Electrical Compliance Testing
The NTS facilities are furnished with a wide variety of electrical test equipment to verify the operating conditions of electronic components, assemblies, and products under various types of environmental conditions. Offering a full turnkey solution for your electronic and electrical testing needs. We have the expertise to provide you the information you require whether it involves active monitoring as part of a larger test program or instead stand-alone analysis of a component, board or device. Material properties such as resistance, capacitance and inductance can be determined in addition to the electrical parameters of current and voltage.
A material property is an intensive property of a given solid. Quantitative properties may be used as a means to evaluate the benefits of one material versus another to assist in material selection for a given application.
A property can either be impermeable or be subject to any given number of alterations to its temperature, consistency or other attributes. Due to the possibility of differing directions of a particular property within a material — a natural phenomenon known as anisotropy — there is some variance within material properties.
Often, materials have properties that share attributes with foreign substances, yet they act linear within a select range of operation. Certain materials properties are placed in accurate equations to foretell the characteristics of a given system.
For instance, when a substance attributed with a precise level of warmth experiences a rise or fall in temperature, the alteration of that substance can then be verified. For the most accurate of measurements, materials properties are best determined through standardized methods of testing. Many of these test methods have been documented by their respective user communities and published through ASTM International. Some tests that fall into this category are:
- Arc Resistance – The intent of the Arc Resistance test is to make a relative distinction between solid electrical insulating materials. The ability of the test specimens to resist an arc at a high voltage but with a weak current in the vicinity of the insulating surface is investigated. The test focuses on the time until tracking paths start to form.
- Dielectric Breakthrough/Strength – Dielectric breakthrough refers to the highest intensity of an electric field that a material can withstand without losing its composition, while Dielectric Strength refers to the lowest intensity of an electric field at which a material breaks down.
- Dielectric Constant – The capacity of a substance to keep electrical energy in proportion to the permittivity of the surrounding space is the dielectric constant. When the constant intensifies but other factors stay the same, the electric force field grows in density. Under these conditions, an object of a specific weight and measurement can hold an electric charge — as well as greater amounts of charge — for lengthier time spans. Capacitates of high value are among the materials that benefit from having high dielectric constants.
However, a high-level dielectric constant is not exactly an ideal condition with every substance. A material that has a high dielectric constant will be more vulnerable to come apart when exposed to extreme electric fields — at least in contrast to substances with lower constants.
Dry air is one example of a substance with a low dielectric constant that nonetheless makes an ideal dielectric substance for capacitors that are utilized by transmitters of fully-powered radio frequencies. In the event that the dielectric conducts an electrical charge and then starts to breakdown, the condition is only temporary. Once the extreme field of electric energy subsides, the air becomes restored to its regular dielectric level. Other substances could incur lasting damage from such conditions. Examples include glass and polyethylene.
- Surface Resistivity – This is the ratio of DC voltage between the length and width of an object’s surface. Surface resistivity is among the characteristics of a given material that can be studied and assessed in order to determine the overall value of the material — which can also be compared and contrasted with the resistivity of other materials. Overall, the testing process aids in the selection of materials.
- Volume Resistivity – The volume resistivity is an inherent quality that measures how intensely a certain substance contradicts the direction of electric currents. Low-level resistivity suggests that the substance will easily permit the flow of an electric charge. The unit of resistance is known as the ohm, which is symbolized by the letter “R”. If a one-ampere current goes through a part where the voltage could be at least one volt different, the resistivity of that part is one ohm.
If a given application of voltage is maintained at a constant level, the electrical circuit in a direct current will generally be in reverse proportion to the resistance. However, in a case of double resistivity, the current will only be half as much. On the other hand, if there’s only half the resistivity, there will be twice as much current. This applies to the vast majority of AC systems that run on low frequencies, like the circuits you’d find in houses. High frequency AC circuits, by contrast, often include parts that are able to hold, emit and convert energy.
- Conductivity – The conductivity of an item is the level at which matter carries out electricity, such as in the rate that heat manages to travel from one point on a given object to another. If a one-ampere current goes through a part in which one volt is present, that part has a conductivity of one Siemens. In most cases, when the voltage application is steadily maintained, the CD circuit will have a relative current to the conductance. If the latter is twice as much, so too will be the current. Likewise, a 1/10 conductance will correlate to a 1/10 current.
- Thermal Coefficient of Resistance – A thermal coefficient refers to the difference in physical makeup of a substance once it has undergone a shift in temperature. Coefficients are identified for numerous processes, such as reactivity and the magnetic and electric attributes of substances. If the resistance level to electrical currents in a piece of material goes up in light of heightened temperature, it’s referred to as positive temperature coefficient (PTC).
Materials that tend to be useful in engineering generally go up along with the temperature, which means they’re high coefficients. Electrical resistance goes up as temperatures increase in materials that are high coefficients. Temperature limits can be applied to PTC materials at set input voltages, thereby eliminating the risk of more electrical resistance should temperatures see a spike.
When the electrical resistance of a material lowers due to a rise in temperature, it’s a matter of negative temperature coefficient (NTC). Materials that benefit the numerous processes of engineering will typically reveal a swift drop as temperatures go down. In other words, they tend to be low coefficients. Electrical resistance goes down in materials with low co-efficiency whenever the temperature sees an increase. One key difference between NTC and PTC materials is the PTC materials are self-restricting.
- Dissipation Factor – Measured to determine the inefficiency of a capacitor’s insulating material. In most cases, dissipation factor is used to measure the loss of warmth that occurs when a dielectric or other insulator makes contact with a different electrical field. A capacitor usually consists of an insulator surrounded by twin plates of metal. When the dissipation of a given piece of material is low, it usually means the efficiency is better.
Dissipation in material is often measured with two tests: one where the material is surrounded by metal plates and one with no plates. Depending on the process at hand, other methods of testing might also be applied, including the use of compartments with varying arrangements of electrodes.
For a dielectric material, the shifting of molecular bonds through electric-field exposure will inevitably consume important sums of energy. Consequently, the energy is impossible to restore once the material is taken out of the field. At times, the dissipation factor is alternately called the power factor — particularly during times when induced currents don’t affect a capacitive circuit with an alternating current. The absence of dissipation is usually signified by a zero-figure power factor.
In order to calculate power losses, multiplications are usually made between the current and voltage of the dissipation. With air, the value of dissipation is usually nothing, though its loss value is so miniscule that it doesn’t even matter in most cases.
Every time a certain material is selected for an electrical circuit, it’s crucial to be knowledgeable of the nature of its energy loss. The dissipation factor is used in various everyday processes, including the concept that applies to the microwaving of food. The microwave oven, with its electric fields of alternate direction, generates heat for cooking by causing water molecules to polarize and depolarize through energy loss.
- HAI (High-Current Arc Ignition) – High-Current Arc Ignition (HAI) performance is expressed as the number of arc rupture exposures (standardized to the electrode type and shape and electric circuit) that are necessary to ignite a material when they are applied at a standard rate on the surface of the material. The number of arc rupture exposures necessary to ignite a material when they are applied at a standard rate on the surface of the material. Performance Level Categories (PLC) were introduced to avoid excessive implied precision and bias.
Electrical Monitoring Capabilities
Along with IPC and CAF testing, NTS has a wide range of instruments to accurately gauge sample performance. These types of measurements are useful to verify sample conformance to applicable standards or for comparative analysis to determine if there is a change in sample performance following any environmental tests:
- CAF (Conductive Anodic Filament) – CAF formation is a well-studied phenomenon that is driven by chemical, humidity, voltage, and mechanical means. It is characterized by a sudden loss of insulation resistance that happens internally in the PCB. CAF dendrites can form between adjacent Plated-through holes (PTH), or between a plated through hole and a line on the PCB. Plating chemistry, material consistency, damage from multiple soldering steps, and excessive voltages (beyond designed voltages) accelerate the onset of CAF. The mechanism of CAF is an electro-chemical transport of ions across an electrical potential between anode and cathode.
- SIR (Surface Insulation Resistance) –SIR is defined as the resistance that is generated when materials made for insulation are surrounded by grounding devices and electrical instruments within certain atmospheric conditions. SIR testing is done to determine whether a product or application is capable of withstanding failure due to leaking currents or short circuits. Conditions of high humidity — preferably around 85°C/85% RH and 40°C/90% — are most ideal for SIR testing. Intermittent measurements of insulation resistance (IR) are also taken during such tests, which are often done for the benefit of printed circuit boards and assemblies.
- ESS (Environmental Stress Screening) – Environmental Stress screening is an essential step in the design cycle of electronic systems, particularly as these systems shrink in size and increase in complexity to satisfy the growing customer need for low-power, portable, high-quality gadgets. Maintaining a high operational reliability and offering fault-free operation in all types of operating environments require careful product design, during which you must keep several factors in view. ESS is a useful process that exposes product weaknesses and allows you to make corrections in the design. Faults you detect during in-house testing are less expensive to correct than equipment failures in the field.
- LLCR (Low Level Contact Resistance) – The resistance of a material falls into two categories: intrinsic and electrical, and contact resistance refers to the latter. Other terms used to describe this process include “transitional resistance” and “interface resistance.”
- Voltage Drop – Explains how the provided energy within a source of voltage is trimmed as the electrical currents travel through things that don’t do not provide voltage to the circuit. There are two categories for voltage drops: desired and undesired. The desired category includes drops that run through elements that play an active role in a circuit, while undesired includes drops for connectors, contacts and conductors. A portable heater, for example, could be powered by wires that have a 0.2-ohm resistance. If the heater has a 10-ohm resistance, the overall circuit resistance would be at 2%, which would, therefore, represent the amount of voltage lost within the wire. When a voltage drop gets too extreme, it renders poor performance from an electrical appliance and can also cause damage.
- Resistance – With an electrical conductor — any substance in which electricity can flow — resistance is known as the level of difficulty a current faces while passing through a substance.
Resistance is the inverse of conductance, which refers to the unimpeded passage of currents. Just as conductance correlates to the amount of flow that is available with a force of pressure, resistance correlates to the amount of pressure that is needed to make flow possible. As such, electrical resistance is conceptually akin to mechanical friction. With the exception of superconductors, every type of material shows a certain level of resistance.
When it comes to wires and other parts, the factors that most commonly determine resistance and conductance are temperature, material and shape. For instance, currents face more resistance along copper wires that are long and thin than ones that are short and thick. The flow of electrical currents can be compared to the passage of water, wherein the pressure drop that sends water through a tube is much like the voltage drop that sends a current across a wire.
The impetus behind the flow of a current through a resistor is the voltage drop, which serves to distinguish the voltages at opposite sides of a resistor. Likewise, when water moves through a pipe, it’s caused by the pressurized difference that lies between the opposite pipe ends, as opposed to the actual pressure.
- RLC (Resistance, Inductance and Capacitance) – An RLC electrical circuit is made up of a resistor, inductor and capacitor, which connect in tandem or sequence, but not necessarily in the order of the acronym. RLCs have numerous uses in terms of oscillation. TV and radio receivers, for instance, use RLC circuits to isolate specific ranges of frequency from radio waves. An issue that sometimes arises is inductor resistance, which can be problematic due to the inductor makeup of wire coils.
- IR (Insulation Resistance) – Insulation resistance (IR) tests — alternately referred to as Meggers—use DC voltage to calculate the resistivity of insulation in kilohms, megohms, and gigohms. For equipment that runs on lower voltage, IRs generally use DC applications of 250Vdc, 500Vdc or 1,000Vdc. On high-voltage items, voltages of <600V and 2,500Vdc and 5,000Vdc are usually applied.
By measuring resistivity, IR testing reveals the condition of insulation that sits between conductive parts — higher resistance means better insulation. While the most ideal result would be infinite resistance, insulators have their imperfections, and leakage currents will ultimately determine set values of resistivity. IR tests are particularly advantageous because DC voltages have no detrimental effects on insulation.
- DWV (Dielectric Withstand Voltage): AC/DC Hi-pot – This is an electrical test administered on products and parts to gauge the strength of insulation, which helps determine a product’s potential to run reliably under various conditions. Withstand testing is performed at high voltages of direct or alternating currents at power or resonant frequencies. The test typically lasts for a minute, though the duration — like the voltage rate — can vary depending on the needs of the product. Testing standards vary between switchgear, military devices, high-voltage wires and over-the-counter electronic equipment.
- CTI (Comparative Tracking Index) – Comparative tracking index (CTI) is used to assess the relative resistance of insulating materials to tracking. The CTI expressed as that voltage which causes tracking after 50 drops of 0.1 percent ammonium chloride solution have fallen on the material. The results of testing the nominal 3 mm thickness are considered representative of the material’s performance in any thickness.
- ECM (Electrochemical Migration) and EM (Electromigration) – The Electrochemical Migration and Electromigration (EM or ECM) test method provides a means to assess the propensity for surface electrochemical migration. This test method can be used to assess soldering materials and/or processes. Electromigration is the transport of material caused by the gradual movement of the ions in a conductor due to the momentum transfer between conducting electrons and diffusing metal atoms. The effect is important in applications where high direct current densities are used, such as in microelectronics and related structures
Continuous Monitoring Capabilities
NTS has a variety of monitoring options to continuously record vital input and output parameters of your sample during testing to ensure continuous operation:
- High Speed Data Acquisition / Monitoring / Continuity
- Agilent Data Logger
- Voltage Drop
Utilizing a wide range of AC and DC and power supplies and loads, we can be sure to provide accurate input power and provide appropriate loading to simulate active operation of your product:
- AC Programmable Power Supply (0-300V, 0-37A, 18-500Hz)
- DC Voltage Supplies (0-200V, 0-400A)
- 120/240/480AC Wall Power
- AC/DC Electrical Loads
- AC/DC Ceramic Loads
Test Methods & Standards
- Arc Resistance: ASTM D495
- Arc Resistance: ASTM D495
- Automated Electrical Testing Capacitance: IPC-TM-650, Method 2.5.2
- Comparative Tracking Index: ASTM D3638
- Conductive Anodic Filament Growth (CAF): IPC-TM-650, Method 2.6.25
Conductivity: ASTM B193
- Dielectric Breakdown: ASTM D149, ASTM D877, IPC-TM-650 Methods 2.5.6, 184.108.40.206, 220.127.116.11, 18.104.22.168
- Dielectric Constant / Permittivity: ASTM D150, ASTM D2520, ASTM D1531, ASTM D924, IPC-TM-650, Method 2.5.5, 22.214.171.124, 126.96.36.199, 188.8.131.52, 184.108.40.206, 220.127.116.11
- Dielectric Strength: ASTM D149, ASTM D877, IPC-2.5.6, 18.104.22.168, IPC-SM-840
- Dielectric Withstanding Voltage (DWV): IPC-TM-650, Method 2.5.7
- Dissipation Factor / Loss Tangent: ASTM D150, ASTM D2520, ASTM D1531, ASTM D924, IPC-TM-650, Method 2.5.5, 22.214.171.124, 126.96.36.199, 188.8.131.52, 184.108.40.206, 220.127.116.11
- Electromigration / Electrochemical Migration (ECM): IPC-TM-650, Method 18.104.22.168, Bellcore GR-78, IPC-SM-840, IPC/J-STD-004
- High Current Arc Ignition: UL746A
- High Voltage Arc Tracking: UL746A
- Hot Wire Ignition: ASTM D3874, UL746A
- Inclined Plane Tracking: ASTM D2303
- Resistance: IPC-MF-150, IPC-TM-650, Method 2.5.13, 2.5.14
- Surface Insulation Resistance (SIR) / Insulation Resistance: Bellcore GR-78, IPC/J-STD-004, IPC-TM-650, Method 2.5.10, 2.5.11, 2.5.12, 22.214.171.124, 126.96.36.199
- Volume and Surface Resistivity: ASTM B63, ASTM D257, ASTM D4496