Practical prototyping with SMD components - Page 1
Forum section: electronics / beginners

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 07, 2016, 09:30:45 am
content: How do people prototype with circuits of more than a couple of SMD components?Straight to PCB from schematic?

author: tautech
author_rank: Super Contributor
timestamp: March 07, 2016, 09:39:48 am
content: Simulate or breadboard, tweak, then final PCB.Yes, I've had to get TH or DIP versions to breadboard proof of concept but you gradually build stocks of what's needed for future projects.Then there's those SMD to DIP adapters for devices without TH equivalents.

author: tggzzz
author_rank: Super Contributor
timestamp: March 07, 2016, 09:44:41 am
content: BoardworXhttps://www.jameco.com/Jameco/Products/ProdDS/2117296%20Users%20Guide.pdfBusBoard Prototype Systemshttp://www.mouser.co.uk/Search/Refine.aspx?Keyword=854-SMT3U

author: dadler
author_rank: Unknown
timestamp: March 07, 2016, 05:15:41 pm
content: I use breakouts like these:https://www.adafruit.com/categories/198And if I don't want to waste/resolder an SMD IC, I have a collection of different sizes of these sorts of sockets:https://www.adafruit.com/products/1284Can also solder components straight to 0.1" proto board if you get a bit creative, or directly to copper clad with some enginuity.

author: KL27x
author_rank: Super Contributor
timestamp: March 07, 2016, 06:07:48 pm
content: Usually by making a PCB, yes. Often with toner transfer to make at least the initial prototype, even if it's not adequate for the final circuit board. Often adding extra headers and pads and test points, if confidence not so high. I try to add a spot to solder header pins for anything I may want to scope.Also I occasionally point-to-point smaller circuits and/or pieces of circuits on protoboard. Regular veroboard works for 8 pins or less SOIC, anyway.I occasionally also use some 50 mil, hole-less veroboard for SOIC. Homemade. Must solder under a microscope to see anything. Very simple to make with toner transfer and pcb software, even if you don't yet know how to use the software very well. DIP parts can also go on this board, trimming down the legs and soldering to every other pad or even just blobbing to two rows of pads per pin.But maybe the reason I can go straight to PCB most of the time, because I'm not often creating interesting circuitry. Mostly simple stuff that any hobbiest already knows and which is well documented. For instance, even building "my own" first DC boost circuit was essentially copying the recommended layout from an IC datasheet, lol.Build first, fix it later, may not work so well if you are making intricate circuitry with discretes and analog. For what I do, mostly I can figure out the smaller pieces I am not familiar with on a breadboard with just a few components. I have the feeling that MOST of the really interesting discrete circuits are already on an IC with cut-n-paste instruction book/datasheet. Maybe I live in a very boring bubble.But no matter what, it still seems like overall a waste of time to do anything more than a few components on a protoboard or breadboard. Debugging is much easier with schematic AND a clean pcb layout. Even though it takes time to transfer and etch the board, initially (a couple hours), it can usually be easily reworked until solution is achieved. Especially easy with no soldermask. 90% of your initial pcb work is going to finished with only minor tweaking. And I was going to do that, anyway. Especially with a microcontroller, it can be very much a waste of time to breadboard it, making scores of arbitrary pin assignments, then finding out an actual pcb layout is completely retarded. Keeping track of pin changes is a headache. And changing things can create other unintended consequences/bugs. I much prefer to work on the pcb layout, first. Figure out the easiest layout to get ANY pin where needed, then refer to datasheet to make sure it is a suitable pin. It's much easier to make these arbitrary decisions when it's not arbitrary. And it's much better if you can makes these decisions only once. In software. When you click on a real life jumper wire, the name of the signal/pin doesn't automatically pop up. Yes, mistakes happen, and board revisions commonly are needed. It's common because it's still the easiest way to do it.Often is the case, I may even do some breadboard work AFTER making the pcb. For instance, I often can verify some basic or cricital functionality of my firmware on a breadboard before firing up the pcb to avoid frying things. My DIY 8 channel logic probe comes in handy here, providing high impedance visual indicators, selectable pullup/downs, selectable tactile switch inputs to either rail, plug in for thruput to 8 channel logic analyzer, and place to plug in pin headers where I can hook a scope probe on each of 8 signals.

author: Zero999
author_rank: Super Contributor
timestamp: March 07, 2016, 08:54:11 pm
content: For SOIC ICs with a 1.27mm pitch I use ordinary stripboard. I cut the tracks in half with a craft knife. It's a pain but doable.SOT23 components are fairly easy too by cutting one of the tracks in half and soldering the middle pin to the uncut track first.

author: pmbrunelle
author_rank: Regular Contributor
timestamp: March 08, 2016, 12:19:56 am
content: At my work, we start with SPICE for tricky stuff, otherwise we skip ahead to schematic capture, and then we do a PCB layout.PCBs are ordered (in small quantities, tens of boards), then the circuit is debugged.When the circuit doesn't work, we change component values, cut traces, add bodge wires, modify firmware; at this state, we hopefully have an electrically functional board.Then, we integrate the ugly patches into the schematic/layout, and then order new PCBs. After a handful of these iterations (lets say 5 to 10), we're ready for production.I don't see the point in prototyping on a breadboard, then moving to SMD parts on a PCB. That's essentially a complete redesign, so whatever lessons you have learned debugging the circuit on a breadboard are for naught.Prototype using assembly methods that are as close to production methods as possible. This is needed to avoid surprises when the method of construction changes something.

author: matseng
author_rank: Frequent Contributor
timestamp: March 08, 2016, 02:31:39 pm
content: Quote from: tggzzz on March 07, 2016, 09:44:41 amThe BoardworX looks really interesting, especially the 200-series with big squares on the bottom and a few vias leading up for power distribution. Have you tried them yourself? I'm tempted to do a batch 10x10 cm boards on my next pcb order...

author: plazma
author_rank: Frequent Contributor
timestamp: March 08, 2016, 02:40:35 pm
content: Smaller circuits with 1.27mm pitch protoboard. Bigger circuits straight to milled or factory made pcb.Many times the first proto is made of a devkit with added smaller boards. The smaller boards include extra memory, sensors, peripherals etc.

author: tggzzz
author_rank: Super Contributor
timestamp: March 08, 2016, 04:29:56 pm
content: Quote from: matseng on March 08, 2016, 02:31:39 pmNo I haven't, and yes I've had the same idea too. I wonder how long it will be before they appear in DirtyPCBs store for everyone to buy?

author: m98
author_rank: Frequent Contributor
timestamp: March 09, 2016, 08:51:47 pm
content: Those BoardworX look interesting, might try that once.At work I do it pretty similar like pmbrunelle. First I specify BOM and do schematic capture. Tricky stuff gets simulated with SPICE when I get to it. When that's done, there are no more issues and all parts are specified, I go on with PCB layout.PCBs are ordered and populated in quantities of 5, firmware is loaded, and then I get to find out why it doesn't work. Only a few weeks, bodge wires and component replaces later the board is fully functional, I try to keep my hand off my face while fixing those blatantly obvious errors and order the new PCBs.Depending on size and complexity, this repeats 1-3 times, before it's ready for compliance testing and production. Only a few of those errors could've been avoided by prototyping on protoboards, because most are minor layout mistakes.

author: NivagSwerdna
author_rank: Super Contributor
timestamp: March 09, 2016, 11:23:20 pm
content: Quote from: m98 on March 09, 2016, 08:51:47 pmThanks to all that replied. The BoardworX is new to me and I really like the look of that in comparison to boards that are just circular pads. Something for the shopping list.