Technical Articles From Heraeus

Troubleshooting SMT Solder Paste Problems

Mar 05, 2018 | Heraeus

Troubleshooting SMT Solder Paste Problems...

New Requirements for SIR Measurement

Feb 27, 2015 | Jörg Trodler; Heraeus Materials Technology GmbHo.KG, Mathias Nowottnick, Prof. University of Rostock.

During the last period of newly assembled electrical devices (pcbs), new component types like LGA and QFN were also qualified as well as smaller passive components with reliability requirements based on the automotive and industrial industry. In the narrow gaps under components, residues can accumulate more by the capillary forces. This is not that much a surface resistance than an interface issue. Also that the flux residues under such types of components creates interaction with the solder resists from the pcb, as well as the component body was not completely described in the standard SIR measurement. On the other hand also, electrical influence with higher voltage creates new terms and conditions, in particular the combination of power and logic in such devices. The standard SIR measurement cannot analyze those combinations.

The paper will discuss the requirements for a measurement process, and will give results. The influences of the pcb and component quality will also be discussed. Furthermore it will describe requirements for nc solder paste to increase the chemical/thermical/electrical reliability for whole devices...

Avoiding the Solder Void

Feb 08, 2013 | Richard Lathrop

Solder voiding is present in the majority solder joints and is generally accepted when the voids are small and the total void content is minimal. X-ray methods are the predominate method for solder void analysis but this method can be quite subjective for non grid array components due to the two dimensional aspects of X-ray images and software limitations. A novel method of making a copper "sandwich" to simulate under lead and under component environs during reflow has been developed and is discussed in detail. This method has enabled quantitative solder paste void analysis for lead free and specialty paste development and process refinement. Profile and paste storage effects on voiding are discussed. Additionally an optimal design and material selection from a solder void standpoint for a heat spreader on a BCC (Bumpered Chip Carrier) has been developed and is discussed....

Challenges of Lead-Free Low Silver Content End Termination Pastes for Inductor Applications

Aug 19, 2010 | Dong Zhang, Meg Tredinnick, Mark Challingsworth

The silver end termination plays an important role for multilayer chip inductors. A basic requirement is to achieve excellent electrical properties with superior adhesion to the chip. Driven by the increasing price of silver, interest has been shown to ...

Why Wide Fine Pitch Pads?

May 07, 1999 | Rick Lathrop, Heraeus SMT Technical Services

Fine pitch SMT devices, although certainly not new, present more of an assembly processing challenge than 50 mil pitch devices. In fact it seems that the finer the pitch the more difficult or narrower the process window becomes. Besides the pitch of the leads being less on fine pitch devices narrower pad width on the board is typical. With fine pitch designs the board fabrication process is also stressed in that the strip of mask between the pads is designed narrower, the alignment of the mask to copper becomes more critical...

An Introduction to Solder Materials

Apr 15, 1999 | Brian Bauer, Rick Lathrop

Solder paste is a seemingly simple material that forms one of the foundations of the surface mount assembly operation. If the solder paste does not do its job correctly then first pass yield will be severely reduced. ...

Speed Printing of SMT Adhesives

Apr 15, 1999 | Richard R. Lathrop Jr., Heraeus

High-speed printing techniques are revealed that break the speed barrier resulting from air entrapment in large apertures at fast squeegee speeds. Adhesive printability test results using conventional thickness stencils to achieve a significant range of d...