Zero Real Estate Bypass Capacitor for Prototype Circuit

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About: Paid to have fun (Electrical Engineer).

This is a simple method for bypassing the power and ground leads of an IC or MCU which has the following advantages:

  • Capacitor lead length is as short as possible.
  • The capacitor takes up zero board space.

Here's how to do it:

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Step 1: Bend the Capacitor Leads to Fit

Using needle nose pliers or other suitable tool, bend the bypass capacitor leads as shown. Be sure that the bends are made carefully, and at right angles, so that they do not accidentally contact other chip pins.

The exact shape and position of the bends made will be determined by the location of the power and ground pins of the IC.

In this example, the power pin is pin 8 and the ground pin is pin 4 (the typical diagonal arrangement).

Most ceramic type bypass capacitors are not polarized, but if you happen to use a polarized capacitor, be sure the positive and negative leads go to the proper pins.

Step 2: Check the Fit

Try to insert the capacitor into the proto-board. Be sure that the capacitor goes into the correct holes (Vdd and GND), that you don't have it backwards (wrong side of the board) and that the leads do not touch any other IC pins or board traces.

Also be sure that the capacitor fits "nicely" (that is, drops right in without any lead bending or forcing required).

If the capacitor does not fit properly, carefully adjust the bent leads and try again.

Try to avoid bending the leads too much, as this may cause the leads to work harden and crack (or worse, be on the verge of cracking and then fail after the prototype board is finished).

Step 3: Fully Insert the Capacitor

When you are satisfied that the capacitor fits properly, goes into the proper pins and doesn't short anything out, fully insert it, then bend the leads over on the reverse side to hold the capacitor in place and cut off the excess. Do NOT solder the leads yet! The IC socket still needs to be inserted! Again, be sure nothing is touching or shorted.

Step 4: Install the IC Socket

Now, carefully insert the IC socket. If your proto-board has very small holes, you will need to be very careful not to bend or damage the IC socket pins that share holes with the bypass capacitor. Slowly wiggling or rocking the IC socket while gently pressing down will help the pins go into the holes.

Solder the two "capacitor pins" first and check that the socket is aligned squarely and seated completely on the board before soldering the rest.

You may notice that the capacitor leads tend to prevent the socket from fully seating flat on the proto-board. This will not cause any problems, but if it bothers you, simply apply light pressure to the IC socket while soldering the pins that share the capacitor leads. The soldering heat will flow through the capacitor leads and allow the socket to locally melt and "flow over" the capacitor leads.

This is perfectly OK, since the IC socket is much thicker than the diameter of the capacitor leads and there is no danger of the leads "melting in" too far and causing a short circuit.

Have fun, and happy making!

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    8 Discussions

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    Victor805

    3 years ago

    This is a neat trick, I can see myself using it when making 555 circuits. Thanks!

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    AlyssonR2

    3 years ago

    A brilliant 'ible. Simple and effective.

    I often solder the bypass cap to the wiring side of the circuit board - but you need to be careful doing this on a PCB rather than a prototype board.

    This was (once upon a time) a standard option that you could purchase, pre-installed, in IC sockets.

    2 replies
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    rakrupskiAlyssonR2

    Reply 3 years ago

    Those sockets are still available, but they are fairly expensive. And usually, they are available only in the "diagonal corners" power pin layout. If your IC has a different power layout, you're out of luck. This method can be installed onto any pins, and there's no extra cost for a special socket.

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    AlyssonR2rakrupski

    Reply 3 years ago

    They ever were expensive - and as you say, diagonal pin only - originally, they were actually specified for 74 series logic chips. I haven't seen them offered for 20 years or so.

    I always preferred to attach one myself. many of the circuit boards I used to work with, designed for socketed chips, actually had pads for fitting bypass caps under the sockets.

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    verence

    3 years ago

    And that has the advantage of short connections. Short connections mean low inductance. Low inductance means better suppression of unwanted spikes!

    1 reply
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    rakrupskiverence

    Reply 3 years ago

    Absolutely correct. The shorter the leads, the better - and this method yields the shortest possible lead path to the IC pins. Another point is that if the capacitor were mounted elsewhere on the board, several jumpers would be required to being the Vdd and Gnd together to meet up with the bypass capacitor. Not only does that waste board space and traces, it also results in excessively long leads which, on high speed IC's, could completely negate the effectiveness of the capacitor!

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    Antzy Carmasaic

    3 years ago

    A clever usage of that wasted space in an IC holder

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    BeachsideHank

    3 years ago

    Clever, tucking it in like that.