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SMT electronics assembly manufacturing forum.


Bismuth containing Solder Paste

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aj

#57722

Bismuth containing Solder Paste | 6 January, 2009

Hi all,

I am currently trialling a solder paste which contains Bismuth.

It is leadfree and reflows at 138 degrees C.

I would appreciate any pros/cons?

aj...

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#57730

Bismuth containing Solder Paste | 7 January, 2009

Hi,

in the beggining of PB free process, there were a lot of solder pastes based on a Bismuth and some other materials, mainly because of their low melting temperature. The feedback shows problems in the mechanical strenght of the joints with the time. may be not all of them, but just keep in mind what vto check. How is the price compared to a SnAuCu?

Regards, Emil

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#57749

Bismuth containing Solder Paste | 12 January, 2009

What is your alloy composition? Although your solder paste may have lower melting point, what about the alloy / metal used for plating solder lands on PCB and component termination? In most cases, there is no reliable joint as such solder may not completely fuse with the plating at such low temperatures.

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#57779

Bismuth containing Solder Paste | 15 January, 2009

One thing you must be very careful with when using Bismuth is that there is no lead anywhere else within the process, either components or boards. Lead-terminated components or hot air solder leveled (HASL) finished boards used in combination with alloys containing Bismuth can result in a low melting (98�C) eutectic, which means that joints will fail when exposed to temperatures above about 98�C. There must be no lead in the supply chain when using this material.

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