I see the term thrown around.

 

Anyone fish a crankbait with one of these?

 

What's the point?

 

Are they super fragile??

I have some OSP and Bill Lewis fitted with CB lips.  The run really well.  There is a minute amount of flex.  They are wearing very well and I’ve yet to break one.  If you hit wood they deflect well.  I wouldn’t hesitate to buy bait with that lip material, especially the Bill Lewis ATV.  

One thing I forgot to ask, do they produce a tighter wobble?

 

I'm mostly wondering if they would excel in cooler water.

they don't produce a tighter wobble in and of themselves, but they are typically found on baits with flat sides and with geometries that make for a tight wobble.  So they are associated with that style of bait.  A rapala OG6 (or OG4) is a good example.  A little john also. The OG6 is balsa, silent, tight wobble, circuit board bill.  All of that makes for a great colder water crankbait if your fish are in the 4-8' range.

They are billed to be tougher. (See what I did) anyway I have several Spro thin cranks that are solid. I drag them along broken chunk rock, sand, pea gravel type bottom comp. I haven’t broke one yet but naturally they show wear from the way I use them..

I think the circuit board just reduces weight and drag as it wobbles side to side. Basically allowing whatever action the body is trying to achieve to be less "muted" by a heavier thicker bill. A flat side will still have that tighter wobble but might be able to achieve a faster rate back and forth, a deep diver might be able to get slightly deeper without the added bouyancy of a thicker bill, a squarebill might "hunt" better without a thicker bill muting it's action when it deflects. 

The traditional plastic used for diving bills are polycarbonate (Lexan) molded into a specific shape to optimize diving depth and lure action.

Circuit boards are layers of fiber glass flat sheet with resin cut to shape used for bills.

circuit board sheet is very strong and combine some flex with rigidity and light weight. However the bills are flat, thin and not cupped good for shallow diving crank baits and some swimbait tails. 
Think of circuit board bill as light weight metal bills.
Tom

I have some spro squarebill crankbaits that have them. I don’t fish them enough to notice the difference.

Have some on my OSP Buzzin Crank Heavy Hitter...

 

They are indeed very strong for how thin they are.