This paper reports the results of an evaluation of tin mitigation processes for components,i.e. converting parts with pure tin (Sn) and other lead-free (Pb-free) finishes to tin-lead (SnPb) finishes.
As early as 2001,leading cellular phone manufacturers had established stable assembly processes that were RoHS compliant for their cellular phone products. Since this time,the products manufactured on these lines have demonstrated equal or better
quality and reliability as compared to cellular phones assembled with tin-lead solder and non-RoHS compliant components. This success may have created the belief that there are few issues remaining in RoHS compliant assembly. This belief is far from the truth. Organizations that need to assemble a wide range of large,thick printed wiring boards (PWBs) continue to have considerable process challenges. These difficulties – combined with the need to assemble RoHS 5 (tin-lead solder paste and components with tin-lead finished leads,the remaining hardware being RoHS compliant),RoHS 5.5 (RoHS 5 with BGAs that have SAC or SACX solder balls) and RoHS 6 (fully compliant RoHS assembly) in one facility – create not only assembly technical challenges,but considerable material handling and logistics issues.
This paper is a review of the work done at Jabil in Billerica,Mass.,to address these challenges. An overview of the process development work in stencil printing,component placement and reflow soldering that was required to develop optimized assembly processes for PWBs with dimensions exceeding 56 cm and thicknesses approaching 0.3 cm will be discussed. The methods developed to handle the logistics issues of having RoHS 5,RoHS 5.5 and RoHS 6 assembly in one facility will also be presented.
The paper will conclude with a review of several of the products currently being assembled with these processes and logistics.
In this report,BGA packages with conventional and green material combination were selected as test vehicles for the investigation of MSL/temperature rating at the packaging level. The IC packaging was also tested at the package level and raw material level to show its RoHS6 compliance. Furthermore,chemical substances testing for halogen and Sb/Sb2O3 show a higher level of green compliance.
The proper grounding of all conductive items in the production workplace is an essential element of ESD (electrostatic discharge) management. ESD damage to components and assemblies in manufacturing is getting more and more attention. Smaller geometry and faster speeds of semiconductors have resulted in devices with increasingly higher ESD sensitivity. A typical sensitivity of integrated circuits and other devices is now in a 100V CDM range and many of the devices are already in 30 to 50V CDM sensitivity range. CDM stands for charged device model,and is defined as when a small device suspended by either pick-and-place vacuum picker or tweezers is charged and then is placed on a printed circuit board (PCB) making electrical contacts to the traces on the board and generating rapid discharge that can be quite harmful. Even if the device itself is not charged,a PCB or any other metal surface on which the device is placed,such as the shuttle in the IC handler,can be.
The phrase "Design For Manufacture" strongly implies the use of manufacturing information while making of design decisions or,in other words,incorporating manufacturing knowledge during initial design. Unfortunately,most currently available PCB DFM tools don?t fit into the design work flow until the PCB design is already complete. There are three nasty consequences to the current approach:
1. Designers are forced to make under-informed design decisions during layout,when DFM is easiest and least expensive to design in to the project.
2. When DFM errors are inevitably identified,they require significant rework,engineering effort and additional money.
3. The additional rework to fix back-end batch DFM increases the risk that your project will miss the market window.
New,more interactive approaches to DFM are becoming available to designers. Rather than postponing DFM checks until the end of the design,for example,the methodology described here enables designers to be notified (almost interactively) of any manufacturability issues as they design. By attending to DFM issues from the onset,designers are not only able to „pass? DFM,but can also invest in optimizing the manufacturability of their designs even from the first prototype. The result can be a cleaner,more manufacturable design that qualifies for production faster and at lower cost,and that also produces higher yields in production.
In this paper,we present case studies and efficiency results,from their implementation of an interactive DFM model to support our manufacturing process.
We have developed a cupric chloride-hydrochloric acid based microetchant process. This process provides a unique roughened copper surface,which yields excellent adhesion for both solder mask and dry film photo resist applications. The process also yields excellent solder mask adhesion through subsequent silver,tin and nickel plating post solder mask application.
The amount of copper etched using cupric chloride-hydrochloric acid based microetchant is not as high as that seen typically in cupric chloride etching systems. Airborne oxygen is efficient enough to be used as an oxidizer in the system. Hydrochloric acid maintains the proper hydrogen and chloride ion concentrations. The cupric ion maintains itself throughout the process.
The chemistry and process are both easily controlled. The process operation is comparable to a mini cupric chloride etcher,whereby copper concentration is maintained by specific gravity and acidity can be controlled by conductivity. It is not necessary to control oxidation-reduction potential,hence the difference as compared to conventional etching processes.
This technology provides highly roughened copper surfaces for conventional acid plated copper such as PPR and DC,and standard regular copper clad,which offers great adhesion for solder mask and dry film photo resist. For solder mask applications,it is necessary to produce a rougher topography by controlling micro etching rate at 1.0-1.5 µm/m to get good adhesion between copper surface and solder mask when the final finish is involved in immersion or electroless plating process with tin or nickel. For dry film photo resist applications,the processed copper surface is rough enough to improve the adhesion at micro etching rate below 1.0 µm/m. The copper surface roughness should be controlled within a range to balance the adhesion and resolution when dryfilm photo resist is used for fine line boards.
An electrochemical device has been developed that deposits non adherent copper metal powder at the cathode,and generates chlorine gas at the anode. The chlorine is contained within the system,and is used to regenerate the etchant in a continuous closed loop process. Chlorine is generated only when the electrochemical process is underway. There is never any stored chlorine gas. The copper metal powder is deposited on rotating disc cathodes,and continuously and automatically removed and stored. The disc cathodes rotate through the recirculating etchant solution,and the copper powder is deposited approximately 750 amperes per square foot and 5 volts DC. The powder is continuously removed from the cathode disc by mechanical scrappers,and flushed into a collection bin by a recirculating water spray. The anodes are inert DSA anodes. The chlorine generated is continuously transferred to the etchant where it reacts to regenerate the etchant. The rectifier is automatically turned on only when the ORP is below a set point. The rectifier is turned off when the ORP reaches a preset upper ORP limit,thus ending the production of chlorine gas. In order to conduct this study the existing unit has been installed and operated and tested in a real production facility. Because of the chlorine production,the unit cannot be operated or tested unless it is connected to a working etching system. The current high price of copper metal has made this technology very economically viable.
Emerging technologies in the printed circuit board industry including smaller holes,higher aspect ratios,three-dimensional features,fine pitch,blind via holes,and new lead free materials continue to challenge standard manufacturing methods. With these new technologies,plasma has become the chosen method for cleaning carbon/resin from laser formed blind vias,treatment of flex materials prior to lamination and etching lead-free materials and composite material constructions. The processing demand of these technologies has required improvements to the vacuum gas plasma process often used for desmear applications. Additional requirements including processing the high value product at a lower cost per panel are directly opposed to this new performance expectation. The new technology requirements translate directly to improved uniformity specifications for the plasma system,where the high value lower cost proposition drive cost of ownership and equipment configuration specifications. New plasma technology is required to meet the technology and cost demands. This paper describes one aspect of the technology development critical for improved uniformity.
More and more political bodies (countries,states,and unions) are enacting legislation designed to protect the environment from the impact of manufacturing. One category of restrictive legislation is called Extended Producer Responsibilities (EPR). The EPR directive with the biggest impact on the electronics industry is the European Union’s (EU) Restriction of Hazardous Substances (RoHS) Directive,finalized in 2003. The RoHS directive restricts the importation into the EU of new electrical and electronic equipment containing six hazardous substances including lead. For manufacturers to successfully comply with RoHS and similar EPR legislation,they need the ability to exchange material content information. This information needs to propagate through the supply chain from the raw material suppliers all the way to the final producer. To deal with this problem,the National Institute of Standards and Technology (NIST) developed a data model to address the underlying material declaration. This data model was used in the development of IPC-1751 Generic Requirements for Declaration Process Management and IPC-1752 Materials Declaration Management. While IPC 1752 was created with a focus on EU RoHS,industry is now faced with a multitude of new environmental legislations and regulations. While many are variants of the RoHS legislation,several address entirely new areas of environmental awareness such as energy efficiency. To address this problem,NIST has developed an updated model for IPC 1752 version 2.0. This model has a larger scope and is more modular making it better suited to address regulations beyond RoHS and meet other supplier declaration needs. This paper looks at the data models used in both version of IPC 1752 and highlights the differences for application developers.
Companies not only need to understand the reliability issues with environmental compliance,but also how to comply with the various regulations from the business end. China is the second jurisdiction with formalized legislation on the restriction of hazardous substances for electronic products.