Soldering Cup Terminals

Recommended Tips for Soldering Cup Terminals

Cup Terminals

(Image source)

A cup terminal is a hollow cylinder with the lead wire inserted and soldered in place. Shape D is the recommended tip for soldering cup terminals.  

The right amount of solder is needed to ensure a strong and stable connection between the terminal and the lead wires. It is easy to know if the solder amount is right with a simple visual check: 

Good Fillet for Soldering Cup Terminals

Too Little Solder Just Right Too Much Solder
  • No solder fillet formed
  • Lead wire is exposed and visible
  • Solder fillet is smooth and concaved
  • Lead wire is sufficiently coated
  • Solder fillet is curved outwards/bulging
  • Solder has overflowed the cup terminal

Before soldering, it is helpful to remove the gold plating of the terminal to allow the solder to adhere strongly. You may do this by adding solder to the solder connection of the terminal (shown in red below), and removing it with a desoldering wire multiple times. It also helps to pre-tin the wire to allow it to be inserted easily into the cup terminal. 

NOTE: It is important to ensure that there is space between the insulation of the wire and the top of the cup terminal which will give it flexibility and allows bending.

Cup Terminal Connector

Removing the gold plating allows solder to adhere better

Space between wire insulator and cup terminal

Allow the wire to be exposed slightly above the cup terminal for flexibility


Shape D (more info)

There are 2 methods of soldering cup terminals.

Method 1

Shape D Soldering cup terminals

1. Place the lead wire into the cup terminal.
2. Put the cut surface of the soldering tip to the lead and terminal together to heat them.
3. Feed solder, allow it to melt and quickly remove the soldering iron.
4. Hold the wire lead wire in place until the solder has cooled and hardened.

Method 2

Coiled Solder Wire Inside the Cup Terminal

1. Fold a length of solder wire onto itself and twist it up.
2. Insert the twisted solder wire into the cup terminal and trim until it is flush to the top.
3. Touch the back of the cup terminal with the soldering tip until it heats and melts the solder wire in the terminal.
4. Once the solder has melted, insert the lead wire, then remove the soldering tip. 
5. Hold the wire lead wire in place until the solder has cooled and hardened.

NOTE: It may require multiple tries to get the right amount of solder in cup terminal. 
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