Crystal Filter n Precautions for Use n How to Adjust the Transformer in the Connected Section of MC L1 MCF L2 MCF 0 2 90 MCF L2 MCF ATT 4 80 6 70 – 8 60 10 50 + + 12 40 – –16 –12 –8 16 20 G.D G.DELAY(μs) 14 30 C L1 L3 ATT.(dB) n How to Adjust the Transformer in the Connected Section of MCF The figure below shows a circuit when the input/output section and the connected section are inductive in the same way as in an overtone MCF. Figures 5a to 5c show (in-band) changes in the filter characteristics when the coil inductance of each LC tuned circuit in the circuit diagram was changed. When the inductance of the coils L 1 and L 3 in the input/output section is increased or decreased, the in-band characteristics (ripple, loss, and bandwidth) are affected to some degree. However, when the inductance of the coil L2 in the connected section is increased or decreased, the in-band characteristics change considerably. Particularly when the inductance is decreased below the specified value, the positive side of the passband width becomes narrower and may sometimes become less than half its normal value. Therefore, in order to obtain the correct inductance value of each coil, check the filter characteristics, using a network analyzer, etc., to adjust the coil. Connection marks In addition, concerning the connection marks of two-element pair type R R MCF MCF products, position the marks so that they face C1 C C1 inward as shown in the right figure. –4 0 4 8 55.025MHz FREQUENCY(kHz) 12 16 Figure 5a Characteristics change by L1 L3 L1 MCF L2 MCF L3 0 0 2 90 ATT 2 80 ATT 4 80 4 70 – + 6 70 6 60 – 8 60 8 50 – + 10 50 + 10 40 + – 14 20 16 10 G.DELAY(μs) 16 20 G.D ATT.(dB) 14 30 G.D 12 30 G.DELAY(μs) ATT.(dB) 12 40 18 10 –16 –12 –8 –4 0 4 8 55.025MHz FREQUENCY(kHz) 12 –16 16 Figure 5b Characteristics change by L2 –12 –8 –4 0 4 8 55.025MHz FREQUENCY(kHz) 12 16 Figure 5c Characteristics change by L3 n Necessity of an LC Tuned Circuit for a Capacitive Circuit Also for a capacitive circuit, a tuned circuit is needed when the capacitance of a circuit used before and behind an MCF and the stray capacitance of the board and the wiring section exceed the capacitance value (specified by terminating impedance). cf06_071102_caution1_e Crystal Filter n Precautions for Use n Terminating Impedance n Filter Grounding Terminating impedance refers to source impedance or load A crystal filter can be grounded with mounting screws or ground impedance viewed from the filter side, and it is generally specified terminals. Use these to ground the filter. separately as resistance and parallel capacitance. When this When this filter is directly soldered to the case, the parts inside terminating impedance is different from the specified value, may be damaged. Therefore, take precautions to avoid this. characteristics in the passband in particular are seriously In addition, make sure to ground the entire bottom surface of the disordered with the insertion loss, ripple, and bandwidth changed, filter case so that there is no potential difference from the ground thereby causing the original characteristics to be unavailable. potential on the circuit side. Therefore, measure the impedance on the circuit side, using an When a double-sided printed board is used, connect the filter impedance analyzer, etc., to meet the termination conditions. through holes so that the potential difference between the patterns Figures 6a and 6b (page 209) show the characteristics of the on both sides is removed. Do not use a solder mask for the passband when the terminating impedance with N being 2 (two pattern on the filter bottom surface. poles) was changed by a crystal filter of which the nominal frequency and the passband width are 10.7 MHz and ±7.5 kHz, respectively. Particularly when the resistance value changes, note n Direct Superimposed Current that the passband deviates considerably from the specified band. Do not pass a direct current that is the same as or more than the n Maximum Level specified value to a balanced filter. When a current exceeding the specified value is used, the transformer winding inside generates heat, thereby causing The input level must be the same as or less than the specified failures, due to insufficient insulation and disconnection. value. When a value more than the specified value is input, the characteristics of the crystal resonator deteriorate, and the original n Mechanical Shock characteristics of the filter cannot be obtained. The input level must be 0.1 mW (–10 dBm or less). Never give any strong shocks to the filter. When carrying the filter or mounting it on another device, be careful not to cause any shocks, for example, by dropping it or n Separation between Input and Output hitting it with a hard object. If a strong shock has been given to the filter, make sure to check In order to prevent electrostatic and electromagnetic coupling, its characteristics before using it. make sure to use a shield between input and output. When this type of coupling exists between input and output, input signals directly enter the output side in the area where attenuation n Custody is large, thereby causing the guaranteed attenuation to decrease, and, therefore, the original characteristics of the crystal filter Keeping the filter in a high-temperature and high-humidity cannot be obtained. As an example of this, Figure 7 (page 209) environment will cause a deterioration in its performance. Keep it shows the characteristics of a crystal filter of which the nominal at a normal room temperature and at a normal level of humidity. frequency, passband width, and N are 10.7 MHz, ±7.5 kHz, and six (six poles), respectively, when electrostatic coupling exists between the input and the output. As you can understand from Figure 7, even extremely small coupling can cause the guaranteed attenuation to decrease considerably. cf07_081216_caution2_e Crystal Filter n Precautions for Use 2 2 4 4 6 6 8 3 4 4 3 R 8 R –12 ATTENUATION (dB) ATTENUATION (dB) –16 R 12 14 f0 10.7MHz Pole N=2 16 Ripple 0.5dB R Specified value Rin Cout –8 Rout Cin –4 4 3 C 10 Rout 18 Cin C C 10 Rin 3 4 0 4 10.7MHz 8 12 16 (kHz) Figure 6a Characteristics change by a resistance value (N=2) –16 –12 12 14 16 f0 10.7MHz Pole N=2 Ripple 0.5dB R Specified value 18 Cout –8 –4 4 0 10.7MHz 8 12 16 (kHz) Figure 6b Characteristics change by a capacitance value (N=2) C 20 Rin Rout Rin=Rout=1kΩ 40 C=0.001pF C=0.0003pF C=0 C=0.0001pF −150 −100 −50 ATTENUATION(dB) C=0.003pF 60 80 0 10.7MHz 50 100 150 (kHz) Figure 7 Change in the guaranteed attenuation by coupling between input and output (an example of capacitive coupling) cf08_071102_caution3_e Crystal Filter n Precautions for Use n Mounting Method 1. How to Install a Conventional Crystal Filter 3. Mounting of a Surface-mount MCF (1) As a rule, do not bend the terminals because they are (1) Rapid temperature change after a board has been installed hermetically sealed. Particularly, never bend terminals with a When the material of the mounting board for a surface-mount size of φ0.6 mm or more. Even when it is necessary to bend MCF package with ceramics has an expansion coefficient that terminals with a size of φ0.6mm or less, do not bend them is different from that of the ceramic material, the soldered fillet directly from the base glass. section may crack if subjected to repeated extreme (2) When cutting terminals short, mount a crystal filter on the printed board and solder the terminals beforehand. Set the tightening torque of mounting screws to values that are the same as or less than those shown in the table below. temperature changes over a long time. Under such conditions, it is recommended that the situation be checked beforehand. (2) Shock by automatic mounting Screw diameter Tightening torque When an MCF is adsorbed or chucked in the course of M2.6 0.392N • m automatic mounting or a shock that exceeds the specified M3 0.49N • m value occurs when mounting on the board, the characteristics will change or deteriorate. (3) Stress by board bending 2. Mounting of a Lead-mount MCF After an MCF has been soldered to a printed board, bending (1) When closely mounting a lead-mount MCF on a printed board, the board surface may cause the soldered part to peel off or align the distance between the holes of the printed board with the MCF package to crack due to mechanical stress. that between the terminals of the MCF. Failure to do this may cause the holder-base glass to crack, resulting in a loss of airtightness and a deterioration of the MCF. (2) When mounting an MCF on a printed board, it is recommended that the MCF be soldered to the printed board as closely as possible in order to prevent lead fatigue caused by mechanical resonance. (Refer to Figure 8-(a).) However, when the printed board is Insulating plate Printed board double-sided, solder flows in through the holes, and this causes a short circuit. Therefore, it is recommended that an insulating plate be attached. (a) Vertical mounting When mounting an MCF vertically, in order to prevent the holder-base glass from cracking, perform bending beforehand so that the lead wire is not bent from the base glass (the broken line in Figure 8-(b)) and then fix the MCF on the printed Printed board Band board with a band, adhesive, etc. Do not move the crystal resonator as shown in Figure 9 after it has been mounted on the printed board as this will cause the (b) Surface mounting Figure 8 How to mount a lead-mount MCF holder-base glass to crack. × Crystal resonator Printed board Figure 9 Precautions after a lead-mount MCF has been mounted cf09_071102_caution4_e Crystal Filter n Precautions for Use n Others 4. Soldering and Ultrasonic Cleaning Soldering temperature conditions for crystal filters are established so that other general electronic parts can be soldered at the same If your crystal filter is found to be abnormal, return it to NDK in its time. However, such conditions may be limited according to the present condition. Inappropriate handling, such as opening of the different types of products. Check the conditions beforehand. In filter, may cause further damage making it impossible to repair. It addition, there is no problem with ultrasonic cleaning of flux, but it is important to do nothing to the abnormal filter. In addition, when may resonate with the oscillation frequency of the ultrasonic you return the filter, to facilitate a speedy and accurate repair, cleaner, thereby causing deterioration of characteristics. Check please include as accurately as possible a description of the beforehand that the mounting board is free of any abnormalities. abnormality. Note that products with a non-enclosed structure cannot be washed. n Precautions 5. Reflow Soldering The recommended temperature profile for reflow soldering of a We manufacture our products according to specifications surface-mount MCF is as follows: requested by customers. We cannot anticipate conditions of use or deal with circuit margins when they are not shown in the lExamples of soldering conditions [°C] 265 specifications. Please inform us of them beforehand. PEAK TEMP. 260 °C +5 –0 Temperature 260 200 lExamples of soldering conditions 180 *Preparatory conditions 150 165±15 °C Time: 90 to 110 seconds • Application of heat: 230 °C or higher Time: 40 to 50 seconds +5 • Peak temperature 260–0 °C 230°Cmin [s] 165±15°C 90 to 110 seconds 40 to 50 seconds TIME n List of Frequencies According to Applications A list of representative frequencies for crystal filters according to applications is shown below. Frequency Application 0.1 0.5 1 2 5 10 20 50 100 200 (MHz) Filter for cordless phones IF filter for mobile radio Filter for marine radio (SSB) Antenna filter Contact us for any applications other than the above. cf10_080911_caution5_e