Lead free and proud

RoHS prototype assembly

Lead free pcb assembly at Screaming Circuits®, an innovator in prototype circuit board assembly, offers leading edge lead-free pcb assembly (Pb-Free) and RoHS-compliant circuit board assemblies.

Lead-Free pcb assembly includes:

  • Lead-Free Rigid or Flexible Circuit
  • Lead free Board Assembly (SMT or THT/PHT)
  • Lead Free Wave Soldering
  • Lead Free Rework
  • Lead Free Printed Circuit Boards
  • Lead-Free Materials Analysis

Our Lead free pcb assembly service utilizes special assembly procedures to assure compliance with Lead-Free and RoHS pcb assembly standards. In addition to leadfree pcb assembly, Screaming Circuits also provides support to help you transition to lead-free and RoHS compliant circuit boards. We are lead free pcb assembly experts.

Screaming Circuits not only assembles your lead-free boards we can also assist you if you need help in determining if the materials in your Bill-of-Materials meet lead free pcb manufacturing requirements. We can even research lead-free components for you and send you a Bill-of-Materials with the appropriate components as part of our Turn-Key lead free proto assembly service.

Download a printable PDF about processing Lead-Free RoHS builds with Screaming Circuits

What you need to know about RoHS compliance:Considerations for assembly of lead-free circuit boards.

RoHS Electronic Assembly Process

Our RoHS manufacturing and lead free prototype assembly processes meet lead-free and RoHS standards. We use IPC 610D soldering standards.

If components arrive in invalidated moisture packets and your components need to be baked to reduce excess moisture, then 72 hours is required to bake the components. The assembly time does not start until the components are baked.

The lead free SMT Assembly Process

The RoHS pcb assembly process requires that none of the hazardous materials listed in the RoHS Directive are used in the board, components or solder. Bare circuit boards used in the typical “leaded process” are often coated with a lead-tin finish, so the finish on the board must be modified significantly to be compliant with lead-free and RoHS standards.

The lead-free prototype process also requires that boards be assembled at higher temperatures—usually 30-50 degrees C higher. The higher temperature may require that the substrate of the circuit board itself and various components be modified to withstand the higher temperatures in the oven. In addition, the IC moisture sensitivity level that indicates how long the board can be exposed to the air is approximately 2 classes higher for lead-free boards, so there can be increased moisture sensitivity. The shelf life of the materials used in lead-free boards may also be shorter.

Profiling:

To ensure proper oven reflow temperature profiling, we ask for one additional lead free pcb along with an extra set of any temperature critical parts; i.e. BGAs, heat slug parts, etc. These can be actual parts, non-functional actual parts or thermally equivalent dummy parts. Most manufacturers of large and expensive components can supply non-functioning "Mechanical Samples" specifically for this purpose. Additionally, suppliers, such as Practical Components provide thermally equivalent parts specifically for this purpose.

Inspection:

Due to the metallic composition of lead-free solder, the visual appearance may differ significantly from that of a standard leaded solder joint. Frequently, a first look will give the impression of a cold solder joint. Our inspection technicians are trained to IPC-610D standards to ensure that the solder joints are solid and of high quality.

What you need to know about RoHS compliance:Considerations for assembly of lead-free circuit boards.
  1. Bill-of-Materials, Board Finish and Components Analysis: It is the customer’s responsibility to verify that the Bill-of-Materials is correct for lead-free parts. We can also consult with you if you need help in determining if your board and components meet the requirements. If the components arrive in invalidated moisture packed and we determine there might be excess moisture issues, we will notify you that we think your components need to be baked prior to assembly.
  2. Applying Board Stencil and Solder Paste: Screaming Circuits begins the assembly process using a lead-free compatible circuit board and applying a stencil to the board. A lead-free compatible solder paste alloy called SAC305 is applied. The SAC305 solder alloy is used in SMT, Wave Solder and Wire (Hand) soldering processes. After soldering, the board is visually inspected for solder coverage and manufacturing acceptability.
  3. Placement of Components: The next step is placement of parts using a Pick-and-Place machine. The parts that are placed are based on the supplied Bill-of-Materials. Each part has a unique part number assigned to it. When a product is programmed to run on the SMT equipment, the part is assigned and the machine will then pick the correct part. Any component on the board must be lead-free process compatible. These components must be able to withstand the higher solder and manufacturing process temperatures.
  4. Placing Board in the Reflow Oven: The final step is placing the board in the oven where the solder paste is melted to form a metallic bond between the component and the circuit board trace. Lead-free and RoHS compliant boards must be processed at higher temperatures in the reflow oven. The process margin (window) is smaller which makes thermal profiling more important for lead-free circuit boards. It is helpful for profiling to have the following: board thickness, board finish, size of the board, and layer count. Screaming Circuits uses ECD’s SuperM.O.L.E.® Gold, WaveRIDER®, and OvenRIDER® thermal profiling products to control the higher temperature reflow soldering processes and track thermal profiles required for lead-free boards.
  5. Thru Hole and Manual Solder: Screaming Circuits can also perform Thru Hole and Hand / Wire soldering of lead-free boards. Lead-Free Pass Thru and Hand soldering will be performed in areas with no leaded parts. We will use lead-free solder and a lead-free soldering iron.
  6. Testing: Screaming Circuits performs a visual inspection right after soldering looking for manufacturing defects. Screaming Circuits uses the IPC 610D soldering acceptability standard. Solder that is “unleaded” looks different after the manufacturing process. Screaming Circuits has trained its staff how to evaluate lead-free solder joints.
  7. Packaging: Fully assembled lead-free Boards are packaged individually in ESD bags for shipment.