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Is 4 layer PCB cheaper than double sided with SMD components on both sides?

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treez

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Hello,
Which method is likely to be cheaper to produce?
1…Having a double sided PCB , with surface mount components on both sides, or
2….Having a 4 layered PCB, with surface mount components only on one side.

(This refers to a 10cm x 10cm offline SMPS PCB which also has some monitoring and control circuitry on the secondary side.)
 

Dan Mills

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Depends on volume, number of parts and the presence of any thru hole components, generally best just to send the BOM to your favored assembly house and ask them to quote for the quantity you need.

Regards, Dan.
 
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treez

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volume is 10,000 per year, yes thee are a few thru hole components.
We would like to have smd on bottom and only thru hole on top, but its tight and we may need to go smd+thru hole on top, and smd on bottom.
Or, we could do it with 4 layer and have smd only on bottom...because the 4 layers would push some of the tracks out of the way, so to speak
 

Dan Mills

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The issue is usually the desire to use reflow for SMT but wave soldering for the thru hole stuff, can be a bit of a pain with parts on both sides.

You should be having a serious talk about capabilities and DFM with your chosen assembler, working with them will make a real difference at those volumes (Not a space I play in, we do very much smaller runs then that).

Regards, Dan.
 
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marce

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2 extra layers or two SMD assembly runs.....As Dan said talk to suppliers.
Which will be best for EMC and signal integrity considering it is a SMPS?
 

isphu

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4 layer also more expensive than 2 layer, I think so.
But, quality of 4 layer is better because that it can be reduce EMI issues and meet some require of signal integrity, power integrity.
 

hobbyckts

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Single side components will reduce your assembly costs and also improve the emi. Whereas for the double side assembly you need to have two different stencils and also it takes more time to complete assembly.
 

ArticCynda

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It also depends on the type of components you'd like to place on the solder side, if the they're small (i.e. jelly bean caps) then they'll stick naturally to the solder. However, larger parts (ICs) will fall off and need to be glued to the board prior to soldering if the board is reflowed upside down, also adding to the cost.
 

SunnySkyguy

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The cost of any circuit board in volume is always proportional to the total weight of copper used in the panel. This becomes a product of the weight per area and number of layers of each. E.g. x cents per oz per sq.cm

Thus a single layer is always cheapest, but must be designed to distribute power and signals with necessary shielding required such as ground planes if RF EMI or controlled impedances are needed.

But this latter area gets into choices between stripline or microstrip and proximity to crosstalk.

When heat dissipation is a requirement, MCPCB's offer better performance. When signals push beyond 1GHz then more expensive low loss tangent dielectrics add to cost ranging from polyamid types that may cost 20% more to teflon types costing 10x more for low dielectric RF losses.

Complexity of board can increase costs by poor design with excessive microvias, BLind or buried vias etc. unless it saves area.
 

marce

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Single side components will reduce your assembly costs and also improve the emi. Whereas for the double side assembly you need to have two different stencils and also it takes more time to complete assembly.

Double sided placement can actually improve the EMC situation.......
 

Bengineer

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I would go with a 4 layer-design and look for a good PCB house based on that. There are always a manufacturer that will do the job for less:)) (maybe it's not going to be the best quality, but poor quality 4-layer board seems to be more reliable than poor-quality board with comps on both sides, like you've described.
 

marce

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Any evidence to correlate you view?
 
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robertpeng

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Any evidence to correlate you view?

Hi Marce

Bengineer is right, first of all, in this case, the price of 4Layer PCBA will be cheaper than the price of 2Layer PCB, When concern components price and assembly price, the gap between 2layer and 4layer pcb price can be ignored.
Secondly, assemble components on 2 side will enlarge the mistake rate of missing components or not assembled tightly.
 
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