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How to weld crystal? Which factors will lead to crystal damage?

Author:晶光华

2019-08-26

Browse volume:404

What are the causes of crystal vibration damage
  1. There is a kind of falling phenomenon in the production process, which means that only the crystal oscillator causes excessive impact force outside, because the crystal oscillator chip is relatively thin and needs to be handled with care.

  2. When the crystal oscillator is welded to the circuit board, the welding temperature may be too high, resulting in poor crystal oscillation.

  3. In the process of welding, there is false welding, which makes crystal vibration not electrified.

  4. After the crystal vibration welding, the solder is connected with the circuit, resulting in short circuit.

  5. In the leak detection process, that is, under the pressure of alcohol, the quartz crystal resonator is easy to collide with the shell, that is, the chip is easy to collide with the shell when vibrating, so that the crystal is easy to vibrate without vibration or stop vibration;

  6. In the process of sealing, it is required to vacuum and fill nitrogen in the crystal. If the sealing is not good, that is, when the crystal is not well sealed, it will show air leakage under the condition of alcohol pressure, which is called Double leakage, which will also lead to vibration stop.

  7. Because the thickness of the chip itself is very thin, when the excitation power is too large, the internal quartz chip will be damaged, resulting in vibration stop.

  8. The Q value (i.e. quality factor) of the crystal will be reduced by the functional load, so that the stability of the crystal will be reduced, which is easily affected by the surrounding active components, and it will be in an unstable state, and it will not vibrate when it occurs.

  9. Because the crystal is easy to produce mechanical stress and thermal stress when cutting feet and soldering tin, and too high soldering tin temperature and too long acting time will affect the crystal, which will easily lead to the crystal in a critical state, and even lead to the phenomenon of non vibration and even stop vibration.

  10. During soldering, when the tin wire penetrates through the hole on the circuit board, which leads to the connection between the pin and the shell, or the single leakage of the connection between the tin point of the pin on the base and the shell during the manufacturing process of the crystal, it will cause a short circuit, which will cause the vibration stop.

  11. When the crystal frequency drifts and exceeds the range of quartz crystal vibration deviation, the center frequency of crystal can not be captured, which leads to the failure of chip vibration.

What should be paid attention to in welding crystal oscillator

First of all, the soldering temperature should not be too high, and the soldering time should not be too long, so as to prevent the crystal from internal change and instability. When the crystal oscillator shell needs to be grounded, it should be ensured that the shell and the pin are not accidentally connected, resulting in short circuit. As a result, the crystal will not vibrate. Ensure that the solder joints of the two pins are not connected, otherwise the crystal will stop vibrating. The influence of mechanical stress should be paid attention to for the crystal vibration which needs to be cut. After soldering, cleaning shall be carried out to avoid that the insulation resistance does not meet the requirements.

We know that quartz crystal vibration welding method is related to its packaging. Plug-in and chip are two different welding methods. The chip crystal vibration can be divided into manual welding and automatic welding.

It's not very complicated to weld the plug-in crystal oscillator. First, put the crystal oscillator on the circuit board with tweezers, and then melt the solder with a hot-air gun, so it can be relatively simple.

The manual welding of chip crystal oscillator is relatively complicated. 1. First, add a proper amount of soldering tin at the chisel shaped (flat spade shaped) or knife edge soldering iron head, dip the soldering flux with a fine brush or apply a small amount of soldering flux on the two ends of the welding pads with a soldering pen, and plate the soldering tin on the pads; one hand holds the chip crystal oscillator with tweezers, pastes it on the corresponding pads in the middle, and does not move after alignment; the other hand picks up the soldering iron. Heat one of the pads for about 2 seconds, remove the soldering iron; then heat the other end of the pad in the same way for about 2 seconds.

Special reminder: during the welding process, pay attention to keep the wafer vibration close to the welding pad and put it in the right place, so as to avoid one end of the crystal vibration from warping or welding askew. If the solder on the pad is not enough, it can be repaired by holding the soldering iron in one hand and holding the solder wire in the other hand. The time is about 1 second.

First, a proper amount of solder is plated on the welding pad. The hot air q1an9 uses a small nozzle nozzle. The temperature is adjusted to 200 ℃ ~ 300 ℃, and the wind speed is adjusted to 1 ~ 2. When the temperature and wind speed are stable, a hand is used to clamp the components and put them on the welding position with tweezers. Pay attention to put them in the right place. Hold the hot air q1an9 in the other hand, keep the nozzle vertical to the components to be removed, 1cm ~ 3cm away, heat uniformly, remove the hot air q1an9 after the solder around the chip crystal oscillator melts, and remove the tweezers after the solder cools down.

In order to save money, many factories will use automatic Mounter for automatic mounting. During welding, we should pay attention to a few problems. If it is welding surface crystal, it is suggested to use automatic Mounter as much as possible. Because the crystal of quartz crystal is thin and small, it is easy to weld by hand welding ceramic crystal. The crystal of quartz crystal is generally controlled at 1. In general, the temperature of soldering iron head is controlled at 1. Control at about 300 ℃.The hot air gun shall be controlled at 200 ℃ ~ 400 ℃; 2. During welding, it is not allowed to directly heat the part above the heel of the chip crystal oscillator pin to avoid damaging the internal capacitance of the crystal oscillator; 3. It is required to use ∮ 0.3mm ~∮ 0.5mm solder wire; the soldering iron head shall always be smooth, free of hook and thorn; the soldering iron head shall not touch the pad again, and it is not allowed to repeatedly heat it in one pad for a long time, and the working temperature of the conventional crystal oscillator is general. At - 40 - + 85 ℃.If the pad is heated for a long time, it may exceed the working temperature range of the crystal oscillator, which will reduce the life of the crystal oscillator and even damage it. In order to avoid resonator damage, please pay more attention to the welding process of major customers, so as to avoid product performance instability.

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