RoHS Material Controls and Visual Management

Estimated reading time: 4 minutes

By Scott Mazur, Benchmark Electronics Inc.

With the industry transitioning materials to RoHS compliance, a mixture of leaded and lead-free components, assemblies, and systems prevails in many manufacturing facilities. This reality of producing both leaded and lead-free product requires diligence, control, and visual management throughout the manufacturing process. Failure to deploy controls can result in a European Union (EU) RoHS misconduct. Cross contamination can result from a company running both RoHS and non-RoHS manufacturing lines.1

Material identification and subsequent segregation become paramount with mixed manufacturing areas. Requirements for material control and visual management are critical, given the many opportunities for error. Material control is one aspect that supports the EU's requirements for a compliance-assurance system or due diligence controls. The focus of this material control phase is compliance of manufacturing areas, associated risk, and subsequent control to mitigate such risk. This article focuses on the material receipt, stock, and SMT processes. The following sections detail a sample of a due diligence system, including material controls and visual management techniques.

Material ControlThe first step of a manufacturing compliance process is control of material,2 given the varied stages of compliance from supplier to supplier and commodity to commodity. The lead-free transition continues to be challenging, with various exemptions such as lead in solder (also known as RoHS-5) and lead as an alloying element in metal hardware and mechanical components. The goal is to confirm compliance and segregate materials. Compliance can be achieved through many avenues, including receipt and storage of the certificate of compliance (CoC) or material declaration from suppliers. Due diligence verification can be completed with portable X-ray fluorescence (XRF) testers. Upon acceptance and assignment of compliance status, the material will be transferred to the stock location. The stock location must be segregated by compliant and non-compliant. The material segregation can include various types of compliance, including exemptions like RoHS-5 or lead in solder.

The immediate goal is to create a method to identify, segregate, and store material through the entire manufacturing process including receiving, stockroom, manufacturing floor, and field returns. Deployment of such a process prevents mixing materials at the component and assembly level, while substantiating the compliance-assurance system. Several methods can be implemented, such as part number identification. Many part number identification strategies are used in the industry adding prefixes and suffixes to existing part numbers, changing part number schemes with specific identifiers detailing compliance, new dedicated compliance part numbers, etc. Upon deployment of the part number identification, the material must be marked or labeled with the compliance part number. Material integrity is the foundation of compliance assurance.

Visual ManagementVisual management tools2 can be used to segregate and identify RoHS-compliant material. Visual management practices are recommended for the entire manufacturing process including receiving, stockroom, SMT, thru-hole, wave solder, all applicable rework stations, and field or customer return areas. Figure 1 illustrates typical signs used in a stock room; the area is confirmed compliant by manufacturer's part number validation, CoC receipt, and acceptance using XRF screening. The visual management details the compliance status of the specific material. This technique is complemented by employee training and communication with the specific manufacturing area, which will raise awareness and reduce cross-contamination opportunity for error.

Figure 2 details visual management used in an SMT process during lead-free solder paste screen printing. This entire SMT line has signs to identify that the product and chemistry being used are lead-free. Additional information can be included, such as specific chemistry, i.e. no-clean or organic acid water-soluble fluxes. The practice suits dedicated lead-free equipment and, more importantly, non-dedicated lead-free equipment. It identifies and communicates the lead-free chemistry in-use to all employees and potential visitors. The procedure for non-dedicated equipment will be a visual management changeover from tin/lead to lead-free chemistry.

The ultimate goal is to identify all equipment that produces lead-free and RoHS-compliant product. Upon completion of the SMT build, the completed assemblies must be identified with product labeling or material-handling signs. This identification will provide the segregation required for lead-bearing and lead-free mixed manufacturing facilities and processes. The final deployment stage of the SMT processes is tooling and manufacturing materials. The tooling used for the manufacturing process (stencils and fixtures) should also be identified and segregated. Labels, signs, or tape can be used to identify and support visual management.

Final deployment relates to the manufacturing materials used in the process. Lead-free solder paste must be identified and verified compliant. The identification can be labels, signs, or tape for segregation purposes from lead-bearing material. Compliance verification can be completed using XRF technology.3

ConclusionDeployment of the above material control and visual management practices will build a foundation that supports a manufacturer's compliance-assurance system, while reducing the cross-contamination risk of RoHS and non-RoHS manufacturing in one facility. SMT

REFERENCES1 "Vendor Admits to RoHS Misconduct," EE Times, October 2007, www.eetimes.com.2 SMTA Successful Lead-Free/RoHS Strategies Conference, Boxborough, Mass., June 2021, 2007.3 "Due Diligence Verification Ensuring RoHS Compliance," SMT Magazine, March 2006.

Scott Mazur, principal engineer and RoHS specialist, may be contacted at Benchmark Electronics Inc. Hudson, N.H., Division; scott.mazur@bench.com.