Best practices and basic techniques used for short run SMT of boards?

ke4pjwke4pjw Posts: 258
I have a Propeller based project that I want bring to market. I want to do a run of about 100 of these. They will be sold as a plug n' go type of product, not a kit. It is a USB based dongle device. My prototype is compete and very solid. I am using ExpressPCB as my layout software. I have used them for other projects and have been very happy with their software and service. Everything I have done so far is thru-hole type design.

Here are some of my question...

Is there any type of good literature that describes how assembly houses do production runs? (As far as component soldering and placement)
Are there any simple or basic techniques I should know about, to best do the layout?
Does anyone have any advice to offer about doing such a project?

Thanks much!

--Terry

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Feel the need for speed between your PC's com port and Prop?
Try the FTDI 245 and the FullDuplexParallel Object.
Feel the need for speed between your PC's com port and Prop?
Try the FTDI 245 and the FullDuplexParallel Object.

Check out my spin driver for the Parallax "96 x 64 Color OLED Display Module" Product ID: 28087

Comments

  • 21 Comments sorted by Date Added Votes
  • FranklinFranklin Posts: 4,747
    edited August 2010 Vote Up0Vote Down
    This should get you going. www.google.com/search?hl=en&rls=com.microsoft:en-us&&sa=X&ei=Se9YTMyXGYacsQOR0bzWCQ&ved=0CBUQBSgA&q=diy+smd+soldering&spell=1 I'vs used an electric skillet to good advantage (not the one my wife uses though, I'm not that crazy)

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    - Stephen
  • LeonLeon Posts: 7,619
    edited August 2010 Vote Up0Vote Down
    The assembly company will use pick and place machines to populate the boards, before reflow soldering them. You will have to provide them with a file describing the position of each component, your PCB software should be able to generate it. If you have an assembly company near you, ask if you can have a look round when you ask for a quotation. Screaming Circuits has a good reputation for small production runs.

    You will probably need to budget for something like CE approval, depending on the regulations in your country. It can be expensive.

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    Leon Heller
    Amateur radio callsign: G1HSM

    Post Edited (Leon) : 8/4/2010 4:53:14 AM GMT
    Leon Heller
    G1HSM
  • WBA ConsultingWBA Consulting Posts: 2,832
    edited August 2010 Vote Up0Vote Down
    Terry,
    This is a bit long, but actually cut very short for my potential answer.

    The basics for a production house are as follows:

    a) RS274X Gerber files with readme describing each file
    b) Assembly DWG
    c) Fab DWG
    d) Excel BOM with AVL (Approved Vendor List) that contains MPNs (Manufacturer Part Numbers)
    optional:
    e) ASCii CAD File
    f) IPC-D-356 Netlist file
    g) Centroid File (X/Y data for components)

    Gerber files should be of each layer in the fab makeup. For a two layer board, an example file set would include:
    Top Silkscreen
    Top Soldermask
    Top Paste*
    Top Copper
    Bottom Copper
    Bottom Paste*
    Bottom Soldermask
    Bottom Silkscreen
    NCDrill File
    *optional and only if PCB has SMT, but these are used by the stencil manufacturer

    Basically, the assembly DWG at a minimum needs to have the solder type (tin/lead or rohs), what industry standard to be built to (IPC-610, class 2 is the typical for Propeller based product), and any special notes such as unused holes that must remain free of solder, programming/functional test required, mechanical assembly functions like heatsink hardware, etc
    The fab drawing will not be necessary if you are supplying the fabs, but would contain layer stackup details, drill details, key dimensions (tooling holes, slots, etc), panelization details, copper weights, and other fab related information

    The Excel BOM with AVL will provide the necessary information for the manufacturer to do two things. One, if you are having the manufacturer procure the material, this will contain the information to source the parts from distributors. Second, whether you are providing the material or not, it gives the manufacturer the ability to determine how to process certain parts. For example, some through-hole switches are not sealed so they cannot be water washed during manufacturing and the assembly house needs to know this.

    I am uncertain as to what ExpressPCB provides you for assembly files, but I do know you have to purchase a gerber package from them when you need them for assembly. I would expect that they would at least supply you with a paste layer for stencil fabrication and a centroid file for machine placement.

    I do actually have a project to create a sample file set that can be shared publicly so everyone can see a real life example of all of these file types and the "right" way to present them for assembly. Right now, the file set I created can only be shared with my work's customers.

    ~~~~~~~~~

    As for the actual assembly, it depends on how your board is designed, what types of parts are on it (IE: SMT, TH, Mechanical, Wires), processing requirements (RoHS, conformal coat, testing, etc), and other details. During an RFQ (request for quote) by an assembly house, they will determine what steps the board will go through. Here are some questions that are part of the quoting process:
    What's the EAU (estimated annual usage) and order size of the product
    Can the SMT parts be placed by machine?
    How will the SMT parts be supplied? (IE: Reel, tube, tray, cut tape, loose in a bag)
    Can the assembly be washed?
    Is it panelized?
    Do any parts hang over the edge which limit automated assembly?
    Does the board have fiducials?
    Can the TH parts be waved or do they require handsoldering?
    Are there special test requirements?

    I could go on for a while, but I think you get the idea. This is something I go through several times a week for PCBs, cable assemblies, and mechanical assemblies at work (an electronics contract manufacturer). I have been building PCBs for 19 years now and the last 11 years have been with two CMs. I have a presentation that will cover all of this on the back burner (was supposed to be a UPEW presentation) because it comes up from time to time on various forums and I would like to share my experience.

    As for the actual assembly process, send me a PM or email with more details on your board and I can write you up a DFM report (Design for Manufacturing). This will explain the processes that your board will typically go through at an assembly house and any limitations that your design will present for a manufacturer.

    In regards to CE marking, most products you see with CE marking are self-certified which costs nada, so do your research before you blow off the European markets.

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    Andrew Williams
    WBA Consulting
    PowerTwig Dual Output Power Supply Module
    My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger
  • LeonLeon Posts: 7,619
    edited August 2010 Vote Up0Vote Down
    You still need testing, for self-certification for CE conformity. You can't simply assume that it meets all the requirements and put a CE mark on it. It's the same in the USA, except that the FCC only requires emissions from the equipment to be checked.

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    Leon Heller
    Amateur radio callsign: G1HSM
    Leon Heller
    G1HSM
  • WBA ConsultingWBA Consulting Posts: 2,832
    edited August 2010 Vote Up0Vote Down
    Agreed, but whether or not that testing will cost you money is my point. I deal with products every day that are CE marked without having gone through third party conformance testing because it is not required for those products to be CE marked. Some of these products are as old as the CE mark itself. I got involved with CE marked product back when it came out (as seen by the sticker on my old HP name tag) and when the RoHS directive was coming, it reminded me of some CE nightmares.

    ps.
    Terry, do not use Google for information on CE marking. The first few pages of results can be confusing and mis-leading (mostly sites with offers to help "for free" but not actually contain any real information as to how to complete the process unless you pay for the "consultation" or "course".

    ec.europa.eu/enterprise/policies/single-market-goods/cemarking/

    Start with the "leaflet for economic operators" PDF there.

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    Andrew Williams
    WBA Consulting
    PowerTwig Dual Output Power Supply Module
    My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger
    448 x 156 - 13K
  • LeonLeon Posts: 7,619
    edited August 2010 Vote Up0Vote Down
    Testing for CE conformity is quite expensive, something like £3,000 upwards if one has to use an external test facility. Testing is generally required for electronic equipment, as every product sold in the EU has to conform if it bears a CE mark, unless it's something like a board or module that will be incorporated in something else. It looks as though the OP's product will require testing if it is sold in the EU.

    Where I used to work we hired a facility for half a day to do our own testing (about £500), fixed any problems, and then the formal testing was just a formality. I designed their first product, the only problem was a VHF emission on the RS-232 cable, which was easily fixed with some filtering.

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    Leon Heller
    Amateur radio callsign: G1HSM

    Post Edited (Leon) : 8/4/2010 7:56:24 PM GMT
    Leon Heller
    G1HSM
  • ke4pjwke4pjw Posts: 258
    edited August 2010 Vote Up0Vote Down
    Thanks for all of your posts everyone!

    @Leon: CE conformity should not be an issue for me as I do not intend to sell it in the EU. This will be a device that is regulated by the FCC as a 47 CFR 15 Subpart B, Class A device. I am researching if a declaration of conformity will be needed. I am sure that I can attenuate any common mode emissions fairly easily, but having to pay someone to confirm what I can test myself could be a deal breaker.

    @Andrew: Wow! What a great wealth of information! I had not considered using an actual assembly house to put the project together. I just can't imagine those places being able to cater to a hobbyist sized run of boards. I will spend some time investigating what you have posted. It's really helpful to have some insight into the way the pros do this. I am sure I will have some follow up questions. Thank you!

    @Stephen: That's exactly the scale of project I am looking at. The reflow toaster oven will probably be my most cost effective choice. [noparse]:)[/noparse]

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Feel the need for speed between your PC's com port and Prop?
    Try the FTDI 245 and the FullDuplexParallel Object.
    Feel the need for speed between your PC's com port and Prop?
    Try the FTDI 245 and the FullDuplexParallel Object.

    Check out my spin driver for the Parallax "96 x 64 Color OLED Display Module" Product ID: 28087
  • WBA ConsultingWBA Consulting Posts: 2,832
    edited August 2010 Vote Up0Vote Down
    Good deal. Also, if you venture into toaster oven reflow, you will have fun. My PowerTwigs are made with toaster oven reflow and it didn't take much to verify temperatures to accomplish proper ramp-to-spike profiles.

    I'll probably be making my M44D40+ Modules with toaster oven reflow once I characterize the toaster oven with the profiler we use at work for our "real" reflow ovens. I'd like to make a controller for the oven, but so far the boards I am doing have not needed any special things to get a desired profile. Plus I still have to finish my other two active projects.

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    Andrew Williams
    WBA Consulting
    PowerTwig Dual Output Power Supply Module
    My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger
  • Bobb FwedBobb Fwed Posts: 1,115
    edited August 2010 Vote Up0Vote Down
    WBA Consulting said...
    I am uncertain as to what ExpressPCB provides you for assembly files, but I do know you have to purchase a gerber package from them when you need them for assembly. I would expect that they would at least supply you with a paste layer for stencil fabrication and a centroid file for machine placement.
    They supply only gerbers and drill files (for $60 -- last I checked). Not included is a paste gerber, or placement files. But assembly houses can usually generate those files for a fee.

    I had Screaming Circuits assemble 50 boards for me from an ExpressPCB fab. It cost more than the quote because they had to generate files, but they came back perfect, other than a couple fab flaws from ExpressPCB. 2 flaws in 50 boards, that is terrible! I've said it before: once you are at this point (thinking about assembly and more than a handful of boards), you need to drop ExpressPCB. They have issues and limit you. Once you look beyond the simple board or two and hand soldering they start costing more than buying a standalone CAD suite and using higher quality fabrication done for cheaper.

    I now use the Sunstone/Screaming combo and all my boards so far have come back perfect. They also offer CE (and other) certification.

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    April, 2008: when I discovered the answers to all my micro-computational-botherations!

    Some of my objects:
    MCP3X0X ADC Driver - Programmable Schmitt inputs, frequency reading, and more!
    Simple Propeller-based Database - Making life easier and more readable for all your EEPROM storage needs.
    String Manipulation Library - Don't allow strings to be the bane of the Propeller, bend them to your will!
    Fast Inter-Propeller Comm - Fast communication between two propellers (1.37MB/s @100MHz)!
    "Humanity is not yet sufficiently advanced to be willingly led by the discoverer's keen searching sense." – Nikola Tesla

    Some of my objects:
    MCP3X0X ADC Driver - Programmable Schmitt inputs, frequency reading, and more!
    Propeller-based Database (SPD-LW) - Making life easier and more readable for all your EEPROM storage needs.
    Check out my website (unrelated to this forum): NimonPro.com
  • ke4pjwke4pjw Posts: 258
    edited August 2010 Vote Up0Vote Down
    Thanks for the suggestions Bobb! I generated a couple of quotes from Screaming Circuits. Not bad for this project. Not so good for one of my more complicated projects that uses thru-hole. Still cheaper for me to solder that one myself. (Or enlist the help of friends and family) For this project, I may try out their "assembly stack" (Sunstone and their software). Do you have a personal preference for a standalone CAD suite that could do the schematic, layout, paste and layout files? And how much does it cost?

    Regards,
    Terry

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    Feel the need for speed between your PC's com port and Prop?
    Try the FTDI 245 and the FullDuplexParallel Object.
    Feel the need for speed between your PC's com port and Prop?
    Try the FTDI 245 and the FullDuplexParallel Object.

    Check out my spin driver for the Parallax "96 x 64 Color OLED Display Module" Product ID: 28087
  • Bobb FwedBobb Fwed Posts: 1,115
    edited August 2010 Vote Up0Vote Down
    I use DipTrace. It starts free as long as you stay small. But more than 300 pads and you have to pay. It does just about everything you would need and its fairly cheap. It's easier to learn than Eagle or some other CAD suites. There is also a very active and helpful community on their forum.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    April, 2008: when I discovered the answers to all my micro-computational-botherations!

    Some of my objects:
    MCP3X0X ADC Driver - Programmable Schmitt inputs, frequency reading, and more!
    Simple Propeller-based Database - Making life easier and more readable for all your EEPROM storage needs.
    String Manipulation Library - Don't allow strings to be the bane of the Propeller, bend them to your will!
    Fast Inter-Propeller Comm - Fast communication between two propellers (1.37MB/s @100MHz)!
    "Humanity is not yet sufficiently advanced to be willingly led by the discoverer's keen searching sense." – Nikola Tesla

    Some of my objects:
    MCP3X0X ADC Driver - Programmable Schmitt inputs, frequency reading, and more!
    Propeller-based Database (SPD-LW) - Making life easier and more readable for all your EEPROM storage needs.
    Check out my website (unrelated to this forum): NimonPro.com
  • WBA ConsultingWBA Consulting Posts: 2,832
    edited August 2010 Vote Up0Vote Down
    I would also recommend DipTrace. Gadget Gangster uses it as well as Parallax. Many of Gadget Gangster's boards have DipTrace files for download so you can poke around to help you learn and Nick has several video tutorials for DipTrace on this page. He also has a DipTrace Library to download for Parallax parts. Parallax has some DipTrace files on their Open Source Hardware items as well.

    As already mentioned, the problem with ExpressPCB is when your design needs to go to the next level which requires a better price for the fab as well as design files for the assembly house. Fab houses hand out "free" software because it gets paid for by forcing you to order from them. DipTrace is just as easy as any fab house freebie software.

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    Andrew Williams
    WBA Consulting
    PowerTwig Dual Output Power Supply Module
    My Prop projects: Reverse Geo-Cache Box, Custom Metronome, Micro Plunge Logger
  • ke4pjwke4pjw Posts: 258
    edited August 2010 Vote Up0Vote Down
    I do have one sort-of off topic question. Are the other fab houses that much cheaper than ExpressPCB? Not on prototype stuff, but on the production runs, with solder mask and silk screen. How come I don't see any over seas (China/Asian) shops doing this kind of stuff?
    Feel the need for speed between your PC's com port and Prop?
    Try the FTDI 245 and the FullDuplexParallel Object.

    Check out my spin driver for the Parallax "96 x 64 Color OLED Display Module" Product ID: 28087
  • W9GFOW9GFO Posts: 3,821
    edited August 2010 Vote Up0Vote Down
    I noticed yesterday that Parallax is recommending DipTrace on their Open Source page. Several months ago they were asking for volunteers to create components in Eagle. Does Parallax still use Eagle? Have they switched to DipTrace?

    Rich H
  • W9GFOW9GFO Posts: 3,821
    edited August 2010 Vote Up0Vote Down
    ke4pjw wrote: »
    Are the other fab houses that much cheaper than ExpressPCB? Not on prototype stuff, but on the production runs, with solder mask and silk screen.

    I haven't used ExpressPCB but in my slight bit of experience, I have found that the over seas shops are only slightly less expensive with noticeably lower quality and longer turn around times. I don't feel the need to take jobs away from my neighbors to save a few cents per board.

    Rich H
  • txmarshtxmarsh Posts: 58
    edited August 2010 Vote Up0Vote Down
    Ooops... a little late to this thread but I though I would mention a great source for getting boards made cheaper than any other place I've found...

    http://dorkbotpdx.org/wiki/pcb_order

    This group compiles multiple orders into one large order. This entices the fab house to offer competitive prices. I've used them and the boards came back looking great!

    Maybe this will help someone.
    Tim
  • K2K2 Posts: 613
    edited August 2010 Vote Up0Vote Down
    This helps me immediately! A friend w/o PCB experience asked me two days ago for recommendations. When it came to picking the fab house, I couldn't find any of the great deals I've seen in the past. I told him I'd keep my eyes open.

    Yet again, the Parallax forum proves its value!
  • Bobb FwedBobb Fwed Posts: 1,115
    edited August 2010 Vote Up0Vote Down
    Sunstone.com (I mentioned them before) is only $3/sq-in +$25 setup. So once your board is larger than 13sq-in Sunstone would be cheaper. And they guaranty 2 weeks or less. One of my boards only took 6 days before I had it in my hands.
    "Humanity is not yet sufficiently advanced to be willingly led by the discoverer's keen searching sense." – Nikola Tesla

    Some of my objects:
    MCP3X0X ADC Driver - Programmable Schmitt inputs, frequency reading, and more!
    Propeller-based Database (SPD-LW) - Making life easier and more readable for all your EEPROM storage needs.
    Check out my website (unrelated to this forum): NimonPro.com
  • txmarshtxmarsh Posts: 58
    edited August 2010 Vote Up0Vote Down
    K2 - Note that you get (3) boards for the $5/sq-in price. The guy who volunteers his time to coordinate the order (James) is also very helpful. He looked over my first design and provided a few suggestions. It was just nice to know that I was on the right path when ordering.

    I'm also going to file Sunstone away in my memory for when I need large boards.
  • K2K2 Posts: 613
    edited August 2010 Vote Up0Vote Down
    With prices like that and Eagle Lite for free, I can understand why people here on the forum have been laying out their own boards. I'm tempted to get some made, now.
  • Terry,
    This is a bit long, but actually cut very short for my potential answer.

    The basics for a production house are as follows:

    a) RS274X Gerber files with readme describing each file
    b) Assembly DWG
    c) Fab DWG
    d) Excel BOM with AVL (Approved Vendor List) that contains MPNs (Manufacturer Part Numbers)
    optional:
    e) ASCii CAD File
    f) IPC-D-356 Netlist file
    g) Centroid File (X/Y data for components)

    Gerber files should be of each layer in the fab makeup. For a two layer board, an example file set would include:
    Top Silkscreen
    Top Soldermask
    Top Paste*
    Top Copper
    Bottom Copper
    Bottom Paste*
    Bottom Soldermask
    Bottom Silkscreen
    NCDrill File
    *optional and only if PCB has SMT, but these are used by the stencil manufacturer

    This post looks like you have shared the complete steps or process of the production house. Amazing!!!
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