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Author Topic: SMD removal hot tweezers??  (Read 446 times)

KD2E

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SMD removal hot tweezers??
« on: February 21, 2021, 06:55:54 AM »

Watched a video on removing leaky SMD caps.
The author used a hot tweezer, that could reflow BOTH sides of the cap at once, and lift out the cap.
Is this a device, or simply a tip for my Weller? Would like to get the correct tools before I jump in.
Thanks for suggestions!!
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KF5LJW

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Re: SMD removal hot tweezers??
« Reply #1 on: February 21, 2021, 09:54:01 AM »

They are called de soldering tweezers. Weller makes a good unit as well as a few others.





FWIW when SMD are installed they do not use solder baths. They use a paste type solder in a hypodermic needle dispenser. Kind of works like glue. Place the board in a infrared oven to set the solder paste.

Great thing about SMD is no inductive wires adding impedance where it does not belong. Wires are the enemy of of circuits.
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KD2E

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Re: SMD removal hot tweezers??
« Reply #2 on: February 21, 2021, 10:28:19 AM »

Do you know if this Weller unit plugs in to the WTCPT base unit, that I already own?  It looks like it needs to plug in to something??
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KM1H

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Re: SMD removal hot tweezers??
« Reply #3 on: February 21, 2021, 12:31:01 PM »

It tells you need 24V right on the unit and it includes the part #
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N8YX

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Re: SMD removal hot tweezers??
« Reply #4 on: February 22, 2021, 09:38:32 AM »

Pace, Metcal and a couple others also make these. Some rework stations offer paste dispensers and hot air jet handpieces which allow the operator to perform no-touch soldering for individual components. If your budget allows, I highly recommend the complete set of SMT tools if you're doing anything more than a one or two-off repair.
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KM1H

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Re: SMD removal hot tweezers??
« Reply #5 on: February 22, 2021, 11:27:37 AM »

I picked up a complete rework station some 22 years ago at a company auction. Not as fancy as the latest but sure works well especially with the B&L stereo microscope.

Carl
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K5LXP

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Re: SMD removal hot tweezers??
« Reply #6 on: February 22, 2021, 04:01:10 PM »

I have the pace station with tweezers.  I do both personal and commercial work and in the span of 20+ years I might have used it 3 times.  It seems like a neat idea but in practice it doesn't buy you much.

Mark K5LXP
Albuquerque,  NM
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SOFAR

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Re: SMD removal hot tweezers??
« Reply #7 on: February 22, 2021, 04:22:28 PM »

I have the pace station with tweezers.  I do both personal and commercial work and in the span of 20+ years I might have used it 3 times.  It seems like a neat idea but in practice it doesn't buy you much.

Mark K5LXP
Albuquerque,  NM

Depends.
I've seen tweezers used to tin multiple sets of pads, before attaching a digitizer connector on an iPhone board.

Some tools are more versatile than the name implies. And people develop their preferred methods.
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W1VT

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Re: SMD removal hot tweezers??
« Reply #8 on: February 22, 2021, 06:26:58 PM »

I use a large tip that will heat both sides of the capacitor at once.  I'll add enough solder to float the capacitor to one side, then pull the capacitor off the board. Finally I'll use Solder-Wik to remove the excess solder.

Zak W1VT
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W9WQA

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Re: SMD removal hot tweezers??
« Reply #9 on: February 23, 2021, 09:08:51 AM »

They are called de soldering tweezers. Weller makes a good unit as well as a few others.





FWIW when SMD are installed they do not use solder baths. They use a paste type solder in a hypodermic needle dispenser. Kind of works like glue. Place the board in a infrared oven to set the solder paste.

Great thing about SMD is no inductive wires adding impedance where it does not belong. Wires are the enemy of of circuits.


but not 100 yrs ago
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K6BSU

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Re: SMD removal hot tweezers??
« Reply #10 on: February 23, 2021, 04:11:47 PM »

Think about this.  A SMD component which is bad doesn't need careful removal.  I have found intermittent resistors, bad caps, etc.

I just break the component into little pieces and remove the old  leads, one at a time.
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N8RKD

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Re: SMD removal hot tweezers??
« Reply #11 on: February 25, 2021, 07:01:35 AM »

I use a large tip that will heat both sides of the capacitor at once.  I'll add enough solder to float the capacitor to one side, then pull the capacitor off the board. Finally I'll use Solder-Wik to remove the excess solder.

Zak W1VT

What's your preferred method for replacement?
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W1VT

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Re: SMD removal hot tweezers??
« Reply #12 on: February 25, 2021, 07:17:11 AM »

I am cross dominant so I hold the capacitor in place with stainless steel tweezers with my left hand and tack solder the part in place with my right hand. 
If necessary I can hold a bit of solder in place with the left hand as well.

Then I solder the other side of the capacitor in place.  Finally, I solder the tack soldered side of the capacitor.

I've built fifty microwave transverters so I have a lot of practice with surface mount parts.

Zak W1VT
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WD4HXG

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Re: SMD removal hot tweezers??
« Reply #13 on: March 01, 2021, 12:52:20 AM »

They are called de soldering tweezers. Weller makes a good unit as well as a few others.



FWIW when SMD are installed they do not use solder baths. They use a paste type solder in a hypodermic needle dispenser. Kind of works like glue. Place the board in a infrared oven to set the solder paste.

Great thing about SMD is no inductive wires adding impedance where it does not belong. Wires are the enemy of of circuits.
I use a large tip that will heat both sides of the capacitor at once.  I'll add enough solder to float the capacitor to one side, then pull the capacitor off the board. Finally I'll use Solder-Wik to remove the excess solder.

Zak W1VT

What's your preferred method for replacement?

I use a low temperature solder paste sold in a barrel syringe with plunger. Use a fine needle such as an insulin pen syringe needle for the solder paste syringe barrel 'Luer Lok' tip. Insulin syringe needles provide fine dispensing but may be a problem to purchase if you are not diabetic. In North Carolina fine gauge needles for use with insulin syringes are sold in CVS pharmacies without a prescription. You simply walk up to the display. Pick up a box and pay the cashier at the front of the store. Alternatively you can buy blunt tip needles for the solder paste tubes from many online suppliers of surface mount tools. While the blunt tips are not designed to puncture skin they can still easily break the surface and cause a nasty wound. Be very careful as it can be embarrassing explaining how solder paste came to be located under your skin. The clean out is not pleasant.

I select #30 and #31 gauge blunt or sharp needles for dispensing paste on fine pitch pads. Pads with spacing greater than 50 mils and  50 mils width I use #28 gauge needles. Ideally a compressed air dispenser is used for paste application. But for just two or three pads, patience and persistence are sufficient.

Melting the solder as close as possible to a production floor technique using hot air is done with a hot air gun. While some use the cheap guns from Harbor Freight etc, I use a Weller Gun which has multiple tips that allows tightly focused low velocity air to heat small spots such as found with 0603 or smaller parts. It also has tips for larger areas. You remove the source of heat when you see the solder paste flow, the part does a quick wiggle and aligns itself on the pad.

While I have in the past used a soldering iron and solder wire to attach capacitor and resistor SMD's I avoid that today. If you read the approved attachment methods provided by the part manufacturers, in many cases they only warranty the parts if you use their approved attachment methods. This is particularly true when attaching high value IC's and transistors with extended temperature ranges and specified for use in high reliability environments.

Be forewarned if the part you are attaching is a part that shipped in a hermetically sealed bag then there is a time limit of 24 to 48 hours nominal to place the part on the board and reflow attach it after breaking the seal on the shipping package. Any hand soldering operation is usually verboten as the temperature contour for the part during attachment is tightly defined and must be uniform to maintain the warranty.

While some may have excellent vision which allows attachment of SMD devices without vision assisting devices, as you grow older that gift usually fades into the sunset. I now use a Bausch & Lomb Stereo Zoom Microscope for new work and rework. Especially when performing post attachment inspection of the work and surrounding area it really is a necessity. If the part is thermally stressed beyond spec, micro fractures can develop on the part terminations such as found on caps and resistors. Without sufficient magnification they will be overlooked.

When attaching surface mount power transistors read up on the approved attachment techniques. It is not unusual for ceramic packages to separate around the area were the lead enters the ceramic body when moisture in the air that seeped in around the lead expands during soldering. The moisture expansion will push the package apart if excessive temperature is used or heat is applied to long or heat is applied non-uniformly. Verify the manufacturer's attachment procedures.

Regards

Chuck
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KH2BR

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Re: SMD removal hot tweezers??
« Reply #14 on: March 12, 2021, 08:37:36 AM »

I just use 2 soldering irons. One in each hand. Don't need a fancy , or outrageous way to remove anything.
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