What is a half-hole board? What is the production process of a half-hole PCB board?
A half-hole board is a type of printed circuit board (PCB) that is mainly used to manufacture certain special types of electronic devices. Unlike conventional PCB boards, half-hole boards usually have some specific design features, especially regarding the layout and treatment of holes.
Features of half-hole boards:
Half-hole (Half-Hole/blind hole): A half-hole board usually refers to a board with partial holes on the PCB or the hole design does not completely penetrate the board. Unlike traditional **through hole** boards, the holes of a half-hole board may only penetrate a portion of the board.
Design: The design of a half-hole board is often used in applications where electronic components need to be inserted into the board but all holes do not need to be completely penetrated. This design can be used to optimize the structure of the board, improve the stability of the circuit, or reduce weight.
Application: Half-hole boards have advantages in some specific application scenarios, such as aerospace applications that need to reduce weight, or special equipment that needs to improve mechanical strength. They can help designers achieve specific functions and requirements when designing circuit boards.
Production process of half-hole board:
1. Outer layer circuit design:
Circuit design: First, engineers will use PCB design software (such as Altium Designer, Eagle, etc.) to design circuit diagrams and layouts, including determining which holes are half-holes.
Design rule check (DRC): Ensure that the design meets manufacturing specifications and electrical requirements.
2. Manufacture of printed circuit boards:
Material preparation: Select the appropriate PCB substrate material (such as FR-4). The substrate is usually composed of an insulating layer and a conductive layer.
Lamination: The conductive layer and the insulating layer are combined through a lamination process to form a multilayer board.
Photolithography: The circuit pattern is transferred to the PCB using photolithography technology. Photoresist forms a protective layer of the circuit pattern on the substrate.
3. Half-hole processing:
Drilling: Drill holes on the PCB according to design requirements. For half-hole boards, the depth of the hole is controlled during drilling so that it does not penetrate completely.
Hole filling: If required by the design, some holes may be filled to support specific welding or component installation.
4. Chemical Etching:
Etching: Remove the unwanted copper layer, leaving the required circuit pattern.
5. Electroplating:
Copper plating: Electroplating the inner wall of the hole to ensure electrical connectivity.
6. Testing:
Inspection and testing: Check the integrity and function of the circuit board to ensure that all half holes and circuits function properly.
Controlling the product quality after the semi-metallized hole on the edge of the board is formed is a key issue, especially when copper spurs are lifted or residual on the hole wall. These problems have always been challenging during the processing process. Especially for those small-aperture PCBs with a full row of semi-metallized holes, these boards are usually used as daughter boards of carrier boards, and are soldered to the motherboard and component pins through these semi-metallized holes. Therefore, if there are copper spurs left in the semi-metallized holes, it will cause a series of problems when soldering in the plug-in factory, such as weak solder feet, cold soldering, and even bridge short circuits between pins.
Reasonable solutions:
1. Optimize the design stage
Aperture design: Ensure that the aperture design is suitable for the manufacturing process and avoid designing too small apertures, which can reduce the formation of copper thorns on the hole wall.
Design review: Conduct a strict design review to ensure that the layout and treatment of the holes meet the manufacturing specifications and reduce problems in subsequent processing.
2. Improve the manufacturing process
Hole wall treatment:
Cleaning: Before copper plating, thoroughly clean the hole wall to remove all grease, dirt and oxides to ensure uniform adhesion of the coating.
Chemical plating: Use an appropriate chemical plating process to ensure the uniformity of the coating and avoid copper thorn problems caused by uneven plating.
Control process parameters:
Copper plating process: Accurately control the parameters of the copper plating process, such as temperature, time, solution concentration, etc., to ensure the quality of the coating.
Drilling: Use high-precision drilling equipment to reduce hole wall burrs. Regularly check and maintain the drill bit to ensure its good working condition.
3. Process monitoring and control
Real-time monitoring: Real-time monitoring of key parameters during the production process, such as hole wall thickness, plating quality, etc., and timely adjustment of process parameters to ensure product quality.
Quality inspection: Use automated inspection equipment to inspect semi-metallized holes to detect and correct potential defects in a timely manner.
4. Post-processing process
Removal of copper thorns:
Mechanical removal: After copper plating, remove the copper thorns in the hole by mechanical means, such as using special deburring equipment.
Chemical removal: Use chemical agents to remove the copper thorns in the hole to ensure smooth hole walls.
Post-plating treatment: Post-process the copper-plated holes to ensure that the copper layer in the holes is uniform and smooth and reduce possible defects.
5. Pre-welding treatment
Hole inspection: Before welding, check the copper thorns in the semi-metallized holes and clean them if necessary to ensure welding quality.
Welding process optimization: Optimize the welding process and equipment to ensure that the copper thorns in the holes will not affect the welding effect during welding, such as adjusting the welding temperature and time.
6. Continuous improvement
Feedback and improvement: Collect feedback from welding factories and end users, analyze welding problems, adjust and improve production processes.
Technical training: Regularly provide technical training to operators to ensure that they master the latest production technology and process requirements.
Through these measures, the quality of products after semi-metallized hole forming can be effectively controlled and improved, the problems caused by copper thorns can be reduced, and the reliability and performance of the final product can be improved.
