Lead-free Compatible OSPs: What Does This Really Mean?


Reading time ( words)

Introduction

The setting: Early 2008. Many fabricators and EMS providers are continuing to push programs for RoHs compliance. This, of course, requires electronic assemblies to be, among other things, free of lead-bearing materials. To adopt such a program, the surface finish, component finish and the solder used in assembly must be lead-free. While the questions surrounding these issues are many, one in particular appears more frequently: How do we know that a particular finish is truly lead-free soldering compatible? This particular question is being addressed by one of the IPC standards writing committees responsible for developing an industry standard specification of organic solderability preservatives (OSP).

The Nature of the Beast

The IPC committee made up of a cross-section of suppliers, PWB fabricators, OEMs and EMS companies is working to complete the development of IPC-4555 (standard for OSP). This committee is developing a protocol to test OSP coatings for lead-free (high-temperature) compatibility. The protocol requires that copper coupons coated with the OSP would be subjected to three lead-free reflows, then tested for wettability with an appropriate wetting balance instrument. It should be noted that after the coupons are processed through the OSP solution, the coupons shall be rinsed with DI water and dried at 105°C. Following the protocol of the ANSI-JSTD-003B, the samples shall be fluxed using the standard 0.5% activated flux and immersed in SAC305 at a temperature of 255°C for 10 seconds. Further:

  • Ten samples per test shall be run.
  • The mean and standard deviation of the maximum force achieved shall be documented.

Interestingly, the committee has also recommended that a second set of test coupons be processed under the same pretreatment conditions. This time, however, without the drying step. Again, the ANSI-JSTD-003B, wetting balance procedure to measure wettability, will be utilized.

Read the full column here.


Editor's Note: This column originally appeared in the November 2014 issue of The PCB Magazine.

Share

Print


Suggested Items

iNEMI’s PCB Roadmap Explained

05/01/2020 | Pete Starkey, I-Connect007
In an informative and enlightening webinar, iNEMI Project Manager Steve Payne was joined by Isola Group CTO Ed Kelley to explain, review, and discuss the details of the recently published “iNEMI 2019 Roadmap for Organic PCBs.” Pete Starkey provides an overview.

Improving Copper Distribution in Pattern Plating Using Simulation Software

04/28/2020 | Pete Starkey, I-Connect007
Technical Editor Pete Starkey had the opportunity to sit in on a webinar presented by Robrecht Belis, manager of the surface finishing business unit at Elsyca—a Belgian company specialising in the simulation of electrochemical processes.

IPC Europe Shares Technical Education and Standards Awareness

04/22/2020 | Pete Starkey, I-Connect007
Against a background of COVID-19 uncertainty and unprecedented challenges, but recognizing the vital importance of continuing to educate engineers and share the knowledge and skills required to manufacture boards and assemblies of the highest yields and reliability, the IPC Europe team hosted a technical webinar for the European electronics industry, featuring the expertise of two of I-Connect007’s regular columnists: Mike Carano and Jan Pedersen. Pete Starkey provides an overview.



Copyright © 2020 I-Connect007. All rights reserved.