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SMT LEDS SOLDERING

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#56399

SMT LEDS SOLDERING | 9 September, 2008

Hi All,

we poduce diferent kind of Keyboards, and use a lot of SMT LEDs.When I looking for reflow soldering Conditions i n the Data Sheets, usually I find "IR-reflow" Soldering profile.Our Reflow owen have onli conventional heating.Is that problem? We have a lot of defects of component LTST T670 (LITEON). is there some with similar problems?

thanks

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#56410

SMT LEDS SOLDERING | 9 September, 2008

We consider "IR-reflow soldering profile" to be the supplier's recommended reflow thermal profile that a component temination 'sees' for proper soldering, regardless of the method used to reach that temperature.

When you say, "We have a lot of defects of component LTST T670 (LITEON)," we don't know type of or anything else about defect that you see. So, if you provide more information, it would be helpful. For instance: * Describe the defect, maybe attaching a picture * Talk about the distribution [scope and breadth] of the problem, including a single lot or from various lots and over components and component types on the board * Tell us about the board (ie, thickness, type, solder mask, pads coating, pad size, etc) * Describe the component(s) (ie, type, termination finish, etc) * Take us through the process steps that proceed the problem, including the thermal profile and its control * Help us with the solder and the flux being used * When measuring temperature, describe how and where is it being measured

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#56464

SMT LEDS SOLDERING | 11 September, 2008

10x , davef, about LEDs - the problem is , that about 1% of all leds wich we soldering have some defect - not blinking, when I make functional test.I chek 300 leds before solderinig - all is ok.After reflow 1 led not blinking, after SW 3 leds not blinking.There have components for 3 different lots.I send you the data sheet.Our soldering profile is similar of recommended soldering profile.

Attachments:

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#56484

SMT LEDS SOLDERING | 11 September, 2008

How are they being stored and handled? It might be an MSD issue.

I think IR reflow would be a worst case scenario.

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#56504

SMT LEDS SOLDERING | 12 September, 2008

Questions are: * Why aren't the defective LED blinking? * Do the defective LED blink when removed from the board and tested according to the functional test that you used prior to assembling the boards? * Do the defective LED blink after the solder is 'touched' with a soldering iron? * How closely did you follow the ESD protection guidance on the data sheet? * What is the process that you call "SW", where the three LED are not blinking?

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#56507

SMT LEDS SOLDERING | 13 September, 2008

Hi,

Why aren't the defective LED blinking? * Do the defective LED blink when removed from the board and tested according to the functional test that you used prior to assembling the boards? - yes,some of them. * Do the defective LED blink after the solder is 'touched' with a soldering iron?yes, some of them.put, after few hours again stoped blink. * How closely did you follow the ESD protection guidance on the data sheet?We use ESD protection gloves * What is the process that you call "SW", where the three LED are not blinking? I mean solder Wave process,

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#56508

SMT LEDS SOLDERING | 13 September, 2008

Tell us more about your ESD gloves. * How are the grounded? * How do you check the effectiveness of the ground? * Where do you get these gloves? Can you attach a link to the supplier or a data sheet? * How measurements of the LED compare with the information from the manufacter's data sheet? [copied below]

"ESD-damaged LEDs will exhibit abnormal characteristics such as high reverse leakage current, low forward voltage, or � no lightup � at low currents. To verify for ESD damage, check for � lightup � and Vf of the suspect LEDs at low currents. The Vf of � good � LEDs should be >2.0V at 0.1mA for InGaN product and >1.4V at 0.1mA for AlInGaP product."

It's common for ESD protection programs to conform to ANSI/ESD S20.20 - Protection of Electrical and Electronic Parts, Assemblies and Equipment (Excluding Electrically Initiated Explosive Devices) [Euroland EN-100015 has been superseded by EN-61340]. ANSI/ESD S20.20 can be downloaded from http://www.esda.org/s2020.html

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#56515

SMT LEDS SOLDERING | 15 September, 2008

We've found that storage of other LEDs from this manufacturer can be very important. On page eight of the datesheet you attached, it says: "It is recommended that LEDs out of their original packaging are IR-reflowed within one week. For extended storage out of their original packaging, it is recommended that the LEDs be stored in a sealed container with appropriate desiccant, or in a desiccators with nitrogen ambient. LEDs stored out of their original packaging for more than a week should be baked at about 60 deg C for at least 24 hours before solder assembly." Make sure you're following these recomendations, or you could be asking for problems.

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#56552

SMT LEDS SOLDERING | 17 September, 2008

We have seen this same defect. Led's not blinking during test and some tops popping off. Ended up being an msd problem. most of the lite-on components are msl level 4-6. We now bake and track them no problems seen in a while.

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#56740

SMT LEDS SOLDERING | 29 September, 2008

Have seen similar problem before with regards the MSD being the cause. But also seen similar defects being found at functional test as the in-circuit test was injecting to much current during test. The devices were walking wounded afterwards. The in-circuit test was attempting a colour check and using a light pipe to take light to sensor. The current was raised to get "stronger" signal to sensor. But even the standard LED test can be a danger.

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