why did mfrs stop placing parts vertically on PCBs?? - Page 1
Forum section: electronics / projects

author: jaunty
author_rank: Regular Contributor
timestamp: February 04, 2020, 12:37:39 am
content: i'm curious as to why after the mid 1970s manufacturer's stopped doing things like mounting resistors and diodes perpendicular to the circuit board. Anyone know about this? seems after that point you'd ONLY see them mounted flat on their through-holes. Was there an issue with parasitic inductance? parts acting like little aerials and picking up strayEMF? Cost and labour (since they had to insulate the leads and it's likely a BIT more work to place the parts? or pick and place machines needing flat mount parts?inquiring minds want to know

author: coppice
author_rank: Super Contributor
timestamp: February 04, 2020, 01:01:01 am
content: vertical mounting reduces the board area, allowing for a cheaper PCB, and makes the whole structure more 3D. This tends to suit packaging requirements better than having large low profile boards. However, vertical mounting makes things less robust. You need to ensure that knocked components don't short or break their leads. I guess you are seeing a crossover point where robust reliable results outweighed the benefits vertical mounting brings.

author: Conrad Hoffman
author_rank: Super Contributor
timestamp: February 04, 2020, 02:08:23 am
content: We still mount vertically at times- when the SMT resistors and caps "tombstone" by accident!

author: Bud
author_rank: Super Contributor
timestamp: February 04, 2020, 03:00:25 am
content: Most likely has to do with moving to automated assembly from manual one.

author: coppice
author_rank: Super Contributor
timestamp: February 04, 2020, 10:06:19 am
content: Quote from: Bud on February 04, 2020, 03:00:25 amBoard stuffing machines deal with horizontal and vertical mounting. I don't know if tthere are different defect rates for the two orientations, but they both generally work OK.

author: nfmax
author_rank: Super Contributor
timestamp: February 04, 2020, 10:10:13 am
content: I don't think they have stopped - you still see this in 'live-chassis' mains thingies, like fan timers, PIR light switches, etc.

author: Ian.M
author_rank: Super Contributor
timestamp: February 04, 2020, 11:42:23 am
content: I think a lot of vertical mounting of axial components went away when SMD became dominant. That certainly wasn't mid 70's, that's far too early unless you are thinking aboutCordwood construction.

author: ogden
author_rank: Super Contributor
timestamp: February 04, 2020, 12:03:00 pm
content: Vertical mounting is still there, especially in low cost AC/DC power supplies & modules:https://www.eevblog.com/forum/buysellwanted/acdc-adapters-12v-4-16a-50w-earth-referenced/

author: jaunty
author_rank: Regular Contributor
timestamp: February 07, 2020, 09:15:06 am
content: alright well thanks - i just haven't seen it since working on mid-70s boards - if you look at audio equipment for example - i work on synthesizers, pro audio and stereo stuff sometimes and it seems ubiquitous and reaching 'peak' levels maybe mid 70s or so and by the 80s on the same kind of equipment i'm seeing all 'flat' componentry

author: poorchava
author_rank: Super Contributor
timestamp: February 07, 2020, 02:20:27 pm
content: Vertical THT is still very much a production thing. When manufacturing in less that 1k unit batches (= when manual stuffing and other manual operations are a thing) this is a common thing to do (in our company anyway, but we do some EMS and clients' designs albo have vertical axial components).

author: ArthurDent
author_rank: Super Contributor
timestamp: February 08, 2020, 02:56:03 pm
content: Here is a photo of a brand new RD6006 power supply module. You can see that there are a lot of flat (surface mount) components but there are also parts mounted vertically on the board where it made sense. The inductors, filter caps, and one big blue resistor are sticking up to save space. If these were laying flat against the board it would have to be much larger as others have pointed out.

author: HwAoRrDk
author_rank: Super Contributor
timestamp: February 08, 2020, 04:09:05 pm
content: Speaking of caps, that seems to be one area where the trend has reversed. Axial electrolytic caps used to be fairly common, but you hardly ever see them used nowadays.

author: coppice
author_rank: Super Contributor
timestamp: February 08, 2020, 04:17:50 pm
content: Quote from: HwAoRrDk on February 08, 2020, 04:09:05 pmAxial electrolytics have only ever been common for smaller parts. I think you are looking at SMD designs, where all the small axial electrolytics have migrated to SMD packages, and the through hole electrolytics are large radial ones. If you look at designs which are still fully through hole I suspect you'll find as many axial electrolytics as in previous decades.