[SOLVED] Some basic tips and help required for SMD soldering

[arbj2]

Hi,

I am based in India (New Delhi), I normally solder DIP devices, I would now like to move to SMD soldering. I am trying to solder this component onto a PCB

http://cds.linear.com/docs/Datasheet/3470fd.pdf

The device (LT3470) is a TS8, TSOT23 package.

Based on some google searches and viewing some youtube videos on SMD soldering techniques, I have compiled the following list of items needed.

1. A 10X Loupe (is the magnificatyioon enough??)
2. Solder Wick
3. Solder Paste
4. Solder Flux
5. Fine Tweezers
6. SMD soldering/rework station (heat gun, with other accessories)

Please advise what other items would be required, also whether the SMD soldering/rework station would be required. I have a temperature controlled goot soldering station, soldering iron with fine soldering tip would these do ??

I find using the goot soldeing iron a bit difficult as the pins of the LT3470 are very small.

Please also mention if normal solder wire could be used, also explain the use of solder flux and paste.

Some youtube videos showed a glue like substance for sticking the device prior to soldering is this available in India.

thanks
a

 

[tpetar]

Hi arbj2,

You need :

- steady hands
- good eyesight
- good spot light for soldering place
- good and sharp soldering iron station with temp regulation
- soldering flux
- bracket for holding and fixing PCB
- several type of tweezers



Soldering paste is for different type of soldering, this is for using with hot air or with oven usage.

Its very useful to have PC microscope for inspection.

I solder 0603 sometimes with free eye, very often and usually 0805, later I use microscope for inspection.

 

[GSM Man]

That's a pretty fine-pitched part to be soldering by hand. If you are only building a couple of boards an inexpensive way to do it is to use a "hot plate". There's quite a bit of info on the Internet for that technique -just Google "smd solder hot plate".

What I use:

• PCB MUST with a solder mask - check the IC manufacturers PCB footprint for the mask size.
• Solder Paste
  
• Loupe (about $10USD) - http://www.opticsplanet.com/carson-triview-5x-10x-15x-folding-loupe-tv15.html?gclid=CP_-yJa01LQCFUid4AodNCgABw&ef_id=UGJiXgAAEFpoBE6z:20130106185550:s
  
• Tool for picking up your components - either tweezers or hand vacuum pick-up tool (about $20USD) http://www.howardelectronics.com/virtual/HVKIT.html]
  
• Hot Plate - (about $20USD) http://www.walmart.com/ip/5871070?adid=22222222227001177655&wmlspartner=wlpa&wl0=&wl1=g&wl2=&wl3=21486607510&wl4=&wl5=pla&veh=sem
• Toothpicks

This is how I do it:

• Place the PCB on the Hot Plate
• Using a toothpick place a small dap of solder on each pad (it takes practice to know just how much solder to use)
• Place components on pads (placement doesn't have to be perfect - the parts will 'slide' into place when the solder becomes liquid)
• Turn on the hot plate to maximum temperature
• Watch the board - after a couple minutes the solder will become liquid
• Turn off the Hot plate - I remove the board at this time, but some people leave the board n the hot plate

The biggest problem is putting too much solder paste on the pads, which will cause shorts. I've done .50mm pitch, 64-pin IC's using this technique on boards up to 20 sq inches.

If you have a lot of parts on the board, or you have problems putting the right amount of solder down, you may want to use a solder stencil to apply the paste. You can get mylar stencils for about $50USD http://StencilsUnlimited.com

 

[keith1200rs]

It isn't that difficult with a little practice. Small tip soldering iron, fine solder, tweezers and a decent magnifier - mine is illuminated and around 3.5x but I have 8x for inspection. Flux can also be useful and desolder braid if it goes wrong. As mentioned - solder resist mask on the PCB is a good idea - I only try to solder properly made PCBs.

Keith

 

[tpetar]

My suggestion is to get some old discarded PC parts such as graphics cards, memory cards, motherboards, ... and try to dessolder and solder parts on this PCBs. For good dessoldering SMD such as SOP, SO, TQFP, connectors, .... will be good to have hot air smd rework station with usage of appropriate nozzle.

You can find lots of video examples on Youtube portal.

 

[wp100]

Hi,

As mentioned a proper pcb with a solder resist mask is essential for anything other than a simple diy board.

To produce a pcb for smd ics like a 64 pin micro you really need to use the UV method to stand any chance of producing the fine tracks needed.

If you search the web there are some good videos on how to hand solder these large chips.

A flux pen to treat the pcb track and component is essential.

A cheap pair of x2 or x3 reading glasses are great for working on the pcb , a x5 or greater loupe is really needed for detailed checking of things like ic pins

Look on ebay for some low cost small kits of smd resistors and capacitors.

Here a pic of my first diy test board under construction.

 

[arbj2]

thanks a lot for all the information..

So a hot air soldering station is useful mostly for reworking..??

I like the hot plate method as I will be soldering some 20-30 pcs a day, I will also be training a guy for doing this..I have a PC microscope that goes upto 200X, so this could be used for inspection.

I will be needing a loupe, some tweezers, any idea what size of tweezers would do for the posted device.

Also what kind of solder paste would be good ?? Is solder paste same as flux ??

thanks
a

 

[tpetar]

So a hot air soldering station is useful mostly for reworking..??

Can be used with soldering paste for soldering instead of oven, and dessoldering is standard.




Solder paste is not flux, its material for soldering. Flux is good and almost mandatory during soldering.

 

[kripacharya]

i strongly suggest you get a Magnifying lamp. This has a wider angle than a loupe and is hands free. I suggest a loupe of 20x or more for inspection only.
In south delhi you can get good ones from https://www.blueskysystem.com/ in East of Kailash. Or any other favourite place of yours.

liquid flux - or flux pen - is important. get that too. A fine tipped lightweight temp controlled solder iron is sufficient
tweezers of course - get the one which has a 'bent' tip rather than straight tweezer

otherwise a steady hand, and a good eye is all that you need. Oh yes - a good quality desoldering pump is very useful to remove solder bridges

then practise on a few bad ic's to get the feel for it, based on whichever technique you have seen on the 'net. Make sure your pcb is fixed/ can't move.

Lastly - you might need to experiment with solder qualities. I find that my standard thickness solder wire is better than even the thin wire. It is because the solder i bought was probably of different composition - it doesn't say on the box !!

Your IC is very small, but fortunately only 8 pins. Knowing the skill of india technicians i think with practise you can do this easily.

Edit: GSM Man's hotplate technique really sounds good - i think i will check that out too !!

 

[arbj2]

thanks kripacharya for the valuable information. I intend to get the flux pen, but is solder paste required ?, or should I use the normal solder wire for my job.

Should I also get a solder wick to remove bridges instead of a desoldering station.

I also intend to use the hot plate technique...

thanks
a

 

[kripacharya]

thanks kripacharya for the valuable information. I intend to get the flux pen, but is solder paste required ?, or should I use the normal solder wire for my job.

i have used normal solder wire quite successfully - with practise. Solder paste would probably be better, but more expensive. It's worth testing both to see what works for you

Should I also get a solder wick to remove bridges instead of a desoldering station.

i find wick/ braid to be too thick for this work. the smd pins are very very fine. A good desolder pump is cheap & easy, and should do the job.

 

[keith1200rs]

I must admit I use desolder braid with small SMD components. I find the recoil of the pump can damage pins. With the braid it doesn't matter if it covers several pins when trying to wick some excess solder off.

Keith

 

[FvM]

Hot-plate or hot-air soldering without solder paste isn't really fun I think. It's unnecessarily complicated.

Solder paste is comprised of solder and flux, you don't need additional flux. It also sticks the components slightly to the board and allows an exact position adjustment of fine pitch components.

A small solder wick (e.g. 1.2 mm) should be at hand to remove shorts at places where too much solder paste has been applied.

A kind of reflow soldering (e.g hot plate) is essential for components with bottom pads like the said TS8, regular SMD parts can be soldered with solder iron and solder wire as well, although it's more time consuming and the finish isn't so excellent.

 

[alexan_e]

The method I use and recommend is drag soldering

The trick is to find a good liquid flux that is active enough to create the tension that pulls the solder, also a use a tip that is not too small.
I have soldered chips like VQFT100 /0.5mm pitch without problem. ()

If I get a bridge I just apply some liquid flux and use the soldering iron to remove the excess solder, I don't use a pump and I think the braid can remove too much solder and also the reheating process may leave a bad joint (unless there is flux added).

For desoldering I only use hot air gun, works like a treat.

 

[GSM Man]

The pitch (pin-to-pin spacing) on your part is 0.65mm. While you may be able to master hand soldering that pitch, it's not going to be easy. As I stated before, the biggest problem is too much solder causing solder shorts. It's easy to destroy the part or lift pads off the board using solder wick to try to clean it up.

If I was doing 20-30 pieces a day, I would use the hot plate method with a solder stencil to apply the solder paste. It guarantees you have the correct amount of solder on the board, eliminating the problems with too much or too little solder. The hot plate method is not at all difficult to do, and if you have small boards you can solder several at one time.

Solder paste is tiny little balls of solder suspended in a paste flux. If you use solder paste, or solder wire that has a flux core, you don't need flux. You should only need to use flux if you are using solder wire that does not have a flux core.

 

[alexan_e]

The pitch (pin-to-pin spacing) on your part is 0.65mm.

No, it is 0.5mm (VQFP100), please check https://www.xilinx.com/support/documentation/package_specs/vq100.pdf
This is another example of LPC1114/ LQFP48 also 0.5mm
or LPC2103/ LQFP48

When you apply the liquid flux (which type makes a difference in the difficulty level )then it becomes quite easy to solder these chip, you just need to get a sense of how much solder to put on the tip and the speed to drag the tip oner the pins.

My recommendation was for a prototype style of work or DIY, if we are taking about 20 or 30 pieces then it is too time consuming but I'm not sure if many would make mass production at home.

I have used solder paste (the one with solder balls in it 25-45um), it is great even with a soldering iron but you have to be very careful of the amount you apply or you get troubles.

 

[GSM Man]

No, it is 0.5mm (VQFP100), please check https://www.xilinx.com/support/documentation/package_specs/vq100.pdf

My response was to the Original Poster - his part has a 0.65mm pitch.

I've soldered boards using just about every method there is including a solder iron, hot air gun, hot plate and even a toaster oven, and I feel that the hot plate is the simplest, most reliable method; especially if you are placing several parts on a board. I've built boards with 40 parts on them using the hot plate method and it's much quicker than trying to hand solder. Also, hand soldering is difficult if your parts are very close together.

I was reticent to use the hot plate method until I had to build 10 boards in a few days and didn't want to pay hundred's of dollars to have them assembled by a contract house. A friend of mine had been using the hot plate method for years and showed me how simple it was. I haven't gone back to hand soldering since.
But "whatever floats your boat"!

 

[alexan_e]

My response was to the Original Poster

Oh, sorry...

 

[arbj2]

Thanks GSM Man for the useful information on the 'hot plate' technique for soldering SMD parts. Its the easiest method around.

I have tried hand soldering the above mentioned part and I had great difficulty doing this...

thanks
a

 

[alexan_e]

Its the easiest method around.

You mean you have already applied it in your PCB?
If not please report back for the results you get using hot plate with your PCB