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Lead-Free PCB Assembly Services
Lead-Free Printed Circuit Board Assembly (PCBA) Manufacturer
SUGA offers PCBA with RoHS control to original equipment manufacturers (OEMs). SUGA works with OEMs throughout the PCBA process, including PCB material checks, soldering method planning, project-specific thermal profile development, and release records to confirm alignment with submitted project requirements.
Review Inputs Before a Pb-Free Build Starts
- Bill of materials and manufacturer part number status check
- Solder alloy and PCB finish check
- Thermal profile planning
- Release record support
When Does a PCBA Need a Pb-Free Build Plan?
When designing PCBA with Pb-free materials, the soldering materials, PCB finishes, component terminations, and flux systems used in the assembly process need to comply with either RoHS regulations or the project’s defined restricted substances. How the full assembly process is performed will ultimately determine what is required for compliance with the final product.
When evaluating an OEM project, the review should cover more than whether the solder contains lead; it should also consider whether the assembly method is consistent with the compliance requirements expected for the finished product.
More Than the Solder Alloy
Lead-free soldering typically draws most of the attention to the solder paste, bar solder, or wire alloys that will be used in a specific application, but the finish of the printed circuit board (PCB) and the terminations of the components also influence the final decision. For example, a PCB assembled with lead-free solder can still create release issues if the populated components do not use lead-free finishes or do not have clear material declarations.
To confirm that a PCB will be assembled using a Pb-free method, SUGA reviews the submitted bill of materials (BOM), MPN status, PCB finishes, soldering processes, and documentation required for lot release prior to confirming the Pb-free process method. Clarify any exemptions from Pb-free requirements, the status of mixed materials, and any project-specific labeling requirements during BOM review.
Define the Requirement Early
Clarifying Pb-free requirements prior to material selection is critical. Compliance expectations define the accepted material set, and the material set then affects soldering temperatures, wetting behavior, inspection criteria, cleaning expectations, rework processes, and documentation required for lot release. Early clarification helps the project avoid treating a compliance-driven assembly like any other standard PCB soldering job.
When purchasing electronic components, double-check the expected RoHS status and its accepted exemptions, the required declarations, PCB finish type, and any special cleanliness or labeling requirements that must be fulfilled prior to shipment.
Materials, Solder Paste, and PCB Finishes to Check
The first step in creating a Pb-free solder assembly is verifying that the materials used for the product and target market align correctly. Solder alloy is just one of many factors that contribute to overall product compliance. The Pb-free solder assembly, including solder alloy, PCB finish, component terminations, solder paste, flux system, laminate type, and cleaning requirements, should conform to the defined requirements for the product and market into which it will be sold.
If even one item does not conform to these criteria, the project can carry greater risk than poor-looking solder joints. Additional issues may include a change in wetting behavior, thermal exposure, residue handling, material traceability, and record-keeping for shipment approval.
Use this material scope as a checklist rather than a fixed promise when determining whether a certain declaration, finish choice, or flux choice will apply to a given assembly. In addition, identify which materials and finishes affect the accepted assembly criteria.
Match Solder Alloy and Flux to the Process
Solder paste, bar solder, wire solder, and flux should be compared according to the soldering methods used for each product. Each soldering method may use a different combination of solder materials. Therefore, the solder alloy chosen for one soldering method may not be suitable for use in another without first ensuring it meets the requirements of that process.
Flux selection is also important because it differs regarding cleaning, inspection, and documentation requirements based on the project. For example, a no-clean flux requires a different set of cleaning, inspection, and documentation requirements than a water-soluble flux, yet both are typically specified in detail for projects that request additional cleanliness criteria.
PCB Finish and Component Termination Shape the Result
Lead-free HASL, ENIG, and ENEPIG finishes can support satisfactory Pb-free solder assembly when both the PCB finish and component terminations conform to the stated requirements and supplier declarations regarding these finishes. Therefore, confirm the PCB finish and component termination types by checking MPN status rather than making an assumption.
When the solder material, PCB finish, and component terminations used for the assembly are not properly matched with each other, there may be an increase in wetting inconsistencies or compliance problems. Therefore, each project file should include the BOM, PCB finish specifications, and the available material declarations.
Treat Halogen-Free Status as a Stated Requirement
When Pb-free solder is requested for a product, do not assume that the PCB containing that solder is halogen-free. Halogen-free status needs to be defined by either the project drawing, material declaration, or contract requirement. If required, identify the specific materials that may be affected, such as laminates, solder masks, fluxes, cable materials, and plastic parts.
Lead-Free Material and Finish Scope
| Item | Lead-Free Option | Evidence Required | Release Check |
|---|---|---|---|
| Solder alloy | SMT reflow: SAC305; wave/selective: SnCu0.7 per process scope; not a default SMT reflow alloy | Valid supplier CoC / declaration; solder paste, wire, or bar alloy record; lot code | Alloy matched to process route |
| PCB finish | Lead-free HASL, ENIG, ENEPIG | PCB finish specification; valid supplier CoC | Finish compatible with lead-free profile |
| Component termination | RoHS-compliant part finish; lead-free terminal finish | MPN RoHS status; supplier declaration | BOM and MPN release check |
| Laminate and solder mask | RoHS-compliant; halogen-free by drawing or contract | Material declaration; laminate or solder mask data; IEC 61249-2-21 basis for halogen-free claims | Compliance scope release |
| Halogen-free limit | Cl ≤900 ppm; Br ≤900 ppm; total halogens ≤1500 ppm for halogen-free claim | Material declaration with test basis | Approval record |
| Flux and residue system | No-clean or water-soluble per cleaning scope | Flux datasheet; cleaning requirement | Cleaning route release |
| Leaded-process segregation | Separated lead-free solder material, pots, tools, and rework consumables where both process types exist | Process route; tooling or material record | Cross-contamination risk check |
The Soldering Method Shapes the Assembly Plan
The soldering methods used to complete a Pb-free assembly project, such as SMT reflow, wave soldering, selective soldering, hand soldering, or a combined method, are based on component type, through-hole location, component thermal mass, fixture accessibility, the need for masking or special handling of certain areas, and component mix in the same project.
Create an assembly plan based on board design, not just solder alloy. A board can be designed to look simple in the BOM but may require tighter process controls during assembly if high-mass connectors and tall through-hole components are located close to each other, if the board has mixed SMT and through-hole layouts, or if heat-sensitive components are located close to other components.
Reflow, Wave, and Selective Soldering Solve Different Problems
When surface-mounted components dominate the layout, SMT reflow is the preferred method. Wave soldering may be used for assemblies with a high percentage of through-hole components, provided that sensitive areas are not exposed when passing over the wave. Selective soldering may be a better soldering solution for assemblies with only certain through-hole parts requiring solder, and where full wave solder exposure is less suitable due to SMT parts being in close proximity to the through-hole joints.
Fixture requirements, masking, board support, soldering accessibility, and inspection planning differ depending on the soldering method chosen. The thermal exposure of components in the assembly will change depending on the soldering method used for Pb-free work.
Mixed Layouts Need Earlier Process Checks
Mixed SMT and through-hole layouts need early processing checks to prepare the assembly for better results. If connectors, relays, terminals, shields, or tall parts are too close to other fine-pitch or heat-sensitive components, this can create problems before and during assembly. This should be planned before assembly, with the assembly method designed to protect heat-sensitive components while providing adequate access for inspection.
To reduce clarification cycles, identify and document special components well in advance, such as tall connectors, high-current terminals, press-fit components, heat-sensitive components, or areas that require no additional flux or solder exposure.
Rework and Touch-Up Are Not Default Fixes
Pb-free rework may increase the stress placed on pads, laminates, and components due to the higher temperatures used during rework. Instead of relying on touch-up to fix defects, include the rework limitations in project drawings, quality requirements, and accepted inspection criteria.
Pb-Free Soldering Needs a Different Process Window
Pb-free soldering may require more thermal exposure than tin-lead soldering. Therefore, each assembly's process window must account for the solder alloy, PCB thickness, copper weight, component thermal mass, and supplier limits from component, PCB, or solder materials. The process window is not one universal profile for all assemblies. It should provide a practical profile that facilitates wetting while minimizing excessive thermal stress on the components, laminate, or solder joints.
Use the temperature and time ranges as general planning references. Temperature and time information provide references for process factors to be validated, while final soldering parameters are based on component limits, PCB construction, material data, and accepted build requirements.
Melting Range Starts the Profile, Not Finishes It
A solder alloy's melting range only defines the starting point of the soldering profile. Within the process, ramp rates, preheats, time above liquidus, peak exposure, heating balance, cooling rates, and related factors all help develop the solder profile.
A delta T across the board or between components can serve as a profiling reference, particularly when there are significant differences in mass and thermal exposure between the components and the PCBs that contain them. Delta T values provide guidance only; the final temperature setting for profile completion is dependent on the limits of the components, the PCB material properties, and the intended soldering method.
Different Soldering Methods Need Different Checks
Reflow profiling involves controlled heating of the assembly to develop a profile appropriate for the component and PCB combination. The wave soldering process includes many additional criteria that affect the solder profile. These criteria include contact time, conveyor speed, immersion depth, and preheating. Selective soldering also has added criteria that must be taken into consideration in developing the solder profile. The added criteria include local heating and joint-by-joint access; these are typically present around connectors, shields, and nearby surface-mounted parts.
If early confirmation of the soldering method and thermal profile is not achieved, the project may experience issues with poor wetting, bridging, excessive thermal stress, or uneven solder fill. Check the process window against the actual layout of the board, not just the solder alloy name.
Lead-Free Process Temperature Reference
| Parameter | Reference Window / Check | Stage | Control Risk | Verification |
|---|---|---|---|---|
| SAC305 melting range | 217–220°C reference | Reflow | Insufficient wetting below melting range | Profile review |
| Reflow peak | 235–250°C reference; component limit checked | Reflow | Package or laminate heat stress | Thermal profile record |
| Time above liquidus | 30–60 s reference | Reflow | Under-wetting or over-exposure | Profile review |
| Board temperature delta | ≤10°C target; board-dependent | Reflow | Uneven heating; warpage risk | Thermal profiling |
| Wave solder pot | 255-265°C starting window | Wave | Thermal shock; copper dissolution | Pot temperature record |
| Wave contact time | 2.0–4.0 s reference | Wave | Insufficient barrel fill; overheating | Dwell check |
| Selective solder pot | 270–300°C starting window | Selective | Localized thermal stress | Program and pot record |
| Selective contact time | 2.0–5.0 s per joint reference | Selective | Wetting variation by joint mass | Joint program review |
| Top-side preheat | 90–130°C reference; 80–140°C extended review | Wave or selective | Flux activation; board stress | Preheat profile |
| Ramp rate | 1–3°C/s reference | Reflow and preheat | Component cracking; solder defect risk | Profile record |
| Conveyor speed | 0.8–1.5 m/min reference; dwell checked by equipment setup | Wave | Wrong dwell calculation | Speed and contact-length check |
| Immersion depth | 50–70% PCB thickness reference | Wave | Bridging; insufficient hole fill | Wave setup check |
| Atmosphere – standard selective | Air; if N2 is specified, see N2 condition row | Selective | Oxidation and wetting variation | Process specification |
| Atmosphere – N2 condition | 99.999% N2 supply; residual O2 target per process specification | Selective | Low-oxidation process requirement | Gas and O2 record |
RoHS and Material Records Behind Shipment Release
Many projects require more than solder statements for Pb-free PCBA; useful records may include RoHS material declarations, PCB finish evidence, component condition, solder alloy lot information, flux and cleaning information, and any label or exemption requirements specified by the contract.
To determine whether the purchased assembly meets RoHS compliance criteria, all records should match the product category, shipping location, project specification, and contract requirements. Supporting records are prepared or collected by SUGA as the project requires them, but compliance with restricted substance regulations relies on knowing the materials used and having the supporting evidence.
Determine the required records based on the acceptance condition. Some projects will only require material declarations and solder lot traceability, while others will require exemption handling, cleanliness evidence, and date-controlled REACH declarations.
RoHS Evidence Starts at Material Level
RoHS evaluations are done at the homogeneous material level and not based solely upon the label of the finished product. As such, solder alloy, PCB finish, component termination materials, cable materials, plastics, and coatings should include supporting documentation when requested by the project requirement.
Start by comparing BOM information to MPN status, PCB finish specification, and supplier declarations. If an exemption is used, make sure to delineate the exemption number, product category, and the agreed-upon conditions for acceptance along with the shipment evidence request.
REACH, Halogen-Free, and Labeling Need Clear Inputs
Declarations for substances identified on the Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH) Candidate List as substances of very high concern (SVHC) are issued based on the project requirement, and as the Candidate List changes, the declaration date and list basis must match the project requirements.
Treat halogen-free status and lead-free labeling as defined project requirements and not as assumptions. Clearly state any additional identification markings, material declaration wording, or shipment documentation requirements on the associated drawing, purchasing specification, or quality agreement.
Cleanliness and Residue Evidence Comes From the Requirement
The requirements for providing evidence concerning no-clean flux, water-soluble flux, and high-activity residues vary. Therefore, ionic cleanliness testing or ROSE testing should only be performed if identified on the drawing, cleanliness specification, or contract.
A value of ≤1.56 µg/cm² NaCl equivalent should be treated as a project-defined or contract-invoked cleanliness limit. Accepted evidence demonstrating cleanliness will depend on the explicit requirement in conjunction with the agreed inspection and cleaning plan.
Compliance Records and Release Gates
| Compliance Item | Record Required | Applies To | Release Gate | Limit / Exclusion |
|---|---|---|---|---|
| RoHS restricted substances | Declaration covering Pb, Hg, Cd, Cr(VI), PBB, PBDE, DEHP, BBP, DBP, DIBP | Solder, PCB finish, component materials, cable and plastic parts | Compliance release | RoHS is not a certification system |
| RoHS material limits | Pb ≤0.1%; Cd ≤0.01%; other listed substances ≤0.1% by homogeneous material | Declared homogeneous materials | Supplier declaration release | Exemptions require product-category review |
| REACH SVHC | Supplier declaration with date and latest ECHA Candidate List basis | Articles, components, plastics, coatings | REACH date check | Declaration date checked after each Candidate List update; renewal window per contract |
| Halogen-free | Material declaration by drawing or contract | Laminate, solder mask, flux, cable materials | Material release | Not default unless requested |
| Alloy traceability | Solder paste, bar, or wire lot; alloy type | Solder materials | Material receiving | No mixing of leaded and lead-free alloy |
| Cleaning and residue | Flux class; cleaning or no-clean status; ROSE or ionic cleanliness if required by drawing | Post-solder process | Cleanliness release | No universal ROSE requirement |
| Ionic cleanliness limit | ≤1.56 µg/cm² NaCl equivalent if drawing or specification requires | Cleaned assemblies or defined cleanliness programs | Drawing or cleanliness specification release | Not a default release limit |
| Exemption handling | Exemption number, product category, and approval record | RoHS exception cases | Compliance release | Do not assume exemptions |
Keeping Pb-Free and SnPb Work Apart
When a supplier performs both Pb-free and SnPb work, separation of solder materials, tools, pots, rework supplies, and lot history needs to be clear. Mixing solder material is not only a compliance issue; a small material mix-up can change how solder joints behave, create discrepancies in shipment documentation, and result in product rejection.
SUGA maintains separation through material receiving, solder preparation, rework material handling, and solder lot history records. The separation process must match the product requirement and mutually agreed-upon acceptance condition for the assembly.
Separate Materials Reduce Cross-Contamination Risk
Identifying Pb-free and SnPb solder paste, solder bars, solder wire, flux, and rework consumables prior to use ensures the correct materials are used for each respective project. Accurate identification of the correct materials will include an identification label that includes alloy type, lot number, and storage condition.
Where both types of solder are used in the same facility, the order should clarify whether dedicated solder materials, separate tools, or additional trace records are required. This is important if RoHS documentation is expected with the finished product.
Assign Tools, Pots, and Rework Supplies Clearly
Having common pots, rework materials, soldering supplies, and hand soldering tips creates a risk if no one knows which materials are assigned to which work. While the process plan provides the list of items, combined with the specific way they are labelled, it must also detail how lots are tracked and any evidence of their use.
The same is true for rework. When reworking a Pb-free assembly, do not use an incorrect solder wire or flux system. For any mixed-material repairs, ensure the approved use and required documentation are clear before continuing with the rework.
Traceability Shows What Was Used
Having records linking the lot to the solder alloy, PCB finish, component conditions, and materials used supports traceability, and they do not replace a RoHS declaration. The records clarify whether the actual manufacturing situation matched the material status of the assembly.
Reliability Questions That Need Extra Attention
Solder joints for Pb-free assemblies will have different reliability issues compared to SnPb assemblies due to changes in wetting properties, thermal exposure, residue conditions, and finish compatibility. Reliability concerns extend beyond visual appearance once the joint has been assembled. The material set and soldering process selected must also be adequate for the environment of use and required acceptance criteria.
SUGA assesses the risks of the assembly based upon the design submitted, materials used, soldering methods used, inspection accessibility, and any tests required by the project. The additional inspections are most applicable for assemblies containing high-thermal-mass components, assemblies with pure tin plating, assemblies using water-soluble flux, hidden solder joints, or assemblies that operate under harsh conditions.
Establish which reliability risks are relevant to that specific product. Different types of products, such as simple consumer accessories, high-current industrial boards, and assemblies exposed to pure tin, may require different documentation to support shipment authorization.
Watch for Poor Wetting and Thermal Stress
Poor wetting can occur during a soldering operation if the solder alloy, PCB finish type, component termination, or flux being used does not match the process. Thermal stress can occur when using large circuit boards, thick copper, heavy connectors, or heat-sensitive components, all of which exhibit varying heating characteristics across the same assembled product.
These conditions should be checked when the soldering process is selected. This helps prevent avoidable defects such as weak joints, bridging, incomplete hole fill, package stress, and localized laminate damage.
Tin Whisker Risk Starts With Finish Choice
When pure tin finishes are used on assemblies where the assembly requires high reliability, the risk of tin whiskers will be a significant concern. In an application where pure tin component terminations must be used, specifying a nickel barrier underplate beneath the tin finish is preferable where the component supplier supports it.
If pure tin cannot be avoided, clearly define all project expectations in the specification or quality agreement regarding mitigation procedures. Treat all annealing, finish approvals, or mitigation records as part of an agreed-upon project condition rather than as a generic step for any assembly.
Residue, Cleanliness, and Test Evidence Follow the Application
Flux residue becomes a significant problem with the use of water-soluble flux, high-activity flux, no-clean residue limits, and sensitive operating environments. The cleaning documentation, ROSE testing results, ionic cleanliness testing results, and other inspection requirements can be discussed when required by the drawings or cleanliness requirements.
Lead-Free Reliability and Test Release Checks
| Risk Area | Trigger | Control Method | Verification Output | Applied Scope |
|---|---|---|---|---|
| Thermal stress | High-thermal-mass parts; thick copper; large boards | Preheat and soldering profile review | Profile record | SMT, wave, selective |
| Poor wetting | Lead-free finish mismatch; flux activity mismatch | Finish and flux compatibility check | AOI for visible joints; X-ray for hidden joints; micro-section where required by inspection scope | Assembly release |
| Copper dissolution | High pot temperature; long dwell time | Pot temperature and dwell control | Process record | Wave and selective soldering |
| Tin whisker | Pure tin finish; high-reliability requirement | Avoid pure tin where feasible; nickel barrier finish such as ENIG or ENEPIG; contract-defined annealing condition where specified | Finish review; approval record | IPC Class 3 or project-defined high-reliability requirement with pure tin risk |
| Tin whisker mitigation level | Pure tin cannot be avoided | Contract-defined mitigation plan; GEIA-STD-0005-2 reference where invoked by contract | Mitigation record | Contract-invoked GEIA-STD-0005-2 or equivalent mitigation requirement |
| Cross-contamination | Leaded and lead-free material in the same manufacturing environment | Separated material, tooling, pot, and rework control | Lot trace record | RoHS projects |
| Residue / ionic contamination | Water-soluble flux; high-activity flux; no-clean residue constraint | Cleaning route review; ROSE or ionic cleanliness per drawing requirement | Cleaning record or defined test result | Defined cleanliness scope |
| ICT trigger | Netlist, test points, and ICT fixture available | ICT setup | Open / short test record | Build release scope |
| FCT / ATE trigger | Functional test fixture and procedure available | FCT or ATE setup | Functional test record | Functional test scope |
| Burn-in / aging trigger | Early-life failure screening required | Contract-defined time, temperature, load, and acceptance rule | Aging record | Reliability screen scope |
What Changes the Quote in RoHS-Controlled Work
A RoHS-controlled PCBA quote can differ from a standard PCBA quote when the project involves more than a different solder alloy. The way the project is constructed around the assembly and the materials used has a greater impact on pricing.
The primary factor driving the price of a RoHS-controlled PCBA is the amount of work required to clarify the condition of the assembly. It is much simpler to quote the price for a generic assembly with all material declarations included than for a PCB that is a mixed-process board with no clarity about exemptions, special cleanliness requirements, or both Pb-free and SnPb variants.
A mixed SMT through-hole assembly that requires selective soldering, masking around sensitive areas, and ROSE testing as specified by the project specification requires preparation work that a reflow-only assembly does not. The cost differential is not a surcharge for using Pb-free solder; rather, it is the result of fixture preparation, masking preparation, cleaning verification, and documentation needed to support acceptance.
Material Availability Shapes Preparation
Solder alloy, solder paste, flux, PCB finish, and component termination status will determine what materials need to be purchased and how many assemblies can be built in a specific time period. If the submitted BOM contains parts with questionable RoHS status, obsolete MPNs, or alternate parts with different finishes, the build plan will need clarification prior to establishing the stability of the build plan.
For supplied materials, missing declarations or mixed labeling requirements cause additional handling effort for suppliers. A quote for a turnkey or hybrid order is based on the appropriate components and materials along with approved supply sources.
Process Setup Creates Preparation Work
Setting up a RoHS-controlled job will create some additional process setup work if the job has certain attributes such as selective soldering, masking, separate solder materials, dedicated rework supplies, and specific high-thermal-mass part handling processes. These attributes may not make a project difficult to quote; however, they can create significantly different preparation work from a standard soldering job.
If the assemblies will include both Pb-free and SnPb variations, separating them during preparation will also affect labeling, lot management, and traceability records. Define these specifics early so that the quote can capture the actual agreed-upon process criteria rather than an assumed generic assembly process.
Evidence Needs Shape the Final Effort
Some orders only require minimal documentation for material declarations and solder lot traceability. Others may require RoHS evidence, REACH declaration dates, cleanliness records, functional test results, and exemption documents. These documentation requirements create additional preparation time and require corresponding acceptance planning, coordinated effort, and approval.
To keep the quote practical, list the SUGA documents required for shipment acceptance as the basis of the quote, and separate these from verifications performed only when product risk warrants them. Doing so reduces assumptions in the quoting process.
Project Files SUGA Checks Before Quoting a Pb-Free PCBA
A quote for a Pb-free PCBA should not be based solely upon the quantity of boards and type of assembly. SUGA requires complete and accurate project documentation to evaluate the soldering process, materials, inspections, and shipment documentation.
A complete set of build documents should include BOM, Gerber files, centroid data, assembly drawing, PCB finish requirements, and any notes that affect soldering, cleaning, marking, or release evidence. Include any RoHS declarations, exemption information, or material restrictions when submitting the quote request.
Core Build Files
The BOM will list MPNs for all items, approved alternates for each item, consigned parts for each item, and any items classified as having special material status. The Gerber files, centroid data, and assembly drawings will serve to confirm placement, polarity, through-hole locations, connector locations, and any areas of the PCB that may hinder the soldering process.
If an item is supplied as consigned material, the kit record should describe the part number, quantity, lot number, and any RoHS status provided by the supplying manufacturer. If a part is missing a clear RoHS status, it could delay quoting because the soldering process and release documentation are based on the actual material combination.
Compliance and Material Inputs
For Pb-free soldering, project files should include RoHS status, PCB finish, solder alloy preference if determined before assembly, component finish issues, and declarations from component suppliers. If RoHS exemptions are used, include the specific exemption category and approval conditions.
When quoting a product, cleanliness, residue, labeling, REACH declarations, halogen-free status, and special inspection documentation should only be included for products that are required to be made in compliance with those items.
Keep quotes focused on real acceptance criteria rather than unnecessary verification, so the quote is more accurate and will not incur undue delay with additional requests for documentation if the initial request is not complete or clear about the requirements.
Upload BOM & Gerber
What SUGA Returns After File Check
After reviewing the submitted information, SUGA identifies missing information, unclear descriptions of material status, concerns about the soldering process, required documentation, and questions regarding the quote.
Pb-free status, material evidence, and acceptance requirements should be clear before finalizing the quote. Higher clarity helps eliminate misunderstandings regarding the assumptions made about the part being quoted and the actual assembly condition.
FAQ
Lead-free PCB assembly means that the solder materials, PCB finish, component terminations, and material records for the PCB comply with a Pb-free or RoHS-controlled specification. While it is primarily a solder material selection, there are other considerations, including BOM, MPN status, PCB surface finish, flux system, and release records required for shipment acceptance prior to shipping.
Lead-free solder is intended to meet restricted-substance requirements. The lead-free designation is based on compliance with defined substance limits, such as Pb ≤0.1% by homogeneous material under RoHS, not zero lead content. Accepted status depends on the solder alloy, component finish, PCB finish, supplier declarations, and any applicable exemptions. Verify that the submitted materials and records support the expected compliance condition.
OEM programs use Pb-free materials for solder as a result of needing to access RoHS-compliant markets, project expectations for Pb-free compliance, or material restrictions placed on their products. The switch from Pb to Pb-free will also affect the selection of solder alloy, PCB surface finish, component design limits, thermal profiling requirements, inspection requirements, and release records. Define this requirement early in the development of the project so that it is not treated as a standard soldering project.
SAC305 is the most commonly used solder alloy for SMT reflow. SnCu0.7 is suitable for wave and selective soldering only if there is agreement on the process condition. Be sure to match the solder alloy to the soldering method, component limit, PCB surface finish, and project requirements. SUGA will review the submittals before confirming the solder material.
Typically, solder alloys that do not contain lead will require a higher temperature, but there is no one-size-fits-all temperature for Pb-free solder. Rather, the type of solder alloy, thickness of the board, copper weight, component limits, and method of solder application will determine the profile. Reference windows can support planning; final settings rely on material data and the accepted process condition.
Yes. The purchasing company should verify with the supplying company how it segregates solder materials, including solder paste, tools, pots, rework consumables, labels, and lot numbers for leaded and Pb-free solder. The main risk associated with using the same supplier is mixing the solder materials between leaded and Pb-free in a manner that could adversely affect how the joints will perform or affect compliance. Identify these two versions of solder in the BOM, drawings, purchase order requirements, and labeling instructions for both versions.
Key documentation includes both the BOM and MPN with RoHS status, supplier declarations regarding compliance with the RoHS directive, evidence of the PCB finish type, solder alloy lot tracking, cleaning and flux data, labeling instructions, and any requested release documentation. When applicable, the drawings, purchasing specifications, or quality agreements should include any request for REACH, halogen-free status, evidence of cleanliness, or any exemptions to the RoHS directive.
In most cases, lead-free solder is selected for compliance with RoHS or other restricted-substance guidelines, but it is not always "better" in all respects. SnPb solder continues to be used in situations where it is deemed permissible or exempt from RoHS compliance. Determining the right decision depends on the type of product, the destination market, the compliance requirement, process risks, and the accepted criteria.
Some common problems are poor wetting, bridging, thermal stress, incomplete hole fill, copper dissolution, and issues concerning residues or tin whisker risk. The factors that can lead to these potential problems will come from the solder alloy, PCB finish, component terminations, thermal mass, flux system, and inspection access. Identify these risks at an early stage and determine the appropriate evidence of inspection or testing when necessary.
Yes. SUGA will support a lead-free SMT assembly process when the demand is based on proper alignment of the BOM, solder paste, component termination, and reflow profile requirements. For greater capability in lead-free SMT process technology, please refer to SMT Assembly Services.
If the lead-free soldering process is conducted in accordance with proper safety standards for material handling, fume control, cleaning, workplace safety, and operator safety, then the process can be handled safely for electronics manufacturing. The "safe" designation is not exclusively based on the "lead-free" label. All areas of flux chemistry, fumes, residue handling, and operator protection are important when evaluating the safety of lead-free soldering. Any additional documents to support specific safety, cleanliness, and handling requirements should be included in the project files.