Hello Folks,

I recently came across a tutorial where they used solder paste to solder JST connectors onto a PCB. It seemed like the pins on the JST connector adhered well without any prior tinning. Does this mean these pins come pre-tinned from the factory? Any insights on this would be greatly appreciated!

By the way, I've attached a picture of the JST connector after solder paste application and before completion of soldering. The connector I'm referring to is highlighted in red .


Thanks in advance

 

Look at the data sheet of the particular connector as there are many different surface finishes available.
but
none of them will have solder on the connector such that you dont need to use solder on the board.

the picture you show, sees to indicate a hand soldered part, with way to much solder / flux applied.
is that damage to the conrenr of the plastic shell as well, as if a hand soldering iron was used and melted the plastic.

 

It seemed like the pins on the JST connector adhered well without any prior tinning. Does this mean these pins come pre-tinned from the factory? Any insights on this would be greatly appreciated!

Tinning isn't required on surfaces that are clean (no oxidation or oily residue). Solder paste contains flux which will clean surfaces that don't have too much oxidation/residue. The connector leads were likely plated with tin to minimize issues with oxidation. Through hole connectors sometimes use gold.

The soldered joints have too much solder. That should be difficult to do when solder paste is applied correctly.

 

Often tin plated connectors are available. They are not solder tinned, but often made from tin plated stock.

 

MODERATOR NOTE: Please use English only according to the AAC rules. Thank you.

TRANSLATION: Yes, usually the contact of the connector will be gilded, and the part in contact with the PCB board will be tinned.

是的，通常连接器的配合触点会镀金，与PCB板接触的部分会镀锡

 

I have never pre-tinned a part before soldering to a pcb.

 

I've only pre-tinned gold plated connectors and pads before soldering to a PCB.
https://www.solder.net/gold-embrittlement-mitigation/

https://forum.allaboutcircuits.com/...ering-discrete-oscillator.183059/post-1682090

 

Some products have an anti-oxidation coating of a material that acts like a solder flux, but it is entirely non-metallic..
So just because something solders very well does not mean it is tinned.
There are brush-on liquid fluxes that make soldering work well even hours after they are applied.

 

If you are hand soldering parts, applying some no clean flux to the pins will help insure a better joint. You can also try using IPA to clean them if there is a chance they were contaminated by handling.