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SMT Components

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SMT Components | 4 July, 2013

Does anyone have a printable ruler for measuring smd/smt tape and reel components?

I currently have one that measures 2 pitch and 4 pitch but it is small and only measures up to 75 parts at a time. I would like one to also include 8 pitch.

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SMT Components | 8 July, 2013

You can use any metric ruler to do that.


Pitch 2mm x 200parts = 400mm length

or Pitch 4mm x 100parts = 400mm length

You can also calculate approximately how many parts you have on the tape by using formula. I don't have the formula but I know there is one and it is based on part pitch, tape thickness and the reel of the tape....probably someone here knows it and will post it for all of us. There are also machines that can count parts on the tape.

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SMT Components | 9 July, 2013

formula(s) attached.


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SMT Components | 12 July, 2013

So why is the number of wraps = (Outside diameter - inside diameter) / twice the the thickness of the tape

surely if the tape thickness was 5mm and you had 20 wraps it would take up 100mm not 200mm.

I made a posting here some time ago, over a year as I could not find it on the 365 day index.

the parts follow the triangle series formula.,

the total number of parts went equal to (Number of parts on the first wrap times the number of wraps) + ((difference in parts between the first wrap and last wrap) times 1/2 the number of wraps).

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SMT Components | 14 July, 2013

"So why is the number of wraps = (Outside diameter - inside diameter) / twice the the thickness of the tape"

2*thickness because we are using diameter

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SMT Components | 18 July, 2013

Thats OK, no doubt your formula works, or you would not keep it.

So does mine, without the 2t, (that is way I asked)

I must go and find it, or rework it out since my old thread has gone from this web site.

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SMT Components | 18 July, 2013

after checking two computers, did not find it.

However after using "google" found it in a flash. (less than 0.22 seconds) using a spreadsheet. how about this for resistor & capacitors with 4mm pitch, all measurements in millimeters. cell A1 "input inside diameter" answer in cell B1 cell A2 "input outside diameter" answer in cell B2 cell A3 "input layer width",(from inner to outside layer) (not used in this example) cell A4 "input number of layers" answer in cell B4 cell C1 =PI()*B1 (gives length in first layer) cell C2 =PI()*B2 (gives lenght of last layer) cell D1 =(PI()*B1)/4 (gives components of inside layer) cell D2 =(PI()*B2)/4 (gives components of outside layer)

minus start 48 parts minus end 95 parts

In total cell =(((PI()*B1)/4 )*B4)+((((PI()*B2/4)-(PI()*B1/4))/2)*B4-48-95

sorry I did not finish it fully with the minus start & finsh.

I got very close to 5000 on a full reel of 5000 resistors, then I counted it by 300mm lengths and got 5006, but I could of missed one of two or ...

then a month later someone replied with another answer "Sounds like a plan." in which case after re looking at the posting think there could be a valid point, since I was not intoxicated at time and I did not explain my system fully.

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SMT Components | 24 July, 2013

To give a better idea of how to calculate the amount of parts on a reel, one might like to survey the attached diagram it is very simple, the extra parts per layer follow a linear fashion.


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