This is too one-sided. There are many boards with double-sided components.

If the circuit board is limited space resources, many components on the back save area.

If from the performance point of view, some components such as decoupling capacitors and chips on the same level, in order to reduce the decoupling path for better decoupling effect.

For example, some RF circuits, the signal line is best not to wear layers, so most of the chips on the same floor, Shanghai chip manufacturers in order to ensure decoupling effect, most of the decoupling devices are also placed on the same floor, so it appears that many devices It is best placed on the same layer to ensure performance, but even then there are still many devices can be placed on the ground floor, the main consideration that through-hole vias have little effect on performance. Put the bottom does not affect.

So, ah, or specific issues specific analysis. Not so absolute.

Look at what kind of circuit board you are, the graphics board you have to pay attention to the two sides are placed.

However, the motherboard touches only one side of the placement of parts, others in order to save costs, factory production of double-sided parts and single-sided parts foundry fee is not the same.

There is the plug-in components (we call DIP) are generally on the front, because we first play patch components (we called SMT), and GPU this is also the heavier components in the positive, if the DIP on Opposite when the tin stove heavier components will fall.