Recommended solder paste 63/37 viscous (not just flux, the paste+flux mix)

[wb0gaz]

I'm having difficulty holding keeping position of SMD part (LQFP48 in this case) properly over the PCB pads before hot air soldering. I'm using 63/37 solder paste from unknown chinese source. Symptom is that the paste's flux seems to be very thin, so the part slides around too easily while making small adjustments to get the part centered on it's pads. I suspect the solder paste itself may make this difficult. I'm using a small stencil from proto-advantage, which seems itself to be working OK.

I'm looking for a slightly viscous or "tacky" solder paste (63/37) - preferably sourced in US - perhaps a little more viscous flux than what I have described above.

Thanks for any advice (particularly supplier or description).

[onsenwombat]

Not sure if this is of any value, but I'd presume any suitable paste type (no-clean / water soluble) for your needs from the chemistry perspective from any major manufacturer, e.g. Alpha / Indium / Kester etc. should be fine when it comes to their tackiness. Certainly more expensive than your no-name lord-knows-what Chinese stuff, but at least the components appear to stay in place well enough in factories running these proper brands.

[wb0gaz]

Thank you - I appreciate the suggestion and will see what I can find in terms of small quantity purchase.

[tooki]

Digi-Key sells a bunch of 63/37 solder pastes. They’ve got 19 no-clean ones in stock right now.

I would probably choose something other than the “smooth flow” series from chip-quik: the smooth-flow stuff really is smooth, but it’s less viscous, so not what you want.

Note also that pastes in jars are often blended a bit “drier” (higher metal content = lower flux content) than the ones in syringes (even if they have the same model number!). So you might prefer a jar.