Practical Electronics/PCB Manufacture
The circuit board provides a reliable contact between components (even in huge circuits), looks nicely and is quite cheap. We can design them for particular circuit or create an universal circuit, where we deliberately place the copper areas (usually as a grid) and then solder the components on the copper side without drilling.
|We can avoid printed circuit in these cases:
For reasonably small circuits it is simpliest to draw the connections on PCB with a felt pen and etch the rest. There is also the possibility of making the template with computer, more suitable for large PCBs or serial production.
- Cuprextite (laminate board with copper)
- New felt pen
- Hobby drill (1 and 1,5mm)
- Some dish for etching (not from the kitchen!)
- Roll of a toilet paper for fast wiping the etching solution from anything
- Iron chloride
Iron chloride is not only poisonous and corrosive, but also incredibly yellow. Reduce the contact to minimum. Other etching solutions are usually even worse.
|The solution of iron chloride (FeCl3) used at most. The iron III likes the reduction to iron II so much, that for the chlorine it is worth to etch the copper, which is almost inert for acids in other cases. We can use another oxidizing solutions, for example hydrochloric acid with hydrogen peroxide.|
Design of the schematic
Draw a diagram on paper and think about it so that the path of least exceeded (wire jumper doing the work).
We will prepare all components that we use. Then chart redraw soft pencil (XWarning, graphite conductive connection may be) on top (laminated) side kuprextitu, we highlight dots for future hole for the legs. Here, we XWarning to ensure that all parts fit and feet to fit into your joints.
The board of our PCB kuprextitu separated from the rest. Usually it is best to re-laminate odlamovacím incised with a knife under the sheet metal fence (with pressure) and carefully break off. You can also carefully odbrušovat laminate 1.5 mm drill.
Prortáme all the holes in the boards. For most components are 1 mm drill bit suitable for tlustonohých 1.5 to 2 mm. Provrtáním we transfer perfectly inverted image of the holes as shown on the bottom (měděnpu) party. Warning When drilling is appropriate kuprextit substantiate something that we have neprovrtali fingers or table.
Coupling of the bottom (copper) Thoroughly clean the steel wool / sponge, a sharp edge will be deducted from burrs after drilling.
Drawing the template
Draw connections between the holes as shown. Around each hole (if possible) leave 1 mm edge to give good solder. We draw carefully and concisely.
We try to cover as much surface. Thus it is not a slender connections between holes, but on the contrary, etching narrow gaps between the copper areas. It is important for the success of the etching and the etching solution for saving. Zabarvíme areas that do not lead nowhere. For a slim gap between the joints can tint the entire surface, and then carved a groove into the paint with a sharp object by the ruler.
Top plate is drawn with a template placed on the surface and let go due to surface tension. When installation is hit first by one edge and then slowly sklopíme the surface to sink or board, or bubbles are left in it. It should be below the depth of 5 mm to ensure complete etching.
The process of etching (for well-drawn plate and the normal concentration of FeCl3) takes about 15-20 minutes. During it's possible to lift the plate and look at the etching process, but very carefully - when handling the paint flakes off easily. Preview Therefore we commit as little as possible and the board should not yet dry from the etching solution.
After doleptání solution pour off back (or to another bottle), it can be reused. Rinse the PCB.
Before the solder surface can be cleaned with alcohol or paint, steel wool, or in advance Can pokalafunovat and contacts (especially to delicate heat and power in components). Errors can scramble into the copper wire together, or vice versa. Now we can join components fitted. Note the PCB sample is a control circuit and a source of rectangular signal for high voltage generator (polomostového connection with two FET transistors IRFP460). The generator generated (> 6000 VDC,> 10 mA?), but was tuned to the wrong frequency at which the transformer started to resonate (in the 3rd harmonic square wave), which led to early termination transistors. After their exchange, and careful tuning of Resonant frequency now works consistently.
Different manufacturers have different specifications to choose. Some companies offer up to 100 sqcm of PCB starting at $13. PCB specs start out with 6 mil spacing, 12 mil min. hole size, 1 oz copper, 2 layers, and 4-day lead time (plus 3-4 day shipping). Tighter spacing is available for tighter spacing down to 4 mil spacing. Small minimum drills are also available for additional charges with drills going down to 8 mils. Up to 10 layer boards, multiple colder mask colors, copper thicknesses, and other advanced options are also available.