APPLICATION NOTES for SMD LEDs / PLCC /SMD LED Display

The full text of these application notes is reproduced below so it can be read and searched directly. The original PDF (202004 version) is available for download at the end of this page.

1. Scope

SMD LEDs are suitable for general electronic products (e.g. instrument equipment, consumer equipment and home appliances). In the event that the product needs to be applied to certain special reliability requirements, as well as when product failure may endanger life and health equipment (e.g. aviation, transportation, traffic control equipment, medical and life support systems), it is necessary to contact Opto Plus LED Corp.

2. Storage Conditions

SMD LEDs must be stored in a clean environment. An unopened moisture barrier bag shall be stored at a temperature below 30°C with humidity below 60%RH.

3. Floor Life After Opening

After the moisture barrier bag has been opened, the SMD LEDs should be used according to the floor life specified in the table below.

Unused products must be repacked in an anti-electrostatic package, folded to close any opening, and then stored in a moisture-proof cabinet.

4. Baking

Baking before soldering is recommended when the package has been unsealed for 72 hours. The conditions are as follows:

• 60 ± 3°C for 12 ~ 24 hours at below 5%RH — taped reel type.
• 100 ± 3°C for 45 min ~ 1 hour — bulk type.
• 130 ± 3°C for 15 ~ 30 min — bulk type.

5. Soldering Pads

Soldering pads (cathode and anode) are plated with gold, tin, or other metals. If the soldering pads are exposed to open air over the long term, the pads easily become oxidized and cause poor soldering. Therefore, opened but unused parts must be stored in a moisture-proof cabinet — ideally kept in their original moisture barrier bag inside that cabinet.

6. Moisture Control for Components Already Mounted on PCB

• If the PCB will not undergo additional reflow soldering or high-temperature processes, then no special treatment is required for the mounted moisture-sensitive SMD LEDs.
• If the PCB will undergo multiple reflow soldering or other high-temperature processes, including rework, then the SMD LEDs’ cumulative exposure time until the final high-temperature process must be controlled to within the specified time limit (please refer to the floor life specification in item 3).

7. Reflow Soldering

Recommended soldering paste specifications:

• Operating temperature: above 217°C, 60 ~ 150 sec.
• Peak temperature: 260°C max., 10 sec max.
• Reflow soldering should not be done more than two times.
• Never attempt the next process until the component has cooled down to room temperature after reflow.

The recommended reflow soldering profile, measured on the surface of the LED terminal, is as follows.

Notes:

1. Do not cause stress to the LEDs while they are exposed to high temperature.
2. The maximum number of reflow soldering passes is 2 times.
3. Reflow soldering is recommended. Other soldering methods are not recommended as they might cause damage to the product.

8. Manual Soldering

Manual soldering is not recommended unless necessary, such as when repair or rework is required.

9. Soldering Iron Conditions

• Soldering iron power shall not exceed 30 W.
• The recommended maximum temperature for leaded and lead-free soldering is 300°C and 350°C respectively.
• For blue (typical λd 465 nm), green (typical λd 525 nm), and all white SMD LEDs, the maximum soldering iron temperature is 280°C.
• Do not place the soldering iron on the component for more than 3 seconds.

10. Reworking

• The tip of the soldering iron should never touch the LED body or the lens.
• Rework should be completed within 5 seconds under 260°C.
• The iron tip must not come into contact with the copper foil.
• A twin-head type iron is preferred.
• For the rework of SMD LEDs without side surface leads, refer to QFN rework methods. Special attention should be paid to proper thermal isolation of the surrounding electronic components.

11. Cleaning

The following are the cleaning procedures after soldering:

• An alcohol-based solvent such as isopropyl alcohol (IPA) is recommended.
• Temperature × time should be 50°C × 30 sec, or below 30°C × 3 min.
• Ultrasonic cleaning: < 15 W per bath; bath volume ≤ 1 liter.
• Curing: 100°C max., < 3 min.

12. Electrostatic Discharge Protection

SMD LEDs are electrostatic discharge (ESD) sensitive. Common symptoms observed in an ESD-damaged device include unusual forward voltage and reverse current measurements. To prevent SMD LEDs from being damaged by ESD, please adhere to the advice listed below.

• Minimize friction between the product and its surroundings to avoid static buildup.
• All manufacturing and testing equipment should be grounded.
• Avoid handling by hand without antistatic garments and wrist straps, and avoid the use of common plastic containers, transport mediums or tools.
• All personnel in an ESD protected area should wear antistatic garments and wrist straps.
• Set up ESD protection areas using grounded metal plating for component handling.
• All workstations that handle IC and ESD-sensitive components must maintain an electrostatic potential of 150 V or less.
• Relative humidity levels maintained between 40% and 60% in the production area are recommended to avoid the build-up of static electricity.
• Use anti-static packaging for transport and storage.
• All anti-static equipment and procedures should be periodically inspected and evaluated for proper functionality.

13. Circuit Design Notes

• Protective current-limiting resistors may be necessary to operate SMD LEDs within the specified range.
• SMD LEDs mounted in parallel should each be placed in series with its own current-limiting resistor.
• Customers should apply resistors for protection; otherwise a slight voltage shift will cause a large current change, and burn-out will happen.
• The driving circuit of the customer’s main PCB should be designed to avoid reverse voltages and transient voltage spikes when the circuit is powered up or shut down.
• High temperatures can reduce SMD LED performance and reliability. Keep SMD LEDs away from heat sources for best performance.
• It is recommended to operate SMD LEDs at the binning current of 20 mA to reduce visible differences in color and intensity. If SMD LEDs are to be driven at a very small current (e.g. 2 mA or 5 mA), please contact Opto Plus first.
• Excess driving current and/or an operating temperature higher than the conditions recommended in the specification may affect the life of SMD LEDs.

14. Restrictions on Product Use

• If a reverse bias is continuously applied to SMD LEDs, it can cause damage.
• The information contained within this document is subject to change without notice. Before referencing this document, please confirm that it is the most current version available.
• Not all SMD LED types are available in every country.
• The light output from UV, blue, and white SMD LEDs may damage the human eye when viewed directly.
• Prolonged reverse bias should be avoided, as it could cause SMD LEDs to develop leakage current or a short circuit.
• Avoid stress on the resin at elevated temperature.
• Avoid rubbing or scraping the resin with any object.
• Electrostatic discharge may cause damage to the component. Please ensure that the equipment is properly grounded. Use of an ionizer fan is recommended.

15. Terms and Conditions for the Usage of This Document

• The information included in this document reflects representative usage scenarios and is intended for technical reference only.
• The part number, type, and specifications mentioned in this document are subject to future change and improvement without notice. Before production usage, the customer should refer to the latest datasheet for the updated specifications.
• When using the products referenced in this document, please make sure the product is being operated within the environmental and electrical limits specified in the datasheet. If customer usage exceeds the specified limits, OPTO PLUS will not be responsible for any subsequent issues.
• The information in this document applies to typical usage in consumer electronics applications. If the customer’s application has special reliability requirements or life-threatening liabilities, such as automotive or medical usage, please contact an OPTO PLUS representative for further assistance.
• All SMD LED operation should refer to the datasheet and these application notes.