Are chip scale packaging a problem for mid-volume designs ?  - Page 1
Forum section: electronics / general

author: autobot
author_rank: Regular Contributor
timestamp: November 18, 2015, 09:10:22 pm
content: How big is the issue of chip-scale packages (like wlcsp) is for mid volume(1K-10K units) designs ? Do such packages prevent many good chips of being used , or usually the alternative packages and chips are good enough ? or at this scale using such packages doesn't even pose a problem ?

author: poorchava
author_rank: Super Contributor
timestamp: November 18, 2015, 09:32:25 pm
content: CSPs have one real problem: ball pitch. Aside from very low pin count ones (eg. 2x2) you are pretty much forced to use advanced pcb fabrication process - most notably very small feature size (<100um trace/gap) and via-in-pad (because it's next to impossible to fit a via in between ball under 0.4mm pitch package). Fine artwork also forces thin copper eg. 0.5oz fina? thickness, which means that having high current circuits on the same layer might be a problem.Another thing is that CSPs are often sensitive to strong light because of photoelectric effect (eg. RPi 2 resetting when a camera flash is fired at voltage regulator).If your budget can eat the additional pcb cost (both per-piece and setup costs) there should not be a problem. Modern PnP machines usually handle CSP-sized stuff well enough.Sent from my HTC One M8s using Tapatalk.

author: autobot
author_rank: Regular Contributor
timestamp: November 18, 2015, 10:16:46 pm
content: Just an idea , what if there was a cheap small, thin(1-2 mm) adapter , that costs say 50-100 cents, that the PnP machine can just put between the csp chip and a a simple cheap pcb , that spreads out the IO so you won't need an expensive PCB ?Of course this has some cost in area too.Would that be interesting ?

author: cowana
author_rank: Frequent Contributor
timestamp: November 18, 2015, 10:42:53 pm
content: Quote from: autobot on November 18, 2015, 10:16:46 pmSounds like really just a bigger IC package is needed (ie not WLCSP) - it's only the minority of parts that don't have an option to come in a 'normal' package...

author: Rasz
author_rank: Super Contributor
timestamp: November 19, 2015, 05:09:50 pm
content: Quote from: autobot on November 18, 2015, 09:10:22 pmYou mostly use them when pcb space is at a premium (mobile), or when there is no alternative (rare)Of course there are companies that use them because they want to be 'cutting edge'. For example Apple, they do stupid things like using smallest possible bga package on laptop pcb when there is 3 square centimetres of empty space around. Saleale`whatever is another, from what I understand they almost went under because one of the founders has an Apple boner and decided to do 0201 in house to be cool.Quote from: autobot on November 18, 2015, 10:16:46 pmwould it be interesting to pay more for something taking more space instead of going with bigger package chip in the first place?

author: AndyC_772
author_rank: Super Contributor
timestamp: November 19, 2015, 06:04:08 pm
content: I design a lot of very small PCBs these days, and haven't had anyone push back or complain about the use of chip scale packages. Remember that one of the major benefits of any BGA type package is the larger ball pitch than a comparable DIP or TQFP would need in order to get the same number of pins in a given area. If a P&P machine can place a 0.5mm TQFP, it can probably place a 0.5mm CSP as well.On a small CSP, there may not be any balls that aren't at the edge of the device, so the fact you can't get a via under one is irrelevant.

author: Jeroen3
author_rank: Super Contributor
timestamp: November 19, 2015, 06:18:28 pm
content: BGA and WLCSP often requires >2 layer pcb. Which is more expensive.QuoteLike QFP or QFN?