New solderpastes: high-speed, fine pitch and lead-free

Soldering & Surface Mount Technology

ISSN: 0954-0911

Article publication date: 1 April 2000




(2000), "New solderpastes: high-speed, fine pitch and lead-free", Soldering & Surface Mount Technology, Vol. 12 No. 1.



Emerald Group Publishing Limited

Copyright © 2000, MCB UP Limited

New solderpastes: high-speed, fine pitch and lead-free

New solderpastes: high-speed, fine pitch and lead-free

Keywords: Loctite, Solderpaste

Soldertite® 3834, the latest solderpaste from Loctite, achieved print speeds of 350mm/sec using the Rheo logical pump system of enclosed head printing. The 3834 was printed on to an FR4 board at a 0.5mm pitch, and, according to the application engineer from Speedline conducting the trials, "produced perfect print quality".

Andy Dodwell, director of Loctite UK's Industrial Division, reckons that many PCB assenblers will switch to the new Soldertite. "It has all the advantages", he claims, listing a 20-hour stencil open-time, a 0.3mm pitch at high speeds, enhanced resistance to humidity and temperature, and its suitability for high volume production with difficult-to-solder components.

A spin-off from the 20-hour stencil open-time is an extended interprint time. Boards can usually be left after printing (depending upon ambient and line temperatures) for one-hour plus, thus negating the need for "awake-up print" after a line halt. This advantage - plus good on-stencil roll formation and a smooth drop-off from squeegee blades - stems from the innovative formulation of the new solderpaste.

It is a homogeneous mix of tin, lead and silver alloy (62 per cent:36 per cent:2 per cent) and processed rosin (10.5% by volume), requiring medium-temperature soldering. Typical re-flow temperature after pre-heat and soak is 210-240°C for five sec. Slump after one hour at room temperature and 20 minutes at 80°C is 0.2mm on both 0.7mm and 1.5mm pads.

A common printing pitch at a standard speed of 150mm/sec is 0.4mm - though 0.3mm pitch is easily attained.

Lead-free grade

Loctite Soldertite 3835 is a new lead-free solderpaste of tin, silver and copper alloy (95.5 per cent:3.8 per cent:0.7 per cent) with a processed rosin flux (11.5% by volume). It has a ten-hour stencil open time, and can be used at speeds of 50-150mm/sec to print a pitch of 0.4mm.

Its lead-free formulation requires a slightly higher temperature: re-flow temperature after pre-heat and soak at 150-160°C, is 220-250°C. Slump after one-hour at room temperature is 0.2mm on 0.7mm and 1.5mm pads, and 0.4mm after 20 minutes at 80°C.

For further information, please contact Loctite on: +49 89 320 800 74.

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