IPC/PERM-2901

Description / Abstract: The intent of this design guide is to assist design engineers in developing electronics that are completely Pb-free and meet the demanding requirements of ADHP systems and products. (For the present time, wiring/cabling is not included in the scope.) It is assumed that the design engineers using this guide are competent and experienced with SnPb based electronics but may not be fully conversant with the detailed vagaries of Pb-free materials, components or manufacturing processes or how these impact equipment reliability and longevity.

a. This guide has been generated to address those ‘delta’ differences between SnPb and Pb-free solder technologies. Information/ guidance that pertain to both technologies are not necessarily included. Any redundant information may be the result of completion or context.

b. The “delta” differences are generally categorized as described in GEIA-HB-0005-3 as follows:

i) Typically poorer wetting ability

ii) Differences in appearance and inspection criteria

iii)Typically higher melting temperature

iv) Potential tighter process window for repair/rework

v) Increased potential of tin whiskers

vi) Solder joint life time under mechanical shock or vibration or under thermal cycling

vii) Aging effects on strength properties

This design guide serves to address the following key areas affecting performance, reliability and service life and offers guidelines on dealing with the risks:

• Pb-free Solders and Solder Joints

• Tin Whiskers

• Printed Board Defects

• Product Qualification

• Manufacturing Processes

• Supply Chain Control

• Obsolescence Management

• COTS Assembly, Selection and Use

• Configuration Management

Presently, there are no industry-accepted reliability models for Pb-free interconnections. Until validated data and modelling methods are developed, projects considering Pb-free ADHP products and systems need to adopt additional steps, many of which will be based on specific applications of the product/system itself (see IPC-WP-014).

Background information will be provided for each of the areas to give the designer a basic understanding of the underlying issues. References (including GEIA resources) are included for those designers looking for more in-depth understanding (see 2.3.1). The design guide includes recommendations for addressing the limitations and risks associated with Pb-free materials.