SMT LED alignment on PCB

Little Ghostman said:

Ah what you describe is described as loctite is sold here as loctite spline something or other, it can be had in small amounts but is incredibly expensive (like eye watering expensive), the stuff I used was clear brittle and also used to to stick skin in surgery! The working time is less than 40 seconds, so it does seem we are talking about slightly different adhesives.

There is also a red adhesive sold as a metal adhesive, this will work but I dont recommend getting it very hot as the fumes are awful. So for the record I would assume most in the UK would take super glue to mean the clear 'finger sticker' glue, its easy to forget similar products are slightly different around the world! You have 'Elmers' (love that name!) we have 'PVA' (rubbish name). You have 'sharpi' we have 'Marker', we could do with a kind of Anglo/American dictionary!!

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Please re-read what I said. I use "super glue." It is not even LocTite branded. In the US, it is sold in several versions. Most common are a water "thin" version, "medium" version, and a "thick" slower setting version.

As for "PVA" being a rubbish name. I have no idea what you mean. In the US, "PVA" is used as a generic name for a series of adhesives based on "polyvinyl alcohol,." Hence the name. Depending on other constituents in the formulations, they have various degrees of water fastness and are sold by such designations. I would not recommend them for the SMD fixation process described. They are good wood glues, have reasonably fast grab and decent working times, and have widely replaced older glues that had formaldehyde or related compounds. Most PVA adhesives can be thinned with a little water (<10%) to extend working time without greatly affecting their strength.

John

jpanhalt said:

Please re-read what I said. I use "super glue." It is not even LocTite branded. In the US, it is sold in several versions. Most common are a water "thin" version, "medium" version, and a "thick" slower setting version.

As for "PVA" being a rubbish name. I have no idea what you mean. In the US, "PVA" is used as a generic name for a series of adhesives based on "polyvinyl alcohol,." Hence the name. Depending on other constituents in the formulations, they have various degrees of water fastness and are sold by such designations. I would not recommend them for the SMD fixation process described. They are good wood glues, have reasonably fast grab and decent working times, and have widely replaced older glues that had formaldehyde or related compounds. Most PVA adhesives can be thinned with a little water (<10%) to extend working time without greatly affecting their strength.

John

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No you misread. I didnt sugest using PVA for components, I was pointing out the different names things are known under. PVA is a general glue for wood and paper etc I didnt suggest using it on a pcb!

OP just use through hole LEDS

Not cheap. Limited life. Non contact dispensing, Epoxy based. https://na.henkel-adhesives.com/industrial/product-search-1554.htm

@KISS, Your link has well over 1000 different adhesives. Can you narrow it down to 100 or so?

Let me re-emphasize what I consider to be a major advantage of CA adhesives for this purpose over most other adhesives, including epoxies. They volatilize at soldering temperatures. Pufff, they are gone, and you have a nice solder joint. Epoxies do not offer that. Of course, if you have an assembly line with robotics, that may not be such an issue. But, shaky-hand assembly lines benefit from that non-critical aspect of were the adhesive is placed. Of course, on 805 devices, I try to keep it between the solder pads, not on them. But a little error doesn't seem to make much difference. With an epoxy (they tend to char rather than volatilize), that might make a difference. Also, with most epoxies, the catalyst and resin are pre-mixed. Such 2-component adhesives have limited pot life and /or long cure time. Some resins can be cured with UV light (namely polyesters). But, why go there? CA is single component, and if treated nicely, a puddle will stay on a copper board for an hour or so, but polymerize when placed on a PCB and pressed with the component.

John

OK, One of THOSE URL's. Type 3621 in the search box.

This http://www.loctite-kleje.pl/sg_obrazki_/00002475_normg_001.pdf is much better than what I posted/

BobW said:

LED bar graph display

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I was playing with a LED vu meter. Some thing like this but MORE.
Using a micro not analog parts. Had problems with LED alignment so.....
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The LED part was a problem. Tried LED array like this:
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Wound up using a very small LCD display. You can get little ones used in cell phones.
Did like this:
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and like this:
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Did not do this! Beyond my ability.
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