The complete text of this application note is reproduced below for reference. The original PDF (2020.04 version) can be downloaded at the end of this page.
Table of Contents
1. Scope
Through Hole LED Display and SMD LED Display are suitable for general module design products. In the event that the product needs to be applied to certain special reliability requirements, or when product failure may endanger life and health equipment, it is necessary to contact Opto Plus LED Corp.
2. Storage Conditions
Through Hole LED Display should not be exposed to an environment where a high level of moisture or corrosive gases are present.
Unopened package
| Product | Temperature | Humidity |
|---|---|---|
| Through Hole (DIP) LED Display | 5°C ~ 30°C | Below 60%RH |
| SMD LED Display | 5°C ~ 30°C | Below 60%RH |
If the storage conditions do not meet specification standards, the pins may become oxidized. Re-plating and re-sorting before use is suggested. We also suggest that customers use up the products as soon as possible and avoid long-term storage of large inventories.
Opened package
| Product | Temperature | Humidity | Storage time |
|---|---|---|---|
| Through Hole (DIP) LED Display | 5°C ~ 30°C | Below 60%RH | Unlimited (MSL as Level 1) |
| SMD LED Display | 5°C ~ 30°C | Below 60%RH | Within 4 weeks (MSL as Level 2a) |
3. Pins and Soldering Pads
The pins of the LED Display and the soldering pads (cathode and anode) are plated with gold, tin, or other metals. If soldering pads are exposed to open air over the long term, it is easy to cause pad oxidation and poor solderability. Therefore, opened but unused parts must be stored in a moisture-proof cabinet.
4. Moisture Control for Components Already Mounted on PCB
- If the PCB will not undergo additional reflow soldering or high-temperature processes, 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 cumulative exposure time of the SMD LEDs until the final high-temperature process must be controlled to within the specified time limit.
5. Through Hole Display Mounting Method
Lead forming
- Do not bend the component pins by hand without proper tools.
- The pin should be bent by clinching the upper part of the pin firmly, so that the bending force does not damage the plastic body.
Installation
- The installation process should not apply stress to the pins.
- When inserting for assembly, ensure the pin pitch matches the hole pitch on the customer’s PCB, to prevent spreading or pinching the pins.
- Through Hole Display shall be placed at least 5 mm from the edge of the PCB, to avoid damage caused by excessive heat during wave soldering.
- For LED Display with 90-degree pin bends, OPTO PLUS recommends at least 10 mm of clearance between the display and the edge of the PCB during soldering and assembly.
6. Soldering Condition
Through Hole LED Display — wave solder profile
| Stage | Duration | Ramp rate / temperature |
|---|---|---|
| Preheat stage | 20 ~ 50 sec | 2 ~ 5°C per sec |
| Soak stage | 30 ~ 120 sec | Up to approx. 125°C |
| Wave stage | 5 sec | 260°C max (solder melting reference 183°C) |
| Cooling stage | 180 sec max | 2 ~ 5°C per sec |
- Recommended pre-heat temperature of 105°C or less (as measured with a thermocouple attached to the LED pins) prior to immersion in the solder wave, with a maximum solder bath temperature of 260°C.
- Peak wave soldering temperature between 245°C ~ 225°C for 3 sec (5 sec max).
- No more than one wave soldering pass.
Soldering general notes
- Through-hole displays are incompatible with reflow soldering.
- If components will undergo multiple soldering processes, or other processes where the components may be subjected to intense heat, please check with OPTO PLUS for compatibility.
SMD LED Display — lead-free reflow profile
| Stage | Temperature | Duration / rate |
|---|---|---|
| Ramp-up | Up to 150°C | 3°C/sec max |
| Preheat / soak | 150°C ~ 200°C | 60 ~ 120 sec |
| Ramp to peak | Above 217°C | 3°C/sec max |
| Peak | 255°C ~ 260°C | 5 sec max |
| Cooling | — | 6°C/sec max, 100 sec max |
- We recommend a reflow temperature of 245°C (+/- 5°C).
- The maximum soldering temperature should be limited to 260°C.
- The number of reflow processes shall be 2 times or less.
7. Manual Soldering
Manual soldering is not recommended unless necessary, such as when repair or rework is required. The soldering iron should not exceed 30 W in power. The tip of the soldering iron should not touch the plastic body, to avoid heat damage.
| Iron tip temperature | Time | Position |
|---|---|---|
| 350°C max | 3 s max | The iron should be situated at least 2 mm away from the root of the leads |
8. Reworking
- Rework needs to be finished within 3 sec at 350°C.
- The head of the soldering iron cannot touch the copper foil.
9. Cleaning
- Mild “no-clean” fluxes are recommended for use in soldering.
- If cleaning is required, OPTO PLUS recommends washing the parts with water only. Do not clean the parts with harsh organic solvents, because they will damage the plastic body.
- The cleaning process should take place at room temperature, and the parts should not be washed for more than one minute.
- When water is used in the cleaning process, we suggest removing excess moisture from the parts immediately with air drying afterwards.
10. Circuit Design Notes
- Protective current-limiting resistors may be necessary to operate the LEDs within the specified range.
- LEDs mounted in parallel should each be placed in series with its own current-limiting resistor.
- The driving circuit should be designed to protect the LED against reverse voltages and transient voltage spikes when the circuit is powered up or shut down.
- The safe operating current should be chosen after considering the maximum ambient temperature of the operating environment.
- Prolonged reverse bias should be avoided, as it could cause the LED Display to leak current or short circuit.
11. Electrostatic Discharge Protection
Static discharge can result when static-sensitive products come in contact with the operator or other conductors. To prevent LED Display 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.
- 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.
12. 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, customers 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 Through Hole LED Display / SMD LED Display operation should refer to the datasheet and application notes.