Microstructures and degradation of heat sink very-thin quad flat package no-leads Pb-free Sn-Ag-Cu solder joints after thermal aging

Author: Fredriksz, W.

Source: Journal of Electronic Materials, Volume 34, Number 9, September 2005 , pp. 1230-1241(12)

Publisher: Springer

Buy & download fulltext article:


Price: $47.00 plus tax (Refund Policy)


Heat sink very-thin quad flat package no-leads (HVQFN) packages soldered with Sn-3.8Ag-0.7Cu on metallized laminate substrates have been put to thermal aging. Temperatures from 140°C to 200°C for times up to 30 weeks were applied. The solder joint microstructure develops intermetallic compound layers and voids within the solder. Due to this, the mechanical reliability of the HVQFN inner lead solder joints is degraded. The intermetallic layers are of the type (Cu, Y)6Sn5, with Y=Ni, Au or Ni+Au, as well as Cu3Sn, and follow a power law with aging time: X=C·tn, where n=0.4 to 1.9 depending on temperature. The voids within the solder are attributed to Sn depletion of the solder in favor of the growth of (Cu,Ni)6Sn5. They are more pronounced the less the solder volume is in proportion to the intermetallic diffusion area. The amount of voids is quantified as a percentage of the residual solder. The time to reach the failure criterion of 50%, i.e., t50%, is related to the absolute temperature according to an Arrhenius equation with an activation energy Ea=0.95 eV. This equation is used for determination of the maximum allowable temperature at a certain required operating lifetime.

Keywords: SAC-solder; heat sink very-thin quad flat package no-leads (HVQFN) package; intermetallic compounds; lifetime estimation; solder joint microstructures; voids

Document Type: Research Article

DOI: http://dx.doi.org/10.1007/s11664-005-0268-1

Affiliations: Email: walter.fredriksz@philips.com

Publication date: September 1, 2005

Related content


Free Content
Free content
New Content
New content
Open Access Content
Open access content
Subscribed Content
Subscribed content
Free Trial Content
Free trial content

Text size:

A | A | A | A
Share this item with others: These icons link to social bookmarking sites where readers can share and discover new web pages. print icon Print this page