How should crystal oscillator products be used correctly? When using crystal oscillators, we should handle them in an appropriate way to reduce the deterioration or failure of crystal oscillator products. This article mainly describes some common factors that can affect the normal operation of crystal oscillators, which may lead to their failure.
One Ultrasonic technology, film coating, cleaning, welding
Ultrasonic technology is widely used in industrial equipment. The common ultrasonic equipment in industry are ultrasonic cleaning process and ultrasonic welding process.
Crystal oscillator products are not suitable for use in any ultrasonic cleaning process.
Ultrasonic welding machines typically operate at frequencies ranging from 20KHz to 60KHz. This frequency may also cause damage to AT cut chips due to resonance effects. Here are some suggestions for reducing crystal oscillator failure during ultrasonic treatment:
1. Check if the ultrasonic instrument is suitable for use with a crystal oscillator. If feasible, please conduct some ultrasonic welding tests on crystal oscillator products in advance to verify if there is any impact.
2. Ensure that there is a certain space between the crystal oscillator and the product casing to avoid the impact of ultrasonic frequency on the crystal oscillator during product assembly.
When placing PCB components, the crystal oscillator should be placed in the center of the PCB.
If any problems are found with the crystal oscillator product in this package, please use other crystal oscillator packages instead.
5. If the ultrasonic instrument has a control function, the ultrasonic frequency should be switched away from the crystal oscillator frequency and the operating power of the ultrasonic instrument should be reduced
When resonance occurs, customers can try changing the crystal oscillator direction according to the ultrasound direction.
II PCB cutting
In most cases, small-sized PCBs are cut from large PCB boards after completing component assembly. The cutting force on the PCB will affect the crystal oscillator placed near the cutting edge. If the cutting force is too strong, it may damage the crystal oscillator structure. Crystal oscillator failure usually depends on the position on the PCB board; Small PCBs with problems are always found in the same position on large boards. Perforation and V-shaped design can reduce forces and stresses during the cutting process
The use of CNC milling machines or milling machines for PCB cutting will be similar to ultrasonic cutting. The rotation of the grinder may resonate with the chip, so the crystal oscillator may be damaged. When resonance occurs, customers can try to change the crystal oscillator direction according to the direction of the force.
When designing PCB layout, try to place the crystal oscillator in the center of the PCB or away from the cutting position, which can reduce the risk of failure caused by cutting.
III Reflow soldering temperature
Two common phenomena:
1. Rapidly increasing or decreasing the reflow soldering temperature may lead to the failure of the crystal oscillator. Therefore, it is strongly recommended to follow the reflow curve provided by the crystal oscillator manufacturer for soldering, or to contact and communicate with the crystal oscillator manufacturer regarding soldering precautions.
2. PCBA may require two reflow soldering processes, especially for PCBA with components on both sides of the circuit board. The crystal oscillator after two reflow soldering processes at high temperatures has a high possibility of failure. Therefore, it is recommended that the crystal oscillator should only be treated once through reflow.
4 PCB board bending
Before installing the crystal oscillator product, it is necessary to check whether the circuit board has a certain degree of bending. If there is bending, installing the crystal oscillator on the bent PCB board may cause bending applications, and this bending stress may lead to the peeling of the soldering part or the rupture of the crystal oscillator on the board
Five drop impact
When a crystal oscillator falls from a workbench onto a hard floor, it may be damaged due to excessive impact. If the crystal oscillator falls on the floor or is subjected to strong vibrations in any situation, it should not be used.
An anti-static carpet can be placed under the workbench to avoid excessive impact on the crystal oscillator when it falls onto the floor. Other potential impacts on crystal oscillators:
1. The impact caused by installing the crystal oscillator on the circuit board.
2. Buzzers, speakers, etc. can cause crystal oscillator vibration.
VI PCBA repair
During PCBA rework, crystal oscillators are usually manually soldered. Therefore, temperature and welding time should be strictly controlled.
It is strongly recommended not to use traditional soldering irons during rework, and to use a standard hot air rework table for any welding rework and follow the welding instructions provided by the crystal oscillator manufacturer.
Please do not reuse the crystal oscillator removed from the PCB. Use a new crystal oscillator during the PCBA rework period.
7 PCB circuit design
Circuit designers should pay attention to the following points to avoid crystal oscillator failure.
1. The crystal oscillator should be placed in a location with less stress on the PCB.
2. The crystal oscillator should be placed in the center position of the PCB and away from parts with mechanical vibration, such as buzzers.
To ensure the accuracy and stability of the crystal oscillator, large parasitic capacitance should be avoided. Therefore, the crystal oscillator should be placed near the IC pins, and the crystal oscillator connection lines should be as short as possible.
4. High frequency signal lines and components that generate high noise should not be placed near the crystal oscillator circuit on the PCB.
Next article: What is a crystal oscillator? How to layout a crystal oscillator on a PCB board?
