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smd and solder paste

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MrDEB

Well-Known Member
Looking at using a 44 pin smd to progress with my latest project. Have board designed using a 40 pin dip but way to big for my project so having never re-flowed smd using a skillet am now considering.
One issue was the shelf life and need of a stencil,
Stencil costs $16
soldering paste that requires no refrigeration? found CHIP QUICK TS391 solder paste in a syringe for under $15
Anybody use this or better recommendation??
I only plan to build 10 boards.
 

Diver300

Well-Known Member
Most Helpful Member
You could try without a stencil. Just put a line of paste along each side of the IC.

I solder down 0.5 mm pitch ICs, and although I use a stencil for speed, the stencil cut-outs for the 0.5 mm pitch ICs have one long slot along the sides of the IC.

I've found that a hot air gun is very good for reflowing a few components. For whole boards I use a toasting oven with a controller and a thermocouple.
 

Beau Schwabe

Active Member
Usually I use a stencil however placing a line works ok. After re-flow, I use a toothbrush and a little water to remove any debris.

Along similar lines, does anyone know of a syringe capable of dispensing a metered amount of solder paste? That would be extremely useful as I find a syringe alone hard to control.
 

jpanhalt

Well-Known Member
Most Helpful Member
Hamilton makes a variety of microliter syringes (https://www.hamiltoncompany.com/products/syringes-and-needles/general-syringes/gastight-syringes ). It has been a few decades since I looked seriously at its offerings. All of them use a hollow-bore needle, and that might not be the easiest to control with a paste. Besides, 1 uL = 1 mm^3, which is quite a bit.

For sub-microliter amounts, I use homemade needles made from various sizes of music wire. You can also buy assortments of fine needles that are made to oil watches. They are usually flattened, so application might be easier. Delivery amounts are calibrated for oil. Dispensing 0.1 uL and smaller is easy to do.

My thinking was that if the pitch were 0.5 mm or larger (preferably 0.65 mm or more), I would just hand solder rather than go through the trials, tribulations, and cost of learning a reflow technique using a hot plate. Temperature regulated hot air, as suggested by Diver300, might be easier. But still, the equipment cost for one off or even 10 off might not be justified.
 

dknguyen

Well-Known Member
Most Helpful Member
Hamilton makes a variety of microliter syringes (https://www.hamiltoncompany.com/products/syringes-and-needles/general-syringes/gastight-syringes ). It has been a few decades since I looked seriously at its offerings. All of them use a hollow-bore needle, and that might not be the easiest to control with a paste. Besides, 1 uL = 1 mm^3, which is quite a bit.

For sub-microliter amounts, I use homemade needles made from various sizes of music wire. You can also buy assortments of fine needles that are made to oil watches. They are usually flattened, so application might be easier. Delivery amounts are calibrated for oil. Dispensing 0.1 uL and smaller is easy to do.

My thinking was that if the pitch were 0.5 mm or larger (preferably 0.65 mm or more), I would just hand solder rather than go through the trials, tribulations, and cost of learning a reflow technique using a hot plate. Temperature regulated hot air, as suggested by Diver300, might be easier. But still, the equipment cost for one off or even 10 off might not be justified.
Agree. Hand solder. Reflow is for many boards (though I suppose 10 is starting to reach the point where you may not want to hand solder if you're doing to be doing something similar down the line) or when you need to but can't get underneath the component.

My understanding is that all solder paste requires refrigeration due to oxidation. I didn't know such a thing existed.
 

hyedenny

Active Member
Iv'e had no problems at all soldering .5mm pitch LQFP-48 packages with no stencil and no solder paste. A clean board, a generous amount of good flux, a nice solder pencil, and a steady hand are all you need.
 

jpanhalt

Well-Known Member
Most Helpful Member
For that chip, I would just hand solder with fine solder and not even use paste. If you really want to use paste, then consider hot air.
 

dknguyen

Well-Known Member
Most Helpful Member
yje pitch I am considering is .65BSC
this is a 44 pin QFN 8 X 8 MM BODY
here is the solder paste https://www.mouser.com/new/chipquik/chip-quik-ts391-solder-paste/
I am thinking of just hand soldering as suggested. I have a temp ctr soldering iron and a fine tip as well as a flat tip. Thinking of just enlarging the pcb pads for this chip.
It's dead easy. Use the big tip, flux and drag/float the solder bead on the tip across a row of pins. Don't go one by one with the fine tip. No need to enlarge pads


 
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hyedenny

Active Member
No need to enlarge pads, that just increases the chances of solder bridging. There are some good examples of fine pitch hand soldering on YouTube. (There are also some not-to-good examples!)
I'm not sure what "yje" or "ctr" mean.
 

hyedenny

Active Member
It's also important to use the correct heat and not spend too much time in one spot. The lower thermal mass of the pins and pads make it easier to damage the chip or lift the pads.
 

hyedenny

Active Member
I've found that using soldering paste with a soldering iron spatters and makes a mess. Save it for hot air or a reflow oven.
 
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