Solder Pastes for mini and micro-LED

Since the launch of LED-backlit LCD screens, the display industry has been eagerly anticipating the next evolution. In response to the rising consumer demand for premier visualization, mini-LEDs and micro-LEDs are increasingly being adopted in the latest display technologies.

Solder Paste for mini/microLEDs

Mini-LEDs have been introduced to backlighting modules for LCD TV screens, making them comparable to OLED screens in terms of contrast but with a longer product lifespan. They are also used in video walls, producing largesize displays with far superior performances to current technology. On the other hand, the tinier micro-LEDs offer even greater change to consumer display products such as TVs, tablets and smartphones. Small enough to act as individual pixels, these self-emissive lights can be lit up for whatever color, adjusted for brightness, or switched off entirely – something that LCD screens cannot do.

The challenge in producing mini and micro-LEDs is with the packing of components onto electronic circuit carriers such as printed circuit boards (PCBs), glass substrates or flexible substrates. With the edge length of <240 μm for mini-LEDs, the soldering pads need to be even smaller.

How can the solder paste deposits be applied effectively onto a circuit carrier so small? To do so consistently, solder pastes with particles smaller than 15 μm are needed, and the best application method is stencil printing. With its tight particle size distribution, Heraeus's WelcoTM technology is designed for fine pitch applications such as mini and micro-LEDs. Its excellent printability makes it the ideal material solution for these latest display innovations.

Your benefits at a glance:

  • Excellent printability over long stencil life
  • Low void and demonstrated reliability
  • Extendable to future generation of products

Your advantage in working with Heraeus:

  • Reliable and fast supply chain worldwide
  • Pretested solutions due to our in-house application centre

Consumer Electronics & Computing

  • Smartphones
  • PCs
  • Tablets
  • Televisions
  • Imaging devices
  • Wearables electronics
  • Other/RFID


  • LCD backlighting
  • Video walls
Product Powder size Alloy Melting temperature Stencil opening
(based on Heraeus pastes)
 Welco LED101 Type 6
SAC305 217-219°C self-alignment
 Welco LED120 Type 7
SAC305 217-219°C > 70µm
 Welco LED131 Type 6
SAC305 217-219°C > 90µm
 Welco AP519 Type 6
SnBiAg1 138-142°C > 90µm
 Welco AP5112 Type 7
SAC305 217-219°C > 70µm