Implementation of Lead-Free Packages

Lead-free Materials Set

Spansion’s lead-free material set has the following characteristics:

• Cu (Copper) leadframe packages - 100% matte Sn (Tin) plating.
• Laminate packages - Solder balls composed of SAC 305 (96.5% weight Tin, 3.0% Silver, and 0.5% Copper).
• Spansion leadframe and laminate package types are listed under compliance.
• Cu leadframe products use the following lead-free plating finishes:

Concerned about Whisker Growth in Matte Sn Plating?

Matte Sn plating has been chosen for Cu leadframe Spansion lead-free memory products for the following reasons:

• Matte Sn is compatible with existing SnPb and lead-free board assembly processes.
• Matte Sn has a higher melting point than other lead-free alternatives, which makes it acceptable for automotive and high temperature applications.

To date, no whisker growth has been observed for the matte Sn plating chemistry qualified for Spansion memory products. Refer to the 100% Sn Whisker Growth Study for further details.

The latest Spansion study of Sn whiskers is: Anocha Sriyarunya and Dhiraj Bansal, Matte Tin (Sn) Plating of Semiconductor Devices – Whisker Growth Study, IPC/JEDEC 6th International Conference on Lead Free Electronic Components and Assemblies, August 2004.

Assembly Process and Reflow Profile Impacts

Some changes in assembly processes—solder paste, type of flux, and reflow profile—may be required to achieve optimal quality and reliability solder joints when using lead-free solder packages. Check with your paste/flux provider for processes/profiles based on your specific application.

Maximum Reflow Temperatures for Lead-Free Memory Packages

All Spansion lead-free memory products are qualified at JEDEC level 3 and JEITA Rank 'E' with a maximum reflow temperature of at least 250°C +0/-5 (250°C maximum).

Additionally, single-chip products and most of our multi-chip products are capable of withstanding a maximum reflow temperature of 260°C +0/-5 (260°C maximum) and a maximum of 3 times reflow at JEDEC level 3 and JEITA Rank 'E.'

Click here for the reflow conditions used for determination of package moisture sensitivity level and a schematic of the reflow profile. This profile is used for internal qualification of packages and only shows the times and temperatures our packages are guaranteed to withstand. This should not be construed as a recommended profile for board mounting of our parts. Customers should optimize their board mounting reflow profiles per their board design, solder paste and flux selection, etc.

Backward and Forward Compatibility between Standard and Lead-Free Reflow Processes

Backward compatibility means that a Spansion lead-free product is capable of being processed using the old (SnPb) solder reflow process. Forward compatibility means that the standard (SnPb) product is capable of being processed using a new lead-free solder reflow process.

These definitions are illustrated in the following table:

Generally speaking, Spansion lead-free parts are backward compatible. In other words, they can be used as a drop-in replacement to the existing lead-based products in a lead-based process. However, in some cases, minor adjustments in the peak reflow temperature may be required to obtain good quality solder joints.