Bead LEDs and Star board/heatsink

[Michael GilliganParticipant @michaelgilligan61133]

I have just made a terrible job of my first attempt at mounting a bead LED onto one of the Star boards.

1. The syringe of heatsink paste initially dispensed liquid instead of paste
2. The identifying mark on the LED tab is almost invisible; and when eventually found, is cryptic
3. This was my first try with lead-free solder … and I despise it

Not a big problem, because they’re cheap and I have plenty to play with; but I would be grateful for advice from anyone competent.

MichaelG.

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P.S. I was using a Weller WTCP iron.

[Michael GilliganParticipant @michaelgilligan61133]

Advice from the experts, please

[Martin KyteParticipant @martinkyte99762]

As you dont specify what led you are using I'll assume they are surface mount.

This is what I do. Tin the pads of the Heat sink board. Remove excess with solder braid. You need a big iron for this stage.

Tin the LED's or LED and likewise remove excess solder from the pads.

Locate LED or LEDs correctly on th eboard and transfer the whole lot to a hotplate at a suitable temperature. I use 220 deg but then I have solder to suit.

I can do LED's with a thermal pad like this without any trouble.

With Heatsink board you really have to preheat the board whatever way you go about things.

regards Martin

[Nick Clarke 3Participant @nickclarke3]

Liquid flux has helped me, but lead free solder took some getting used to

[Neil WyattModerator @neilwyatt]

Try using solder paste. Be aware it doesn't have a great shelf life.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin Kyte on 22/04/2020 16:44:57:

As you dont specify what led you are using I'll assume they are surface mount.

[…]

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Sorry, Martin … I had assumed [wrongly, it appears] that all ‘Bead’ LEDs and ‘Star’ boards were of the same general [surface mount] style. 

Thanks for the advice.

MichaelG.

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Similar products to mine are listed here:

https://www.ebay.co.uk/itm/10x-50x-1W-3W-5W-7W-LED-SMD-COB-Chip-With-Star-PCB-High-Power-Beads-White-Light/372261574533

I have Bead LEDs and bare Star boards upon which to mount them.

Edited By Michael Gilligan on 22/04/2020 18:30:37

Edited By Michael Gilligan on 22/04/2020 18:37:16

[Michael GilliganParticipant @michaelgilligan61133]

Thanks also to Nick & Neil

MichaelG.

[Anonymous]

Some pointers:

Heatsink paste tends to separate in the tube, just expel the liquid on some scrap and bin it

Forget lead free solder and use tin/lead solder

In this application forget solder paste and liquid flux

To an extent I agree with the procedure set out by Martin. I'm not sure of the size of the LED or board, but is a heatplate or pre-heating needed? For soldering I use an 80W iron running at 350C.

Unfortunately LED markings are often not clear. Worse, while the mark normally indicates the cathode it's not universal.

Andrew

[Ian PParticipant @ianp]

Is there a special reason you want to use unleaded solder?

I would just use common 60/40 by tinning both pads, putting conductive paste on the LED and hold it in place with the tip of a scriber or toothpick and touch the tip of the soldering iron onto each tab.

Solder paste is another option but its expensive if you only need a little bit as it all seems to have limited life. It may be that for amateur/hobby use the 'use by' date can be taken with a pinch of salt unless you are making something critical.

I'd not heard the term 'bead' LED before but thought you might be referring to something like this Very small LED now they would be fun! (0.65 x 0.35 x 0.2mm)

Ian P

[Michael GilliganParticipant @michaelgilligan61133]

Thanks, Andrew and Ian

• The heatsink paste separation was just a surprise [no real problem]
• I tried lead-free solder because that’s what Nanny says we should use [and the chap who sold me the Weller had included some] … probably won’t bother again !
• Sorry for not being exact about the LEDs and boards … ebay is awash with similar items, using those descriptions, so I assumed they were pretty standard
• I do have some very small surface-mount LEDs to solder sometime …
• Haven’t done much soldering for best part of 20 years, so I definitely need practice and probably need to learn some new tricks

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

For my penance:

.

MichaelG.

[Author]

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