Solderability Failure on LGA/QFN Print E-mail
User Rating: / 0
PoorBest 
Written by Chris Hunt   
Thursday, 02 August 2012 17:59

The standards and customers are often at odds.

Quad flat no lead (QFN) and land grid array (LGA) packages often do not have solderable side terminations or are poorly solderable due to the component manufacturing process. The lack of a wettable surface is due to the package separation process, leaving exposed base material on the exposed edges of the lead frame or smearing resin on the plated surfaces.

There is no requirement for the side terminations to be solderable based on IPC-A-610 requirements; however, customers often like to see a joint, and it makes automatic optical inspection (AOI) possible. Poor solderability of the edge termination is typically caused by the lack of a protective coating like tin on the surface of the copper lead frame or resin smearing during component singulation. Solderability is best tested using a wetting balance or in production with paste and a glass slide for reflow simulation.

These are typical defects shown in the National Physical Laboratory’s interactive assembly and soldering defects database. The database (http://defectsdatabase.npl.co.uk), available to all this publication’s readers, allows engineers to search and view countless defects and solutions, or to submit defects online. To complement the defect of the month, NPL features the “Defect Video of the Month,” presented online by Bob Willis. This describes over 20 different failure modes, many with video examples of the defect occurring in real time.

Chris Hunt is with the National Physical Laboratory Industry and Innovation division (npl.co.uk); This e-mail address is being protected from spambots. You need JavaScript enabled to view it . His column appears monthly.

Last Updated on Friday, 03 August 2012 12:47
 

Columns

Eastern-US: China’s New Competitor?

Parity emerges among EMS Factories from Asia, Mexico and the US.

For the first time in years we see parity in the Eastern US among EMS factories from Asia, Mexico and the US. This EMS market condition will permit American OEMs (the EMS industry refers to OEMs as customers) to have more EMS pathways to choose from. Now more than ever, such EMS assignments will require deeper investigation relating to the OEMs’ evaluation of manufacturing strategies.

Read more...
 
The Human Touch

For those who count on the electronics industry for big feats, it’s been a remarkable couple of years.

Read more...
 

Features

Advances in Concentration Monitoring and Closed-Loop Control

Contaminated bath water skews refractive index results. New technology can accurately measure aqueous cleaning agent concentration.

Read more...
 
Circuits Disassembly: Materials Characterization and Failure Analysis

A systematic approach to nonconventional methods of encapsulant removal.

Read more...
 

Search

Search

Login

CB Login

Language

Language

English French German Italian Portuguese Russian Spanish
 

Products

Techspray Introduces Fine-L-Kote High Viscosity AR Conformal Coating
Fine-L-Kote high viscosity AR acrylic conformal coating reportedly widens the process window and flexibility. Can use as-is for dipping or thin down for spray systems. Is for selective spray systems...