2015 Meetings

The possible effect on Cu roughness on pad strength is being investigated by using angled Hot Bump Pull to test pads on coupons made with two different laminates with copper foils of different roughness. The use of a surface treatment (primer) to improve the adhesion of the foil to the laminate complicates the interpretation of the results because it, too, can have an effect on pad strength and even on failure mode. This effect was studied by testing a smooth foil with and without primer.

High Tg PCB Laminates On Demand

- by Pericles Kondos

The first leg of the study of the effect of multiple "hot" reflows on many high-Tg laminates is nearly complete. For each laminate material, resin content and reflow history, 24 pads (from 2 different coupons) are being tested with Cold Bump Pull. This presentation focuses on a detailed discussion of a few cases rather than presenting all the available results. Of interest were not only any changes in strength due to the reflow exposure, but the magnitude of the pad strengths and how these values varied from laminate to laminate. The failure surfaces were also examined in detail.

Paste Print Correlation to Reliability On Demand

-by Michael Meilunas

Through numerous printing trials, the naturally occurring variabiility in paste deposit volumes has been identified for various printing parameters. Instances of 'outlier' low volume deposits typically flagged as printing defects were carefully noted. Such paste print 'defects' have been designed into testable assemblies at high risk solder joint locations using a custom designed stencil. CSP, LGA, SMR and QFN components are being evaluated on TB2015. Assembled boards are in thermal cycle test.

Stencil Printing Considerations for 0.3mm Pitch CSP Assembly On Demand

-by Jeff Schake

A detailed stencil printing optimization study is underway for the assembly of 0.3mm CSP components. Stencil printing factors such as aperture design (squares, circles, rotated squares), aperture size (from 140 mm to 200 mm) and printing process technology (standard squeegees, active squeegees) have been investigated. Detailed results and data analyses will be presented.

Broadband Paste Printing On Demand

-by Michael Meilunas

Complex board designs are increasingly using fine pitch components such as WLCSP in close proximity to much more massive components such as large body BGAs. This study is being defined to evaluate the limits of conventional stencil printing to position fine pitch, high resolution prints adjacent to much coarser print deposits. PCB design considerations such as label ink and top surface traces are considered. The design limitations of stepped stencils, with and without nanocoating is also included.

Progress with Pb-free Solder Alloys On Demand

- by Babak Arfaei

The AREA research portfolio includes multiple studies examining the performance of alternate lead free solder alloys under various conditions. Highlights from these various projects will be presented, including the effects of solder composition, joint volume and PCB surface finish on room temperature shear fatigue and accelerated thermal cycling performance. Additionally, the effects of processing parameters on joint microstructure and resulting mechanical behavior will be discussed. Updates on the status of current projects will be provided.

Brittle to Ductile Transition in Bi-based Solder On Demand

-by Harry Schoeller

One drawback of bismuth-based solders is the brittle nature of bismuth leading to sudden unexpected failures. However at elevated temperature, where slip is more prevalent, bismuth can dynamically recrystallize into a fine grain structure which changes the primary deformation mechanism of the solder, making it much more ductile. This work reports on the brittle to ductile transition in bismuth solder and suggests the responsible mechanism change.

Reliability of Pressureless Sintered-Ag Die Attach On Demand

-by Harry Schoeller

Sintered-Ag technology provides a Pb-free interconnection for high power/temperature applications. Previous consortium research has reported on the reliability of pressureless sintered-Ag joints with thin bondline thicknesses (<1mil). This update looks at the reliability of joints made with thicker bondline thicknesses (3-5mils) in high temperature storage and thermal shock.

March Meeting

Agenda

March AREA Introduction

- By Jim Wilcox

March AREA Introduction

- By Jim Wilcox

MAT6B : Reliability of Sintered Ag Die Attach On Demand

- By Harry Schoeller

REL6A : Paste Print Correlations to Component Reliability:Effect of Print ‘Outliers’ On Demand

- By Michael Meilunas

MAT7F : New Pb Free Alloys: Effect of Solder Composition on ATC Reliability On Demand

- By Babak Arfaei