Why are flex PCB's so expensive?

[allanw]

I came across this: http://www.synopticlabs.com/blog/?p=97

And thought it'd be cool if I turned my TLC5947-based RGB stick into a flex PCB that was spaced out much wider.

However, flex PCB's seem to be ridiculously expensive. The cheapest I found was Golden Phoenix which has them for $280/100 sq in (650 sq cm). If my strips were to be 100cm by 3cm, they'd cost $150 in PCB costs alone. Why are they so expensive when you can buy LED strips like this for so cheap?

http://www.adafruit.com/index.php?main_page=product_info&cPath=37&products_id=306

http://cgi.ebay.com/1M-30-SMD-5050-LED-RGB-Remote-Control-16-colors-Strip-/180578978021?pt=LH_DefaultDomain_0&hash=item2a0b5888e5#ht_2247wt_905

[JohnS_AZ]

It's been many years since I was involved in commercial PCBs, but here's my understanding;

Regular PCBs are made on a fiberglass substrate, a VERY inexpensive material.
Flex circuits are made on something like a very thick (relatively) Kapton-like material which is a lot more expensive.

Long linear material, like the LED strip stuff, where the pattern is simple and repetitive can actually be made by screen printing the pattern with a conductive material, and then plating the copper on top of that. On a lot of flex circuits if you look on the metal side you see copper, but if you look at the back side through the substrate the patterns all look jet black. While the substrate is still more expensive the producer completely eliminates all the photo-lith etch processes, and saves a boat load of money.

An aside, most people don't know that flex circuits with components mounted are not rated to be continually flexed. You'll get micro fractures where the components are soldered. Thus Ladyada's LED belt isn't going to last all that long. 

[gobblegobble]

Let me toss a guess on instict.

They're much less common and therefore the lower market volume drives the prices up. Correspondingly everything manufactured in hefty amounts becomes available for masses at cheap prices.

[Mechatrommer]

An aside, most people don't know that flex circuits with components mounted are not rated to be continually flexed. You'll get micro fractures where the components are soldered. Thus Ladyada's LED belt isn't going to last all that long. 

isnt there any possibility for workaround of this matter? sort of mechanical stuff (padding, support etc) to avoid fracture, excessive flex and shorter life?

[joelby]

isnt there any possibility for workaround of this matter? sort of mechanical stuff (padding, support etc) to avoid fracture, excessive flex and shorter life?

Just use a thicker substrate. FR-4 is pretty good!

[alm]

Just stick an nVidia GPU on there