How to keep certain position of component on a pcb for mass production ? - Page 1
Forum section: electronics / projects

author: Kedar264
author_rank: Regular Contributor
timestamp: December 15, 2016, 06:53:59 am
content: Hello Friends,I am working on some sensores related stuff and wanted to mass produce sensor pcb but the requirement is the mercury tilt switch should be installed in same angle and orientation on pcbCurrently i am thinking about making a plastic assembly that will hold the tilt sensors , are there any better ideas , if you have any better solution please let me know . pictures are attached belowThanks

author: jeroen79
author_rank: Frequent Contributor
timestamp: December 15, 2016, 07:25:14 am
content: How close will your relationship with the factory be?Can you ask for special work? Do you trust them to do it correctly? Can you verify it before too much goes wrong?A custom plastic cradle would make it easier to do the placement in bulk. Just place the switch and cradle, then push switch into cradle.A variant on this is to seperately produce a special part consisting of a plastic cradle with the switch already in it. The workers would then only have to place it onto the board as a regular component.But this will still require a seperate production of this custom part.Perhaps there already exist flat and 45 degree tilt switches?You could split the manufacture process into two steps:1. Normal workers do placement and soldering of the regular components.2. Special workers do placement of the tilt switches according to special requirement.

author: Jeroen3
author_rank: Super Contributor
timestamp: December 15, 2016, 07:55:21 am
content: I recently overhauled some firmware for a tilt sensor thing (old 8051 went eol). It uses a milled aluminium block with two steel balls and a few optosensors. It's as accurate as the m3 screws have wiggleroom in the pcb.How many units are you looking at? Could you use mems sensors?You'll also need to test it, by means of putting the board in a jig and test if the catch and release points are within spec.

author: DTJ
author_rank: Super Contributor
timestamp: December 15, 2016, 08:32:24 am
content: Make an additional very small PCB - a triangle at the required angle, with a tab down one edge.Put a slot in the PCB next to the mercury switchPush the PCB into the slot and lay the switch against it.You can get around having to have a whole additional PCB design by having the triangle parts as a break off from your main PCB.

author: mariush
author_rank: Super Contributor
timestamp: December 15, 2016, 08:56:08 am
content: On the same concept .. tiny PCB with a couple of holes in them drilled and a couple of traces to solder the wires of the sensor to, use a small zip tie to tie the sensor to pcb in the 45 degree position and a 90 degree connector to solder the pcb to the base board. The sensor would be locked at that angle by the zip tie AND the wires soldered to the pcb.Maybe put the second sensor on the same pcb as well, and use 4 pin or wider connector for better rigidity between the two boards.I guess you could replace zip ties with some selastic / adhesive material, one one hand you wouldn't need holes in pcb (but making holes in pcbs is basically free) but it would probably be more expensive than zip ties and take more time to manually make those assemblies.ps2. or instead of zip ties you could have just a couple of jumper wires (or U shaped metal parts) soldered in 2-4 holes on pcb (on either side of the sensor), to keep the sensor in position. Would make the board look nicer (and you won't have zip tie plastic on the back side of the tiny pcb, but it would take more time to solder the wires holdingps3. or you could even repurpose fuse holders, solder them at the right angle, to make sure the sensor would sit right, here's an example :http://www.digikey.com/product-detail/en/bel-fuse-inc/FC-102/507-1702-ND/622585ps. The board could be just a tiny triangle but instead of using one zip tie you would use two zip ties , one at the top of the sensor and one near the bottom of the sensor and basically your sensor would sit on the edge of the pcb with zip ties holding it to the tiny pcb. You would get more tiny pcb triangles from a base pcb but would take more time to manually make these tiny boards and you'd have to use 2 zip ties I guess.

author: jeroen79
author_rank: Frequent Contributor
timestamp: December 15, 2016, 09:42:28 am
content: Or put some other component in such a place that when the switch is pushed against it it will lean at just the right angle.

author: Kedar264
author_rank: Regular Contributor
timestamp: December 15, 2016, 10:14:17 am
content: One of the easiest and reliable solution i think is to use a tube which is cutted at a defined angle and slide it over tilt switch and secure it with some kind of adhesive it is vere easy to cut these tubes although some wierd angles are still the point of testing wheter this methood works reliably .

author: DTJ
author_rank: Super Contributor
timestamp: December 15, 2016, 11:00:49 am
content: The angle cut tube would work but it might also add extra mass that over time will vibrate, wiggle around and perhaps fatique the Hg switch leads.Can you change the pcb orientation so the switches can both lay hard flat against the pcb but are at an angle to one another. Then the mounting holes and silkscreen can be used for alignment and a dab of glue can hold them in place.

author: nctnico
author_rank: Super Contributor
timestamp: December 15, 2016, 04:19:01 pm
content: If the board has a microcontroller then I like the MEMS (gravity) sensor a lot more than a toxic mercury switch and the hassle to have it installed in the right way.

author: cdev
author_rank: Super Contributor
timestamp: December 15, 2016, 07:13:58 pm
content: There are switches which replace the use of mercury which are just as reliable. Mercury really shouldn't be used any more, IMHO. If you break a mercury switch in a building it can cause a mercury problem for residents that could under some circumstances be quite difficult to get rid of. Mercury uses up glutathione thelack of which when needed can cause birth defectsand all sorts of other health problems.

author: Nauris
author_rank: Regular Contributor
timestamp: December 16, 2016, 05:14:08 pm
content: Looks like perfect application for hot glue. Make some jig to aid alignment.