What Is Chemical Testing?
Chemical testing and analysis spans a wide variety of services, from ion chromatography to high voltage arc tracking. With the assistance of international standards for guidance, chemical testing can ensure regulatory compliance while also providing information about the chemical composition of product material.
What Are Chemical Testing Standards
A number of organizations offer standards for products in many industries:
- The IPC (Association Connecting Electronics Industries), accredited by the American National Standards Institute (ANSI), is a trade organization dedicated to standardizing assembly and production requirements for electronic equipment. The entire electronics manufacturing industry applies IPC standards, including IPC-A-610, Acceptability of Electronic Assemblies.
- ASTM International (the American Society for Testing and Materials), is another standards organization that publishes technical standards for material, products and services. The ASTM offers over 12 thousand consensus standards around the world, some of which are mandatory in certain jurisdictions.
- The United States Department of Defense also provides standards called MIL-STD or MIL-SPEC standards, used to ensure products meet certain requirements. Not only do defense contractors use these standards, so do technical organizations committed to high quality and reliability.
- UL is an independent safety science company that provides standards to assess products, test components and materials and also evaluate environmentally sustainable products.
What Chemical Testing Services Are Provided
The following are a number of approaches to chemical testing that may be helpful when evaluating your product components. Standards such as IPC and ASTM guide each approach.
Alloy Composition: IPC/J-STD-001, IPC/J-STD-006
With demand for metal and alloy production increasing, safety and reliability requirements have never been more important. Below are some of the methods used to test alloy composition.
- The IPC J-STD-001 Requirements of Soldered Electrical and Electronic Assemblies have become the accepted standard in electronics assembly and soldered electrical manufacturing. The standard sets forth the materials, methods and verification criteria for producing high quality soldered interconnections. The standard provides guidance in component placement, insertion, handling, attachment and joining techniques, in addition to cleaning prior to coating and encapsulation.
IPC J-STD-001 establishes standards for electronic products that offer continued performance and extended life, and for products that require high performance because of harsh end-use environments or because of the importance of continued function, as with life support machines.
- The electronics industry also maintains standards prescribing the requirements and test methods for soldering materials. IPC J-STD-006 establishes the nomenclature requirements and test methods for electronic grade solder alloys. It’s a quality standard that’s not meant to verify a material’s performance in the manufacturing process. Soldering alloys are classified by alloy composition, impurity level, solder form and dimensional characteristics of the solder form.
To test the performance of a material, one may need to thermally bond the material between substrates of interest. IPC-TM-650, Method 126.96.36.199, provides recommended procedures for pre-tacking and for bonding anisotropically conductive films (ACF).
Chemical Resistance / Solder Resistance: ASTM D543, IPC-SM-840, IPC-4101, IPC-TM-650
Solder mask materials should prevent the formation of solder balls, solder build-up, solder bridging and physical damage to the printed board substrate. The materials should also reduce electromigration and other forms of detrimental or conductive growth.
- ASTM 543 offers standardization of the relative resistance of various plastics to typical chemical reagents.
- IPC-SM-840 defines the method of obtaining the most trustworthy information about solder mask material with the minimum test redundancy. IPC-SM-840 provides requirements for the evaluation of solder mask materials, the conformance of solder mask materials and the qualification assessment of the solder mask in connection with the appropriate test substrate and the standard printed board system. IPC-SM-840, however, does not test the compatibility between solder mask materials and post soldering products.
- IPC-SM-4101 provides specifications for base materials (laminate or prepreg) for rigid and multilayer printed boards. Specifications cover nominal laminate thickness, metal cladding type, nominal weight/thickness and thickness tolerance (laminate).
- IPC-SM-650 establishes methods for testing electronic and electrical parts such as basic environmental, physical and electrical tests.
- Method 2.3.2 tests the chemical resistance of flexible printed board materials, subjecting the material to hazardous chemicals to generate data.
- Method 2.3.3 tests the chemical resistance of insulating materials.
- Method 2.3.4 tests the chemical resistance of marking paints and inks.
- Method 188.8.131.52 tests the resistance of core (dielectric) materials used in printed wiring boards to methylene chloride.
Cleanliness / Ionic Impurities: IPC-TM-650, Delphi-Q-1000-119, Delphi-Q-1000-127
Cleanliness testing on the printed circuit board and assembly determines the amount of contaminant material. The use of different analytical techniques for cleanliness testing can help detect unexpected and unknown contaminants.
- IPC-TM-650, Method 2.3.25 tests are used for the detection and measurement of ionizable surface contaminants through resistivity of solvent extract (ROSE).
- IPC-TM-650, Method 2.3.28, prescribes an ionic analysis for circuit boards using ion chromatography.
- IPC-TM-650, Method 184.108.40.206, measures the level of chloride, bromide and fluoride in a soldering flux or paste using Ion Chromatography (IC).
- IPC-TM-650, Method 220.127.116.11, measures the level of anionic and cationic residues on the surface of unpopulated printed boards using Ion Chromatography (IC).
Composition: IPC/J-STD-004, IPC-TM-650
When making guarantees about the chemical composition or products, it’s often vital to confirm that composition as well as to check for impurities. IPC J-STD-004 standard prescribes requirements for the classification and characterization of fluxes for high quality solder interconnections.
The standard was designed to classify tin/lead and lead-free soldering flux materials needed to produce electronic metallurgical interconnections for printed circuit board assembly. Flux materials include liquid flux, paste flux, solder paste, solder cream and flux coated solder wires.
Flammability: ASTM D635, ASTM D2863, IPC-4101, IPC-SM-840, IPC-TM-650, UL94
Flammability testing assesses the flammability of materials used in electrical devices.
- UL94, the Standard for Safety of Flammability of Plastic Materials for Parts in Devices and Appliances, establishes flame classifications to distinguish a material’s burning characteristics when exposed to test flames. Test programs determine the tendency for a flame to spread or extinguish, and also the ignition resistance of the plastic.
- ASTM D635 prescribes a test method for determining the rate of burning or time of burning plastics in a horizontal position.
- ASTM D2863 provides guidance on measuring the minimum concentration of oxygen in a flowing mixture of oxygen and nitrogen to support flaming combustion.
- IPC-TM-650, Method 2.3.8, describes the procedure for determining the relative flammability of organic films and reinforced compositions by measuring the minimum oxygen and nitrogen needed to support combustion.
- IPC-TM-650, Method 18.104.22.168, provides test methods to determine the degree of flame resistance of flexible printed wiring.
- IPC-TM-650, Method 2.3.9, outlines a method for determining the degree of flame resistance of laminates less than 0.5 mm.
- IPC-TM-650, Method 2.3.10, prescribes a method for determining the degree of flame resistance of metal clad or unclad laminate.
- IPC-TM-650, Method 22.214.171.124, evaluates the relative flame resistance characteristics of a permanent solder mask coating on printed wiring laminates.
- IPC-TM-650, Method 2.3.29, prescribes a test procedure required to determine if flexible flat cable is flame retardant.
Heavy Metals/Lead Content: ASTM E1613, CPSC-CH-E1002-08.2, CPSC-CH-E1003-09.1
Lead detection remains an important part of chemical testing — these tests should be able to test for trace elements of lead in plastics, paints, coatings, composites, solders and other materials. Below are some of the methods used to test for lead content.
- ASTM E1613 addresses the collection and preparation of samples (dust, soils, air particulates and dried chips) obtained during the mitigation of lead hazards from buildings. The method can use inductively coupled plasma atomic emission spectrometry (ICP-AES), flame atomic absorption spectrometry (FAAS) or graphite furnace atomic absorption spectrometry (GFAAS).
- CPSC-CH-E1002-08 provides the standard operation procedure for determining total lead in non-metal products.
- CPSC-CH-E1003-09.1 provides the standard operating procedures for determining the lead in paint and other surface coatings.
Ion Chromatography (IC): IPC-TM-650, Delphi-Q-1000-119, Delphi-Q-1000-12
Certain ionic substances can lead to corrosion or even cause electrical performance issues. Ion chromatography separates and detects these trace ionic substances to determine the quality of molecular materials and minerals, in addition to the purity of food, soil and water.
- IPC-TM-650, Method 2.3.28, prescribes an ionic analysis for circuit boards using ion chromatography.
- IPC-TM-650, Method 126.96.36.199, measures the level of chloride, bromide and fluoride in a soldering flux or paste using ion chromatography.
- IPC-TM-650, Method 188.8.131.52, measures the level of anionic and cationic residues on the surface of unpopulated printed boards using ion chromatography.
De-fluxing chemistry should remove all fluxes and pastes from post-soldered printed circuit assemblies. IPC-TM-650, Method 2.3.30, outlines a test method to measure the pH in anhydrous fluorocarbon azeotropes and blends for cleaning and defluxing equipment.
Porosity: ASTM B735, IPC-TM-650
Gold coatings are usually specified for the contacts of separable electrical connectors and other devices. Electrodeposits are forms of gold most often used on contacts, although clad metals are also used.
Gold is a popular choice for electrical connectors because of its resistance to the formation of insulating oxide films that interfere with reliable contact operation. Porosity and other defects in the coating should be minimal, although tolerable levels of porosity depend on the severity of the environment to the substrate, the reliability of contact operation and design factors for the contact device.
ASTM B735 prescribes standards for determining porosity in gold coatings, particularly for electrodeposits and clad metals used on electrical contacts. The test method is very sensitive and can detect virtually all porosity and other defects in gold coatings.
IPC-TM-650, method 2.3.24, provides standards for determining the porosity of gold plating on both copper and nickel surfaces.
Purity: IPC-TM-650, IPC-6012, IPC-6013, MIL-PRF-31032
Purity testing help determine the purity of materials used in electronics.
- IPC-TM-650, method 2.3.15, prescribes an electrogravimetric method for determining the purity of copper foil or plating.
- MIL-PRF-31032 establishes performance requirements used for printed circuit boards or for printed wiring boards. The specifications were designed to give printed board manufacturers the flexibility to implement best commercial practices while providing products that meet military performance needs.
High Voltage Arc Tracking: UL746A
UL 746A establishes standards for polymeric materials. Requirements cover short-term procedures used for the evaluation of materials used in electrical end products for certain applications. Products that involve risk of fire or of electric shock or injury should be evaluated according to these requirements.
Resistivity of Solvent Extract (ROSE): IPC-TM-650, IPC-6012, IPC-6013, IPC-6018, J-STD-001
The ROSE test is a method of quality control used in the manufacturing of printed wiring boards and printed wiring assemblies. The test provides an assessment of overall printed circuit board/assembly cleanliness. This is an important test to conduct because electronics undergo chemical and mechanical processes that can put residual stress on components. The ROSE test should be able to identify failures or unintended residues resulting from the manufacturing process.
The ROSE test has been used for decades and is the only cleanliness test that can be relied upon as a process control tool in a production line environment. It’s also useful for its ability to demonstrate gross levels of conductive materials.
- IPC-TM-650, Method 2.3.25, is the industry standard for this type of analysis: It provides guidance on the detection and measurement of ionizable surface contaminants by resistivity of solvent extract (ROSE).
- IPC-6012B provides guidance on the performance specification for rigid printed boards.
- IPC-6013C provides guidance on the performance specification for flexible printed boards.
- IPC-6018A provides detailed performance criteria on high frequency printed boards.
- IPC J-STD-001F provides requirements for the manufacture of soldered electrical and electronic assemblies.
Solderability: IPC/J-STD-002, IPC/J-STD-003, IPC-SM-840
Solderability testing measures the weight and speed in which molten solder climbs upward on various components. Below are some of the methods used to test solderability.
- IPC J-STD-002 prescribes methods for assessing the solderability of electric component leads, terminations, solid wires, standard wires, lugs and tabs. Solderability evaluations verify that the solderability of component leads and terminations meets requirements and that storage has no adverse effect on the ability to solder to an interconnecting substrate. J-STD-002 can also be used to verify that metallized terminations remain intact throughout the assembly soldering processes.
- IPC J-STD-003 prescribes test methods for printed boards, with guidance on the solderability of printed board surface conductors, attachment lands and plated-through holes.
- As discussed above, IPC-SM-840D defines the methods for obtaining the most information about cured permanent solder mask material with the lest test redundancy.
Tack/Slump/Wetting/Dryness/Spitting: IPC/J-STD-005, IPC-TM-650
There are a number of additional tests to evaluate solder paste quality.
- IPC J-STD-005 prescribes general requirements for the testing of solder pastes used to make high quality electronic interconnections. The standard defines the characteristics of solder paste, formed from solder powder and solder paste flux. Solder powders are classified according to the shape of the particles and the size distribution.
- IPC-TM-650, Method 2.4.35, determines vertical and horizontal slump for solder pastes.
- IPC-TM-650, Method 2.4.44, prescribes a tack test for solder pastes.
- IPC-TM-650, Method 2.4.46, provides indication of activity of wave solder fluxes and solder paste.
- IPC-TM-650, Method 2.4.47, assesses the tackiness of soft soldering flux residues.
- IPC-TM-650, Method 2.4.48, measures the spitting characteristics of flux-cored wire and ribbon solder.
Viscosity measures fluid flow properties for quality control purposes. As discussed, IPC-TM-650 establishes methods for testing electronic and electrical parts, including basic environmental, physical and electrical tests.
Method 2.4.34 specifies procedures for determining the viscosity of solder paste in the range of 300,000 to 1,600,000 centipoise.
Viscosity For determining the viscosity of solder paste.
IPC-TM-650, Method 2.4.34, determines vertical and horizontal slump for solder pastes.
IPC-TM-650, Method 184.108.40.206, determines the viscosity of solder paste in the range of 50,000 to 300,000 centipoise
Choose NTS for Your Chemical Testing Needs
NTS offers the expertise and industry knowledge to provide the most thorough chemical testing in the market today. Our chemical engineers and chemists are experienced with all of the above standards, and can offer suggestions and solutions for all of your chemical testing needs. When it comes to ion chromatography (IC) and cleanliness testing, NTS has proven itself an innovative leader.
As one of the largest commercial test laboratory networks in the United States, we’re well-equipped to provide chemical analysis in the engineering phase and the supply management phase. We offer a wealth of cutting edge services, from software and wireless testing to component-testing for NASA. Our industry experts can provide test programs with short turnaround and competitive prices.
For more information about specific test programs, please contact NTS. We’ll analyze your needs and provide a free, no-obligation quote.