Home PCB prototypes and assembly. - Page 1
Forum section: electronics / general

author: nardev
author_rank: Unknown
timestamp: February 10, 2018, 12:27:04 am
content: I have seen that many people who decide to do most of it at home, for prototypes, need to experiment quite a lot.Could you share some experiences and how you do it?The things what i consider as easly doable at home, and what i wish you share with others:- pcb making, 2 layer- drilling- stencile making- reflowPCBa is definitely not for home and prototype use so.. lets skip that one.But hod do you do those 4 things?I really hope, soon, there will be "all in one" device that can do all of this for reasonable price.. SO far i have seen one device which doesn't have drilling ans which costs like 3-4k USD so.. definitely no no.. Looking for stable workflow, for much less.. and easy to do.p.s. if there is similar topic, please share...

author: asmi
author_rank: Super Contributor
timestamp: February 10, 2018, 01:48:19 am
content: Youcando all of that at home, but that doesn't mean youshould. With fabs like PCBWay which will manufacture your board for $5, doing this at home just doesn't make any sense (except maybe to do it once or twice just to prove yourself that you can)There is a ton of videos on Youtube on how to do all that, but let me warn you - the process involves quite nasty chemicals, so you will need to take safety precautions and make sure you know what you're doing before you actually do that. Also fiberglass dust will be created during drilling (and perhaps cutting depending on how exactly you will do it), so you will need some kind of protection from it as well.Bottom line is this - yes, it can be done, and it's not particularly difficult either, but it takes quote some time and can be dangerous if you're careless. I'd advise to just order the board at any of cheap fabs - unless you've got a burning desire to do that against all warnings. In this case be my guest, but please please THINK about what are you doing before you actually do it, or it all might end up horribly wrong.

author: NorthGuy
author_rank: Super Contributor
timestamp: February 10, 2018, 03:48:20 am
content: I used to make PCBs, but now it just doesn't make any sense - ordering PCBs is cheaper than the materials.Assembly, on the other hand, can be done at home rather easily.

author: cdev
author_rank: Super Contributor
timestamp: February 10, 2018, 04:19:19 am
content: I etch PCBs using hydrogen peroxide, vinegar and salt. Have been doing it this way for years. It only takes a little bit if your board is small and its maybe a 30 minute to an hour at most process from printing it out, abrading and cleaning the board, ironing the toner to the board, and them soaking it in water and peeling the paper off and then etching it.The most time consuming part is drilling and vias, especially if it is an RF board. That can easily add another half hour to an hour.Quote from: asmi on February 10, 2018, 01:48:19 am

author: nanofrog
author_rank: Super Contributor
timestamp: February 10, 2018, 04:49:44 am
content: For quick prototyping, you can use double sided hole per pad. This allows you to either use PTH or 0805 SMD parts. As per IC's, you have the option of using an adapter board, or dead bug it (flip over and solder wires to the appropriate pad).Here's a BGA device that's been dead bugged.These methods aren't very expensive either; even the Adapter boards are cheap. If you have the time to wait (~couple of weeks), nothing beats a board you have made to your specifications.

author: phil from seattle
author_rank: Super Contributor
timestamp: February 10, 2018, 04:59:29 am
content: Yeah, I used to make PCBs at home. But, I found I was spending way too much time making the PCBs and tools to make PCBs. And home made boards are nothing compared to professionally made boards. No solder mask, no silkscreen. And when you compare it to the cost of getting PCBs made today, it just doesn't make sense to me.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 10, 2018, 05:45:15 am
content: Early on, I put my money on assembly stuff - cheap hot air, microscope, good tips for my soldering iron, paste dispenser and a variety of luer lock sizes. I never bothered with home etching and feel like I got so much more out of being able to solder .4mm QFN's and 0402 passives by hand.I did not spend much money at all to get to where I could very quickly assemble PCB's with hundreds of parts.Eventually, I added an oven, stencil printer, thermal wire strippers, better soldering gear, etc.

author: cdev
author_rank: Super Contributor
timestamp: February 10, 2018, 09:46:23 pm
content: I have to say, if you can hand solder such tiny parts, I am quite impressed.Thats truly difficult. Do you use anything besides tweezers to hold them down? (glue?)Quote from: rx8pilot on February 10, 2018, 05:45:15 am

author: rx8pilot
author_rank: Super Contributor
timestamp: February 10, 2018, 09:54:18 pm
content: I gave up on standard tweezers in favor of the vacuum pen. Far easier, especially if you pick some good tips.For a QFN or similar, I have T5 solder paste and a 24ga teflon lined needle. That can put down dots or lines of paste that the hot air will solder. Use a soldering iron to pull out bridges.I also have a triple tape dispenser with 3 sizes of Kapton tape. Super useful to protect adjacent parts from the hot air.Short and misplld from my mobile......

author: cdev
author_rank: Super Contributor
timestamp: February 10, 2018, 10:15:03 pm
content: Oh, this makes much more sense to me. I thought you were saying you hand soldered the tiny resistors and capacitors -I thought you were saying you literally hand soldered the tiny parts down. I can handle it with the larger sizes, but the very small ones they just stick to the iron. Its almost hopeless that way. It makes me crazy trying to do that.So, you use a vacuum pen for larger parts with a flat area on top- Is it connected to a vacuum pump? It must be. When I need to lift up a part Ive just used tweezers. I have some larger longer tweezers but they are not very good ones.What kind of paste do you use? My problem is I use so little of it, it goes bad.If my paste wasn't old and stale I would be more confident in how I used it.I should just buy new and throw it away.I am kind of stupid about that. I hate to throw things away even when I know its likely much less hassle that way.Quote from: rx8pilot on February 10, 2018, 09:54:18 pm

author: rx8pilot
author_rank: Super Contributor
timestamp: February 10, 2018, 10:33:55 pm
content: On the passives, I do both paste/air and hand soldering. The paste/air method is generally when I am assembling a whole pcb. When I need to change the value of a resistor or capacitor, I remove it and install a different one by hand with regular tweezers and soldering iron. Generally, this is done with a stereo microscope.MLCC caps are easily damaged by hand soldering.... it takes some consideration of technique to put them down safely.Short and misplld from my mobile......

author: phil from seattle
author_rank: Super Contributor
timestamp: February 10, 2018, 10:54:11 pm
content: I have a teflon lined needle, 24Ga from McMaster Carr, and reasonably fresh Kester EP256 paste (from CML supply). It is still just way too hard to push through the needle. And, the blobs are pretty big for QFNs and LGAs. I've had much better luck with stencils - too bad 'cause that drives up the cost. I'll use it for bigger stuff but for QFNs and LGAs, it's unsatisfactory.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 10, 2018, 10:58:06 pm
content: The only paste I can get through a 24ga teflon is Type 5 with a pneumatic dispenser. Typical type 3 won't fit, the solder balls just get stuck.Short and misplld from my mobile......

author: phil from seattle
author_rank: Super Contributor
timestamp: February 10, 2018, 11:04:07 pm
content: where do you get your Type 5 paste? Small quantities in a syringe preferred.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 10, 2018, 11:41:52 pm
content: The last one came from DigiKey - ChipQuick digiKey#: SMD4300AX10T5-ND10cc Leaded Type 5.

author: phil from seattle
author_rank: Super Contributor
timestamp: February 11, 2018, 01:34:05 am
content: pricey. dunno if I'll try it. I'm liking stencils.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 11, 2018, 03:07:32 am
content: I use stencils as much as possible - no doubt they are much easier if you have them. The syringe-based approach is what I use when I have no stencil or doing a repair or modification.There are many boards that I did not get the stencil and was very thankful for the pneumatic syringe system. The cost of stencils has come down to the point were I now rarely order a PCB without one.

author: nardev
author_rank: Unknown
timestamp: February 12, 2018, 02:00:17 am
content: Over all, as i see, it has no point to bother with PCB etching but PCB Assembly, soldering... that is another story...(Although i often only need 1 or two PCBs.. hate when i have to order 10pcs and wait PCBWay...)So..1. What and how to make cheapest stencils?2. What is affordable way to solder SMD parts except hand soldering and microscope?p.s. I live in a country which has quite low standard and 20 USD here and somewhere else is VERY different amount.. Also, shipping to Bosnia is always 2-3 times more than to USA or EU countries. So.. building PCB's at home, despite the cost for a manufacturing equipment, usually more comfortable.

author: Mark
author_rank: Frequent Contributor
timestamp: February 14, 2018, 04:07:49 pm
content: You can get good results with Laser printer, UV exposure, solder mask, cheap stencil cutter, solder paste and home-made reflow oven.On this PCB:56 pin VQFN with gnd pad.VSON 10 boost converter.Some 0402 resistors for fun.160-pin "Low pin count" surface mount SAMTEC ASP-127797-01 to mate with Xilinx Zedboard.The 160-pin connector is on the bottom of the board, mounting holes and kapton kept it in place and it all went into the oven for one cycle.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 14, 2018, 06:06:32 pm
content: Are all those vias riveted?How much time from setup to soldering did the PCB take?

author: nanofrog
author_rank: Super Contributor
timestamp: February 14, 2018, 06:38:33 pm
content: FWIW, Chip Quik offers Type 5 in 63/37 as well (syringes and jars).

author: jmelson
author_rank: Super Contributor
timestamp: February 14, 2018, 09:10:20 pm
content: I rarely make PC boards, but do when I have a need for something really special. Other people seem to get by with toner transfer. I got set up with Riston dry-film resist from think-n-tinker. This stuff is quite amazing. You need a transparent master artwork. I built my own laser photoplotter, but you can get by with a GOOD laser printer. Check your laser printer by printing a 1" grid twice, then flip one of them and lay them on a light table. If the grids don't line up well, then that printer is not a good candidate for double-sided PC boards.The PC board needs to be super-clean, I scrub them with fine sandpaper, water wash and then finally wipe with acetone before laminating the resist.I have a Kepro laminator specially made for this process, but I think there are other hot-roll laminators that will also laminate a rigid board.exposure is in a vacuum frame made of thin Plexiglas with a bank of filtered fluorescent black light bulbs. That takes a 1 minute exposure per side.Let the boards sit for 10-15 minutes for polymerization to complete, then develop in warm sodium carbonate for 1-2 minutes. Wash in water and dry.Etch in warm Ferric Chloride spray etcher for about 3 minutes, and it is done. SMT is great, a LOT less holes to drill.Jon

author: jmelson
author_rank: Super Contributor
timestamp: February 14, 2018, 10:47:11 pm
content: Quote from: nardev on February 12, 2018, 02:00:17 amOK, since I have the technology to make PC boards (laser photoplotter, dry-film resist and etch) I figured I could make stencils, too. They are kind of a PC board without the fiberglass laminate inside. So, I laminate both sides of a 0.003" thick brass shim stock material, and then prepare mirror-image artwork for both sides, just like for a double-sided PC board. Print and develop resist, and etch. Now, I get a sheet of thin brass with holes in it. Voila, stencil!You ought to be able to do this with transparency film on a laser printer, as long as the registration is repeatably good.Jon

author: phil from seattle
author_rank: Super Contributor
timestamp: February 14, 2018, 11:04:21 pm
content: Quote from: jmelson on February 14, 2018, 10:47:11 pmWhat's the finest size you've done? QFN and/or LGA?

author: jmelson
author_rank: Super Contributor
timestamp: February 15, 2018, 11:31:23 pm
content: Quote from: phil from seattle on February 14, 2018, 11:04:21 pmI regularly do 0.5mm 144-lead FPGAs, but have done 0.4mm stencils, and they came out OK. That is really pushing the limits, my photoplotter is 1000 DPI, so those apertures were only about 7 pixels wide. I generally hand-solder those chips as they are custom ASICs and my P&P is not accurate enough to align them well. The thinner stencil helps keep the amount of solder paste from being too much, and it also etches quicker with less sideways etching under the resist. I only do leaded parts. I did do one board with 65 leadless chip-scale comparators on it, but had LOTS of solder shorts under the chips. Drove me MAD fixing all that!My laser photoplotter is quite accurate, it aligns well to the PC board even with a board 10+ inches wide. You probably will never get that good overall alignment with a laser printer.Jon

author: Mark
author_rank: Frequent Contributor
timestamp: February 16, 2018, 10:48:02 am
content: Quote from: rx8pilot on February 14, 2018, 06:06:32 pmAll vias riveted using the Favorit press and 0.6mm internal rivets.https://www.megauk.com/through_hole_rivets.phpThe bottom part of the tool set has a spring loaded pin and the top part has a fixed pin. I've broken it twice but found that it still works well even without the fixed pin. To eliminate the risk of the rivet making a bad contact to the via copper, I now place an octagonal SMT pad top + bottom so that the rivet gets pasted with solder.The steps are:1. When creating the print preview in Altium, mirror the TOP layer so that the toner is next to the PCB.2. Print onto LaserStar transparencies using the HP LaserJet Pro M201dw.3. Warm up the LV204 UV exposure box for 1000 seconds.4. Expose for 120 seconds.5. Develop the image on the PCB.6. Pre-warm the bubble etch tank and etch at XX?C for approximately 15 minutes.7. Clean with methylated spirits or acetone, then used deionised water and wire wool to get a really clean and shiny surface.8. Ensure the board is perfectly clean and dry, then immerse in tin plating solution for 10-15 minutes or in “Liquid Tin” for 3-5 minutes.9. Wash and dry the board.10. Pre-warm the laminator.11. Cut a hole in a piece of cardboard the same size as the PCB. The cardboard will become a carrier for the PCB as it travels through the laminator.12. Remove the matte side from the dry-film soldermask and apply to one side of the PCB as it goes into the laminator.13. Apply the dry film soldermask to the other side of the PCB.14. Pass through the laminator several times.15. Expose to UV for 60 seconds.16. IMMEDIATELY after exposure, the top piece of gloss polyester liner should be removed and the panel allowed to stand for 15-20 minutes.17. Develop the soldermask with agitation and use a soft brush over the surface.18. Cure the soldermask for 30 minutes in the UV unit, then at 100°C in a fan oven for 1 hour. (Alternatively, expose for 1 hour in the UV unit).19. Drill with 0.8mm bits for the through-holes and install the 0.6mm (internal diameter) Bungard rivets.20. Create stencil files and send to Silhouette portrait (A4) craft cutter. Stencil cutting is much faster when there are fewer angles, so avoid round holes where possible, use octagons instead.21. Apply the solder paste and place the components.22. Pop it in the oven.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 16, 2018, 06:11:07 pm
content: Any estimate of the total end-to-end time for the PCB portion (excluding the paste, placements, and re-flow)

author: Mark
author_rank: Frequent Contributor
timestamp: February 18, 2018, 04:18:04 pm
content: Quote from: rx8pilot on February 16, 2018, 06:11:07 pmProbably 2 or 2.5hrs in total to include drilling, riveting and cutting/trimming edges.

author: rx8pilot
author_rank: Super Contributor
timestamp: February 18, 2018, 06:53:09 pm
content: Wow, that is actually quite impressive. I did not expect such a short turnaround.Short and misplld from my mobile......

author: noras
author_rank: Contributor
timestamp: March 05, 2018, 07:57:32 am
content: I personally think that the prototype assembly can be done at home, otherwise, you have to buy the components and then sent to the factory assembly, and then sent back by courier, the whole process is too cumbersome, the cost is high.An electronic assembly at home goes through six steps:Paste StencilingPlacementReflowManual AssemblyInspection and TestingWashingDoing solder reflow work can be expensive and difficult, but thankfully there exists a simple and elegant solution: Toaster Ovens.