Cutting a Cree XPG star.. how do you solder after that?

[KevinL]

I'm looking at one of these XPG stars....
http://www.dealextreme.com/details.dx/sku.44305

Unfortunately I am going to have to cut it to 8mm size to fit on a turbosink, which means removing the existing solder pads. Is there a way to scrape off enough insulation from the top to reveal additional PCB traces that I can create new solder pads from?

 

[AnAppleSnail]

I'm looking at one of these XPG stars....
http://www.dealextreme.com/details.dx/sku.44305

Unfortunately I am going to have to cut it to 8mm size to fit on a turbosink, which means removing the existing solder pads. Is there a way to scrape off enough insulation from the top to reveal additional PCB traces that I can create new solder pads from?

You might be better soldering to the corners of the LED. I've never had good luck digging out traces.

 

[ShineOnYouCrazyDiamond]

I've had success using the flat edge of an x-acto knife to drag it across the top cover and slowly expose the copper trace. Just don't use the point to dig down into it.

 

[Mettee]

The guy that makes the brass drop ins for E series surefires(kuku?) solders directly to the led. Almost all the star is cut away with the method he uses. I have seen them up close and they look good and work just fine. It might be easier to solder to the led. You will for sure need a small point on your iron, and small wire.

 

[tx101]

I use XPGs mounted on 10mm boards that are available from Cutter.
I then use a nail clipper to cut the board to size.
If you wanted a neater looking board you could use a file but be careful
not to damage the dome.

Alternatively you could get XPG bare emitters and reflow them onto
Rebel 8mm boards that are available from The Sandwich Shoppe

Soldering onto copper traces or onto the emitter itself sounds way too
difficult for my tried old eyes :sigh:

 

[Justin Case]

You could solder to the pads on top of the XP-G substrate board. But they are very tiny.

I also thought that Kuku/Veleno Designs soldered to those pads for their E-Series tower, but perhaps they changed in Version 2 of the tower. It seems clear that Kuku now solders to the side of the XP-G, taking advantage of the recommended Cree solder pad configuration:

If you measure the E-series reflector opening, you can see that even after trimming/filing off the hookup wire solder pads on the MCPCB for the XP-G to fit through, you still have the small 0.5mmx0.4mm "stubs" (for lack of a better term) that protrude out from the LED+ and LED- solder pad contacts. The two photos above show the hookup wires soldered to those stubs, not to the pads on the top of the XP-G substrate board.

The DX photos are a bit lacking in contrast, but the MCPCB might allow you to use the same connection approach as shown above.

 

[KevinL]

Aha, many thanks!!

I have a couple of the Steve Ku E2e modules, they are awesome. I was looking at mine and indeed it is soldered into the side.

So the stubs aren't just solder balls left over from the reflow process as I thought they were.. you can actually use them.....

I think I'll give the DX star a try. I suppose I'm out $7 if I fail, but I've done worse before..... (the road to hotwire glory is lined with the debris of thousands of shattered bulbs..)

 

[Fichtenelch]

Why you just don't buy it on a smaller star?
They sell it completely ready on a really small one

 

[KevinL]

Cool, thanks for the tip! That is a really good find.

The reason why I don't is because of shipping charges. DealExtreme sells the 14mm MCPCB version for less than US$7, whereas once I add shipping and such from the site it comes up to US$17. If I can achieve a similar result with a cutter (and I've cut six stars for other projects recently!), it would be worth saving the additional $10 for beer (to de-stress.. especially if the mod is unsuccessful!)

 

[kosPap]

I think Cutter.com.au also sells 8mm PCB mounted XPGs....postage might be more agrreable...

 

[Justin Case]

As tx101 said, you can trim a 10mm MCPCB to fit on a turbosink (I assume to go into a SureFire TH). An XP-G on an 8mm round MCPCB definitely fits without any trimming needed. You could try removing the XP-G from the 14mm board and reflowing it onto a blank 8mm board from The Sandwich Shoppe. For all diameters, you may have to use a shim or file down the MCPCB to get the LED at the right focus height.

 

[CKOD]

I've had success using the flat edge of an x-acto knife to drag it across the top cover and slowly expose the copper trace. Just don't use the point to dig down into it.

+1 to this, scrape across the top and the mask should come off, just scrape carefully, and dont dig and cut the trace. If you jack up the trace, you can solder to the corners of the LED like others said, so not all is lost.

Soldermask it tough stuff, well bonded to the copper/PCB, pretty solvent resistant, decently abrasion resistant.

 

[alphazeta]

I solder to traces all the time.

As with the other posters, I recommend using an #11 xacto blade to SCRAPE (not cut) away the top layer.

I hold the cutting edge at about 90 degrees to the surface & then scrape. Unless you have ham hands, there isn't that much chance of destroying the trace.

AZ

 

[Justin Case]

Aha, many thanks!!

I have a couple of the Steve Ku E2e modules, they are awesome. I was looking at mine and indeed it is soldered into the side.

So the stubs aren't just solder balls left over from the reflow process as I thought they were.. you can actually use them.....

I think I'll give the DX star a try. I suppose I'm out $7 if I fail, but I've done worse before..... (the road to hotwire glory is lined with the debris of thousands of shattered bulbs..)

Those stubs are really tiny -- I think smaller than the solder pads on top of the XP-G substrate. So upon further review, I think that the Veleno Designs E-series towers uses XP-Gs whose MCPCBs are trimmed back with still some of the hookup wire solder pad area remaining. I mic a SureFire E-series lamp "stem" at a hair over 0.250" diameter. Putting my calipers up to an XP-G on a 10mm MCPCB from Cutter, 0.250" diam would allow over half of the existing hookup wire solder pads to remain after trimming the MCPCB down to size. That would give you plenty of solder pad area to attach your hookup wires.