How do you remove an SMD that has plastic? How did they solder it in the first place?

Thread Starter

rambomhtri

Joined Nov 9, 2015
551
Hi, I was traying to remove an SMD port that has a plastic housing, like this:

1698234268085.png
(3 black ports at the left)

...and I was not able to do so. With a heat gun for electronics, I set it to 340ºC and by the time the solder joints were starting to move (but still had a long way), the plastic was already deformed and starting to burn.

I ended up switching to the most powerful soldering tip and removed the whole SMD with pure heat destruction and revenge, and soldered the cables directly to the board, quite hard, so tiny, and added some glue to make it tough.

So... first question is, how do you remove these?
I can only think of desoldering manually each pin/leg, really time consuming and tedious.

Second question, how do they solder these in the factories?
I am guessing you can't do it by heat as the plastic would melt, so... really, manually? So costly compared to "soldering ovens".

Third and last... thinking about heat gun destroying SMDs... microphones. Your typical SMD microphone:

1698234658321.png
1698234673117.png

Since that cannot be soldered with a soldering iron, it must be done with hot air by design, how do you avoid damaging the really thin membrane/diaphragm inside while doing so? How do you desolder these without destroying them?
 

Externet

Joined Nov 29, 2005
2,182
- Second and third... The parts can be meant to solder with some heat shield that is removed later; you do not know.

-First ... Perhaps parts were not designed as removable. Or removable by humans. Or are removable by the way you did and replace with a new as it is $0.01. The tedious part does not play here as work is work.

Ball grid arrays are another example, U3 on your image above ?
 

MisterBill2

Joined Jan 23, 2018
17,814
Externet is certainly correct!! Many products are designed with no intention that they would ever be serviced, ever. The design goals do not include allowing the product to ever be repaired. This is not an error or oversight, it is deliberate.
 

Ian0

Joined Aug 7, 2020
9,502
MEMS microphones will withstand the hot air gun treatment.
Surface mount pin headers are annoying. They are designed to withstand the standard soldering profile which doesn't get much above 240°C, whereas a hot air rework is rather hotter, because it is designed to get the job done quickly.
 

MisterBill2

Joined Jan 23, 2018
17,814
Why remove the microphone? If the intention was replacing a failed device, one option is to grind it away with a small rotary tool,, which can be very effective, as it will leave remains that can easily be unsoldered by conventional soldering devices. If the intention was to use the device for other applications, then other methods would be required.
 
The easiest way would be to use a reflow oven. Components that need to stay can be protected with high temperature tape. Those you want to remove leave unprotected. When temperature reaches its peak, open the oven and remove the components with tweezers.
 
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