Copper Electrodeposition By Hydrogen Evolution Assisted Electroplacing
Fabriciton of NiCo Alloy and Rh Coating Using Electroplating Method
Reliability of New SAC-Bi Solder Alloys in Thermal Cycling with Aging
Plasma Polymerization
Protocol Development for Testing Solder Reliability
Insulation Resistance of Dielectric Materials
QFN I/O Pad Solder Paste Overprint on Thermal Pad Void Reduction
Cavity Board SMT Assembly Challenges
Latest Industry News
Designing Customized 'Brains' for Robots
VIEWPOINT 2021: Mr. Daisuke Yoshihara, General Sales Manager, Yamaha Motor Europe IM Business
VIEWPOINT 2021: Justin Cody Worden, Director of Business Development, Austin American Technology
Hon Hai's new AI algorithm cuts inspection manpower at plants
FAA Files Reveal a Surprising Threat to Airline Safety: the U.S. Military's GPS Tests
CES 2021: FEMA's Emergency Alert System Coming to a Game or Gadget Near You?
It's Time to Look at FD-SOI (Again)
Finding the Cause of Cold Solder Joints

Effect of Fine Lead-Free Solder Powder on the Reflow Property Pastes

Effect of Fine Lead-Free Solder Powder on the Reflow Property Pastes
This paper evaluates the effect of particle size distribution and oxidation on the reflow performance of solder paste.
Analysis Lab


Authored By:

Amir H. Nobari, Ph.D. and Sylvain St-Laurent, Ph.D.
5N Plus Micro Powders Inc.
Montreal, QC, Canada


Miniaturization of components and printed circuit boards (PCB) has increased demand for finer pitches both on PCBs and on chip level. In order to meet this demand, more advanced solder pastes with finer particle sizes are needed. However, determination of the real effect of particle size distribution on oxidation, reflow performance and paste properties is still required. It is the object of this paper to evaluate the effect of particle size distribution and oxidation on the reflow performance of solder paste. The powder investigated here was produced with a proprietary atomising technology particularly effective in producing powder ranging from 1 to 25 μm. Solder powder was classified into the different size categories. Powders were then admixed with fluxes and reflow characteristics were evaluated. The reflow property of pastes is then discussed as a function of the particle size, and oxidation level.


Surface characterization of SAC305 solder powder was performed and effect of powder oxidation on the reflow performance of solder paste was studied. The following conclusions were obtained:

(i) Oxide thickness is the main factor that affect the solder balling; however, some other powder characteristics and/or some external factors play role in reflow performance of solder pastes.

(ii) The oxide thickness formed at the powder surface is the range of 3-5 nm.

(iii) The thickness of tin oxide at the surface powder is not dependent on the particle size.

(iv) When the oxide thickness of powder is thin enough, powder with difference sizes exhibit the same reflow performance. Therefore, finer powders can have same reflow performance as coarser powders.

(v) Finer powder is more sensitive than coarser power to oxidation, i.e. reflow performance is more affected by higher level of oxidation for fine powder.

Initially Published in the SMTA Proceedings


No comments have been submitted to date.

Submit A Comment

Comments are reviewed prior to posting. You must include your full name to have your comments posted. We will not post your email address.

Your Name

Your Company
Your E-mail

Your Country
Your Comments

Board Talk
Finding the Cause of Cold Solder Joints
Sticky Residue Under Low Clearance Parts
Printing vs. Dispensing
Soldering Relays Intrusively in Lead Free Process
Is There a Spacing Spec for SMD Components?
Maximum Board Temperature During Tin-Lead
Is HASL a Good Choice for Surface Finish?
Connector Bowing During Reflow Process
Ask the Experts
Insufficient Barrel Fill on Through-hole Components
Package-on-Package Rework
Toe Fillet Requirements on Gull Wing Components
Gold Plating and Embrittlement
Soldering Multilayer Ceramic Chip Capacitors
Mixing Different SAC305 Solders
Dross Particles Sticking to PCBs
Cleaning with Sodium Bicarbonate