High reliability components are disabled and limited in structural, material and process requirements

Because high-reliability components are subject to severe environmental stresses and have long-term storage and work requirements, they are generally used for key projects. Therefore, the banned and restricted structure, materials and process requirements for electronic components in different use departments have gradually formed. It is worthy of attention from relevant personnel. First, disable the process 1, disable the welding point, bonding point conductive adhesive covering process. The conductive adhesive will be deformed, which will generate a lot of stress and break the bonding wire; cover the welding and bonding point defects, causing hidden dangers. 2. Disable pure tin, pure zinc and pure chrome materials. These materials are prone to grow whiskers (no gravity, especially in vacuum), resulting in short-circuit failure. Zinc and chromium have significant sublimation physical properties, forming a metal film, resulting in parallel resistance, which affects the transmittance of optical components. Regarding the lead-tin solder problem, we require lead-tin solder (including lead-tin-silver solder) to have a lead content of more than 3%. In this case, the crystal whiskers are not. 3. Non-rigid leads disable nickel plating. Nickel plating is brittle, and the bending stress causes the nickel plating layer to fall off. 4. The inner surface of the non-sealed component is banned from pure silver material. The use of pure silver material on the inner surface of the unsealed component will cause silver migration, and silver migration will cause short-circuit failure. Silver migration is strong, and some departments also control the use of silver in the inner layer (especially the long-life components working in high temperature environment). 5. The direct contact structure of gold, aluminum and gold tin is prohibited. Gold-aluminum compound is formed between gold and aluminum. This compound is brittle and has high resistivity; "tin eats gold" - gold has a large solid solubility in tin; about "gold crisp": when tin contains gold The amount (3% to 19%) will have a "golden brittle" phenomenon. When the thickness of the outer lead gold plating is greater than 2.5 μm, the soldering process shall adopt a tin plating process. 6. Leadless components (especially ceramic chip capacitors) are disabled for secondary manual soldering processes without a reasonable temperature thermal platform.

This welding produces a large thermal stress. Case In 2012, a batch failure of a product provided for xx hospitals was investigated. This batch failure was caused by the secondary solder assembly process of the same pad. 7. Seal the cavity components to disable the desiccant. Desiccants can mask harmful excesses; form harmful excesses. 8. Disable active chips without surface passivation. When the active chip is not surface passivated, the surface will adsorb harmful substances and affect the stability of the electrical parameters. Such as leakage current, breakdown voltage. 9, long storage cavity sealing components (except electric vacuum devices) disable the internal cavity vacuum structure. There is no absolute seal. "Vacuum" means that gases outside the control of the external environment will enter the cavity. Especially for long-term storage of weapons and equipment. 10. Disable the post-package plating process. Sealing the edge of the micropores, blind holes to absorb acid, alkali and other harmful substances, forming a hidden danger. After long-term work, it will cause rust and air leakage failure. 11. Disable leadless surface mount ceramic capacitors with an aspect ratio of not less than 2. (ceramic capacitors with a ceramic layer thickness less than 20 microns). Ceramic capacitors are piece by piece. If the aspect ratio is too large, the ability to withstand stress will be weak. We have experienced many failures for this reason. 12. Disable glass bonding chips and glass fuses. The glass is very brittle and has poor heat and mechanical stress resistance. 13. Ultrasonic cleaning is disabled on the printed circuit board. The natural frequency of the spacer wire of the device in the soldered circuit board may be close to the frequency of the ultrasonic wave, thereby generating resonance, causing the internal line of the device to break. This is an example of what happened in the Space X Academy. Second, the limited process 1, the component manufacturing process is limited to the ultrasonic cleaning process. A large number of practices at home and abroad have proved that improper ultrasonic cleaning can induce or enlarge the micro-defects of the parts to be washed, especially on the joint surface. Requirements: Give ultrasonic cleaning process conditions (such as frequency, power, time, etc.) and adequate harmless test data. In 2011, a PIND test of a factory in Beijing was not a measure. From the shell and the unreasonable ultrasonic cleaning process. 2. Restrictions on organic polymeric materials. Degradation produces harmful gases, stress release; low pressure or vacuum organic polymeric materials will decompose, deflate, and expand to affect device reliability. 3, the sealed cavity is limited to plastic components (some aerospace engineering is listed as a disabled process). Plastic components release harmful gases. 4. The rigid member is limited to the electrical connection crimping structure (some aerospace engineering is listed as a disabled structure, and foreign aerospace is disabled). The temperature has a large influence on the contact resistance of the crimped structure surface. 5. Restricted flip chip structure (some aerospace engineering is listed as a disabled process). As a trend in device development, the biggest problem so far is that there is no means to check the mechanical strength of each connection interface. 6. Limit beam lead structure (some aerospace engineering is listed as a disabled process). The beam-type lead structure has poor mechanical stress resistance. 7. Limit nickel electrode ceramic chip capacitors. We are not familiar with such products, and we have not accumulated a large amount of reliability data. As technology develops and a large amount of reliability data is accumulated, such products may be cancelled as a limitation. 8. The anti-irradiation bipolar device is limited to ion implantation, dry etching and plasma cleaning. This process produces micro damage to the surface, resulting in micro defects.

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