What SMD parts are more likely to fail from excessive reflow time - Page 1
Forum section: electronics / general

author: Psi
author_rank: Super Contributor
timestamp: June 03, 2017, 04:52:04 am
content: Does anyone know what types of components are more susceptible to failure after spending a bit long in the reflow oven? (max temp <230C)(guess who walked away from the toaster oven and forgot. heh, they got ~8min instead of 4min)All the PCBs seem to work fine, i'm just curious if there's anything i should replace by hand for long term reliabilityTant/Elec caps and LEDs come to mind?

author: Ampera
author_rank: Super Contributor
timestamp: June 03, 2017, 04:59:58 am
content: In my noob experience, standalone transistors tend to die from heat fairly easily (a bit too heavy on the soldering iron killed one for me iirc)Silicon in general doesn't stand up well to heat. Short bursts are fine, but you'd be hard pressed to find an IC that can stand 230C for extended periods of time.Anything plastic I'd imagine to not last that long, but if everything looks good, then that's alright.

author: German_EE
author_rank: Super Contributor
timestamp: June 03, 2017, 07:06:50 am
content: Some capacitors depending on the insulation used, a polystyrene device will have problems. Didn't Dave melt a connector on a flat screen TV once during some soldering?

author: KL27x
author_rank: Super Contributor
timestamp: June 03, 2017, 07:30:08 am
content: Any SMD ceramic resonators are toasted. Even if they work, they will be far out of spec.

author: SeanB
author_rank: Super Contributor
timestamp: June 03, 2017, 08:00:24 am
content: To be fair to polystyrene, it starts to soften at 70C, and polystyrene capacitors were always put in with long leads or with a heat shunt on the lead, and a short solder time. Film capacitors in general are the issue, they will eventually melt but that is easy to see. Electrolytics will survive till they pop. Connectors, LEds, displays and precision analogue IC's, zeners and reference diodes will all have some parameter shift, and probably for some a shorter lifetime, but hard to say without knowing what, how long and how they look and compare to the reference parts in the next position in the reel.

author: Kjelt
author_rank: Super Contributor
timestamp: June 03, 2017, 11:18:35 am
content: Leds, not the die but the lens and devicehousing are pretty picky.If you reflowed for double the time at the max temp than I would suggest to inspect the solderconnections under a microscope. The flux starts to evaporate pretty quickly at those high temperatures keep on heating after the flux is gone could cause bad joints, mechanically brittle, oxydation of pads, and who knows what. The same troubles you get if you handsolder remove the tin with flux and keep on heating the connection, not good. So if lead paste check if the solder is shiny and without cracks or polution.

author: Zero999
author_rank: Super Contributor
timestamp: June 03, 2017, 03:34:18 pm
content: Yes capacitors are easily killed by heat, especially polystyrene, which I haven't seen in surface mount packages designed for re-flow, only through hole.

author: cvanc
author_rank: Frequent Contributor
timestamp: June 03, 2017, 03:53:22 pm
content: Years ago I had an entire production run of video A/D converter boards that went thru the wave soldering machine too slowly. Those boards had ceramic SMD caps that had pretty much a 100% failure rate in the next 2 years or so. Huge problem for the company I worked for.