Introduction: Hand Solder Embedded Pin Smd Ics Like Qfn

What is embedded pin IC (my term)

Packs of SMD ICs like QFN ,DFN  have  pins embedded to the plastic body.
So as you place  the  IC  on  the board soldering appears to be difficult.
why ? because u cant align the ic pin by pin easily  as pins are hiding below.

,a slight 10 degree misalignment  will result in bridge of solder .

The steps elaborate the trick to perfectly align the chip and hand solder .

Read the link below  before doing this..
My instructible is inspired by :https://www.instructables.com/id/hand-soldering-teeny-tiny-chips!/



 

Step 1: What Tools You Need

Just a few usual tools : 

A fine point soldering iron cheap ones will do, fine solder wire  low melting type (180deg ) like  WBT.
(This will make the task easy),cleaning sponge , paste flux,tweezers.12x magnifier
 if you have good eyes u can manage without it . 

One strong LED light 1 -2 cm round  preferred. I used  SE w810i mobile phone LEd light.
other tools like helping hand etc.



Step 2: Place the Ic Properly

Check for  PIN 1 :

There is a dot indicating pin 1 . Check the proper placement  from the documents you have or your pcb design.


Flux the IC pads on PCB. Add a little  solder to each pin pad at the PCB .When done, Put a little flux to all pads again.
Add little solder on IC pins too .


TIP:  Use very small amount of solder , clean the pins with PCB cleaner or scratch lightly with blade.
Add flux and solder ,try to  touch the pins only  with soldering Iron to prevent damage to plastic pack.

File the soldering Iron tip to make it thin ..heat just enough to melt the solder..otherwise the tip will bend  as it is filed .



now hold the chip in tweezers and place  according to  the  pin 1 dot .



Step 3: Examine Under Light

Now use the strong LED light from "backside of PCB" at 45degree .

Why ? this angle will let the copper part on the sides of the QFN and PCB pads visible together .

Carefully align the IC till two adjoining corner pins match with pads.

IMPORTANT. :
 See that IC is placed in such a way that pads are a little visible.You will touch the pads to attach the IC.



Step 4: Tape It

Recheck all pin alignment with light .. then use the duct tape to make it stay in that position.

Remember: taping can misalign the IC a little , recheck and remove the tape if needed .
Make sure that final taped position is correct. 



Step 5: Anchor It and Final Solder

Well all complicated  things done  now start anchor point soldering .

Corner two pins you solder first . see the position of the I C , adjust a little
 by melting the solder if needed.


After this you can remove the tape,now the IC is secured . 
Just solder the other pins by touching the pads .  add a little  flux time to time .


Tip : Dont heat the chip continuously, do it for 5 -6 sec and stop.
 Let it cool ... then gain do other pins .

 Refer this instructable for that process: https://www.instructables.com/id/hand-soldering-teeny-tiny-chips!/



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