月: 2024年1月

What Is a Screening Test?

A screening test refers to the preliminary sorting of products or chemicals to prioritize samples for detailed testing. These tests serve various purposes, including assessing disease risk, pharmaceutical development, substance toxicity, and identifying defective semiconductor products.

Uses of Screening Test

Screening tests have broad applications in semiconductor development, pharmaceuticals, toxicity assessments, and more.

1. Exclusion of Initial Defects in Semiconductors

Precision electronic components like semiconductors undergo extensive screening tests, including visual, electrical, and environmental stress screenings. Products that pass these tests are shipped as finished goods.

2. Initial Development of Pharmaceuticals

In pharmaceutical development, screening tests help select potential pharmaceutical compounds from a large pool of candidates. These tests evaluate compounds’ effects on receptors, enzymes, ion channels, and proteins to identify effective pharmaceuticals.

3. Risk Assessment of Chemical Substances

Screening tests under chemical regulations assess the risks posed by chemical substances, focusing on environmental pollution, toxicity to humans, animals, and plants, residue absence, and explosion or ignition risks. Substances that cannot be confirmed as safe may be designated as priority assessment chemicals.

4. Initial Assessment of Allergy Labeling

Screening tests are crucial for food allergy labeling, ensuring the safety of allergy patients. Two different screening tests verify the validity of food allergy labeling on processed food products.

5. Parts for Satellites, Rockets, Among Others

Components used in aerospace applications, such as satellites and rockets, undergo rigorous reliability tests and screening to prevent failures. Screening test methods are established to ensure their reliability.

Principle of Screening Test

The term “screening” implies sorting. Screening tests involve the selection or testing process through medical or chemical experiments. Some tests can be burdensome and costly. In such cases, screening tests are conducted on the entire population to identify potential risks. There are three main types of screening tests: visual screening, electrical screening, and environmental stress screening. The choice of method depends on the target and environmental factors.

Characteristics of Screening Tests

Screening tests aim to identify potential risks using relatively simple methods while minimizing financial and physical burdens. However, false positives may occur, leading to further detailed testing to confirm or rule out issues.

What Is an AMS Test?

AMS test, also known as the Ames test, is an examination that assesses whether a chemical substance can induce mutations in genes (mutagenicity) using bacteria.

Uses of AMS Test

The Ames test (mutagenicity test) is conducted to detect the mutagenic properties of chemical substances. It is commonly employed in safety evaluations during the development of new pharmaceuticals and pesticides, assessing their safety. Additionally, when there is a concern that a chemical substance may cause health hazards in the environment, the Ames test is used for its evaluation.

Due to regulations such as the Industrial Safety and Health Act, Pharmaceutical Affairs Law, and the Pesticide Control Law, the implementation of genotoxicity tests, including the AMS test, is mandatory for assessing the safety of chemical substances that may pose harmful effects to human health or the environment.

Principle of AMS Test

1. Principle

The principle of the AMS test involves using bacteria that have been genetically modified to be incapable of synthesizing amino acids, thus making them dependent on externally supplied histidine. Chemical substances are added to the medium in which the bacteria reproduce, and a genetic mutation test is performed to detect bacteria that have undergone spontaneous mutations. Chemical substances with higher mutagenicity are known to induce more mutations.
As many carcinogens are mutagenic, the strength of their mutagenic effects can be used to assess their carcinogenic potential. The size and formation of bacterial colonies are examined to determine the mutagenic properties of the sample.

2. Test Method

Specifically, strains of Salmonella typhimurium with a histidine requirement are used. These strains are mutants that cannot grow unless histidine, an essential amino acid, is provided in the environment. The histidine-requiring strains are cultured in a medium containing the chemical substance.
If the chemical substance is mutagenic, mutations occur during bacterial division, allowing the bacteria to produce histidine on their own. As a result, the bacteria proliferate and form colonies, and by measuring the number of colonies, the mutagenic nature of the substance can be determined.

3. Association with Carcinogenicity

While the AMS test examines the mutagenic properties of chemical substances, it does not determine whether they cause cancer. However, as a significant portion of known carcinogens are mutagenic, the results of the AMS test may be used to assess potential carcinogenicity. Nevertheless, determining carcinogenicity solely based on the AMS test results is not feasible, and a comprehensive judgment is required by combining results from other types of tests.

Types of AMS Test

There are two types of AMS tests: direct test and indirect test.

In a direct test, chemical substances directly affect bacteria. In contrast, an indirect test evaluates chemical substances after passing through metabolic organs like the liver, where they produce metabolites indicating mutagenicity. To enhance metabolic activation, a reagent called “S9 mix,” obtained by treating rat liver, is added to the medium containing bacteria and the chemical substance.

Other Information on AMS Test

Testing Regulations

In Japan, domestic guidelines (Pharmaceutical Affairs Law, Pesticide Control Law, Industrial Safety and Health Act, etc.) stipulate the implementation of preliminary and main tests. On the other hand, OECD chemical guidelines, used in Europe and elsewhere, require the repetition of the main test under identical conditions as part of the reproducibility confirmation. Combining the preliminary test and main test results involves conducting the test three times.

The cost of testing chemical substances for carcinogenicity through animal experiments is substantial. The AMS test is rapid, relatively low-cost, and offers the advantage of accurately evaluating the mutagenicity of chemical substances. However, as the test uses bacteria, it cannot assess the complex reactions or side effects present in living organisms, compared to animal experiments.

What Is an Aging Test?

An aging test refers to an examination where products undergo intentional degradation through continuous operation under harsh conditions. These conditions include exposure to high temperatures, low temperatures, high humidity, and heavy loads over an extended period. The primary purpose of this test is to assess the durability and lifespan of the product.

Typically, aging tests are an integral part of pre-shipment testing and validation during new product development. They play a crucial role in quality assurance.

The aging test process involves subjecting products to conditions that accelerate wear and tear, allowing for the early detection of potential failures. Simulating extreme conditions helps manufacturers evaluate how well their products can withstand real-world usage over an extended period.

This type of testing has gained significance, particularly with the trend toward product miniaturization. Understanding how increased heat generation affects the lifespan of smaller devices is essential for producing reliable and durable products.

As a result, the demand for aging tests has been steadily increasing as manufacturers strive to ensure the longevity and quality of their products.

What Is an EMC Test?

EMC test, or electromagnetic compatibility (EMC) test is an examination conducted to verify the performance of EMC.

EMC test consists of two components: the EMI (Electromagnetic Interference) test and the EMS (Electromagnetic Susceptibility) test. EMI test measures the electromagnetic waves emitted by electronic devices and similar equipment to the external environment. This test ensures that the levels of electromagnetic waves radiated into space from electronic devices comply with specified standards.

Specifically, the test measures electromagnetic waves emitted to the external environment through radiation or conduction from electromagnetic waves or power and communication harnesses. On the other hand, the EMS test evaluates the resistance of electronic devices to external electromagnetic waves.

In the EMS test, external noise such as static electricity and radiated electromagnetic fields is applied to electronic devices. The test verifies whether electronic devices operate normally even when subjected to noise within the specified standards.

Uses of EMC Test

EMC test is conducted to meet the standards set by EMC regulations and specific EMC standards for various countries and regions. During the pre-sale product development stage, the purpose is to perform EMC tests as defined by the standards and confirm compliance.

Once the standards are met, electronic devices can be sold in the market.

Principle of EMC Test

EMC test adheres to international standards established by the IEC (International Electrotechnical Commission) and its committee, CISPR (International Special Committee on Radio Interference). While IEC primarily focuses on EMS test standards, CISPR concentrates on EMI test standards.

EMC regulations in various countries and regions are based on IEC and CISPR standards. The United States and Europe have stringent regulations on EMC through legal measures. In Japan, there are no specific regulations regarding EMC, and industry organizations like VCCI have adopted voluntary regulatory measures.

Types of EMC Test

1. Radiated Emission Test

Quantifies electromagnetic waves radiated from electronic devices using an antenna and verifies if the measured values are within predetermined standards. The test is conducted in a radio wave darkroom or open site, measuring frequencies above 30MHz.

2. Conducted Emission Test

Quantifies electromagnetic waves conducted and radiated from the power or communication lines of electronic devices using a spectrum analyzer. The test is conducted in a radio wave darkroom or shield room, measuring frequencies from 9kHz to below 30MHz.

3. Electrostatic Discharge Immunity Test

The test checks if electronic devices operate normally when subjected to static electricity. The test is conducted by applying static electricity from an electrostatic discharge gun to electronic devices.

There are direct discharge tests where static electricity is applied directly to electronic devices and indirect discharge tests where static electricity is applied from conductive objects near electronic devices.

4. Radiated Electromagnetic Field Immunity Test

This test verifies if electronic devices operate normally when exposed to high-frequency electromagnetic waves. The test is conducted in a radio wave darkroom or open site, using a test antenna to apply frequencies above 80MHz to electronic devices.

5. Electrical Fast Transient/Burst Immunity Test

This test checks if electronic devices operate normally when transient abnormal voltages occur during the interruption of coils or inductors. The noise is applied to the power or communication lines of electronic devices.

For the power line, noise is applied to the electronic device’s inlet. For the communication line, the electronic device’s communication harness is clamped using a coupling device, and noise is applied to the communication line.

6. Surge Immunity Test

This test checks if electronic devices operate normally when transient abnormal voltages occur during lightning strikes or ON/OFF switching of switches. The noise has a longer cycle than transient bursts. A dedicated test apparatus is used to apply noise to the power or communication lines of electronic devices.

What Is Ferric Chloride Etching?

Ferric chloride etching is a method of wet etching, a process used to shape the surface of materials such as metals, glass, and ceramics. This technique involves removing material through erosion by solutions, differing from dry etching, which uses gases and beams.

Ferric chloride (FeCl3) solution is used in this wet etching method, being suitable for almost all metals except a few, like titanium.

Uses of Ferric Chloride Etching

Ferric chloride etching is widely used in metal processing for its precision compared to traditional machining methods. It’s particularly prevalent in the electronics industry for creating detailed wiring patterns on printed circuit boards (PCBs) and manufacturing IC lead frames. This technique is also used in the fine processing of metals and ceramics in various manufacturing industries and art for copper plate etching in printmaking.

Principle of Ferric Chloride Etching

The process begins by applying a resist to parts of the metal surface that should remain unetched. On PCBs, this is typically done using metal resists like solder or tin, or organic resists such as ink or film.

When the material is immersed in ferric chloride solution, an oxidation-reduction reaction occurs, where copper transforms into cuprous chloride (CuCl), and ferric chloride reduces to ferrous chloride (FeCl2). This reaction involves electron exchange between copper atoms and ferric ions, resulting in the removal of copper from the surface.

After etching, the resist is stripped using acidic solutions for metal resists or alkaline solutions for organic resists. Finally, the substrate is cleaned to remove any remaining chemicals or resist residues.