Notes on prototyping circuit boards: breadboards, perfboards, and beyond
The circuit board is the substrate of nearly all electronic circuits.
Custom printed circuit board design and fabrication can be useful for a final product, but early in development, it is often more convenient to build on a board designed for prototyping.
Shown on the left: several blank 5x7cm paper PCBs for prototyping.
I began with a full-size and miniature breadboard:
A bigger but more expensive breadboard would be the 3M 922327, maybe for another time. Instead I purchased a cheaper 830 tie board from Aliexpress:
the reviews warn it arrived warped. Mine was perhaps slightly bent but not too much and easy enough to bend back to fairly straight. Here is the 830 tie board from Aliexpress ($1.63) in action, on the left, side-by-side with the 830 tie board from Sparkfun ($5.95) on the right:
So far so good. (Update: since have rewired on a bigger breadboard, see: Upgrading to a giant breadboard for Raspberry Pi GPIO peripherals) Breadboard are useful for quick prototyping, but for anything slightly more permanent, or when your breadboard fills up (as mine has, shown above), something else is needed: printed circuit boards.
I also purchased this lot of perforated printed circuits boards at Aliexpress:
- 99003 Free shipping 10Pcs new Prototype Paper Copper PCB Universal Experiment Matrix Circuit Board 5x7cm Brand $1.56
note they are “paper”… not the more common woven fiberglass FR-4 material. These boards are also single-sided. At 15.6¢/each, you get what you pay for, but they are better than nothing and I was in desperate need of prototyping boards. So how well do they work in practice?
Here’s my first test, board #1, transferring the buzzer circuit from Pulse-width modulation: using PWM to build a breathing nightlight and alarm:
And the reverse side, poorly soldered, including wire with melted insulation:
I made some minor changes, using a 1N4148 diode, also salvaged, because the leads of the 1N5404 diode were too thick to fit into the holes, but fortunately the smaller diode is more appropriate in any case.
For completeness, here’s the schematic (added in GitHub: nightlight):
The 3-wire cable is hooked up as follows:
- 1 (yellow): ground
- 2 (white): GPIO 19 (board pin #35) input to Raspberry Pi
- 3 (green): power
Works quite well, much more reliable than the flaky sky-wired circuit that would stop working if you looked at it funny:
Test using a script to send an AC waveform using PWM:
and then with nightlight.py, available at:
At a local electronics store, also bought a Schmartboard 0.1" through hole w/ 0.05" offset grid, 2x2 in 201–0001–01, $5:
This board has some good things going for it: double-sided, 0.1" spacing with a 0.05" offset grid for more flexibility, but on the other hand it is smaller (2x2" = 5.080x5.080cm) and much more expensive, $5 vs $0.156 each. My 2¢, I do not believe this is a good value, especially considering:
Custom PCB Manufacturing
Can we make our own?
dirtypcbs.com Dirt Cheap Dirty Boards offers 10 boards of 5x5cm for $14, or $1.40/each! And in any custom design, not specific to grids of plated through-holes.
What dimensions? Sick of Beige case PCB specifications:
DP5050 = 50x50 mm = 5x5 cm, but “6.0mm recommended keepout”. Would dirtypcbs 5x5cm order be suitable for these templates?
- Eagle PCB templates
What kind of board would be most generally useful to have ten copies? To start out with, a plain old perforated board with 0.1" spacing for through-hole components. Of course, the real advantage of ordering from PCB manufacturing companies is you get to design your own board.
Comparing the options:
- $5.000/ea (1x), Schmartboard 5.080x5.080cm, 0.1" + 0.050", 2-side
- $1.400/ea (10x), Dirtypcbs 5x5cm, 2-side, custom design
- $0.156/ea (10x), 99033 Aliexpress paper PCB, 5x7cm, 1-side
custom PCB manufacturing beats the Schmartboard, but nothing beats the Aliexpress paper PCBs in price.
Ordering custom PCBs seems like a very attractive option, I have not yet so cannot vouch for these services at this time, but in the meantime let’s consider some completely different alternatives:
Sky-wiring is soldering component leads directly together, no board involved. My least favorite technique, granted it could be useful for smaller confined circuits, but for anything moderately complex this quickly becomes unwieldly: difficult to trace, debug, and often mechanically unstable:
I only used sky wiring out of necessity when I lacked available board space. The above picture is the “before” from Tools upgrade: Hakko FX-951 soldering iron and more, since superseded by a tidier printed circuit board assembly.
Island Pad Copper Clad
Are through-holes even necessary? w2aew demonstrates in #122: Electronic Circuit Construction Techniques: review of some prototype circuit building methods a novel technique using a copper-clad board, drilling out islands for isolated solder tie points, QRPme Island Cutter Kit. The copper can also be cut with an X-Acto knife. Through-hole components can be soldered on top of the board as if they were surface-mount; plated through-holes are not strictly necessary. Hackaday cutting islands into copper-clad PCBs:
Building on top of the copper-clad has the advantage it can function as a ground plane, for high-speed circuits. Aka “island pad” prototyping.
One could start with a copper clad board such as 5pcs Epoxy Fiber FR4 Copper Clad Plate Laminate Board Double Side PCB 75 x 100 x 1.5mm 10X7.5cm, $4.50 on Aliexpress:
However a downside of the island pad method is there is no solder mask:
a thin lacquer-like layer of polymer that is usually applied to the copper traces of a printed circuit board (PCB) for protection against oxidation and to prevent solder bridges from forming between closely spaced solder pads
this is important for closely-spaced surface-mount chips, of course.
The island pad technique with its built-in ground plane may be useful for higher-frequency radio circuits. For now, I am passing on this idea.
Surface Mount Boards
Surface-mount prototyping is a whole ‘nother can of worms.
Schmartboard sells SMT to DIP adapter boards (including for Quad Flat No-leads QFN packages, with grooved traces as seen in EEVBlog #408 — Schmart Board 0.4mm QFN SMD Soldering). As does Adafruit, such as the SMT Breakout PCB for SOIC-20 or TSSOP-20–3 Pack! for $4.50.
PCBs are essential for surface-mount. See the Adafruit Soldering an SOIC guide and StackExchange. Schmartboard EZ Discrete #1 and #2 supports many SMD package types, but with specific footprints for each, what about something more general? There is a retired product from Sparkfun, the Bandicoot Protoboard:
and another one with thru-hole and surface, the Diprotodon Protoboard:
The (retired) Diprotodon almost looks like a good compromise, but the through-hole spacing is 0.1" (100 mil), and this is also the size of the surface-mount pads — but many surface-mount chips have smaller spacing.
Neither the Bandicoot nor Diprotodon have pads on the back, a possible improvement. A hypothetical improved protoboard layout could have:
- 2 layer PCB design, solderable on both sides
- Dimensions within 5 cm x 5 cm, for cheap production
- Support for common surface-mount component footprints
Another data point, @cloidnerux’s homemade SMD prototyping boards:
a grid of solder pads of various sizes.
Found this intriguing ProtoPadV2 on dirtypcbs:
PCBs for prototyping surface-mount is nothing new, Analog Devices’s Rarely Asked Questions: How do I build breadboards with tiny surface mount (SM) ICs?:
There is a solution. If we build small PC boards with pads and tracks fitting these small packages, but leading to relative large (0.1" × 0.2" [2.5 mm × 5 mm]) pads around their edges, we can mount the ICs on the PCBs and then breadboard with conveniently- sized leaded components.
A purpose-built surface-mount PCB may be more practical than a generic design, due to the multitude of footprints of chip packages available. This may be a bridge I’ll cross later, but not at this time, not for this article.
There are infinite options for prototyping circuits. Expensive full-featured breadboards, custom circuit board fabrication, novel techniques, and the classic perforated circuit board. Although there is more that could be done in the future for greater capabilities, for a few bucks:
- Breadboard 830 Point PCB Board MB-102
- 99003 Free shipping 10Pcs new Prototype Paper Copper PCB Universal Experiment Matrix Circuit Board 5x7cm Brand
…total $3.27, I expanded my prototyping capabilities significantly. To recap, the first usage of these paper PCBs for a circuit, the sky-wired kludge before: