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NEED SOLDERING HELP
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NEED SOLDERING HELP

by Sajeel on Fri May 04, 2018 4:50 pm

What soldering method (Hot air flow, wave soldering, hand soldering, machine soldering ................... ..... ) should be used to solder neo-pixels on a Flexible printed circuit boards?

What should be the soldering temperature at which no led will damage?

Thanks'

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Re: NEED SOLDERING HELP

by adafruit_support_mike on Sat May 05, 2018 12:03 am

Reflow soldering would be the easiest, but the temperature and heating profile would depend on the kind of solder you use, the size of the oven you use, and several other factors. There are no one-size-fits-all answers.

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Re: NEED SOLDERING HELP

by Sajeel on Sat May 05, 2018 5:44 pm

In particular, Neopixels are temperature susceptible. what type of soldering method is preferable on neopixels if I am gonna soldering it on flexible Printed circuit board?

Btw, your previous answer was a great help for me.

Thanks.

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Re: NEED SOLDERING HELP

by adafruit_support_mike on Sat May 05, 2018 11:55 pm

We use a standard lead-free reflow process for our NeoPixel boards, but usually have to run a few prototype boards to find the exact temperatures and timing that work best.

In general, do a good preheat phase at temperatures that don't put any stress on the pixels, then a short hot phase to melt the solder and make the joints. You'll need to experiment to find the values that work best for you though. Everything about the board's size, layout, surface treatment, component count, and component density will factor into the reflow profile. So will the size, power rating, and thermal mass of the oven you use, the kind of solder you use, and the kind of flux you use. It's all interconnected.

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Re: NEED SOLDERING HELP

by Sajeel on Sun May 06, 2018 10:09 am

I have downloaded eagle cad files of neopixel based 8x8 matrix from Adafruit website to see how you make flexible led panels and to make my own and to learn new techniques and tips. Moreover, I had also ordered two neopixel based rgb led panels to see physically how it looks and to observe the engineer practices. I had observed the panel was very thick and have good flexibility. So I want to know what is the thickness of flex pcb of your neopixel based led panels so I can learn and explore more about it.

Thanks Adafruit for continuously helping me and answering me.

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Re: NEED SOLDERING HELP

by adafruit_support_mike on Mon May 07, 2018 11:53 pm


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Re: NEED SOLDERING HELP

by Sajeel on Wed May 09, 2018 2:12 pm

What should be the coverlay thickness and what kind of coverlay films can be used on flex circuits especially for flex led panels?

I am really thankful for Adafruit responses. THANKS ADAFRUIT

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Re: NEED SOLDERING HELP

by adafruit_support_mike on Thu May 10, 2018 12:12 am

There are too many options and too many variables to give a meaningful answer. You'll need to talk to the board house to see what they have, and what they recommend.

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Re: NEED SOLDERING HELP

by Sajeel on Thu May 10, 2018 3:38 am

I have uploaded my design file so you can check whether I am going right or not. I have tried to make it 100% reliable. Please check, I have just one doubt related to data/clock signal. Upon bending maybe due to stress it will break. What o you recommend.

Thanks
Attachments
Design1.png
Design1.png (121.44 KiB) Viewed 132 times

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Re: NEED SOLDERING HELP

by jps2000 on Thu May 10, 2018 6:22 am

do you miss capacitors?

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Re: NEED SOLDERING HELP

by Sajeel on Thu May 10, 2018 6:34 am

Yes, because I have used sk6805-2427 led and this led is very small and the distance between two consecutive leds is very small too so it is very difficult to place capacitors in between them. Moreover, I want to use this panel in location where I need to maintain flexibility without disturbing led placements. If I use capacitor, the panel will no longer be flexible because you know space between capacitors will occupy. However, to prevent from on rush current to leds I have used 10uf in parallel with 0.1uf ceramic capacitor on the input side.

What do you suggest on bending does data line endures the stress??

Your suggestions and principles are highly important for me.

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Re: NEED SOLDERING HELP

by jps2000 on Thu May 10, 2018 7:57 am

When you look into app circuit they suggest 100nF per chip. however you have low impedance supply planes so every 5 to 10 leds you should place a smd cap or at least provide a place for it. Between the leds is enough room for it.
this avoids not only operation problems but should also lower EMI.
Wrt bending: it is clear that bending of a flexprint can only happen between components. so placement of components should take care of that.
Look careful in supplier spec of flexprint what radius is allowed.
Note that using components in series always have the danger that in case a device stalls in particular at the beginning the whole row or panel is dead.
You may overcome this by having groups with individual control

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Re: NEED SOLDERING HELP

by Sajeel on Thu May 10, 2018 9:53 am

I have attached snapshot of my design. Please refer to this.

For the case of bending, you said, stress occur on traces that are passing in between leds. What should be the best way to pass data lines? and what should be the best placement of leds although i cannot disturb the leds because this is an optimized design and according to the needs where it gonna place.

What do you mean by this statement: "Look careful in supplier spec of flexprint what radius is allowed". I did not understand what really radius is?

neopixels data/clock are always connected in series. If data line of first led breaks so it means whole bunch of leds will not glow. According to you statement: "You may overcome this by having groups with individual control" What I interpret is: I must have to use some redundant lines to provide data to leds in case if one line breaks then redundant line should take the control.

Your guidelines are highly important for me. Thanks for continuous helping.
Attachments
Design.JPG
Design.JPG (97.41 KiB) Viewed 95 times

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Re: NEED SOLDERING HELP

by jps2000 on Thu May 10, 2018 12:06 pm

I am sorry when my suggestions confuse you more than they help.

I assume that you want to wrap the flexprint around something? And this something is what? A cylinder?, a cloth? Is ist bend just once in lifetime ( glued on a cylinder?) or is it on a cloth bend thousands of times?. The cylinder has a radius and that is what I meant. A thinner cylinder cause more bending thats clear.

~ 250 Neopixel are connected in series. You determine how many you put in series. For example in your case you may control every row from another controller pin. The row is then the "group " I was talking about. Obviously it depends what pattern you like to display if this kind of grouping may help or not.
It is a kind of risk assessment what happen if a component or - more likely a solder joint - fails. But you dont need to go for that its your decision.

I do not share your concern about data lines as long as you fulf - il supplier requirements wrt trace with etc.
Stress mainly occurs at solder joints to trace border.

However, I still have concerns about missing capacitors all around

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Re: NEED SOLDERING HELP

by Sajeel on Thu May 10, 2018 12:41 pm

I want to paste this flexible board on a cylinder that has radius of approx. 7cm. What i have understood by your though is that: I need to ask from my manufacturer about the copper foil which is wrapped on a cylinder having same radius as of my cylinder. Am i right ??

Moreover, I have some other customized designs that i want to use in fabrics/clothing, mostly those panels have size of 6x6 inches. And you know, in clothing the panel bend thousand of times. I do not know anything how that problem i will overcome but your support is very important for me.

Apart from this, What do you suggest f i pass data lines not between the leds but direct below the leds on a bottom layer? Is it a wise decision?

You have used one statement in your last reply. here it is: "It is a kind of risk assessment......" I want to know after how many trials Adafruit got success in designing these type of flex. led panels? (This will boost my hope to keep struggle :) )

For the case of capacitors, i will put small capacitors after every 10 leds. Thanks for intimation!

Thank you
Best regards
Sajeel

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