Where to start with PCB Schematic optimization

Question

I am new to PCB and electronics design and I just finished designing a PCB that includes POE flyback converter, Ethernet Phy, a li-ion battery charger, and a DC/DC converter. My design is based on the reference design and BOM/datasheet recommendation of all the ICs to be on the safe side. I ended up with about 300 total and 120 unique components. Mostly it is different resistor and capacitor values but also different FETs for the various power switching converters. Assembly service is very expensive due to the high component count. How is PCB Schematic simplification and optimization usually done? Where to start? Are there any best practice tips or resources?

Answer 1

In case someone is still having the same question, this video pretty much nailed it:

https://www.youtube.com/watch?v=RwVzLOI4cmA

Summary:

• Try to reduce unique component count as each unique component needs a seperate component reel on the pick & place machine.
• Consolidate close values if possible (e.g. if you have a 11kOhm and a 10kOhm resistor, can't you just use the 10kOhm?)
• Put parts in series/parallel instead of using single parts (e.g. for 5kOhm put two 10kOhm in parallel)
• Try to avoid 0201 components as typically a special pick & place head needs to be used on the machine for handling these parts. He also talks about if 0402 are really necessary...
• Try to just omit components if they are not necessary (e.g. some decoupling caps may not be necessary - but test it in prototype first!)

Answer 2

It is not clear if you intend to go to production or just for yourself. PCBA is very expensive for small runs regardless of complexity, generally one sees prices start to fall once you hit 1ku for moderately complex embedded boards

If this is a production board, First prototypes will be expensive but they are good place to start tinkering and eliminating components, and rethinking certain circuit sections But you should at least prove to yourself your basic design works.

There is no real step by step process it's a basically project management and cost optimization a very complex topic .

Typically during design process , requirements are identified and a target BOM or target cost is identified and kept track of roughly. Requirements are important, for example the input voltage range of the SMPS and Max power hugely influence the cost of components needed to roll the regulator.

At this point this may not have happened, but you may still apply a target cost, and go slashing and hacking starting with the highest per $ part and rethink some circuits.

As an example if you have many different resistors of similar values, and you determine the value isn't very critical it's better to just nudge them all to one value so only one unique part is needed instead of several.

Going through a retroactive requirements exercise will help identify low hanging fruit/useless features/overkill in your design.

Keep in mind it isnt very easy, it is quite possible given a set of requirements that no significant optimization can be done outside of mass volume, in that case it may be valuable to rethink certainty requirements or radically rethink your design.

Sometimes there is something silly you are doing that explodes production costs, the manufacturer could provide consultation on any cost savings they can see, e.g. an expensive process step.

As an example

• if you use ten fewer unique parts we do not need to run through pick n place twice because of reel limitations
• these components must be hand soldered, if you make some change it could be automatically placed.