage This parameter ensures the safety of the connector under overload voltage. Avoid accidental overload under the short circuit, resulting in fire and other accidents.

Test results and many factors, including the test environment, such as air pressure, and humidity; test the role of the pressure, the role of frequency and duration, electrode form; test voltage frequency & waveform; product geometry (and the role of stress); the two conductors (or two circuits) between the media conditions and spacing and so on. Withstand voltage value is generally set to work for the rated voltage of 3 times or the breakdown voltage of 3/4, for cell phone connectors, 100VAC Min./minute can meet the requirements.

Insulation Resistance

Purpose: To confirm that the connector between the two conductors (or two circuits) maintains a high enough impedance to prevent the generation of weak currents sufficient to affect the signal (especially high-frequency transmission) and energy transfer.

Test Method: EIA-364-21 or MIL-STD-1344A.  

Test Points:

a. Generally, the point of measurement is placed between the two nearest conductors (or two circuits), or two conductors (or two circuits) are designated, and every two conductors (two circuits) are measured if necessary.       

b. Test voltage level DC 100V, 500V, 1000V, 1500 V; according to the product functional requirements to determine .       

c. Duration: 2 minutes (if time affects the results, the duration of the test needs to be determined)

d. If necessary, the test samples need to be cleaned, baked, and then tested.       

e. The test process must not have sparks or insulator breakdown phenomenon. 

Specification requirements: cell phone connectors are generally 100MΩ Min.

Definition of insulation impedance This parameter is designed to minimize the effect of weak currents on signal/energy transmission.

Insulation impedance is particularly influential in high-impedance circuits, and weak currents generated by thermoelectric effects, electromagnetic induction, etc. can be determined by the value of insulation impedance. The test voltage is generally the rated voltage of the product, and the test environment such as pressure, temperature, and humidity will affect the results.

Temperature rise

Purpose: To confirm the current loading capacity of conductors (circuits) in connectors and to ensure the safety of connectors under long-term loading.  

Test method: EIA-364-70.  

Test points:

a. Measurement of temperature change can be started only when the whole loop reaches thermal equilibrium under load current.      

b. Test current/voltage is rated operating current, operating voltage.         

c. Load current and voltage duration are based on the time it takes for the circuit to reach thermal equilibrium.  

Specification Requirement: The temperature rise at any point of the system conductor (circuit) shall not exceed 30 degrees Celsius at room temperature of 25 degrees Celsius, 1 atmosphere of pressure, with a current @250VAC Min.

The purpose of the temperature rise requirement is to avoid the adverse effects of temperature rise (such as thermoelectric effect, accelerated elastic parts creep, etc.), to maintain the function and life of the connector under sustained loads, and at the same time to avoid the impact of the product temperature rise on consumers. For example, the surface temperature of a cellular phone rises when the phone is used for too long, making the consumer feel uncomfortable.

Contact Capacitance

Purpose: To determine the value of capacitance between connector conductors to avoid current or signal penetration and interference. 

Test Method: EIA-364-30.  

Test Points:

a. The test frequency is generally 1k Hz or 1M Hz.       

b. Generally, the measurement point is placed between the two conductors (or two circuits) nearest to each other, or two conductors (or two circuits) are specified, and every two conductors (or two circuits) are measured if necessary.  

Code requirements: capacitance values are typically 2pF Max.

Mechanical Performance Test

The connector in the use of the process will act as force generation, to determine the force requirements of the connector to ensure that the connector can be firmly connected, the mechanical properties of the connector have:

Mating and uniting force

Purpose: to confirm that the connector in the use of the process of generating force is sufficient to maintain the connector function and suitable for the consumer feel.  

Test Method: EIA-364-13 or MIL-STD-1344A.  

Test Points:

a. The test pair is the whole connector, full ass’y.        

b. The test axis of action is the direction of normal connector use.       

c. Unless otherwise specified, test speed is defined as minute.  

Specification Requirements:

a. Insertion force is normally set at max. (35N Max.).       

b. Withdrawal force is normally set at the minimum value (7N Min. initial; 3N Min. initial; 3N Min. initial). (7N Min. initial; 3N Min. final), but some customers require a maximum value.

The insertion force is defined to fit the consumer’s hand, and the withdrawal force is defined to ensure that the connector stays connected in the event of an accidental force, and does not result in the disconnection of the two connected products due to an accidental force.

Insertion force is the force generated from the complete separation of the two connectors from each other to the working state; pull-out force is the force generated from the working state of the two connectors from each other to the complete separation of the two connectors. Insertion force is generated when consumers use the product, just having a docking end (io/plug, jack/plug) party will produce insertion force, generally no docking end, such as battery/sim conn. do not define the insertion force. The force graph produced during the testing process contains a lot of information, which can be used to understand the stress condition of the connection system during the plugging and unplugging process and to find out the anomalies for design improvement.

Locking force

Purpose: To confirm that the connector is not separated from the contact interface under accidental conditions (force) in the course of use, to ensure the function under accidental conditions (force).

Test points:

a. Test for the whole connector object, full ass’y.

b. The test axis of action is the direction of normal use of the connector.       

c. Unless otherwise specified, test speed is defined as minute.

Specification requirements: generally set the minimum value (30N Min.)

The locking force is the force generated by the locking mechanism while it is still in action to harden the two mating connectors from the working state to complete separation. This test is destructive, for self-locking or semi-self-locking systems the locking force is equivalent to the pull-out force.

Retention

Purpose: to ensure that the connector in the manufacturing or use of the process of contact terminal (conductor) state (position), to avoid external forces (such as the manufacturing process of soldering wire pull; SMT process of thermal deformation of the force; insertion and removal of the force, use of the process of impact or vibration generated by the force, etc.) to make the contact terminals (conductor) out of position, resulting in the loss of the function of the connection.  

Test Method: EIA-364-29 (EIA-364-05).  

Test Points:

a. The test pair for the entire connector, full ass’y        

b. The test axis of action is the direction in which the connector is normally used (opposite direction of terminal assembly).       

c. Unless otherwise specified, speed is MINUTE.

d. Tests are performed in the direction of the connector.

e. Destructive testing.   

Specification Requirements: Generally set minimum (Min.).

The definition of terminal retention force is to ensure that the terminals (conductors) fixed in plastic, have been assembled in plastic terminals in the manufacturing process (such as the soldering/product handling process of pulling / SMT process) and the use of the process (such as male-female pairs of insertion process, or the product is subjected to vibration and shock) will be received by the external force, so the terminals and the plastic retention force must be sufficient, will not make the terminal in the accidental force generated after the withdrawal of the PIN, resulting in connection interruption, connection function failure.

Normal force

Purpose: to maintain the connector in the use of the process of positive contact stress to ensure that the connector in the use of the process maintains sufficiently low contact impedance and friction; and to ensure that the function of the connection (does not occur instantaneous break).  

Test Points:

a.Positive contact stresses generated by elastic contacts in the system under operating conditions.   

b. Unless otherwise specified, the speed is MINUTE.  

Specification Requirements: generally defined between 60-150 gf (over the operating period).

The definition of positive force on resilient terminals is intended to maintain a sufficiently low contact impedance and to prevent the product from being subjected to vibration or other unintended forces that could result in a broken signal during use. Positive force is the force required to bring a resilient terminal from its initial state to its operating state, and it must be ensured that the connector’s positive force remains adequate before and after a life test or environmental test.  

The relationship between terminal forward force and contact impedance is an inverse relationship. As the forward force increases, the contact impedance decreases, and as the forward force increases to 60 gf, the decrease in contact impedance becomes very small. In addition, the greater the forward force, the greater the friction generated by the contact process (f = F * u; f —- friction, F —- forward force, u —- friction coefficient), the more detrimental to the wear of the contact interface, so the general definition of the forward force is not more than 150gf.

Durability

Purpose: To confirm that the connector meets the functional requirements within the service life.  

Test Methods: EIA-364-09 or MIL-STD-1344A.  

Test points:

a. Test the axis of action for the normal use of the direction of the connector.       

b. Unless otherwise specified, the speed is generally 200-500 cycles/H.

c. The test procedure is generally without current loading. (unless otherwise required).  

Specification Requirements:

a. Parameters to be determined during and after testing: insertion and extraction force (or forward force), contact impedance (terminal OR iron shell), insulation impedance, voltage withstand, sealing, etc. by product specification.       

b. Appearance inspection: wear and tear, relaxation or fatigue, metal fragments, terminal displacement or bending damage, etc.

Life expectancy, also called durability (endurance), refers to the period of use of a product. It is usually defined as the number of times a connector is used to evaluate the wear of the terminal plating and the change in mechanical/electrical characteristics before and after insertion and removal of the connector after continuous use (insertion and removal or positive pressure). The force graphs generated during life testing analyze the changes and trends in insertion and removal forces before and after life to assist in design corrections. Before the life test, it is necessary to confirm that the samples have gone through the complete manufacturing process, for example, board-end products need to go through SMT first before entering the test program.

Cable Pull-out

Purpose: Ensure that the cable and connector are firmly connected to avoid the cable or connector being damaged by the external force on the cable and the connector.   

Test Method: EIA-364-38.  

Test Points:

a. Load speed: 89 +/- 4 N/minute; load time: 1H.       

b. General static load 40N for one minute (or by Condition A-E).  

Specification Requirements:

a. Appearance check: the outside of the cable is damaged; connector insulator or conductor damage; cable clamp failure; cable out of the clamp or displacement beyond the permissible value; cable to connector sealing damage; connector metal body twisted deformation, etc.

b. Functional check: impedance; instantaneous breakage, etc. Cable Pull-out This parameter is only for plug ass’y containing cable, to confirm the appearance and function of the cable when it is pulled by external force. There are 90-degree and 180-degree pulling directions, if the customer wants special requirements, then according to the customer’s requirements.

Visual and Dimensional Inspection

Purpose: To confirm the appearance and dimensional quality of the product (system).  

Test Method: EIA-364-18. 

Test Points:

a. Appearance section defines personnel vision, lighting environment, sample placement, visual distance, and time.                           

b. Dimensional part defines measuring instruments and measuring methods, sample requirements, etc. (e.g., measurements after 24H placement of molded plastic parts, etc.).  

Specification requirements:

a. Surface finish requirements (e.g., plastic surface roughness; terminal plating), appearance requirements (e.g., no crush injury; burrs).       

b. Dimensions by the requirements of the drawing.

Other mechanical properties, connectors in the use of the process involve the force of the part, with solidity (such as male and female with the up and down left and right swing) and combined with solidity (such as the finished product of the upper and lower shell of the drop performance) and so on, when necessary to add to the product specification within the definition.

Environmental performance test

Connectors in the use of the process will encounter different environmental conditions, to confirm the electrical characteristics or mechanical characteristics of different environments, to ensure that the connector functions in different environments, the environmental characteristics of the connector are.

Mechanical Shock

Impact: The purpose is to determine the electrical connector to withstand the separation and fall to the ground when the impact may be encountered the ability of this test only applies to the design of the electrical connector in line with the requirements of the program.

Test Methods: EIA-364-27 or MIL-STD-1344A,2004

Test Points:

a. Impulse pulse: half-sine or sawtooth (both peak acceleration is not the same)

b. The sample is fully wired and mated, and loaded, load: 100mA Max.  

c. Three times in each of the six directions on three mutually perpendicular planes, for a total of 18 times.

d. Pulse in general use, peak acceleration is 30Gs, cycle time is 11ms.

Specification Requirements: a. no discontinuities of one microsecond

Mechanical shock is to simulate the condition of consumers using the product under accelerated motion loads, to ensure the connection function of the product under different accelerated environments.

Random Vibration

Vibration: The purpose is to determine the electrical connector in the life of the possible encounter in the main frequency band or random vibration frequency band range and its amplitude by the impact of vibration, to confirm that the connector in the use of vibration conditions encountered under the function. Random vibration is to simulate consumers using the product under vibration conditions (e.g., using the product in a moving vehicle) to ensure that the product connects under different vibration environments.

Test Method: EIA-364-28 or MIL-STD-1344A,2005

Test Points:

a. Sample placement; samples need to be fully ass’y or installed (simulate the use of conditions)

b. Vibration parameters: acceleration = m/s2, amplitude =; frequency amplitude & time & mode; duration, all to be determined.

c. Sample is loaded Load: 100 mA Max.

Specification Requirements:

a. no discontinuities of one microsecond

b. other dimensional, and functional inspection

Collision

Purpose: To ensure the ability of the connector to resist collision. To ensure the function of the system in the event of an accidental landing and other collisions.

Test Method: EIA-364-42

Test Points:

a. Concrete floor, H=Min.

b. Height and number of drops (related to product requirement level)     

c. Drop orientation

Specification Requirements: Type of Failure  

a. Loss of sealing

b. Loss of electrical function

c. Loss of mechanical properties (male/female fit; component construction)

Crash testing simulates the condition of a product subjected to an accidental impact. Ensure that the connector connects when subjected to accidental impact, such as landing. 

Impact purpose: to ensure the connector’s ability to resist collision, and to ensure the function of the system in the event of an accidental landing and other collisions.

Test Methods: EIA-364-42

Test Points:

a. Concrete floor, H= Min.

b. Height and number of times (related to product requirement level)     

c. Drop orientation

Specification Requirements: Type of Failure  

a. Loss of sealing

b. Loss of electrical function

c. Loss of mechanical properties (male/female fit; component construction)

Crash testing simulates the condition of a product subjected to an accidental impact. It ensures that the connector will function when subjected to an accidental impact such as hitting the ground.

Summary: usually for the connector in the specified frequency and acceleration conditions of vibration, shock, and collision when the electrical continuity of the contact pair, because the contact pair in this dynamic stress will occur in the phenomenon of instantaneous disconnection, and the specified instantaneous break time is generally 1μs, 10μs, 100μs, 1ms, and 10ms. to pay attention to how to determine the contact pair of instantaneous brake failure. In this case, when the voltage drop at both ends of the closed contact pair (contact) exceeds 50% of the electric potential of the power supply, it can be judged that the closed contact pair (contact) has failed. In other words, there are two conditions for determining whether a transient fault has occurred: duration and voltage drop, both of which are indispensable.

Temperature Shock

Shock: The purpose is to determine the suitability of electrical connectors and their accessories to withstand shocks that occur during rough work, transportation, and military operations. Ensure that the connector is in the extreme temperature (high or low temperature) environment of normal application (storage; transportation; use).

Test Methods: EIA-364-32 or MIL-STD-1344A, and

Test Points:

a. Samples must be identified as mating or unmating.

b. The sample must have 75% exposed area in the greenhouse and be insulated during the transition between the two greenhouses; the duration of the test is related to the weight of the sample.

c. The medium in the greenhouse is liquefied nitrogen, with high-temperature testing conditions of 85 to 88 degrees Celsius and low-temperature testing conditions of -55 to -58 degrees Celsius.

d. Duration is generally 30 minutes; cycle default 5cycles (according to product features or customer requirements)

Specification Requirements:

a. Sample dimensional variation.

b. Damage or displacement of components (seals, electrical components, etc.)

c. Failure of elastic parts of the sample.

d. Changes in the electrical and mechanical characteristics of the sample.

e. Samples with specific requirements for high or low-temperature resistance are subject to customer requirements.

Temperature shock is a simulation of the consumer’s use of the product under different temperature conditions, for example, near the equator or at the North Pole. This ensures that the connector will function properly under different temperature conditions.

Humidity life

Purpose: To confirm the function of connectors in high-temperature and high-humidity environments.

Test Methods: EIA-364-31 or MIL-STD-1344A.

Test Points:

a. Avoid condensation on the sample, the sample will be dried before testing, drying conditions: 50 ℃, 24H b. Test air exchange rate: 5 times the volume of the test space/minute; wind speed: 46m / minute Max.

c. Test sample load: 100VDC;

d. Test duration according to the product function or customer’s request.  

Specification requirements:

a. Sample size variation condition.

b. Damage or displacement of components (seals, electrical components, etc.).

c. Failure of elastic parts of the sample.

d. Changes in the electrical and mechanical characteristics of the sample.

e. Comparison of parameters before and after humidity testing.

Salt Spray Test

Purpose: To confirm the function of connectors under salt spray air. Mainly evaluates the corrosion resistance (electrolytic corrosion) of connectors, especially surface-treated hardware.

Test Methods: EIA-364-26 or MIL-STD-1344A, EIA-364-26 or MIL-STD-1344A, EIA-364-26 or MIL-STD-1344A.

Test Points:

a. Jet requirements (gas, relative humidity, temperature, air pressure, relative concentration).

b. Salt solution concentration: 5 +/- 1 % pH= Temperature: 35 +1/-2 °C.

c. Sample placement requirements, the test process can not accumulate saltwater.

d. Test time is generally more than 8H for tin plating and more than 12H for gold plating (or according to customer’s requirements) e. Samples should be cleaned and dried after the test.

Specification requirements:

a. Corrosion status (degree of destruction of the protective layer).

b. Dimensional variation.

c. Whether there is any change in the electrical and mechanical characteristics of the samples.

Solderability

Purpose: To ensure that the soldering area of the connector meets soldering requirements.

Test Method: EIA-364-52.

Test Points:

a. Also known as tin-eating properties, tested by dip.

b. Usually not used to assess the solder cups, solder holes, manual soldering, or SMT.

c. Pay attention to the temperature profile when evaluating the suitability for SMT processes.

Specification Requirements:

a. Soldering area 95% tin-eating, define the solderability is to confirm the product soldering area of the soldering performance (i.e., soldering quality issues), but also need to define the solder resistance (i.e., soldering duration of the problem). Because the soldering process generates heat, the heat will affect both the plastic and the terminals and may cause the plastic to melt resulting in a loss of terminal retention.

Flammability

Purpose: To confirm the flame retardant properties of the connector (mainly refers to the plastic part).

Test Method: UL 94-V0;V1;V2;HB or EIA-364-104.

Test Points:

a. Whether the sample is placed horizontally or vertically during the test.

b. After the sample burns away from the source of ignition, how long will the burning last?

Code Requirements: a. Compliance with UL fire ratings (generally UL 94-V0).

Flame retardant ratings are in ascending order from HB, V-2, V-1 to V-0.

Among them, HB samples are placed horizontally, which is the lowest flame retardant grade in UL 94 standard, and requires that for samples of 3 to 13mm thickness, the burning speed is less than 40mm/min; for samples of less than 3mm thickness, the burning speed is less than 70mm/min; or extinguished before the mark of 100mm.

V-2; after two 10-second burn tests on the sample, the flame is extinguished within 60 seconds, and there can be burning material falling.

V-1; after two 10-second burn tests on the sample, the flame is extinguished within 60 seconds and no incendiary material can fall.

V-0; after two 10-second burn tests on the sample, the flame is extinguished within 30 seconds and no incendiary material can fall.

The development trend of connectors can be summarized as follows: high-speed, lightweight, intelligent, miniaturization, and integration. The connector industry chain, from raw materials to finished products, is based on this trend to make corresponding changes. The connector is a key component of a system or machine circuit unit that connects electrical connections or signals for transmission. It has been widely used in fields such as military, communications, automotive, consumer electronics, and industry. Various application scenarios correspond to different testing requirements.