Key Points for Crystal Oscillator Protection in PCB Manufacturing

1. PCB Cutting

   - In most cases, small-sized PCBs are cut from large PCBs after component assembly is completed. Crystal oscillators placed near the cutting edges of the PCB can be affected by the cutting force on the PCB. If this cutting force is too great, it can damage the structure of the crystal oscillator. The position of the crystal oscillator on the PCB often determines whether the oscillator will fail; problematic small PCBs always appear at the same position on the large board.

   - Perforated and V-groove designs can reduce the force and stress during cutting. If the PCB cutting is completed by CNC milling or a milling machine, the cutting effect will be equivalent to the ultrasonic cutting process. The rotation of the grinding machine may resonate with the chip, thus damaging the crystal oscillator. When resonance occurs, customers should consider adjusting the direction of the applied force to change the orientation of the crystal oscillator and reduce the impact of resonance.

   - When planning the layout of the printed circuit board (PCB), place the crystal oscillator in the central area of the PCB or away from the cutting edge to reduce the probability of damage that may be caused by the cutting process.

2. Reflow Soldering Temperature Control

   - There are two common phenomena:

     1. For double-sided assembly of PCBA, it may be necessary to perform two reflow soldering processes. Crystal oscillators have a high probability of failure after two reflow solderings at high temperatures. Therefore, to maintain the quality and performance of the crystal oscillator, it is recommended that it undergoes a single reflow soldering in production.

     2. Crystal oscillators may fail due to rapid temperature fluctuations during the reflow soldering process. Therefore, it is crucial to follow the specific reflow soldering temperature guidelines provided by the manufacturer or seek professional advice from the crystal oscillator manufacturer to ensure understanding of safety and operational standards during soldering.

3. PCB Board Bending

   - Before installing the crystal oscillator product, it is important to check the circuit board to ensure it remains flat and not bent. If there is bending, installing the crystal oscillator on the PCB will apply bending stress, which may cause the soldered parts to peel off or break the crystal oscillator on the board.

4. Ultrasonic Process: Coating, Cleaning, Soldering

   - Ultrasonic technology is widely used in industrial machinery. Ultrasonic cleaning technology is not suitable for crystal oscillator products and may cause damage. The ultrasonic equipment for cleaning tasks and the ultrasonic process for welding tasks are the main two types of equipment applications of ultrasonic technology in industry.

   - When applying ultrasonic welding technology, the equipment generally has a frequency working range of 20KHz to 60KHz. And this frequency, due to the resonance effect, may damage the AT-cut crystal chips. To reduce the failure of crystal oscillators during ultrasonic processing, the following suggestions are made:

     1. Before starting the ultrasonic processing process, assess the compatibility of the equipment to ensure it is suitable for crystal oscillator products. Conduct ultrasonic welding experiments on crystal oscillators as early as possible when conditions permit, to explore their effects and potential risks.

     2. To avoid the impact of ultrasonic frequency on crystal oscillators during product assembly, ensure there is a certain space between the crystal oscillator and the product casing.

     3. When placing PCB components, the crystal oscillator should be placed in the middle of the PCB.

     4. If there is a problem with the encapsulated crystal oscillator product, consider using a different crystal oscillator encapsulation.

     5. When resonance occurs, customers can try changing the direction of the crystal oscillator according to the direction of the ultrasonic wave.

     6. If the ultrasonic device has control functions, the ultrasonic frequency should be switched away from the crystal oscillator frequency and reduce the operating power of the ultrasonic device.

5. PCB Circuit Design

   - To avoid crystal oscillator failure, pay attention to the following points:

     1. The crystal oscillator should be installed at the geometric center of the PCB, and also away from other components that may generate vibrations, such as buzzers and motors.

     2. Crystal oscillators are very sensitive to mechanical stress and should be placed in positions on the PCB where stress is minimal.

     3. High-frequency signal lines and components that generate high noise should not be close to the crystal oscillator circuit on the PCB.

     4. To ensure the accuracy and stability of the crystal oscillator, large parasitic capacitance should be avoided. Therefore, the crystal oscillator should be placed close to the IC pins, and the connection lines of the crystal oscillator should be as short as possible.

6. PCBA Rework

   - When PCBA needs to be repaired, the soldering of the crystal oscillator is usually done manually. Therefore, temperature and soldering time should be strictly controlled. Remember not to use traditional soldering irons during rework; rework soldering should always be carried out on a standard hot air rework station and in accordance with the soldering instructions of the crystal oscillator manufacturer. During the rework phase of PCBA, do not reuse crystal oscillators that have been removed from the PCB, but use new ones.

7. Drop Impact

   - When the crystal oscillator falls from the workbench to the floor, it may break or be damaged due to excessive impact force. Crystal oscillators should not be used for any application after experiencing a fall or strong vibration.

   - To avoid excessive impact when the crystal oscillator falls to the floor, an anti-static carpet can be laid under the workbench. For other potential impacts on the crystal oscillator:

     1. Buzzers, speakers, etc., can cause vibrations of the crystal oscillator.

     2. The impact caused during the process of installing the crystal oscillator on the circuit board.

About Mandu Technology

Shenzhen Mandu Technology Co., Ltd. has steadfastly centered its operations on the distribution of high-performance, high-quality, and highly reliable integrated circuit products. Its portfolio encompasses memory chips, differential crystal oscillators, and MCU microcontrollers, while progressively integrating analog signal chain products. The company prides itself on delivering comprehensive and cost-effective solutions to its customers. Its products find applications across a broad spectrum of industries, including but not limited to network communication, industrial control, robotics, medical equipment, personal health, and numerous other fields.

Business: sales@manduic.com

Website: www.manduic.com

Sales: +86 150-1290-5940

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