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PCBA outsourcing processing requirements and standards
During the reflow soldering process of the PCBA, the pins of the surface mount components are washed by the solder flow, causing some surface mount components to tilt after reflow soldering, resulting in the component body exceeding the silkscreen frame. Therefore, the post-reflow soldering personnel need to properly repair it.
Many electronics factories have a demand for PCBA processing. The following is an introduction to the requirements and standards for PCBA processing in electronics factories.
I. Bill of Materials
Strictly follow the bill of materials, PCB silkscreen printing, and outsourcing processing requirements for component insertion or mounting. If discrepancies are found between the materials and the list, PCB silkscreen printing, or if there are contradictions with the process requirements, or if the requirements are unclear and cannot be operated, contact our company immediately to confirm the correctness of the materials and process requirements.
II. Anti-static Requirements
1. All components are considered electrostatic sensitive devices.
2. All personnel in contact with components and products must wear anti-static clothing, anti-static wrist straps, and anti-static shoes.
3. During the raw material entry and warehouse stages, electrostatic sensitive devices are packaged using anti-static packaging.
4. During operation, use an anti-static workbench, and components and semi-finished products should use anti-static containers.
5. Soldering equipment should be reliably grounded, and soldering irons should be anti-static type and must be fully tested before use.
6. Semi-finished PCB boards are stored and transported using anti-static boxes, and anti-static pearl cotton is used as the isolation material.
7. Complete machines without casings use anti-static packaging bags.
III. Regulations on the Insertion Direction of Component External Markings
1. Polarity components are inserted according to polarity.
2. For components with silkscreen printing on the side (such as high-voltage ceramic capacitors), when inserted vertically, the silkscreen printing faces to the right; when inserted horizontally, the silkscreen printing faces down. For components with silkscreen printing on the top (excluding chip resistors), when inserted horizontally, the font direction is consistent with the PCB silkscreen printing direction; when inserted vertically, the top of the font faces to the right.
3. When resistors are inserted horizontally, the tolerance color ring faces to the right; when resistors are inserted vertically, the tolerance color ring faces down; when resistors are inserted vertically, the tolerance color ring faces the board surface.
IV. Soldering Requirements
1. The pin height of plug-in components on the soldering surface is 1.5-2.0mm. Chip components should be flat on the board surface, the solder joints should be smooth, without burrs, and slightly arc-shaped. The solder should exceed 2/3 of the solder terminal height but not exceed the solder terminal height. Insufficient solder, spherical solder joints, or solder covering the chip are all considered defects.
2. Solder joint height: The solder climbing pin height for single-sided boards should not be less than 1mm, and for double-sided boards, it should not be less than 0.5mm, and it must be through-hole soldering.
3. Solder joint shape: Conical, covering the entire solder pad.
4. Solder joint surface: Flat, bright, without black spots, flux, or other debris, without sharp points, pits, pores, exposed copper, etc.
5. Solder joint strength: Fully wetted with the solder pad and pin, no cold solder joints or false solder joints.
6. Solder joint cross-section: The component leads should be cut as little as possible to avoid cutting into the solder. There should be no cracks at the interface between the lead and the solder, and there should be no sharp points or burrs at the cut end.
7. Socket welding: The socket must be installed on the bottom board, with the correct position and direction. After socket welding, the bottom floating height should not exceed 0.5mm, and the tilt of the socket body should not exceed the silkscreen frame. The socket arrangement should also be neat and orderly, and misalignment or unevenness is not allowed.
V. Transportation
To prevent PCBA damage, the following packaging should be used during transportation:
1. Container: Anti-static turnover box.
2. Isolation material: Anti-static pearl cotton.
3. Spacing: There is a distance greater than 10mm between PCBs and between PCBs and boxes.
4. Placement height: There is a space greater than 50mm from the top of the turnover box to ensure that the turnover box does not press on the power supply, especially the power supply of the wires.
VI. Cleaning Requirements
The board surface should be clean, without solder balls, component pins, or stains. In particular, there should be no welding residue at the plug-in soldering points. The following components should be protected during cleaning: wires, connectors, relays, switches, polyester capacitors, and other easily corroded components. Relays should not be cleaned with ultrasonic waves.
VII. All components are not allowed to extend beyond the edge of the PCB board after installation.
During PCBA reflow soldering, due to the scouring of the solder flow on the pins of the plug-in components, some plug-in components may tilt after reflow soldering, causing the component body to extend beyond the silkscreen frame. Therefore, the post-reflow soldering personnel need to properly repair them.
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