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Ask and Answer

Local fiducials under package, it's ok?

1282 1 Jan 17.2020, 17:26:57

Hello. I was seeing a pcb design with a big module, and this board have 2 local fiducials, one of them below the module itself, and the other outside the module. Is that a good practice?. Could be useful to save board space and have more freedom to route the board. What do you think about it? Cheers.

UV Exposure times

1695 1 Jan 15.2020, 17:54:19

I am about to create my first home made PCB using photo resist board. I have a UV box, and a transparency with the artwork. All I need to do is place the artwork on the glass, then the board on top of it, close the lid, and set the timer for a few seconds. I am not sure how long I need to set the UV timer for, does anyone know?

Self-Laminating Two FPC halves?

1513 1 Jan 13.2020, 18:06:55

I have a research project wherein I need to place an array of components between two layers of flexible PCB (FPCB). The components, which are piezo ceramics, will be glued with a Henkel conductive epoxy (TBD, but likely an Eccobond). What is involved in the laminating process on a DIY scale for proof of concept? I obviously don't want to crush the ceramics. I think I might have painted myself into a corner... It seems I would need a custom plate to avoid crushing my components - or very careful ironing. Anyone have experience with such a thing?

RF PCB House?

1519 1 Jan 11.2020, 11:43:29

I'm looking to do a couple 4 layer PCBs that have RF components in the 5-7GHz range. Does anyone have a favorite house for doing these sorts of things?

Is there having zero size via pads on outer layter of 4L PCBs?

1576 1 Jan 09.2020, 17:45:41

Just looking at the feasibility of a potential stupidly dense design on a 4 layer PCB Ideally it would use a lot of blind vias between layers 1-2 and 3-4, but it seems this is an expensive process (compared to buried vias between 2-3). I may be able to live with all the vias going all the way though if I could avoid having via pads on the layers that the don't connect to, particularly the outer layers. so for example I'd have a 0.15mm hole with 0.4mm pads on layers 1&2 only, or 3 & 4 only. This is low-volume so needs to be compatible with a normal process I don't think I've seen a board like this, but can't immediately think why it shouldn't be possible - Anyone done this?

Buried vias and their effect on PCB cost

1447 1 Jan 07.2020, 17:06:34

I'm trying to get a quote from a PCB manufacturer in China but their form is a bit confusing to me. There is a box asking me if I have lined or buried vias and then there is a selection box asking for "times of buried via" I'm not sure what this means I can choose between one and 5 and the price increases steeply each time I add one. Are they asking how many types of buried via I have? In this case it would seem that have completely through vias is much much cheaper?

SMD Tray Return/Recycle

1763 1 Jan 04.2020, 11:27:40

Hey, Does anyone have any tip on what to do with empty SMD trays? Do you just throw them away or do you return them somewhere for reuse? Im working for a PCB manufacturer, and as time goes by we have about 350 trays stored. Seems like a shame to throw them away.

TG grade for PCB manufacture / Assembly.

1948 1 Jan 02.2020, 18:13:00

Would be interested to know of your experiences of using various TG Grades of PCB, and why you choose the various things; My end product is'nt goign to run hot, so that is not a driver for the selcetion. its a pretty standard 4 layer stack, 1.6mm thick. The solder process is lead free ( PbF ). The new PCB assembler I'm auditioning with a few project wants to use TG-170 but the boards end up nearly twice the price of TG-140 or TG-150 I've not had delamination issues using it before. Is this an ultra cautious approach on their part or should i run with this suggestion?

Keeping the lint out of final mechanical assembly?

1352 1 Dec 30.2019, 17:21:18

I'm wondering if there are any top-tips for getting rid of lint, fibres and hairs eradicated from mechanical assembly. The issue I am fighting is that I my ABS enclosures come back from CNC machining already a bit swarfy and beginning to attract collecting dust etc. I then fit the PCB, LCD and self-adhesive graphic overlay with clear window. Occasionally after fixing the overlay, then there are a few specs of dust or a white fibre waving at me through the window. (Only once have a had an eyelash in there). This all fails my own QC and I scrap the overlay and start again. I've started using adhesive tape to pick up stray dust/fibres but this feels like a hack. Not sure what direction to try next - Compressed air? Some other sticky pickup tool? Thanks.

standards for in PCB programming pads

1448 1 Dec 27.2019, 17:44:25

Are there any standards for in PCB programming pads? size? shape? pad spacing? location on board? pad ordering? supply pins required as pads? Also, how are these details given to the PCB manufacturer? What about flashing software, and how to use it, and what OS it requires?

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