Test Capabilities Overview - Informational Data Sheets

www.thetestlab.com 1-800-878-6601

Independent Materials Testing for — Composites — Laminates — Electronics.

MICROTEKLA BO RATO RIES

Microtek Laboratories has over 25-years of experience performing PCB and PCA evaluations. Microtek’s personnel are leaders in the microelectronics industry and have established the industry standard for consistent high-quality Microsectional Analysis and test reports.

Microsectional Analysis remains the most widely accepted means for analyzing the PCB plated through-hole integrity. A PCB is a combination of different types of materials such as glass, aramid fibers, kapton, copper, acrylic adhesive, epoxy, polyimide, Teflon, solder, etc. Each of these materials has a different relative hardness and, coupled with that of the mounting media (epoxy, acrylic, etc.), makes the PCB microsection one of the most difficult to perform.

This process is further complicated by the fact that it is essential to complete microsectional preparation in an area within 10% of the center of the plated-through hole. Using the latest technology, Microtek’s expert staff utilizes an automated coupon extraction station with a precision router-cutter (milling tool) for drilling two positioning holes and extracting the test coupons. Microtek can accurately microsection high-aspect ratio PCB’s including blind and buried vias down to 0.001”, SMT devices and solder joints. Whether you require regular conformance Microsectional Analysis, vendor qualification, or lot verification, Microtek has the experience and knowledge base to provide you with the highest quality and fastest turnaround available.

Microtek Laboratories is the electronics industry leader with over 25-years of experience in microsectional preparation and analysis. Specializing in PCB testing, Microtek is an approved DSCC facility and a registered ISO-9001:2000 firm. In addition to your in-house and customer specifications, Microtek can perform Microsectional Analysis in accordance with the following Military and Commercial specifications:

• IPC-A-600 – Acceptability of Printed Boards

• IPC-A-610 – Acceptability of Electronic Assemblies

• IPC-6012 – Qualification and Performance for Rigid Printed Boards

• IPC-6013 - Qualification and Performance for Flexible Printed Boards

• IPC-6016 - Qualification and Performance for High Density Interconnect (HDI) on Layers or Boards

• IPC-6018 – Microwave End Product Board Inspection and Test

• IPC-TM-650 – Test Methods Manual

• MIL-PRF-55110 - Performance Specification – General Specification for Printed Wiring Board, Rigid

• MIL-PRF-31032 - Performance Specification - General Specification for Printed Circuit Board/Printed Wiring

• MIL-P-50884 - General Specification for Printed-Wiring, Flexible and Rigid-Flex

CAF, SIR and ECM/EMR Testing:

As spacing and part sizes on PCB’s decrease, the need to verify Conductive Anodic Filament (CAF), Surface Insulation Resistance (SIR) and Electrochemical Migration Resistance (ECM/EMR) have become increasingly necessary. These tests use high temperature/humidity environments in order to understand a product’s reliability by accelerating any failures that might happen. Electrical attributes are evaluated during or after accelerated environmental exposures to further ascertain the product's performance under these severe conditions.

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.

Surface Insulation Resistance (SIR) testing is a methodology used to characterize the PCB manufacturing and electronics assembly process residues and their impact on reliability. It is usually performed on industry standard test board coupons containing patterns, typically interlocking comb test patterns designed for process testing purposes. The patterns are exposed to a high humidity environment which mobilizes any surface contaminates and reduces the insulation resistance of the test pattern.

Electrochemical Migration Resistance (ECM/EMR) is the transport of surface materials 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. As the structure size in electronics decreases, the practical significance of this effect increases. Electrochemical Migration decreases the reliability electronics by causing high resistance shorts of the circuitry. In the worst case it leads to the eventual loss of one or more connections and intermittent failure of the entire circuit. Since the reliability of interconnects is not only of great interest in the field of space travel and for military purposes but also with civilian applications such as anti-lock braking system of cars and telecommunications.

Microtek Laboratories has over 22-years of experience with Environmental Simulation and Accelerated Life testing including CAF, SIR and ECM/EMR testing and can help you in understanding the reliability and performance of your product. Microtek provides the fastest possible turnaround and highest level of technical support for testing your products. Utilizing the latest technology, Microtek Laboratories possesses the technical expertise to meet even your most demanding testing requirements and can perform testing to military and commercial applications such as the BELLCORE GR-78-CORE , specific customer standards and IPC test methods.

Microtek Laboratories is the electronics industry leader with over 20-years of experience in MIL-SPEC testing services. Specializing in PCB testing, Microtek is an approved DSCC facility and a registered ISO-9001:2000 firm. We can assist you through every step of your qualification process and provide you with the highest level of technical support on all of your Military testing requirements.

• MIL-PRF-55110 - Performance Specification – General Specification for Printed Wiring Board, Rigid o Qualification o Group A Inspection o Group B Inspection

• MIL-PRF-31032 - Performance Specification - General Specification for Printed Circuit Board/Printed Wiring o Qualification o Lot Conformance Inspection o Periodic Conformance Inspection

• MIL-P-50884 - General Specification for Printed-Wiring, Flexible and Rigid-Flex o Qualification o Group A Inspection o Group B Inspection o Group C Inspection

• MIL-STD-202 - Test Method Standard Electronic and Electrical Component Parts o Method 103 – Humidity (Steady State) o Method 106 – Moisture Resistance o Method 107 – Thermal Shock o Method 108 – Life (at Elevated Temperature) o Method 111 – Flammability (External Flame) o Method 208 – Solderability o Method 211 – Terminal Strength o Method 215 – Resistance to Solvents o Method 301 – Dielectric Withstanding Voltage o Method 302 – Insulation Resistance o Method 307 – Contact Resistance

• MIL-STD-810 - Environmental Engineering Considerations and Laboratory Tests o Method 501.2 – High Temperature o Method 502.4 – Low Temperature o Method 503.4 – Temperature Shock o Method 507.4 – Humidity

Contact us today and talk directly to one of our MIL-SPEC Test Engineers at: 1-800-878-6601

Plane-Strain Fracture Toughness and Strain Energy Release Rateof Composite and Plastic Materials: ASTM D5045 Fracture toughness is a property which describes the ability of a material containing a crack to resist fracture, and is one of the most important properties of any material for virtually all design applications. Test methods such as ASTM D5045 are designed to characterize the toughness of composites and plastics in terms of the critical-stress-intensity factor, KIC, and the energy per unit area of crack surface or critical strain energy release rate, GIC, at fracture initiation.

Fracture toughness is a quantitative way of expressing a material's resistance to brittle fracture when a crack is present. If a material has a large value of fracture toughness it will probably undergo ductile fracture. Brittle fracture is very characteristic of materials with a low fracture toughness value. Fracture toughness is an indication of the amount of stress required to propagate a preexisting flaw. It is a very important material property since the occurrence of flaws is not completely avoidable in the processing, fabrication, or service of a material/component. Flaws may appear as cracks, voids, metallurgical inclusions, weld defects, design discontinuities, or some combination thereof. Since engineers can never be totally sure that a material is flaw free, it is common practice to assume that a flaw of some chosen size will be present in some number of components and use the linear elastic fracture mechanics (LEFM) approach to design critical components. This approach uses the flaw size and features, component geometry, loading conditions and the material property called fracture toughness to evaluate the ability of a component containing a flaw to resist fracture. A parameter called the stress-intensity factor (K) is used to determine the fracture toughness of most materials. A Roman numeral subscript indicates the mode of fracture and the three modes of fracture are illustrated in the image to the right. Mode I fracture is the condition in which the crack plane is normal to the direction of largest tensile loading. This is the most commonly encountered mode and, therefore, for the remainder of the material we will consider KI.

The stress intensity factor is a function of loading, crack size, and structural geometry. The stress intensity factor may be represented by the following equation:

Where: KI is the fracture toughness in s is the applied stress in MPa or psi a is the crack length in meters or inches

B is a crack length and component geometry factor that is different for each specimen and is dimensionless.

Plane-Strain Fracture Toughness Testing

When performing a fracture toughness test, the most common test specimen configurations are the single edge notch bend (SENB or three-point bend), and the compact tension (CT) specimens.

Where: B is the minimum thickness that produces a condition where plastic strain energy at the crack tip in minimal

KIC is the fracture toughness of the material

sy is the yield stress of material

When a material of unknown fracture toughness is tested, a specimen of full material section thickness is tested or the specimen is sized based on a prediction of the fracture toughness. If the fracture toughness value resulting from the test does not satisfy the requirement of the above equation, the test must be repeated using a thicker specimen. In addition to this thickness calculation, test specifications have several other requirements that must be met (such as the size of the shear lips) before a test can be said to have resulted in a KIC value. When a test fails to meet the thickness and other test requirement that are in place to insure plane-strain condition, the fracture toughness values produced is given the designation KC. Sometimes it is not possible to produce a specimen that meets the thickness requirement. For example when a relatively thin plate product with high toughness is being tested, it might not be possible to produce a thicker specimen with plain-strain conditions at the crack tip.

Plane-Stress and Transitional-Stress States For cases where the plastic energy at the crack tip is not negligible, other fracture mechanics parameters, such as the J integral or R-curve, can be used to characterize a material. The toughness data produced by these other tests will be dependent on the thickness of the product tested and will not be a true material property. However, plane-strain conditions do not exist in all structural configurations and using KIC values in the design of relatively thin areas may result in excess conservatism and a weight or cost penalty. In cases where the actual stress state is plane-stress or, more generally, some intermediate- or transitional-stress state, it is more appropriate to use J integral or R-curve data, which account for slow, stable fracture (ductile tearing) rather than rapid (brittle) fracture.

Uses of Plane-Strain Fracture Toughness

KIC values are used to determine the critical crack length when a given stress is applied to a component.

Where: sc is the critical applied stress that will cause failure

KIC is the plane-strain fracture toughness

Y is a constant related to the sample's geometry

a is the crack length for edge cracks or one half crack length for internal crack

KIC values are used also used to calculate the critical stress value when a crack of a given length is found in a component.

Where: a is the crack length for edge cracks or one half crack length for internal crack

s is the stress applied to the material

KIC is the plane-strain fracture toughness

Y is a constant related to the sample's geometry

Microtek Laboratories capabilities extend beyond those of a typical test facility. Through active involvement in professional industry groups and continuing education programs, Microtek has earned a reputation for uncommon insight and visionary thinking. In addition to anticipating industry trends, Microtek is helping to shape the future direction of the composites, polymer materials and electronics industries and provides the full spectrum of testing, analytical and education services. Our technical staff can produce customized test programs that aid in identifying the cause of manufacturing problems. Working in close partnership, Microtek Laboratories serves as an extension of its customers' facilities, helping to sharpen the product manufacturing and development picture.