The above video demonstrates tinning on SOIC type components. During this video demonstration, the solder pot shroud and nitrogen inerting was removed to clearly show the tinning process.
Outline
The guides in section 10 cover the requirements for manual tinning and robotic hot solder dip to replace the finish on various electronic components.
Two primary reasons to solder dip electronic components are solderability concerns and tin whisker mitigation. Solder dip for tin-whisker mitigation differs from solder dip for solderability. For tin whisker mitigation, the termination must be coated over its entire length up to the package surface. During solder dip, the piece part experiences temperature differences that are more significant than those present during typical board-level assembly. In addition, the fluxes used during the dipping process can become trapped in minor delamination, like that commonly found in plastic piece parts, leading to reliability issues. The solder dip process must be qualified and carefully controlled to avoid these concerns.
Section 10 includes requirements for performing robotic hot solder dipping to decrease the possibility of failure of the electronic components after being solder dipped and ensure a quality process is performed each time.
These guides cover replacing pure tin and Pb-free tin alloy finishes with tin-lead (SnPb) finishes for subsequent assembly with tin-lead solder. The guides in section 10 may also apply to other component lead finish changes. Replacement finishes other than SnPb should be evaluated for tin whisker mitigation before implementation.
Caution: Due to the need to completely control the rates of immersion and emersion of the component terminations and the dwell times in and between each process step, robotic hot solder dip is recommended for electronic component tinning. Semi-automatic or purely manual solder dipping processes may not be capable of completely controlling the rates of immersion and emersion of the component terminations and only provide approximate dwell dipping times in the solder bath. Greater variation in the process may cause a higher chance of damage, including latent reliability problems. Manual dipping required for full finish replacement differs from manual dipping currently practiced for meeting solderability requirements because of the increased need for 100% coverage to the component body to prevent whisker growth. Certain electronic component package styles may not lend themselves to robotic hot solder dipping and may require alternative processing.
Note: For detailed information, refer to GEIA-STD-0006 Requirements for Using Robotic Hot Solder Dip to Replace the Finish on Electronic Piece Parts.
GEIA-STD-0006 defines the requirements for fully replacing undesirable surface finishes using robotic hot solder dip. Requirements for qualifying and testing the refinished components are also included. This standard covers the replacement
of pure tin and Pb-free tin alloy finishes with SnPb finishes with the intent of subsequent assembly with SnPb solder. This standard covers process and testing requirements for a robotic dipping process and does not cover semi-automatic or purely manual dipping processes.
GEIA-STD-0006 does not apply to manufacturers who initially build components with a hot solder dip finish. It applies to refinishing performed by a robotic hot solder dip service supplier or production facilities at the customer whenever the intent of the dipping is to have full coverage and replace Pb-free tin. Replacement of BGA spheres or CGA columns is not included in the scope of this standard. IEC TS 62647-4 may be used to replace BGA spheres.
GEIA-STD-0006 is for suppliers and customers to incorporate these requirements into their operations to provide a consistent and well-controlled process for product applications that require significant control. Complete conversion of termination finishes from pure tin or Pb-free solder to SnPb will allow the use of electronic components for any of the Control Levels of GEIA-STD-0005-2 without mitigations. In addition to eliminating tin whisker risks, electronic components processed to this standard will exhibit enhanced solderability and joint reliability compared to most COTS finishes.
Requirements for Robotic Hot Solder Dipping Apparatus
Robotic Hot Solder Dipping Apparatus shall include the following.
Feature a vacuum or mechanical pickup mechanism
Not damage the piece part or its terminations
Not utilize metal surfaces that may scratch or cause solder smears
Be capable of controlling the dwell time in the pre-heat and solder pot within ±0.1 second
Be capable of controlling the exit speed out of the solder pot to within ±0.12 inch (0.3 cm)/s
Be capable of controlling the depth of immersion to within ±0.004 inch (0.01 cm)
Ensure dipping of the full termination or other tin or Pb-free tin finished surface into the solder pot, including the side of the package (if applicable)
Apparatus for Gull-Wing Formed Leads
In addition to those requirements above, the dipping apparatus used for robotic hot solder dipping gull-wing formed leads shall also be capable of edge dipping the piece parts with the following controls:
Solder dip immersion angle and direction of travel
Solder dip withdrawal angle and direction of travel
Ability to rotate piece part to allow each side to be solder dipped independently
Apparatus for J-Leaded Formed Leads
In addition to the requirements above, the dipping apparatus used for robotic hot solder dipping J-lead-formed leads shall be capable of edge and planar dipping the piece parts to cover neighboring termination surfaces not obstructed by the package body.
Overall Process Flow
Qualification of Process - Before production, qualification of the refinishing process shall be performed per GEIA-STD-0006.
Dry Bake - The MSL of piece parts shall be obtained/verified from/by the customer. All piece parts with MSL 2 or greater shall be dry-baked before refinishing following J-STD-033. Dry bake is not required for electronic components received in labeled dry bags with desiccant and humidity indicators reading less than 5% RH or for electronic components Type 1. Once the packaging has been opened, it shall be handled following J-STD-033. Moisture-sensitive electronic components received in unknown conditions shall be dry-baked per J-STD-033. The cumulative bake time limits of J-STD-033 shall not apply to baking before refinishing.
Fluxing - The flux used shall be per GEIA-STD-0006 or customer requirements and shall be applied to the piece parts consistently and repeatedly.
Preheat - Components shall be preheated before robotic hot solder dipping. Preheat ramp-up rates shall not exceed the original piece part manufacturer's specifications, J-STD-020, J-STD-075, or as specified in engineering documentation.
Application of Solder - After flux and preheat, the part terminations shall be immersed in the molten solder by a robotic hot solder dipping apparatus. The total time in solder shall not exceed 5 seconds per immersion. A dynamic wave or another method that removes solder dross shall be used.
Cool Down, Cleaning, and Drying Methods - Cooling rates shall not exceed the component manufacturer’s specifications, J-STD-020, J-STD-075, or as specified on engineering documentation. Cleaning shall be performed within 1 hour of solder dipping following the flux manufacturer's recommendations or J-STD-033 and J-STD-075, where applicable. Drying shall be accomplished to prevent the re-deposition of ionic material onto the electronic components or reduce the solderability of the component.
Rework - Piece parts within the production lot shall not be reworked more than twice. A single rework process is defined as one complete throughput through the robotic hot solder dipping process for any combination of package side(s) after the initial robotic hot solder dip. Any piece parts damaged shall be segregated, marked as defective, and returned to the customer; this includes piece parts dropped into the solder pot or on the floor or exhibiting physical damage after a fall.
Inspection and Testing - Electronic components shall be tested following applicable test methods defined in GEIA-STD-0006 or as defined by customer drawings. If there are any failures during applicable test methods of the production lot testing, then the customer shall be notified. Failed tested electronic components shall be segregated, marked as defective, and returned to the customer. Production electronic components of failed lots shall be identified and returned unless screened for defects in the sample devices.
Post-Process Baking - After all processing and inspection, electronic components that were dry baked shall be dry baked again following J-STD-033 and dry packaged in moisture barrier bags. The cumulative bake time shall be reset to "zero" upon final packaging.
