Summary

Precautions for Use

Precautions for Use

Be sure to read the following precautions in order to use our crystal units correctly and to demonstrate its full performance.

1.To satisfy electrical performance

1-1 Crystal Oscillation Circuit
Crystal units are the same passive components as resistors and capacitors.
Therefore, it is important that the oscillation circuit is sufficiently considered in order to start up in a short time and obtain the required accuracy as a stable oscillation output.
Typical examples of oscillation circuits are listed in a separate section. The oscillation frequency of the crystal unit is determined by the load capacitance (CL) and the equivalent constant inherent to the crystal unit.
Although this value is specific to the circuit, the circuit constants shown in the example may not have the same characteristics if the IC or transistor is changed or the wiring pattern is different.
The load capacitance of the basic oscillator circuit shown in Figure 11 can also be obtained by the following equation.
CL={C1 C2/(C1+C2)}+CS+CIC
Where CS: stray capacitance CIC: internal capacitance of IC
CL: Load capacitance C1,C2: External capacitance
For example, if CS=2pF, CIC=4pF, C1=C2=20pF, the load capacitance of this circuit is CL=16pF.
In this case, it is necessary to use a crystal unit with a load capacitance of CL=16pF and a center frequency adjusted.

1-2 Oscillation Capability of Oscillator Circuit and Its Verification
The figure shows the equivalent circuit of the crystal unit and the oscillator circuit at the start of oscillation.
It is shown by the series circuit of load capacitance CL and negative resistance-R of the circuit.
The crystal unit side is equivalently a series circuit of effective inductance X=ωLe and effective resistance Re.
In this case, satisfying the following conditions at the same time is a necessary and sufficient condition for oscillation.
(1) Phase condition: ωLe-1/ (ωCL) = 0
(2) Amplitude condition: Re ≦ |-R| (-R is a negative resistance value)
The phase conditions in (1) are determined by the oscillation frequency and the load capacitance CL as described above.
The amplitude conditions in (2) are required to obtain a stable oscillation output as the rising edge of oscillation and the oscillation duration conditions.
It is necessary to design a circuit that ensures that the absolute value of the negative resistance value-R of the circuit is sufficiently larger than the effective resistance Re of the crystal at the rising edge of the oscillation.
The larger the negative resistance, the higher the oscillation capability (with an oscillation margin) can be said to be a circuit.
(Oscillation margin) = |-R| -(Re)
The value of the required oscillation margin depends greatly on the customer's product application, operating environment, frequency, model and characteristics of the crystal, etc., but it is generally about 300 Ω to 3000 Ω as the minimum If the required oscillation margin cannot be secured, it will not function as an oscillation circuit. Be sure to check it.

 Figure 11 Example of Crystal Oscillation Circuit

―Simplified verification method―
Insert a fixed resistor corresponding to the desired oscillation margin into the crystal in series (position marked with * in Fig. 11) and turn ON-OFF the power supply. Confirm that oscillation starts reliably each time.
(In this case, the oscillation frequency changes because a resistor is connected in series with the crystal unit.)
At this time, it is presumed that the amplitude condition described above is not sufficiently satisfied if oscillation does not start, it takes time to start, or oscillation is unstable.
The circuit configuration seems to be inappropriate for some reason and requires to be improved. If oscillation is started reliably and stable, remove the inserted resistance before use.

1-3 Level of drive of the crystal unit

The vibration state of the crystal oscillator during excitation is mechanical vibration.
However, if the amplitude of this vibration is not limited to some extent, the frequency continuity may be lost at a specific temperature or the effective resistance of the crystal oscillator may become large. Use the crystal at an appropriate level of drive.
When frequency stability is particularly required for mobile communication applications, etc., use of 10 to 100μW is recommended.

1-4 Frequency temperature characteristics

 Figure 12 Influence of Circuit on Frequency Temperature Characteristics

It is different from the frequency temperature characteristic measured by the crystal unit alone and the frequency temperature characteristic measured by mounting the crystal unit as an oscillator.
The standard may not be satisfied when the standard of frequency temperature characteristic becomes narrower as an oscillation circuit.
This is because not only the crystal unit but also the oscillator circuit has a temperature characteristic.
In such a case, you must carefully investigate the temperature characteristics of the oscillator circuit used and order a crystal with frequency temperature characteristics that compensates for this.(Refer to Fig. 12.)
If stricter standards are required, use of a temperature-compensated crystal oscillator is recommended.

2. To satisfy functional performance

The crystal resonator has a special internal structure, and in order to maintain their performance, the inside of the holder of the crystal unit is vacuumed or filled with an inert gas.
2-1 Use of ultrasonic welding machines
When ultrasonic welding machine is used, the frequency of the ultrasonic wave and the crystal element may resonate, resulting in deterioration of characteristics.
Please check with our sales representative for details of our resonance-proof products.

2-2 Mounting of surface-mount type crystal units
(1) Rapid temperature changes after mounting on board
If the material of the mounting board has an expansion coefficient different from that of ceramics in the package of a surface mount type crystal unit using ceramics, cracks may occur in the fillet part of the soldering under an environment where severe temperature changes are repeated for a long time.
If such environmental conditions are anticipated, we recommend that you check it beforehand.
(2) Shock caused by automatic mounting
Please note that if a shock exceeding the standard is applied to the crystal unit when it is absorbed or chucked by automatic mounting or when it is mounted on a substrate, it may lead to changes in or degradation of the characteristics of the crystal unit.
(3) Stress caused by bending substrate
Please note that bending the substrate surface after soldering the crystal unit to the printed substrate may cause the soldered part to peel off due to mechanical stress or cause cracks in the package of the crystal unit.
(4) Treatment of Grounding terminal
If the crystal unit has a grounding terminal, please be sure to solder it to GND or to the power supply terminal.
The correct frequency may not be obtained in the floating state.

2-3 Soldering and ultrasonic cleaning
The soldering temperature conditions of a crystal unit are designed so as to allow the simultaneous work with other general electronic components, but the conditions may be limited depending on the type of products.
Please confirm the conditions before use.
Basically, the ultrasonic cleaning of flux is allowed, but in some cases, the resonance with the oscillation frequency of the ultrasonic wave cleaner might cause the characteristics of the crystal unit to deteriorate.
Please check that no abnormality occurs on the mounting board before use.

2-4 Effect of corrosive materials
If the crystal unit comes in contact with salt or corrosive materials, or is exposed to an atmosphere containing chlorine or sulfide gas for a long period of time, corrosion may result in a fatal disadvantage, such as the failure to maintain the airtightness of the package.
Care should be taken when selecting an adhesive or potting agent to be used at around a crystal unit.

2-5 Mounting a lead-mount type crystal unit
(1)When mounting a crystal unit on a substrate, it should be mounted below the height of other electronic components in order to prevent damage to the glass part of the crystal unit holder due to impact from the top.
If the glass part is damaged, the airtightness will be lost and performance may deteriorate.
(2) When mounting a lead-mount type crystal unit in close contact with a printed substrate, adjust the spacing of the holes on the printed substrate to the spacing of the terminals of the crystal unit.
The slightest error in pitch may cause cracks in the glass part of the crystal unit holder.
(3) When mounting a lead-mount type crystal unit on the printed substrate, we recommend that the crystal unit should be soldered in close contact because mechanical resonance may cause the lead portion to fatigue and break. (see Fig. 13).
(4) After mounting a crystal unit on a printed substrate, be careful not to move the crystal unit as shown in Figure 14, as this may cause cracks in the glass part of the holder base and deteriorate its characteristics.

 Fig.13 Mounting method of crystal unit Fig.14 Cautions after mounting the crystal unit

3. Reflow Soldering

The following reflow temperature profiles are standard for surface mount crystal units.
temperature profiles of surface-mount type crystal units
Examples of Soldering conditions

 ＊Peak temperature: 260±5 °C Max. within 10 seconds 　Main Heating :230 °C or higher for 30 ±10 seconds＊Ramp up rate: Max. 3 °C/second or less＊Ramp down rate: Max. 6 °C/second or less＊Preheating : 150 to 180 °C for 90 ±30 seconds

Prohibitions

Do not use these products under any conditions that exceed the following , as it may cause the deterioration of characteristics or destruction of the products.

Heat Resistance of SMD Crystal Products
[Reflow Soldering Heat Resistance]
Peak-temperature: 265 °C, for 10 sec.
Main Heating : Min. 230 °C or higher, for 40 sec.
Ramp-up rate: 3 °C/second
Ramp-down rate: 6 °C/second
Preheating : 150 to 180 °C, for 120 seconds
Number of reflow passes: 2 times
[Manual Soldering Heat Resistance]
Operating condition: Press a soldering iron at 400 °C to terminal electrode for 4 seconds.
Number of use : 2 times
(1) Glass-sealed product
When using a soldering iron for glass-sealed products, the soldering iron tip should be placed on the lower side of the sealing part, and the soldering iron tip should not be put on the sealing glass part.
the iron touching the sealed glass part
(if the iron tip comes into contact with the glass part, the glass may melt and impair the airtightness)
2) Au/Sn-sealed product
Do not touch the tip of a soldering iron to the sealed part of an Au/Sn-sealed product. (The iron tip may melt the sealing material and break the airtight seal.)
In addition, if possible, it is recommended that this product it to be mounted with reflow without using a soldering iron or an air-heater.
In purpose of reworking crystal unit, during removing from the substrate or module, or removing module from substrate, any excessive heat may melt the Au/Sn , , which is the sealing material, resulting in the deterioration of characteristics or destruction of the airtight seal.
Therefore, please handle the products in accordance with the above thermal conditions.
However, in case an air-heater is need to be used, do not exceed the following heating conditions.
Air-heater temperature: 280 °C, time: 10 seconds
Heat Resistance of Crystal Products other than SMD

[Reflow Soldering Heat Resistance]
Soldering temperature: 265 °C, 10 sec.
Number of flow applications: 2 times
[Manual Soldering Heat Resistance]
Operating condition: Press a soldering iron at 400 °C to terminal electrode for 4 seconds.
Number of use : 2 times

4. Guaranteed items

Regarding the environmental and mechanical characteristics of crystal units, we test items such as temperature, humidity, shock resistance, and heat resistance.
Each test item and condition is set for each product, and the characteristics of the product are guaranteed.
However, the guaranteed items and conditions vary depending on the shape, characteristics, application, environment, etc. of the crystal unit.

(*) General consumer products: Products used in the most general equipment, such as AVs and OAs

No. Test Items Conditions Standard 720 hours at +85 ± 3°C ＊1 500 hours at -40 ± 3°C ＊1 500 hours at a temperature of +60 ± 3°C and humidity of 90 to 95% ＊1 -40±3℃／+85±3℃500 cycles each for 30 minutes as one cycle ＊1 Frequency range: 10 to 55 HzTotal amplitude or acceleration: 1.52 mmCycle time : 1 minuteNumber of times: 2 hours in each of three orthogonal directions ＊1 Shock: 981 m/s2 6ms half-wave sine wave　Number of times: 3 times in each XYZ 6 direction*1 ＊1 3 times of natural drop from a height of 75 cm onto a hard wooden board (30 mm or more) ＊1 Pre heating temperature: +150 ± 10°C; Pre heating time : 60 to 120 secondsSMD temperature: 30 ± 1 seconds afterreaching temperature of +215°CPeak temperature: +240 ± 5°CSolder type: lead-free solder (Sn-3.0 Ag-0.5 Cu)Flux:Performed with rosin-based methanol solution (rosin: methanol = 1:4) At least 90% of the electrode covered with solder Pre heating temperature: +150 to - 180°CPre heating time : within 90 ± 30 secondsMain heating temperature: +230°C or higher;Main heating time within 30 seconds;Peak temperature: +260 ± 5°C;Peak temperature time : within 10 seconds ＊1

(*1) ΔF/F ≦ ±5×10-6、ΔCl ≦ ±15% or 5Ω , whichever is greater

5. Please check before you think there is a malfunction

If a problem occurs in the use of a quartz crystal unit, we will make every effort to identify the cause of the problem as soon as possible and to minimize the inconvenience to the customer.
Accordingly, customers are asked to address the following points before returning products

5-1 Cross-checking to identify potential issues (crystals/oscillator circuit parts)
Please prepare a PCB (A) that generates NG and a PCB (B) that does not cause any trouble.
Next, remove the crystal unit mounted on the PCB, replace it, mount it, and judge whether it is acceptable or not.

(Case 1) After replacing the crystal unit, PCB (B) is NG and PCB (A) is OK.

(Case 1) After replacing the crystal unit, PCB (B) becomes NG and PCB (A) is OK.
If PCB (A) becomes NG again after being replaced, there is a high possibility that the crystal unit is NG or there is a problem with the matching between the crystal unit and the oscillation circuit.

(Case 2) After replacing the crystal unit, PCB (A) becomes NG and PCB (B) is OK.
Please cross-check ICs and other components to identify the defective component.

(Case 3) In cases other than Case 1 and Case 2, when both PCBs are OK, both PCBs are NG, or when there is no reproducibility after repeated replacement, it is assumed that the matching between the crystal unit and PCB (oscillation circuit) is bad.

5-2 Please inform us of the problem symptoms.
In Cases 1 and 3 above, there may be issues with the crystal itself or with the usage conditions, so please inform us of the problem symptoms.
① Please inform us of the failure symptoms (output stop, defective images, noise, etc.) on the customer's PCB.
② When a malfunction occurs at a specific temperature, such as low temperature, high temperature, the temperature at which it becomes defective.
③ If you notice any of the characteristics (frequency shift, etc.) of the crystal that causes the PCB to malfunction, please let us know.
④ Other details of failures (number of incidences, affected lots, etc.). Please include photos of the display and the label on the defective product

5-3 Return of defective products
Please return the defective product to our sales office with the results of cross-checking by the customer and the symptoms of the defect.
If you have already measured the characteristics of the crystal by yourself, please let us know the result.
When returning the product, if it is returned with PCB mounted, we will analyze whether it is a crystal resonator problem or a matching problem.

5-4 Circuit study
If there is a problem with the matching of the oscillation circuit and the crystal unit, we will propose to improve the problem phenomena such as the deviation of the oscillation frequency and the oscillation instability by changing the circuit constant.
In addition, please cooperate with teaching how to connect (VCC, ground, outputting, etc.) for circuit study.
If you use a crystal unit as a standard component, and if you use a crystal unit on several different PCBs, please let us know so that we can study the circuit separately.

Please refer to the oscillation circuit in the application note for an overview of the oscillation circuit.

5. Preventive measures against ion migration problems

Though the non-cleaning after PCB soldering is becoming popular, please consider to prevent ion migration from occurring in advance.
Even when using a non cleaning type solder paste, it is recommended to perform reliability confirmation such as high-temperature and high-humidity tests beforehand, because some conditions such as temperature and humidity may cause problems due to ion migration. Also, in order to prevent ion migration, please consider the following items.

(1) If the product is used under high temperature, high humidity, and energized conditions, clean the PCB and remove the flux.
(2) After cleaning, coat with moisture-resistant resin.
(3) When used without cleaning, a type of flux with low corrosivity and reduced active force after soldering should be used.

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