UniFi Express Soldering Quality Issue - Page 1
Forum section: electronics / projects

author: JimnyVR5
author_rank: Newbie
timestamp: December 19, 2023, 09:20:33 pm
content: Hi everyone...Just took apart my UniFi Express... Is this USB-C port soldered correctly?(device works)

author: moffy
author_rank: Super Contributor
timestamp: December 19, 2023, 10:00:06 pm
content: As you suspect it is not soldered correctly each pin should be filled and have a fillet of solder above the board. You'll need to touch it up by hand.

author: Shonky
author_rank: Frequent Contributor
timestamp: December 21, 2023, 04:55:58 am
content: Reminds me of this "issue" I found in two different BMWs of mine. One of which absolutely was a problem until I properly soldered it.https://empegbbs.com/ubbthreads.php/topics/363385/Press_fit_pin_header_or_bad_BMA bit hard to see from the photo but is it possible they're meant to be some sort of interference/friction fit? The shield connections look poorly soldered.

author: uer166
author_rank: Super Contributor
timestamp: December 22, 2023, 12:16:23 pm
content: The most reliable connection is a cold weld via a press fit, it is standard in well designed automotive ECUs.. Also have to add that nobody in that forum thread has any clue about high-rel automotive designs work.

author: coromonadalix
author_rank: Super Contributor
timestamp: December 22, 2023, 04:07:11 pm
content: i would say not soldered properlyon press to fit connectors, or any model / brand, you normally see the press pin, and you see correctly on how they fill the holes once pushedand sorry, to doubt the previous answer but press to weld, not sure on how they react over time with thermals and vibrations ...on the ecu's i've scrapped, i only saw soldered connectors with screws, or mechanical ways to hold them on pcb's

author: moffy
author_rank: Super Contributor
timestamp: December 22, 2023, 10:28:30 pm
content: Quote from: Shonky on December 21, 2023, 04:55:58 amI don't think they are interference fit, way too much gap between the pin and the hole, if you download the image and zoom in it's more visible.

author: uer166
author_rank: Super Contributor
timestamp: December 23, 2023, 03:09:33 am
content: Quote from: coromonadalix on December 22, 2023, 04:07:11 pmLawl:QuoteOP's USB-C or whatever connector is definitely not soldered properly (press fit makes no sense for consumer stuff), but wanted to do one last hijack to clarify press-fit misconception; It's used extensively in automotive, and just because you haven't seem one, doesn't mean it's not the most reliable way in an apples-to-apples comparison.

author: Shonky
author_rank: Frequent Contributor
timestamp: December 23, 2023, 06:36:38 am
content: Quote from: uer166 on December 22, 2023, 12:16:23 pmAnd yet it failed. So it wasn't reliable.

author: tooki
author_rank: Super Contributor
timestamp: December 23, 2023, 10:42:04 am
content: Quote from: coromonadalix on December 22, 2023, 04:07:11 pmIn the past it was mostly soldered. But the automotive industry has been progressively moving to press-fit connectors, which were already used widely in telecom, because of the increased reliability.Like the related process of crimping, it only achieves that reliability if the process tolerances are tightly controlled. Not necessarily feasible for hobby and low-volume production, but for mass production, it is done.

author: tooki
author_rank: Super Contributor
timestamp: December 23, 2023, 10:42:50 am
content: Quote from: Shonky on December 23, 2023, 06:36:38 amReliability isn’t calculated based on a sample size of one.The real question is what percentage fail when you’ve manufactured thousands or millions of units.

author: tooki
author_rank: Super Contributor
timestamp: December 23, 2023, 10:45:20 am
content: Quote from: moffy on December 22, 2023, 10:28:30 pmDisagree. Press-fit pins work by having a section of the pin stamped to widen it, creating a defined amount of pressure in the hole. It wouldn’t work if the pin filled the hole to start with.

author: Shonky
author_rank: Frequent Contributor
timestamp: December 23, 2023, 11:33:30 pm
content: Quote from: tooki on December 23, 2023, 10:42:50 amAbsolutely but this is inside the cabin with a very light duty cable harness so any vibration, stress etc would be minimal and there was no corrosion or excessive exposure to moisture. I fail to see how soldering is a lower reliability option here.Why isn't this method used everywhere in vehicles if it's more reliable? Apart from maybe an extra process.

author: tooki
author_rank: Super Contributor
timestamp: December 24, 2023, 01:58:24 am
content: I’m sorry, you think the passenger cabin of a carisn’ta high-vibration environment?!? Just because it’s not in the engine compartment doesn’t make it a low-stress environment. Everywhere in a car is a harsh environment to some extent or another: vibration of all kinds, temperature extremes, temperature cycling, humidity, humidity cycling, extremely dirty electrical supply, …Crimping, the sister process, is widely used throughout cars instead of soldering. As far as I know, press-fit PCB connectorsarebeing used throughout cars for critical ECUs.As for why not: it requires extremely tight control over the PCB manufacturing process since hole tolerances must be very tight. So that may not be worthwhile for less critical systems like the radio. (I know that solderless technologies are used even for things like tail lights, where LEDs are welded to metal frames instead of soldering them to PCBs. Solder is really bad with vibration and thermal lights, which cars experience a lot of.)

author: uer166
author_rank: Super Contributor
timestamp: December 24, 2023, 03:25:18 am
content: Quote from: Shonky on December 23, 2023, 11:33:30 pmThe method can be more expensive than soldering, especially if a PCB already has TH soldered pins anyway. It IS used absolutely everywhere in modern vehicles in extremely critical ECUs such as airbag controllers, brake boosters, ABS, power steering ECUs, etc etc.

author: ajb
author_rank: Super Contributor
timestamp: December 24, 2023, 04:13:06 am
content: Back to the OP's question, if they're still around....Clearly that connector was reflowed, as any other process wouldn't have left bare gold pads on the bottom. As I understand it, IPC standards only require 270/330° wetting at top/bottom and 75% barrel fill for that process, and even looser standards may be acceptable for some applications (it can be REALLY hard to get enough paste into a footprint for a full barrel, and many applications don't NEED a full barrel). It'd be hard to tell how much solder is in there even with the board under your nose, let alone through a single off-axis picture, but it may have been perfectly reasonable for inspection to pass this. Would be easier to judge by how the top looks, if the joints are visible, or with a straight-on view of the bottom so you can see down the barrel.And the OP has said the device works, so clearly this sample-of-one proves that every one of those connectors is perfectly soldered