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How would you go about designing a PCB with weight constraints? Suppose, the PCB has a weight constraint that say it must weight less than 140grams.

In searching for parts and components, I realized most if not all components' datasheets do not have any weight information. For example, I need to use two DB25 connectors among a few other connectors on board. None of them carry weight info in their datasheets. Similarly, ICs, discretes etc do not have weight information.

Do I just need to sample components and actually weigh them?

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    \$\begingroup\$ You could try guessing the mass. For example most SMD components will have lower mass than through-hole components and usually the smaller the package is, smaller mass will be. Also a major contributor to the mass will be the PCB and its mass will depends on the substrate, number of layers and amount of copper you leave on it. A point which will be difficult to measure is the amount of solder you put on a board, so in the end, you'll have to measure each component an the empty PCB in order to get a precise mass of solder which remains on the board. \$\endgroup\$ – AndrejaKo Jun 2 '11 at 9:00
  • \$\begingroup\$ Another thing to note is that manufacturers sometimes change the shape of the package a bit, but that usually doesn't have a major impact on the weight. \$\endgroup\$ – AndrejaKo Jun 2 '11 at 9:01
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    \$\begingroup\$ I'd go for the big parts first and try to find lightweight DB25 connectors, if need be by sampling them. Compared to those you can probably ignore discrete SMD parts. \$\endgroup\$ – starblue Jun 2 '11 at 14:20
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    \$\begingroup\$ If you have a need for a DB25 connector, it seems like an unlikely design for a light-weight device. If you're interfacing to a serial cable, a DB9 (technically DE9) , or even a stereo phone plug connector would probably be a better choice. You could then provide an external adapter cable if it absolutely has to go to a DB25. \$\endgroup\$ – Toybuilder Jun 2 '11 at 17:12
  • \$\begingroup\$ I would be curious to see what kind of answer you would get if you sent an email to the manufacturer's support group asking about component weight. \$\endgroup\$ – Jon L Jun 2 '11 at 17:37
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The short version is that most manufacturers don't provide weight data because it's rarely needed in most designs. So, yes, you'll most likely have to sample all the relevant parts. If you are building a device for volume, you can usually get free samples from the manufacturers (or their reps) - so you won't have to shell out money for parts that might or might not work.

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  • \$\begingroup\$ Even if it isnt for volume, most will still give samples. They especially like to get college students "addicted" to them early. \$\endgroup\$ – Kellenjb Jun 2 '11 at 17:18
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    \$\begingroup\$ If it's for volume, have your purchasing agent call the manufacturer and have them weigh it instead of waiting for it to get shipped to you... \$\endgroup\$ – Kevin Vermeer Jun 6 '11 at 4:13
  • \$\begingroup\$ @Kellenjb Really? Hm, what's the best way for a current college student to take advantage of that without completely abusing the point of free samples? \$\endgroup\$ – NickHalden Jun 19 '11 at 3:38
  • \$\begingroup\$ @JGord You just need to ask the company. Every company does it slightly differently. I have found TI to be very good with samples. They have a method to order samples from their site and then are pretty clear on how many of what items you can get samples of. \$\endgroup\$ – Kellenjb Jun 20 '11 at 14:35
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If you are really concerned about weight, you can always try ordering PCBs made with a different material. Most PCBs (I think) are made with FR4 but you could get them made with Polyimide which is lighter. In addition, you could even make thinner PCBs. On Advanced Circuits you can order PCBs as thin as 0.02" for a 2 or 4 layer board but that might be extreme. Since you are gonna have on-board connectors you can stick/glue the PCB on some other light but sturdy material (assuming all your components face up/are on the same side of your board). At this point, the only weight you'll really have in my opinion are the ICs.

Since I have no idea what your project is, this is merely a suggestion. Good luck!

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