Beware when it comes to solder e-caps in PCBs
One of the electronic components that is widely used nowadays is the e-caps (electrolytic capacitors). They can be found in all the electronic appliances (more than one) of any brand or model.
As you can see in the pictures above there are some symbols, but at the end, it’s for the same electronic component. But the most important fact, as can be seen in the photos above is that this component has polarization (+ and –) and this cannot be violated by any way when you solder it in the PCB. Why? The e-cap can explode.
What is an electrolytic capacitor? An electrolytic capacitor (“electrolytic”) is a capacitor in which one electrode is made of a metal on which a thin oxide layer forms. This layer acts as the capacitor’s dielectric. An electrolyte covers the surface of the oxide layer and also serves as the second electrode. Electrolytics have a capacitance to volume ratio much higher than to ceramic capacitors and film capacitors, but smaller than super capacitors. Electrolytics can be made with aluminum, tantalum or niobium as the metal electrode and use various liquid (water based or solvent based) or solid electrolytes (excerpt from Wikipedia).
Sometimes when you are going to solder this component, you have to be very careful regarding the polarization. For example, take a look at the photos below.
As you can appreciate in the figures 1; 2 and 6 the manufacturers have been very clear in marking the polarizations. In these three cases the + symbol is very well marked on the PCB.
In the rest of the figures the manufacturers have used another method for the signalization of the polarization, by using colors or marks. For example:
- In the figures 3; 4 and 7 the + is white-marked
- In the figure 5 the – is black-marked.
The above marks can be used as reference.
In some occasions I’ve de-soldered some e-caps from a circuit, and when I’m going to solder the new one I’ve presented some doubts about polarization, and then here’s my advice: as all the electronic circuits use more than one e-cap I see carefully how the rest of them are connected in the circuit and now the new e-cap can be soldered in the PCB taking in consideration the accurate polarization, you can see this in the figures 3; 4; 5 and 7.
If possible before any repair work, you can take a photo of the circuit board, wire connection, connectors and etc so that you can always refer to it back when you want to fix the things that you had removed from the equipment.
Well, I hope this material can be useful for this blog readers. Thanks.
This article was prepared for you by Humberto Rodriguez, one of our ‘Master Authors’ from Cuba.
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