QCB: QUICK CIRCUIT BOARD

QCB stands for Quick Circuit Board.

The concept of QCB is based on scoring the non-connections rather than laboriously draw connections on the copper clad board. The complexity of technology of making traditional PCBs can be virtually reduced to pencil and paper technology using QCB. Though very complex circuits might not be possible with QCB, moderately complex circuits involving one or two ICs are indeed possible. Complex circuits might be developed using modular approach.

Salient features of QCB:

• Quick process
• Layouts can be easily documented
• Easy templates
• Easy and quick reproduction
• Pure mechanical process with no chemicals
• Professional quality
• Very small footprints possibles
• Very simple tools required
• Easy checking of circuit
• Easy conversion of schematic into circuit
• Low resistance circuit

Step 1: Tools and Materials

Let's start with what you do not need:

1. Etchant of any kind
2. Masking of copper clad boards
3. Hefty PCB designing software
4. A lot of time, tools, problem solving, cleaning, disposing off, etc.

Now, what you do need:

1. Copper clad board
2. Schematic of the electronic circuit (even hand drawn wiring diagram will do)
3. Inkscape and inkjet printer OR pencil and paper (plain, graph or sticker paper)
4. HSS hacksaw blade (NOT shown in figure; cutter was tried earlier but was found to be inconvenient; HSS blade is best as it can cut any material with ease)
5. Straight edge (anything straight will do)
6. Manual pen type PCB drill (see figure) with 0.8 mm drill bit
7. Center punch
8. i-Can-Hold
9. Glue stick
10. Scrap piece of wood
11. Some spare time

Optional requirements (does not matter much if you don't have)

1. Oregano (optional: It's free and easily simulates schematics)
2. Multimeter or continuity tester (optional: For checking connections)

Step 2: From Schematic to Artwork

This step is basically preparatory step. All your thinking is to be done in this step. You will require a nice drawing software. I prefer inkscape because it is a very good software available for free. All work done on inkscape can also be done by just pencil and paper. The images of circuit fabricated and other helpfull inkscape images can be seen in this step. Monostable operation of IC555 circuit was built feasibility of QCB. This circuit worked successfully when fabricated as QCB.

This step is the only time consuming step of this instructable. After that it is as simple as drawing lines on paper.

The basic concept behind a QCB is drawing non-connections rather than connections. This change in point of view reduces the number of lines to be drawn, makes circuit layout simple, makes use of simple drawing software possible.

Now the steps:

1. First set the line thickness equal to 110% of thickness of hacksaw blade.
2. Draw component profiles using simple shapes such that their dimensions correspond to the outer dimensions of your component. Save this file as it can be reused for any new circuit.
3. Draw 0.8 mm circles. These circles will represent places for drilling holes for pins.
4. Divide your components in two groups - IC and non-IC.
   1. Non-IC components include resistors, LEDs, transistors, etc. These components can be simply represented by rectangle or circles.
   2. ICs can also be represented by simple shapes but require a little work on their part. First, make small rectangles to represent connections for each pin. Like IC555 timer has 8 pins so draw 8 small rectangles. Now place the IC profile with 8 circles on top of these rectangles.
5. Once your individual component drawings are ready we can start making the circuit. Using your schematic and using the union option of inkscape to combine the small rectangles. Layers can be used for drawing the layout. Let's call this drawing with components as component side layout (see first figure).
6. Now, you just require the holes and the black lines for your copper side. In a copy of drawing delete everything else so that only black outline and black dots for holes remain. Now mirror the image and print. Lets call it copper side layout (see second figure).
7. Print both component side and copper side layouts on a plain paper.

Step 3: From Artwork to QCB

This is final step in construction of QCB. The procedure is divided into following steps:

1. Cut and paste copper side layout on copper side of the copper clad board.
2. It is recommended to first center punch on the black dots. Then drill all the holes.
3. Now scribe all the black outlines using an empty ball point pen before starting to score.
4. Next score all the black outlines using HSS hacksaw blade. In case you over score, the score may be corrected by shorting the two copper blocks while soldering.
5. Finally, clean your QCB using appropriate emery paper.
6. Optional: Check the continuity of copper blocks for any short circuits. If present you might require to score that path again.
7. It is recommended to visually check the short circuits after soldering.
8. QCB is ready for soldering.

Further reading:

1. https://www.instructables.com/id/The-Saltwater-etch-process/
2. https://www.instructables.com/id/Rapid-prototype-PCB-engraving/