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  • Author Author: genebren
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Trying out some new assembly techniques - SMD/SMT build.

genebren

Back in October, was sharing his prize from the project14 'Electronic Toys for Fun and Learning' competition which gave me some ideas to speed up my soldering/assembly process.  As a result of that conversation, I started looking for small containers for SMD/SMT parts. What I found were these:

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It wasn't until recently that I had an opportunity to try these out.  I had just received a request from a client to replenish stock on a DMX-based motion sensor/trigger, so I had ten boards to assemble.  Having ordered PCBs and acquired any necessary parts, I set out to assemble the boards.  First, I placed most of the fine pitched components (USB jack and all of the active components.  This left me with 38 passive components that needed to be applied to the top and bottom of each board.  In the past, I would drop components, one at a time, to a side of the board and solder them in place.  This time, I decided to take each component type and drop the required quantity of them into individual containers.  Prior to filling the containers, I decided to mark the container lids with the necessary information (taken from the BOM). Here is a screen shot of the labels:

 

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Each label contains the part name(s), the component value/description and the quantity required (for each board).  The target labels were Avery 15667, 1/2" x 1 3/4" clear (return address labels).  These labels were split into two labels halves, with borders drawn to simplify the cutting that would take place, prior to placing them on the lids. Here are the labeled containers:

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Ready to give it a try!  Here is a picture of the Microscope, board holder and part containers ready for action (my soldering iron is just visible on the right hand side of the image):

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My plan is to fully populate the top side of the board with all of the passive components and then flip the board and populate the bottom side.  After all the boards are populated, I will go back and add the bulkier items (power/DMX connectors and the PIR sensor).  To start, I add solder to on pad on each of the component footprints (top most or right side pads) in preparation for placement. I then open one container at a time and place the component(s) as close to the footprints as possible using my tweezers (just to the right of the container in the above picture).  I repeat the process for all of the components on a side.  Then I use the microscope to fine tune the part placements (flip components face up where appropriate).  I then proceed to hold the components in place with the tweezers in my left hand, while I re-heat the pad (with solder) using my iron in my right hand.  I then position the board holder to center the next component.  When necessary, I rotate the board holder 90 degrees and repeat the process for any components that were up/down oriented.  Once all of the components are tacked in place, I rotate the board again and solder the other side of the component (I also touch up any of the joints for the first pad if it needs it).

 

With the top finished, I flip the board and repeat the process on the bottom.

 

While this process is a marked improvement on my earlier process, it is by no means perfect.  A couple of thoughts that I had after completing the boards are as follows:

  1. On the lid labels, add a component count for top and bottom sides, so that I know how many of the parts to pull out.  I did find a couple of times that I did not have all the parts in place when I went to align the components.
  2. Add lid labels to BOM so I did not have to do so much editing to get the label text correct.  (or build a script/program to process the information from the BOM)
  3. Come up with ruler-like device to mark out multiples of ten on the component tapes, so I don't spend so much time counting when filling the containers.
  4. For larger boards, or boards with more components, maybe it would make sense to have separate containers for top and bottom sides of the boards.
  5. Do a better job of numbering components, maybe even adding a 'T' for top and 'B' for bottom to the entries on the BOM (and then the labels), as I spent a lot of time locating the components on the PCBs.
  6. I was a little less than happy with the container bottoms, as they had rough spots (sprue marks) that and tight corners that made picking up parts difficult at times (not sure what to do about this yet).

 

Also, I was a little disappoint in the lid mechanisms on these containers.  First several of the lids where broken (missing hinge pins) and some of the lids did no pop open freely (some needed a little help opening).  But all in all, things went fairly smoothly.  Here is a picture of the fully assembled and tested boards getting ready for shipping:

 

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I tried not to build too many boards, but I do find a need from time-to-time to build batches of board (10 - 25) at a time.  I will continue to hone this process and I will share any ideas as I come across them.

 

Gene

Parents

  • Some co-incidence!  I did exactly the same for SMD passives with containers, even to the extent of marking out cutting lines on labels.  I marked up the labels differently as I’m using the containers as permanent storage rather than WIP containers.  The ones you use look like they clip together so in theory you could make a storage area as large and shaped as you want?  I ended up with a fixed storage hold-all with the containers but the lids are all working with very positive open/close action.  From Amazon, but I don’t remember paying £25 for it so I think it might have gone up in price.

Comment

  • Some co-incidence!  I did exactly the same for SMD passives with containers, even to the extent of marking out cutting lines on labels.  I marked up the labels differently as I’m using the containers as permanent storage rather than WIP containers.  The ones you use look like they clip together so in theory you could make a storage area as large and shaped as you want?  I ended up with a fixed storage hold-all with the containers but the lids are all working with very positive open/close action.  From Amazon, but I don’t remember paying £25 for it so I think it might have gone up in price.

Children
  • in reply to Andrew J

    It seems like great minds think alike, or maybe there art not too many creative ways to approach this sort of problem.  I liked the flexible concept of these containers, being able to clip them together into different sizes and shapes, so for that they work well.  I was very nervous about using containers as a form of permanent storage, as I was very concerned about spillage.  Also, I have several hundred parts in my active inventory of parts, and the cost of that many containers might have been a little more expensive and difficult to store.  That said, those storage containers that you are using look awesome.  I might have to check them out for some of my other components/parts.

  • in reply to genebren

    The lids fit very tight and the box folds in half and clips tight shut - I can't imagine that dropping from height would cause spillage, even if the box itself broke open, the compartment lids would stay shut.  But yes, at that price several hundred parts would cost a fortune!  They would only fit SMD parts because the compartments are tiny.