making sheild cans DIY ? - Page 1
Forum section: electronics / projects

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 15, 2014, 10:56:32 pm
content: What is a good material for making shielding cans with?If I make a circuit board I could spread out several points on the top that have solder and via connections to ground plane (bottom) surrounding the sensitive electronics. I think that the shield should work quite well even if its stitched on at several points, instead of a continous soldered connection (I only ever saw this in the spectrum analyzer video).I would imagine it be easy to cut a rectangular shielding can out of a copper sheet, so long the right technique is used. I would like to draw outlines in the material that I can then cut out and bend precisely to make rectangular enclosures (using angled blocks to bend the material at right angles).In my head this seems easy enough to do if the right dimension of copper sheet is chosen so that it can be worked easily and the right cutting tools are had so that it could be cut to the required shape precisely without excessive deformation.What would you suggest? I imagined solder coated copper sheet, or maybe even some kind of aluminum sheet metal?I could even epoxy in balsa wood/nylon rod/something cribbing so that the material is more robust (since I imagine a softer material will be easier to work with, I don't need this prototype to be able to survive 500g drops).I would really prefer a solution that I could bend out of a single piece of metal. I know there are Manhattan style tutorials but they usually have you cut out thicker copper plates to solder together, this is too much work IMO.http://leaningforwardtogether.files.wordpress.com/2012/09/cube.giflike the paper boxes we made when we were kids trapped in elementary school. I have alot of different dimension sharp angled steel blocks on hand which I could make clean bends with.Also I have NO idea about the thickness of these materials to make them easily hand workable. If you tell me to use copper and you know the thickness, please tell me.I can always paint copper with solder if there is no precoated cheap materials available.I envision using a strait edge and a ruler to draw cuts into the metal using a scribe and then bending the metal along the cuts to form the box shape.also, I do not want to use PCBs (I.E. panel left overs) to make a Manhattan shield cube. This is an excellent technique no doubt but I do not want to use external labor.****I do like the idea of copper tape on card board cut out from a cereal box howeverand I watched a bunch of copper sheet videos and to me it seems that 10mil is perfect for this.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: April 16, 2014, 12:42:57 am
content: Do you have copper clad PCB stock?If you're printing a main board, you can leave large rectangular openings in the solder mask to "surface mount" the shield (or just tack it in places). You can then use traditional "dead bug" copper clad methods to finish the rest. Or use the copper foil, but it will be difficult to solder, even 10 mil stock. Tinned steel is also good, and easier to solder in bulk.Traditional through-hole shields have pins cut into the edge, which go through the board and get soldered on the bottom side (or both sides, if available). Slot holes are typical; these can usually be plated-through for little hassle these days.Tim

author: Unknown
author_rank: Unknown
timestamp: April 16, 2014, 01:11:41 am
content: Copper sheet tends to be a bit soft - it's OK for one-offs, but a PITA if you're doing more than one. It's also ugly - it's very hard to keep a smooth flat face on it while folding & fitting, and will tarnish. And it's really only good for shielding in the 10's or 100's of MHz.Nickel-silver sheet is the stuff - it's harder (but easy to bend e.g. with the little vise-fitting 'panbrake' sheet metal benders), holds tension (good for clip-on shield covers), doesn't tarnish (much), shields fairly well across a wide range of frequencies, is easy to cut (a jeweller's saw or tin snips is enough), is reasonably easy to solder (at least with leaded solder & flux), and is commonly found at jeweller's supplies & some hobby stores for cheap.edit: the stuff I've got at the moment is 0.32mm (#28?). Cost me ~AU$10 for a 15cmx15cm sheet.

author: Richard Head
author_rank: Frequent Contributor
timestamp: April 16, 2014, 06:35:55 am
content: Some of the SMD stencil manufacturers can (and do) make small RF enclosures/shields for PC boards. They generally use stainless steel these days for stencils but brass is available for shields and it solders well. Incidently, the stencils are laser cut and if they can accurately cut tiny smd apertures then accuracy shouldn't be a problem. For a bend line have tiny little rectangular holes cut in a row. You can then probably bend the shield yourself as it will bend along the cuts.Dick

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 16, 2014, 05:23:21 pm
content: well, I bought 30ga copper sheet and 30ga nickel silver.i was going to buy some mu-metal stuff but I noticed its thermally sensitive...copper/nickel cost me like 30$ total, so I have spare $, do you think a magnetic foil is worth it? I am near and around audio frequencies.http://www.lessemf.com/mag-shld.htmlbut IDK how to attach it to a PCB without soldering. Will soldering stitches on the iron-nickel sheet ruin the whole sheet or just slightly damage it?it says absolutely do not solder etc... but its an EMF fear fool website I think.I have no slots on my PCB. The shield will be connected from top to bottom by 1.5mm vias, and hopefully I can cut little tiny V's into the sheild that will fit into the vias, so I can solder it down right to the ground plane. I will NOT have any cut outs in my board. Or I may drill larger openings, extend a segment of sheild metal through the opening and bend it to attach it to the ground plane( and then solder)******Unless I buy a dremel and do it myself. A dremel is a bit of an investment but if it is necessary to spring load the shield I could.I don't know what the resistance of that nickle-iron might be, but do you think conductive epoxy would work for it maybe, since I assume that it is a somewhat lossy medium. ?I assume the copper and nickel silver will bend and solder easily.

author: hagster
author_rank: Frequent Contributor
timestamp: April 17, 2014, 08:27:48 am
content: Just a question. Can you not just buy some ready made shields? Laird and Wurth Electronics have a fair selection of different sizes that aren't expensive. You can get them through Digikey. They also come with removable lids which makes testing much simpler.For DIY I'd recommend cutting and folding a thin strip for the sides and having a seperate piece for the lid.

author: turbo!
author_rank: Regular Contributor
timestamp: April 17, 2014, 01:05:08 pm
content: Quote from: Tac Eht Xilef on April 16, 2014, 01:11:41 amHow come copper sided cube can only shield through 100s of MHz?

author: Unknown
author_rank: Unknown
timestamp: April 17, 2014, 01:58:14 pm
content: Quote from: turbo! on April 17, 2014, 01:05:08 pmI should probably have said "from the 10's of MHz upwards".As averyrough rule-of-thumb, you tend to want magnetic shielding for lower frequencies and electrical shielding for higher frequencies, though it varies a lot with factors like shield material, thickness, & effective diameter eg. copper will work for 50Hz if it's >1cm thick or the shield diameter is measured in metres....Nickel silver, while strictly speaking neither magnetic nor a great conductor, makes a reasonably good compromise & is pretty commonly used.

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: April 17, 2014, 02:20:42 pm
content: Quote from: turbo! on April 17, 2014, 01:05:08 pmThe cut-on frequency of a shielding material is related to its magnetic permeability -- that's why mu-metal works so well. Electric fields can be canceled, but magnetic fields must be diverted. So you're stuck using a material with a high permeability or designing your circuit such that there are no pick-up loops to interact with the magnetic field.

author: MisterDiodes
author_rank: Frequent Contributor
timestamp: April 17, 2014, 02:26:55 pm
content: Depending on what you're shielding against and the size of your board, check LMBHeeger. You can get plated steel drawn boxes for a few bucks. These are great for lower freq's, offer some thermal isolation and power-line interference.You have to look at are you shielding against a near field magnetic flux - and at low freq's copper doesn't do as much as you'd like - or is it more RF in nature?For moderate frequencies MuMetal is really the best (if you can get it) - and at higher freq's the metal RF shield, in either plain aluminum or many Nickle-based plating will work well.Don't forget to shield the bottom of the PCB and board connectors - and wiring too. Especially if you're around fluorescent lights.If you're making just a few items - if you can find an older TEK & HP CRT oscilloscopes that don't work, say from the 70's or 80's - it will almost certainly be loaded with lots of MuMetal around the CRT. At least I've been able to scavenge from these types of units before they go into the dumpster.

author: N2IXK
author_rank: Frequent Contributor
timestamp: April 17, 2014, 02:48:43 pm
content: Mumetal is tricky to work with. You can't simply salvage pieces of it from old equipment unless you can utilize them as-is. Any cutting, bending, or machining operations will destroy or seriously impair the magnetic properties of the material unless it is annealed (generally in a hydrogen atmosphere furnace) in its final form.

author: SeanB
author_rank: Super Contributor
timestamp: April 17, 2014, 03:28:28 pm
content: That is the thing about mumetal, bending it destroys the properties in that region. If you do want to solder to it you simply make a tab that extends past an existing side and solder to that, so that the overlap still provides a magnetic shield.

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: April 17, 2014, 03:36:41 pm
content: Quote from: SeanB on April 17, 2014, 03:28:28 pmI had no idea. Huh.How about metglas? Not that you can really bend it, but if you strain it?

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 17, 2014, 05:42:37 pm
content: Hmm, well how badly is it compromised? That guy is clearly cutting the sheet he is selling off a roll...And I noticed a drastic reduction in noise on a DC circuit that I put in a copper box (maybe 0.8mm thick) and the noise on the ADC (which has a 700khz bandwidth) plummeted by two decimal places.Now, I don't know if that means 10MHz was being transformed into lower frequencies that were effecting the ADC/interface electronics.BTW I am looking for shielding something INSIDE my box. THe project already has a nice ferromagnetic box, I need cans that go over specific circuits... I was going to use copper sheet because I noticed such a drastic improvement when I put a project in my copper box, so I figured that covering the high gain section with a copper tent would make it quieter.I will make identical enclosures out of nickel silver and copper and test them out... but I am having trouble believing copper does not work for lower frequencies when my box worked so well on something that should not be able to pick up 10MHz. But you cannot argue with the numbers (I had the ADC connected to a computer drawing historgrams of the data it collects. shield = BIG LSB noise difference). Like from 13.5 bits to 16 bit no noise.*I never hooked it up to any kind of spectrum analyzer though, so I have no idea what it was shielding. I just assumed in my head that it was blocking out 60Hz, might not be the case.when you say it destroys the field in the region of the bend, what does this mean, that if I make the box then the top of the box is essentially magnetically isolated from the sides of the box? If I folded a box out of nickel-iron then it would be like cutting 5 plates of nickel iron then gluing them together with non conductive glue? Does the resistance of the bend go up drastically?SeanB almost sounds like he is encouraging the magnetic field shielding foil but the other posters seem to say it wont work....

author: Alexei.Polkhanov
author_rank: Frequent Contributor
timestamp: April 17, 2014, 06:04:36 pm
content: What sizes of the area you need to shield? Why not buy pre-made shields? like here:http://www.digikey.ca/product-search/en/rf-if-and-rfid/rf-shields/3539677?k=shieldsSometimes I use shields that come in two parts so that you can solder bottom part to PCB and slide the top on it - you still have access to shielded area when you need it without unsoldering or unscrewing.

author: MisterDiodes
author_rank: Frequent Contributor
timestamp: April 17, 2014, 06:16:02 pm
content: Quote from: N2IXK on April 17, 2014, 02:48:43 pmYes, sorta. If you bend it back and forth a lot, and long enough, you will certainly see degradation. Its fairly forgiving though if you're just testing - Each time you bend it sharp you get a slight deterioration of some few percent permeability, and only where ever the fold is. 99% will be OK unless you really crumple it up. Just fold it up with sharp corners as little as possible.If you cut a piece out of a salvage piece to test out, it'll be fine. Any welding shop or good machine shop will have a hydrogen heat-treat furnace if you got to stamping out thousands of cans with lots of sharp corners. If you just form the sheet with gentle radii, you probably don't need the heat treat at all.Evey application is different, though.Then there is the "flexible" stuff here:http://www.lessemf.com/mag-shld.html

author: Andreas
author_rank: Super Contributor
timestamp: April 17, 2014, 06:32:23 pm
content: Quote from: SArepairman on April 15, 2014, 10:56:32 pmYou can etch them yourselves like a PCB by using brass boards with photosensitive negative coating.http://www.bungard.de/index.php?option=com_content&view=article&id=27%3Asmd-schablonenbleche&catid=3%3Abungard-produkte&Itemid=78&lang=englishWith best regardsAndreas

author: SArepairman
author_rank: Frequent Contributor
timestamp: April 17, 2014, 06:54:14 pm
content: Quote from: Alexei.Polkhanov on April 17, 2014, 06:04:36 pmI don't want to design my board around a premade shield. that makes board layout a potential PITA. I hate dealing with bullshit like working within a form factor (choosing box before yoou make PCB) and trying to design weird big things into a PCB (transformer, shield, etc). I will be god damned if my complicated expensive, beautiful and wonderful electrical system is bound by the dimensions for a cheap and primitive box that some chinese guy in china decided to sell on ebay that was probably made from recycled car accidents.I had epic amounts of frustration trying to get a product down to a size. I will make the layout electrically nice then choose a (CUSTOM) shield.I recall dave jones ranting about this in his PSU design videos. This is part of what makes mass production not fun... even if it does save you money its damn frustrating.Suddenly it leads to riser boards, bodge wires and just generally unsightly things if your enclosure size changes during the middle of design. Why is the mains capacitor epoxied onto the system processor? Is it really appropriate to cool the rectifier with that GPU heat sink>??Having to constantly reference back to DIGI KEY to see what dimensions are ok, will this part fit, etc, is time consuming also.. or some part becomes unavailable, this way I could make RAPID modifications. Especially on a prototype, I have no idea if some part is ok. I might need to solder in a mid-air regulator/buffer/filter/capacitor.. if I have the shield making materials on hand in 20 minutes (i cant imagine it being that difficult to fabricate) I could have a working prototype. I would never do this for a volume product.I got one of my designs working by splicing in a levitating dead bugged low pass filter and buffer above another chip. It looked goofy but it made it work... if I had to make a similar modification to something under a shield it would be problematic if I could not custom make it.basically, I (like a cat) like to keep a death grip on my PCB manufacturing "tools" (mechanical engineer, industrial designer, boss, investors etc) to make sure my product feels right electrically and thermally and is made in my own vision.I will work diligently to scare people away from board revisions with scooby-doo type antics.I might just make this board 6 inches bigger so it looks like the way I envisioned in my head on the nice clean block diagram rather then a compressed spider web. It could make a beautiful design grow like the roots of a plant in too small a container. it is not very zen.the sad thing is that I actually had someone tell me of a co-worker of his that sabotaged a design by choosing inappropriately specced components that would lead to a failure in order to dismiss one of his co workers ideas (causing thermal failure and making the idea look stupid). The guy thought the product was too haphazard, and he did not feel a "bandaid" solution was appropriate for something he was involved in, and that a complete redesign was necessary. Perhaps he just wants to protect his name, but sabotage is rather outrageous.Also, I could make really weird shapes by soldering multiple boxes together.*and to anyone that says these modifications are a sign of bad planning, well I disagree. Sometimes making something and seeing what its missing could be faster then trying to think of some perfect solution to a problem. it could also allow you to spend more time on other areas that have bigger problems.+ this sounds fun! compared to alot of assembly tasks building a little shield sounds alot like building models, which is something I enjoy. You could even draw on your shield so it looks like a little house.... its like building your own shanty town! maybe it is a shelter for obsolete parts...

author: Unknown
author_rank: Unknown
timestamp: April 17, 2014, 11:02:24 pm
content: Quote from: SArepairman on April 17, 2014, 05:42:37 pmFair enough. Feel free to read Kaiser's "Electromagnetic Shielding" or "Electromagnetic Compatibility Handbook" for exact details.

author: CaptnYellowShirt
author_rank: Frequent Contributor
timestamp: April 19, 2014, 04:51:24 am
content: Quote from: Tac Eht Xilef on April 17, 2014, 11:02:24 pm+1