Types and sel-ection method of SMD diode

Types and sel-ection method, SMD diode

1 Sel-ection of detector diodes

The detector diode can be used for point contact germanium diode, such as the 2AP series etc.. When used, should be based on the specific requirements of the circuit to sel-ect high working frequency, the reverse current is small, the detector diode forward current large enough.

2 sel-ection of rectifier diode

SMD diode manufacturers introduced rectifying diode is generally planar silicondiode, used for a variety of power rectifier circuit. Sel-ection of rectifier diode, the main consideration should be given to its maximum rectified current, maximum peak reverse current, cut-off frequency and reverse recovery time and other parameters. The rectifier diode using ordinary series regulated power supplycircuit, to reverse the cutoff frequency recovery time requirements are not high, as long as according to the circuit requires the sel-ection of maximum rectified current and maximum peak reverse current rectifier diodes can meet the requirements of the. For example, 1N series, 2CZ series, RLR series etc.. Rectifier diode rectifierswitching power supply circuit and pulse rectifier circuit, should choose a high operating frequency, rectifier diode reverse recovery time shorter (such as the RU series, EU series, V series, 1SR Series) or sel-ect a fast recovery diode.

Sel-ect the 3 zener diode

Zener diode is generally used in power supply as a reference voltage source or in the over-voltage protection circuit as a protection diode zener diode sel-ection, the main parameters of the application circuit shall meet the requirements. The stablevoltage stabilizing diode value should be the reference power and applicationcircuit of pressure values are the same, the maximum stable should be higher than the current regulator diodes the application circuit of the maximum load current ofabout 50%.

Choice of 4 switching diode

Switching diode is mainly used in tape recorders, televisions, DVD players and other home appliances and electronic equipment switch circuit, detection circuit,high-frequency pulse rectifier circuit. Medium speed switching circuit and detection circuit, can choose 2AK series of ordinary switch diode high-speed switching circuitmay use RLS series, 1SS series, 1N series, high speed switching diode 2CK seriesmain parameters. According to the application circuit (such as forward current, the maximum reverse voltage, reverse recovery time) to sel-ect a specific type of switching diode.

The 5 variable capacitance diode sel-ection

Sel-ection of variable capacitance diode, which should be considered in the working frequency, maximum reverse voltage, maximum current and zero biased junctioncapacitance parameters meet the requirements of the application circuit, should choose the junction capacitance changes, high Q value, reverse leakage current of the varactor diode.

Application of two, SMD diode (welding)

1) manual welding (we do not recommend using this method)

1.1) welding tin material: SN 6/4 alloy or silver

1.2) in order to prevent rupture, please manually before welding, baked products

1.3) to keep the iron edge temperature between 300 and 5 DEG C MAX (25W) andin 3 seconds to complete the welding. If the temperature is higher, the welding timeshould be shortened accordingly (increases every 10 DEG C shorter 1s)

1.4) SMD in manual welding process, pay attention not to damage the product appearance, especially the connection point or resin (welding products don't giveany pressure applied)

1.5) do not use has been a repeated welding products

1.6) suggest the use of temperature controlled soldering iron

2) reflow soldering

2.1) suggest that tin glue specifications for the use of

The melting temperature at 178~192 degrees a)

B) ingredients: tin 63%, Pb 37%

2.2) absolutely not allowed in products is not cooling back to room temperatureunder the situation that the next operation

2.3) need to return process map (obtained in LED resin surface test)

3) rework

3.1) rework required under 260 degrees, 5 seconds to complete

3.2) the iron head can not come into contact with the copper foil

3.3) the best use of double iron

4) cleaning welding after the cleaning requirements

A) the use of alcohol solvent, such as isopropyl alcohol (IPA)

B) x temperature time: less than 50 DEG x for 30 seconds or less than 30 DEG xfor 3 minutes

C) ultrasonic cleaning: less than 15W/ room, room capacity: the maximum 1 litres

Operation method: D) is smaller than 100 DEG C, less than 3 minutes