Product - Relay - Technical
A Relay General Application Guidelines

A relay may encounter a variety of ambient conditions during actual use resulting in unexpected failure. Therefore, testing over a practical range under actual operating .conditions is necessary. Application considerations should be reviewed and determined for proper use of the relay.

METHOD OF DETERMINING SPECIFICATIONS

In order to use the relays properly, the characteristics of the selected relay should be well known, and the conditions of use of the relay should be investigated to determine whether they are matched to the environmental conditions,contact conditions, and the ambient conditions for the relay that is actually used must be sufficiently in advance. In the table below, s summary had been made of the points of consideration for relay selection. It may be used as a reference for investigation of items and points of caution.

 

Specification item

consideration points regarding selection
Coil a)Rating
b)Pick-up voltage (current)
c)Drop-out voltage (current)
d)Maximum conditions impressed voltage (current)
e)Coil resistance
f)Impedance
g)Temperature rise
h)Input frequency for AC type
1)Select relay with consideration for power source ripple.
2)Give sufficient consideration to ambient temperature and the coil temperature rise.
3)When used in conjunction with semiconductors, addition attenton to the application should be taken.
Contacts a)Contact arrangement
b)Contact rating
c)Contact material
d)Life
e)Contact pressure
f)Contact resistance
1)It is desirable to use a standard product with more than the required number of contacts.
2)It is beneficial to have the relay life balanced with the life of the device it is used in.
3)Is the contact material matched to the type of load?
It is necessary to take care particularly with low level usage.

Operate time a)Operate
b)Release time
c)Bounce time
d)Switching frequency
1)It is beneficial to have the bounce time short for sound circuits and similar applications.
Mechanical characteristics a)Vibration resistance
b)Shock resistance
c)Ambient temperature
d)Life
1)Give consideration to performance under vibration and shock in the use location.
2)In particular, when used in high temperature application, relay with class B or class F coil insulation may be required.
Other item a)Mounting method
b)Cover
c)Size
1)Selection can be made foe connection method with plug-in type, printed circuit board type, soldering, tab terminal, and screw fastening type.
2)For use in an adverse atmosphere, sealed construction type should be selected.
3)Are there any special condition?.

 

BASICS ON RELAY HANDLING

To maintain initial performance, care should be taken to avoid dropping or hitting the relay.

Under normal use, the relay is designed so that the relay will not detach. To maintain initial performance, the care should not be removed. Relay characteristics cannot be guaranteed if the case is removed.

Use of the relay in an atmosphere at standard temperature and humidity with minimal amount of dust, SO2, H2S, or organic gases is recommended. Also note that use of silicon-based resins near the relay may result in contact failure. For installation in advance environment, one of the sealed types (plastic sealed type, etc.) should be considered.

Care should be taken to observe correct coil polarity (+, -) for polarized relays.

Proper usage required that the rated voltage be impressed on the coil. Use rectangular waves for DC coils and sine waves for AC coils.

Be sure the coil impressed voltage does not continuously exceed the maximum allowable voltage.

Absolutely avoid using switching voltages and currents that exceed the designated values.

The rated switching power and life are given only as guides. The physical phenomena at the contacts and contact life greatly very depending on the type of load and the operating conditions. Therefore, be sure to carefully check the type of load and operating conditions before use.

Do not exceed the usable ambient temperature values listed in catalog.

Use the flux-resistance type or sealed type if automatic soldering is to be used.

Use Freon or alcohol based cleaning solvents when cleaning is to be performed using a sealed type relay.

Avoid ultrasonic cleaning of all types of relays.

As a guide, use a Faston mounting pressure of 4 to 7kg or 8.8 to 15.4lbs for relays with tab terminals.

For proper use, read the main text for details.

 

PROBLEM POINTS WITH REGARD TO USE

In the actual use of relays, various ambient conditions are encountered, and because unforeseen events occur which can not be though of on the drawing board, witch regard to the conditions, tests are necessary under the possible range of operation. For example, consideration must begiven to variation of performance when relay characteristics are being reviewed. The relay is a mass production item, and as a matter of principle, it must be recognized that the relay is to be used to the extent of such variations without the need for adjustment.

 

RELAY COIL

AC operation type

For the operation of AC relays, the power source is almost a commercial frequency (50 or 60HZ) with standard voltage of 6, 12, 24, 48, 110, 220 and 240V AC. Because of this, when the voltage is other than the standard voltage, the product is special order item, and the factor of price, delivery, and stability of characteristics may create inconveniences. To the extent that it is possible, the standard voltage should be selected.

Also, in the AC type, shading coil resistance loss, magnetic circuit eddy current loss, and hysteresis loss exit, and because of lower coil efficiency, it is normal foe the temperature rise to be greater than that for the DC type. furthermore, because humming occurs below the level of pick-up voltage (minimum operation voltage), care is required with regard to power source voltage fluctuation.

For example, in the case of motor starting, if the power source voltage drops, and during the humming of relay, if it reverts to restored condition, the contact suffer a burn damage and welding, with the occurrence of s false operation self-maintaining condition.

For the AC type, there is a inrush current during the operation time (for the separated condition of the armature, the impedance is low and a current greater than rated current flows; for the adhered condition of armature, the impedance is high and the rated value current flows), and because of this, for the case of several relays being used in parallel condition, it is necessary to give consideration to power consumption.

 

DC operation type

For the operation of DC relays, standards exist for power source voltage and current, with DC voltage standards set at 5, 6, 12, 24, 48 and 100V, but with regard to current, the values as expressed in catalogues in milliamperes of pick-up current.

However, because the value of pick-up current is nothing more than a guarantee of just barely moving the armature, the variation in impressed voltage and resistance values,  and the increase in coil resistance due to temperature rise, must be given consideration for the worst possible condition of relay operation, making it necessary to consider the current value as 1.5 to 2 times the pick-up current. Also, because the extensive use of relays as limit devices in place of meter for both voltage and current, and because of the gradual increase or decrease of current impressed on the coil causing possible delay in movement of the contacts, there is the possibility that the designated control capacity may not be satisfied. Thus it is necessary to exercise care. The DC type relay coil resistance varies due to ambient temperature as well as to its own heat generation to extent of about 0.4%/°C, and accordingly, if the temperature increases in pick-up and drop-out voltage, care is required.

 

Impressed voltage of AC coil

in order to have stable operation of the relay, the impressed voltage should be basically within the range of  of the rate voltage. However, it is necessary that the waveform of the voltage impressed on the coil be a sine wave. There is no problem if the power source is commercially provided power, but when a stabilized AC power source is used, there is a waveform distortion due to that equipment, and there is the possibility of abnormal overheating. By meanings of shading coil for the AC coil, humming is stopping, but with a distorted waveform, that function is not displayed. Fig. 1 below shows an example of waveform distortion.

          

Fig. 1 Distortion in an AC stabilized power source

 

If the power source of relay operating circuit is connected to the same line the motors, solenoids, transformers, and other loads, when these load operate, the line voltage drops, and because of this the relay contacts suffer the effect of vibration and subsequent burn damage. In particular, if a small type transformer is used and its capacity has no margin of safety, when there is long wring is slender, it is necessary to take precautions because of the normal voltage fluctuation combined with these other factor. When trouble develops, a survey of the voltage situation should made using a synchroscope or similar means, and the necessary counter-measures should be taken, and together with this determine whether the special relay with suitable excitation characteristics should be used, or make a change in the DC circuit as shown in  Fig. 2 in which a capacitor is inserted to absorb the voltage fluctuation.
           
Fig. 2 Voltage fluctuation absorbing circuit using a condenser

 

In particular, when a magnetic switch is being used, because the load becomes like that a motor, depending upon the application, separation of the operating circuit and power circuit should be tried and investigated.

 

Power source for DC input

As a power source for the DC type relay, a battery or either a half wave or full wave rectifier circuit with a smoothing capacitor is used. The characteristics with regard to the excitation voltage of the relay will change depending upon the type of power source, and because of this, in order to display stable characteristics, the most desirable method is perfect DC.

In the case of ripple included in the DC power source, particularly in the case of half wave rectifier circuit with a smoothing capacitor, if the capacity of the capacitor is too small, due to the influence of the ripple, humming develops and an unsatisfactory condition is produced. With the actual circuit to be used, it is absolutely necessary to confirm the characteristics.

 

Coil temperature rise

Proper usage requires that the rated voltage be impressed on the coil. Note, however, that if a voltage greater than or equal to the maximum continuous impressed voltage is impressed on the coil, the coil may burn or its layers short due to the temperature rise. Furthermore, do not exceed the usable ambient temperature range listed in catalog.

 

Temperature rise due to pulse voltage

When a pulse voltage with ON time of less than 2 minutes is used, the coil temperature rise bares no relationship to the On time. This various with the ratio of On time to OFF time, and compared with continuous current passage, it is rather small. The various relays are essentially the same in this respect. (Fig. 3).

Current passage time
For continuous passage Temperature rise value is 100
ONOFF=31 About 80
ONOFF=11 About 50
ONOFF=13 About 35

 

         
 Fig. 3 

Pick-up voltage change due to coil temperature rise (hot start)
In DC relays, after continuous passage of current coil, if the current is turned OFF, then immediately turned ON again, due to the temperature rise in the coil, the pick-up voltage will become somewhat higher. Also, it will be the same as using it in a higher temperature atmosphere. The resistance/temperature relationship for copper wire is about 0.4% for 1°C, and with ratio the coil resistance increase. That is, in order to cause operation of the relay, the current necessary becomes higher than the pick-up current, accompanying the rise in the resistance value.

Operate time
In the case of AC operation, there is extensive variation in operate time depending upon the point in the phase at which the switch is turned ON for coil excitation, and it is expressed as a certain range, but for miniature types it is for the most part 1/2 cycle (about 10msec.). However, for the somewhat large type relay where bounce is large, the operate time is 7 to 16msec., with the release time in the order of 9 to 18msec. Also, in the case of DC operation, to the extent of large coil input, the operating time is rapid, but if it is too rapid, the “A” contact bounce time is extended.

Stray circuit (bypass circuits)
In the case of sequence circuit construction, because of bypass flow or alternate routing, it is necessary to take care not to have erroneous operation or abnormal operation. To understand this condition while preparing sequence circuits, as shown in Fig. 4 with two lines written as the power source lines, the upper line is always (+) and lower line (-) (when the circuit is AC, the same thinking applies). Accordingly the (+) side is necessary the side for making contact connections (contacts for relays, timers, limit switches, etc.), and the (-) side is the load circuit side (relay coil, timer coil, magnet coil, solenoid coil, motor, lamp, etc.).
          
   Fig. 4 Example of a vertically written sequence circuit

Fig. 5 shows a example of stray circuit. In Fig. 5(a), with contacts A, B, and C closed, after relays R1, R2, and R3 and the relays will hum and sometimes not be restored to the drop out condition.
The connection shown in Fig. 5(b) are correctly made. In addition, with regard to the DC circuit, because it is simple by means of a diode to prevent stray circuits, proper application should be made. 

             
     Fig. 5 Stray circuits

 Gradual increase of coil impressed voltage and suicide circuit
When the voltage impressed on the coil is increased slowly, the relay transfering operation is unstable, the contact pressure drops contact bounce increases, and an unstable condition of contact occurs. This method of applying voltage to the coil should not be used, and consideration should be given to the method of impressing voltage on the coil (use of switching circuit). Also, in the case of latching relays, using self contacts “B”, the method of self coil circuit for complete interruption is used, but because of the possibility of trouble developing, care should be taken. The circuit shown in Fig. 6 causes a timing and sequential operation using a reed type relay, but it is not a good example with mixture of gradual increase of impressed voltage for the coil and a sucide circuit. In the timing portion for relay R1, when the timing times out, chattering occurs causing trouble. In the initial test (trial production), it shows favorable operation, but as the number of operations increases, contact blackening (carbonization) plus the chattering of the relay creates instability in performance.
            
Fig. 6 A timing and sequential operation using a reed type relay

Phase synchronization in AC load switching
If switching of the relay contacts is synchronized with the phase of the AC power, reduced electrical life, welded contacts, or a locking phenomenon (incomplete release) due to contact material transfer may occur. Therefore check the relay while it is operating in the actual system. However, if problem develop, control the relay using an appropriate phase. (Fig. 7).
           
 Fig. 7

Erroneous operation due to inductive interference
In situations where both control and load wiring are in close proximity, thought should be given to separating or shielding the conductors in order to prevent false relay operation. This becomes increasingly important with long wire runs, and can be achieved by using separate conduit for load control conductor. Inductive coupling can also be minimized of the load and control wiring.

Influence of external magnetic fields
Many modern electro-mechanical relays are of polarized, high sensitivity design. Care should be exercised in the placement of these devices when strong, external magnetic fields are prevent, such as in proximity to power transformers or permanent magnets (speaker, etc.).
Operational characteriatics may change under an external magnetic influence.

Long tern current carrying
In application \s which involve lengthy duty cycles, the preferred configuration would be the use of the form B or N.C. contacts for long term duty. In those instances where the form A contact is held closed for extensive time period, coil heating will increase contact “T” rise and may result in shorter than optimum life. Alternately, latching types may be considered for these applications, using a storage capacitor to “Reset” the relay on power-down.

Regarding electrolytic corrosion of coils
In the case of comparatively high voltage coil circuit (in particular above 48V DC), when such relays are used in high temperature and high humidity atmospheres or with continuous passage of current, the corrosion can be said to be the result of the occurrence of electrolytic corrosion. Because of the possibility of open circuit occurring, attention should be given to the following points.
The (+) side of the power source should be connected to the chassis. (Refer to Fig. 9) (Common to all relays)
In the case where unavoidably the (-) side is grounded, or in the case where grounding is not possible.
Insert the contacts (or switch) in the (+) side of the power source, and connect the start of the coil winding the (-) side. (Refer to Fig. 10) (Common to all relay)
When a grounding is not required, connect the ground terminal to the (+) side of the coil. (Refer to Fig. 11) (NF and NR with ground terminal).

Contact Protection Circuit Use of contact protective devices or protection circuits can suppress the counter emf to a low level. However, note thatincorrect use will result in an advance effect. Typical contact protection circuits are given in the table blow.

 

Circuit Application Features/Others Device Selection
AC DC
CR circuit

If the load is a timer, leakage current flows through the CR circuit causing faulty operation.
*If used with AC voltage, be sure the impedance of the load is sufficiently smaller than that of the CR circuit.

As a guide in selecting r and c, r:0.5 to 1W per 1V contact voltage c:0.5 to 1mF per 1A contact current Values vary depending on the properties of the load and the variations in relay characteristics. Capacitor c acts to suppress the discharge the moment of contacts open. Resistor r acts to limit the current when the power is turned on the next time. Test to confirm. Use a capacitor with a breakdown voltage of 200 to 300V. use AC type capacitors (non-polarized) for AC circuits 

If the load is a relay or solenoid, the release time lengthens. Effective when connected to both contacts if the power supply voltage is 24 or 48V and the voltage across the load is 100 to 200V.
Diode circuit

× The diode connected in parallel causes the energy stored in the coil to flow to the coil in the form of current and dissipates it as joule heat at the resistance component of the inductive load. This circuit further delays the release time compared to the CR circuit. (2 to 5 times the release time listed in the catalog). Use a diode with a reverse breakdown voltage at least 10 times the circuit voltage and a forward current at least as large as the load current. In electronic circuit where the circuit voltage are not so high, a diode can be used with a reverse breakdown voltage of about 2 to 3 times the power supply voltage.
Diode and zener diode circuit

× Effective when the release time in the diode circuit is too long. Use a zener diode with a zener voltage about the same as the power supply voltage.
Varistor circuit

× Using the stable voltage characteristics of the varistor, this circuit prevent excessively high voltage from being applied across the contacts. This circuit also slightly delays the release time. Effective when connected to both contacts if the power supply voltage is 24 or 48V and the voltage across the load is 100 to 200V.

             

 

 

Avoid using the protection circuits shown in the Fig. 8. Although DC inductive loads are usually more difficult to switch than resistive loads, use of the proper protection circuit will raise the characteristics to that for resistive loads.


Fig. 8
Although extremely effective in arc suppression as the contacts open, the contacts are susceptible to welding since energy is stored in C when the contacts open and discharge current flows from C when the contacts close. Although extremely effective in arc suppression as the contacts open, the contacts are susceptible to welding since charging current flows from C when the contacts close.

 

Mounting the Protective Device
In the actual circuit, it is necessary to locate the protective device (diode, resistor, capacitor, varistor, etc.) in the immediate vicinity of the load or contact. If located too far away, the effectiveness of the protective device may diminish. As a guide, the distance should be within 50cm.

Abnormal Corrosion During High Frequency Switching of DC loads (spark generation)
If, for example, a DC value or clutch is switched at s high frequency, a blue-green corrosion may develop. This occurs from the reaction with nitrogen in the air when sparks (arc discharge) are generated during switching. For relays with a case, the case must be removed or air holes drilled in the case. A similar phenomenon occurs in the presence of ammonia-based gas. Therefore, care is required in circuits where sparks are generated at a high frequency.

Type of load and Inrush Current
The type of load and its inrush current characteristics, together with the switching frequency are important factors which cause contact welding. Particularly for load with inrush currents, measure the steady state current and inrush current and select a relay which provides an ample margin of safety. The table on the right shows the relationship between typical loads and their inrush currents.
Type of load Inrush current
Resistive load Steady state current
Solenoid load 10 to 20 times the steady state current
Motor load 5 to 10 times the steady state current
Incandescent lamp load 10 to 15 times the steady state current
Mercury lamp load Approx. 3 times the steady state current
Sodium vapor lamp load 1 to 3 times the steady state current
Capacitive load 20 to 40 times the steady statecurrent
Transformer load 5 to 15 times the steady state current

 

Load Inrush Current Wave and Time
    

When Using Load Wires

If long wires (100 to 300m) are to be used in a relay contact circuit, inrush current maybe become a problem due to the stray capacitance exiting between wires. Add a resistor (approx. 10 to 50W) in series with the contacts. (fig. 9)
           
Fig.9

Phase Synchronization in Switching AC Loads
If switching of the relay contacts is synchronized with the phase of the AC power, reduced electronic life, welded contacts, or a locking phenomenon (incomplete release) due to contact material transfer may occur. Therefore, check the relay while it is operating in the actual system. However, if problem develop, control the relay using an appropriate phase. (Fig. 10).
            
Fig.10

Connection of load and contacts
Connect the load to the side of power supply as shown in Fig. 11(a). connect the contacts to the other side. This prevents high voltage from developing between contacts. If contacts connected to both side of the power supply as shown in (b), there is a risk of shorting the power supply when relatively close contacts short.             
Fig.11


RELAY DRIVE BY MEANS OF A TRANSISTOR

Connection method
The voltage impressed on the relay is always full rated voltage, and in the OFF time, the voltage is complete zero for avoidance of trouble in use. (Fig. 1)

        
 Fig.1

Countermeasures for surge voltage of relay control transistor
If the coil current is suddenly interrupted, a sudden high voltage pulse is developed in the coil. If this voltage exceeds the voltage resistance of the transistor, the transistor will be degraded, and this will lead to damage. It is absolutely necessary to connect a diode in the circuit as a means of preventing damage from the counter emf.
As suitable ratings for this diode, the current should be equivalent to the average rectified current to the coil, and the inverse blocking voltage should be about 3 times the value of the power source voltage. (Fig. 2)
        
Fig.2

Snap action
(Characteristic of relays with voltage rise and fall of voltage)
Unlike the characteristic when voltage is impressed slowly on the relay coil, this is the case where it is necessary to impress the rated voltage in a short time and also to drop the voltage in a short time. (Fig. 3)
        
Fig. 3

Schmitt circuit (Snap action circuit)
(Wave rectifying circuit)
When the input signal does not product a snap action, ordinarily a Schmitt trigger circuit is used to product safe snap action.
Characteristic points
1.  The common emitter resistor RE must have a value sufficiently small compared with the resistance of the relay coil. (The voltage impressed on the relay must not be greater than the excitation voltsge.)
        
Fig. 4

2.  Due to the relay coil current, the difference in the voltage at point P when T2 is conducting and at point P when T1 is conducting creates hysteresis in the detection capability of the Schmitt circuit, and care must be taken in setting the values.
3.  When there is chattering in the input signal because of waveform oscillation, an RC time constant circuit should be inserted in the stage before the Schmitt trigger circuit. (However, the response speed drops.) (Fig. 4)

Avoid Darlington circuit connection
(High amplification)
This circuit is a trap into which it is easy to fall when dealing with high circuit technology. This does not mean that it is immediately connected to the defect, but it is linked to troubles that occur after long periods of use and with many units in operation. (Fig.5)

        
Fig. 5

Residual Coil Voltage
In switching applications where a semiconductor (transistor, UJT, etc.) is connected to the coil, a residual voltage is retained at the relay coil which mat cause incomplete restoration and faulty operation. By using DC coil, there may be a reduction in; the danger of the incomplete restoration, the contact pressure, and the vibration resistance. This is because the drop-out voltage is 10% or more of the rated voltage, a low value compared to that for AC coil, and also there is a tendency to increase the life by lowering the drop-out voltage. When the signal from the transistor’s collector is taken and used to drive another circuit as shown in Fig. 6, a minute dark current flows to the relay even if the transistor is off. This may cause the problems described above.
        
Fig. 6 Connection to the next stage through collector

RELAY DRIVE BY MEANS OF SCR

Ordinary drive method
For SCR drive, it is necessary to take particular care with regard to gate sensitivity and erroneous operation due to noise. (Fig. 7)
        
Fig.7

Caution points regarding ON/OFF control circuit
(When used for temperature or similar control circuits)
When the relay contacts close simultaneously with an AC single phase power source, because the electrical life of the contacts suffers extreme shortening, care is necessary. (Fig. 8)
        
Fig. 8

1. When the relay is turned ON and OFF using a SRC, the SRC serves as a half wave power source as it is, and there are ample cases where the SRC is easily restored.
2. In this manner the relay operation and restoration timing are easily synchronized with the power source frequency, and the timing of the load switching also is easily synchronized.
3. When the load for the temperature control is a high
current load such as a heater, the switching can occur only peak values and it can occur only at zero phase values as a phenomenon of this type of control. (Depending upon the sensitivity and response speed of the relay)
4.  Accordingly, either an extremely long life or a extremely short life results with wide variation, and it is necessary to take care with the initial device quality check.

RELAY DRIVE FROM EXTERNAL CONTACTS
Relays for PC board use have high sensitivity and high speed response characteristics, and because they respond sufficiently to chattering and bouncing, it is necessary to take care in their drive.
When the frequency of use is low, with the relay in response time caused by a condenser, it is possible to absorb the chattering and bouncing. (Fig. 9) (However, it is not possible to use only a condenser. A resistor should also be used with the capacitor.)

        
Fig. 9

ELECTRNIC CIRCUIT DRIVE BY MEANS OF A RELAY
Chatterless electronic circuit Even though a chatterless characteristic is a feature of relays, this is to the fullest extent a chatterless electrical circuit, much the same as a mercury relay. To meet the requirement for such circuits as the input to a binary counter, there is an electronic chatterless method in which chattering is absolutely not permissible. Even if chattering develops on one side, either the N.O. side contacts or the N.C. side contacts, the flip flop does not reverse, and the counter circuit can be fed pulsed without a miss. (However, bouncing from the N.O. side to the N.C. side must be absolutely avoided.) (Fig. 10)
        
Fig. 10
Triac drive
With an electronic circuit using a direct drive from a triac, the electronic circuit will not be isolated from the power circuit, and because of this, troubles due to erroneous operation and damage can develop easily. The introduction of a relay drive is most economical and most effective solution. (Photo coupler and pulse transformer circuit are complicated.)
When a zero cross switching characteristic is necessary, a solid state relay (SSR) should be used. (Fig. 11)
        
Fig. 11

PC BOARD DESIGN CONSIDERATION
Pattern Layout for Relays
Since relays affect electronic circuits by generating noise, the following point should be noted.
Keep relay away from semiconductor devices. Design the pattern trances for shortest lengths. Place the surge arrester (diode, etc.) near the relay coil. Avoid routing pattern trances susceptible to noise (such as for audio signals) underneath the relay coil section. Avoid though-holes in places which cannot be seen from the top (e.g. at the base of the relay). Solder flowing up through such a hole may cause damage such as a broken seal. Even for the same circuit, pattern design considerations which minimize the influence of the ON/OFF operations of the relay coil and lamp on other electronic circuits are necessary. (Fig. 12)
        
Fig. 12

When it is necessary to use hand soldering for one part of a component after dip soldering has been done
By providing a narrow slot in the circular part to the foil pattern, the slot will prevent the hole from being plugged with solder. (Fig. 13)
        
Fig. 13

When the printed circuit board itself is used as a connector
The edge should be beveled. (This prevents peeling of the foil when the board is inserted into its socket.)
When only a single side is used as the connector blade, if there is a distortion in the circuit board, contact will be defective. Care should be taken. (Fig. 14)
        
Fig. 14

A Relay TTi Soldering and Cleaning Guide

Process

 Guideline

1. Mounting of relay

Avoid bending the terminals to make the relay self-clinching.
Relay performance cannot be guaranteed if the terminal are bend.

2. Flux coating

Adjust the position of the PC board so that flux does not overflow onto the top of it.
Use rosin-based flux, which is non-corrosive and required no washing.
Do not use Automatic Flux coating Method to dust-cover type relays.
Do not overflow onto the top of PC Board, in which a case, the flux may even penetrate a flux-esistant type relay.

3. Preheating

Preheating acts to improve solderability.
Preheating according to the following conditions.
Temperature 100°C 212°F or less
Time Without approx.
 

4. Soldering

 

Automatic Soldering Hand Soldering

Flow solder is the optimum method for soldering.
Adjust the level of the solder so that it does not overflow onto the top of the PC board.
Unless otherwise specified, solder under the following conditions depending on the type of relay.

?Keep the tip of the soldering iron clean.
Soldering iron 30W to 60W
Iron Tip Temperature Approx. 300°C 572°F
Soldering Time Within approx. 3 seconds
Solder H60 or H63
Solder Temperature Approx. 250°C 482°F  
Soldering Time Within approx. 5 second
Solder H60 or H63
5. Cooling
Automatic Soldering Hand Soldering

Immediate air cooling is recommended to prevent deterioration of the relay and surrounding parts due of soldering heat.
Although the environmentally sealed type relay (plastic sealed type, etc.) can be cleaned, avoid immersing the relay into cold liquid (such as cleaning solvent) immediately after soldering. Doing so many deteriorate the sealing performance.

           

6. Cleaning


Do not clean dust-cover type relays and flux-resistanct type relays by immersion. Even if only the bottom surface of the PC board is cleaning (e.q. with a brush), careless cleaning may cause cleaning solvent to penetrate the relay.
Plastic sealed type relays can be cleaning by immersion. Use a Freon-or alcohol-based cleaning solvent. Use of other cleaning solvent. (e.g. Trichlene, chloroethene, thinner, benzyl alcohol) may damage the relay case. However, some type of relays use materials which are chemical resistant. Select the suitable relay or solvent compatibility chart below.
Cleaning with the boiling method is recommended. Avoid ultrasonic cleaning on relays. Use of ultrasonic cleaning may cause breaks in the coil or slight sticking of the contacts due to the ultrasonic energy. 

7. coating



Do not coat dust-cover type relays and flux-resistant type relays, since the coating material may penetrate the relay and cause contact failure.
Do not use this coating method in TTi  relay.


        
Fig. 11  Automatic soldering process