Pros and cons of using resistor networks over individual resistors?

Question

I've been looking over some board designs and have been trying to identify the reasons behind using resistor networks over individual resistors. Some guesses I can think of are a reduced part-count and complexity. Does it also follow that a design using a resistor network is cheaper than one that uses individual resistors? Because of this, I would think one would try to maximize use of networks, but many of the designs use several individual resistors instead and I can't figure out why.

And a separate but relevant question: are capacitor networks in the same boat?

Answer 1

Typical advantages of using resistor networks:

• Smaller part count, as mentioned. Therefore faster assembly.
• Better matching of individual resistor values and drift, by being in the same package.
• Saving board space: Not always, but when you account for the keepout area for individual parts, it's an even bet.
• Cost of BOM: Not necessarily, but for sufficient volume, almost certainly.

Why every design does not use resistor networks:

• Availability - Not as ubiquitous as individual resistor values
• Coupling between resistors: Especially a risk with the smaller network packages
• Cost: For smaller volumes, likely to be more expensive than the individual resistors
• Layout convenience: It can sometimes get exasperating to fit traces around a 8-lane highway toll bridge of a network.
• Flexibility: All the resistors in a network are typically the same value (R-2R networks do exist), while actual designs do not always need 4 or 8 resistors of the same value at the same location on the board.
• As @ThePhoton mentions in his answer: Tolerances available

Answer 2

Resistor networks generally take up less space than an equivalent number of discrete resistors.

And placing a resistor network involves only a single pick-and-place operation, which could reduce your assembly costs.

On the other side, networks are generally only available off-the-shelf in 5% tolerance, so if your design requires 1% or better you might prefer individual resistors.

Some reasons to prefer individual resistors:

• You need to place the different resistors in physically separate locations (for example, to minimize track lengths)

• You might need to change a resistor value while debugging your circuit, and you won't want to have to change several values in the same way.