Author Topic: New technique to solder the QFN chipset or it's just a failed soldering?  (Read 1886 times)

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Offline kamcmTopic starter

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My 5 bay HDD enclosure works for 3 months and suddenly stop working, so I decided to take it apart and fix it.
But I found out somethings odd with the QFN chipset.:palm:  The QFN chipset is surrounding by solder ball :-//

Is it some kinds of new technique to solder a QFN chipset or it's just a failed soldering.


http://kamserver.com/upload/2018-8/towerraid.jpg



Please let me know,

Thanks!

Kam





« Last Edit: August 10, 2018, 11:30:23 am by kamcm »
 

Offline Howardlong

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Not the best, for sure.

It could certainly do with flux and a reflow.

I had some application specific QFN parts a few years ago that were hard to wet and solder, part of it was the pad finish itself and part was that the pads weren’t continuously wrapped around the edge, there was about a 0.15mm of package plastic on the edges. It was hard to achieve a good looking joint as a result.
 

Online wraper

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I don't think there is anything wrong with it. Most likely it happened because of the package itself. Exposed metal on sides seem to be somewhat elevated from the bottom, therefore solder did not attach with it. Not that it affects anything as actual pads are under the chip.
 

Offline TomS_

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I dont think that is a new technique. Just dodgy soldering.

Solder should form a fillet, not a ball. Thermal expansion and contraction, potentially even vibration, will wreak havoc with those joints over time leading to unreliability, which you are now experiencing.

Probably its a combination of poor quality solder, poor reflow profile, tarnished pads on the package, perhaps because they havent been stored or handled properly or maybe because they are counterfeit and thus substandard manufacturing quality. If its a cheap item, its no wonder really.
 

Online wraper

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Solder should form a fillet, not a ball. Thermal expansion and contraction, potentially even vibration, will wreak havoc with those joints over time leading to unreliability, which you are now experiencing.
Solder fillet won't form to something where is no metal or it was not tinned at factory. This is punched QFN or even has PCB substrate on the bottom and plastic on top. And terminals likely are similar to the picture.

« Last Edit: August 10, 2018, 03:56:57 pm by wraper »
 
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Offline helius

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First thing to check on HDD enclosures is the power connector if it is PCB mounted. They can get a lot of force applied and it can break the PCB traces.
 

Offline KL27x

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I looked at that pic and came up with nothin... if those are badly flowed joints, the heck it ever worked. (And awesomely easy fix for the OP). Wraper's response makes the only sense.
 

Online Bud

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Look at the resistors in the top left, they also appear to have balled solder. Could be old solder not wetting the pads well.
Facebook-free life and Rigol-free shack.
 
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