What if you soldered vertical pins (nail shaped) to the Cree pads, made holes in the PWB and mounted the Cree LED on the back side of the PWB with the pins in the through holes? Or in other words, mounted the PWB over top of the Cree LED letting it shine through the board?
Al Grant email@example.com wrote in news: firstname.lastname@example.org:
Pre-heat the entire unit to about 150F (65.5 C)
That way, when you go to flow the solder joint, it will ocuur correctly.
Without pre-heat, the unit sucks up all your solder tip's capacity to sink heat into the joint.
With pre-heat, the forming of the good solder joint in easy because you are not requiring the solder iron to sink so much heat in. Use a flux pen to wet to pads lightly first. Also SPC (silver plated copper) wire takes solder way easier and better than tin plated copper, especially if it has PVC sheathing.
Another way is to use solid wire (SPC as well) and form the runs like "hard line", cover with teflon tubing and they will actually help sink heat away from the unit when in operation a little bit.
Yeah, for removability and reliable connection, wire-wrap solutions are good. It doesn't have to be the skinny 30-gage wire, there's tooling for heftier wires. Hand-soldering looks like the way to go for that package, the heatsinks and epoxy come later (epoxy can mess with solder adhesion, and heatsinks are not very reflow-friendly anyhow).
Some CF lamps are done with wire-wrap to board, if you want to see examples.
John Larkin <jlarkin@highland_atwork_technology.com> wrote in news: email@example.com:
No teeth needed if One uses SPC bus wire with a teflon tube on it cut the the right length. The Silver takes the solder immediately and perfectly.
Heavy gauge transformer wire shaped to ride mid air from point A to point B and Point C to point D as if they were little steam pipes. Just like the above SPC jumpers would. Insulated, and therfore insulative, and stiff, so also supportive. The heaviest gauge defined by the smallest hole of each pair of holes meant for each wire. Likely the same but could differ. If the LED AND the PCB are "fixed" to the same mechanical device (heat sink?) then flexible wires ar enot needed, but usually get used because shaped solid wires require (more) preparation. They usually key designs toward quick manufacturablity with (as) little or no human intervention or fabrication steps.
I bought a tank robot with ultrasonic obstacle sensing and an HD camera and drive motors and tracked wheels... It came in pieces though. I had to put it together and then add the rPi to it.
Sometimes things like this come not quite complete so they can sell it to you cheaper.
Hey, I know... Use a small gauge Litz wire, like 20 Ga 40 strand or such. (40 strands of 44 AWG). Very flexible. Almost like speaker cone wire.
Wirewrap is a mechanical bond with only ductile wire and a post; it's cheap, robust, and fast. If you can solder a post into a plated-through hole, subsequent attachment to that post is a two-second task.
Here's a wire-wrapped logic board...
The logic wirewrap was mainly fine (30 ga) wire, onto 0.025" square posts. Other appliances also use wire-wrap, typically 24ga, it's a reliable connection method. Figuring out just which posts need the next wire, though, is not reliable. For a simple two-terminal item, which benefits from wire compliance (reducing strain on the joint) hand-solder and wire-wrap are both convenient.
It's not robust or cheap or fast and signal integrity is ghastly. Crosstalk is big and different on every board. Impedances are unknown.
PDP11s were buggy nightmares until the wire-wrapped unibus backplanes were replaced with PC boards. Then they got somewhat better.
Times every post on the board.
Yikes! What a mess. Crazy labor intensive, even if you have an automatic wrapper.
It's the traveling-salesman problem. I've written programs to sort netlists to minimize wire-wrap runs for automatic wrap machines. I don't think there is a true solution, but some simple algorithms can do pretty good.
But nobody uses DIPs in sockets any more. Maybe a few amateurs.
When I was a grad student, circa 1985, the good folks at Grinnell donated a large image processor gizmo that replaced an already-ancient Lithicon scan converter.
It allowed us to turn essentially arbitrary scanning microscope images into video and (eventually) hardcopy form.
It was a 42U EIA rack with a wire-wrapped backplane showing--all the wires were yellow. Even at the clock rates of the era, I have no idea how they made that work reliably or produced it even vaguely economically.
But bunches of
Problem is, it isn't that easy to strip without nicking it. I sometimes use fine pliers to grab the insulation and tear it off, but that's tough in tight spaces when one end is already attached.
Am 02.09.21 um 05:55 schrieb firstname.lastname@example.org:
Wire Wrap may be ancient, but it was not horrible. It was absolutely reliable. In the institute where I made my 1st diploma thesis in EE we had a hall where the floor was plastic with 2 cm dia circles on it as anti-slide, LEGO style. There was a ritual with new 19" crates: when they were finished, the were put on a lab car and moved 100 meters through that hall. When they survived that, they would survive a start with a Saturn 5 rocket. There were failures, but there was never ever a wire wrap failure.
This here is from my diploma thesis in CS. Yes, one tries to stay on one's home turf. Multibus 1 80186 with WesternDig floppy controller, Zilog 2*Z8500 serial + parallel IO, TI TMS9914 GPIB/Ieee488, 1MB DRAM. The 80186 is part-time Multibus master, part of the 1 MB DRAM is dual-ported MB-slave, could run DOS. :-) That was at the time when you had to have excellent connections to Intel to get a proto 80186. Hand-wrapped by yours truly.
Some chips have found a more interesting job in the mean time.
Joe Gwinn email@example.com wrote in news: firstname.lastname@example.org:
PVC sheathing is the nastiest crap whenever there is soldering involved. It works fine on cinch type terminations. But soldering melts the sheathing almost immediately at which point it shrinks away from the heat. Nasty stuff.
One does not use a stripper correctly if one is a "clasp and drag type stripping idiot. The right way to use the stripper is to make the cut at the strip point, then release and move over a few mm and grab the sheath with the same strip hole without cutting it through and pull the strip segment off. Forming the cut and then dragging the strip segment off is the WRONG way to strip a wire.
It goes like this... cut-release-shift-regrab-pull off.
The cut-drag method is stupidity in your workers rearing their ugly don't know much zero common sense heads. A failure on the part of the person that taught the idiot how to use the strippers.