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PCB Connector Repair Procedures

Published Date
Author Cadence PCB Solutions

Key Takeaways

  • An overview of the manual PCB connector removal and replacement process.

  • Why larger connectors are more liable to experience failure.

  • A step-by-step guide for edge connector repair.

Stacks of connectors rising above PCB.

PCB connector repair can be a common area of rework due to repeated insertion and removal of cables.

Connectors are a standard interface option for off-board I/O that facilitates system communication. While connectors are durable by themselves, constant mating cycles can be a source of failure if proper design and manufacturing guidelines do not adequately resolve the forces encountered during operation. Whether in the hands of end-users or at production facilities, PCB connector repair is an involved process that can lead to additional issues; like all rework, a robust DFM approach avoids connector repair by mitigating poor assembly practices at the source.

Common Causes of PCB Connector Repair

Defect analysis

Solution

Mating force

Mating cycles above product ratings Excessive force during insertion or removal Mechanical damage from an overly strained cable connection

Ensure connector is suitable for the expected number of mating cycles during service life Provide necessary slack in wire harness

Moisture

Extreme moisture events can immediately short a connector Persistent, low-level moisture can eventually degrade surface finishes

Be mindful of enclosure design, especially for devices with environmental exposure Ensure testing accurately accounts for moisture

Corrosion

Corrosion forms oxidative layers that increase contact resistance and can ultimately result in open circuits Even in connectors that are permanently mated, vibration and thermal expansion can wear down surface finishes

Employ connector housing that reduces the ingress of materials Use mechanical simulation to add fasteners where appropriate to minimize movement

PCB Connector Repair: Overview and Issues

PCB connector repair should always start with a diagnostic stage to assess the source of error. Repair of the connector is either accomplished with rework while the device is still within the assembly house or field replacement. Most connectors are simple electromechanical housings for wires and cable assemblies, and repair focuses on desoldering the connector from the board:

Connector repair can arise from manual hand soldering as connectors may be too large or protrude too far off the board for automated wave or reflow soldering processes. Solder joint quality formed by manual soldering tends to exhibit higher variation in quality than automated systems. While this is unsurprising, technicians and inspectors must understand the minimum level of acceptability as determined by the board’s IPC classification. Fortunately, larger connectors' pitch and pin size corresponds to a relatively greater land pattern size; inspection magnification levels need not resolve to the same power of finer pitch devices. In other words, solder joint criteria for these larger components will be more forgiving, which can be a double-edged sword.

An Overview of Edge Connector Repair Following IPC Standards

Edge connectors of RAM card.


Edge connectors require additional rework considerations.
 

Edge connectors commonly require repair due to their exposed contacts. Corrosion or mechanical damage to the contacts may necessitate secondary electroplating rework for resurfacing. Deep gouges or other significant abrasions are unlikely to correct and require replacement. For quality and safety, technicians should use protective equipment and proper ventilation due to harmful chemicals.

Repair follows some straightforward steps:

  • Solder contamination removal - Clean the area to prevent the inclusion of contaminants. Around the rework area, place plating tape to prevent board or component exposure to the stripping and plating solutions. Flow solder over the rework areas and remove contaminants with desoldering methods, then apply a solder solvent to remove any remaining solder from the contacts. Buff the contacts with a light abrasive to remove residual solder and rinse with deionized water.

  • Plating/defect removal - The process differs slightly from the above in repairing physical defects. Tape off the surrounding area to prevent processing materials from coming in contact with solutions that could degrade performance or function. Buff the areas needing rework, then use a copper burnishing tool to fill in any gaps in the surface. Finish with a second, lighter buff to level the contact surface.

  • Busing - Establishing a conductive path is paramount to a successful electroplating procedure. Therefore, a reliable connection is vital. A few methods are available to implement the bus connection:

    • Wiring/Conductive paint - Attach high-temperature tape to the contacts needing replating; cover the contact surface with the exception of the closest edge facing inward towards the bend. Attach a wire or conductive paint to the exposed area. Note that the paint will have to extend past the board edge to make an attachment point for a clip, and either implementation will result in an unplated area on the exposed edge.

    • Probe - Technicians can apply a plating probe individually for every requisite contact. While this method requires manual input, there is less of a concern about introducing impurities than with soldering or painting.

    • Pin fixture - A standard or custom-built pin fixture can plate multiple contacts simultaneously but is likely not the most efficient choice for repairing a small number of contacts or single-board rework.

  • Plating - Connect the cathode to the contact using a clip or other connection method. Dip the plating probe (anode) into the appropriate solution and apply it to the contact; continuously move the probe to coat evenly with the plating solution and prevent burning. Lightly buff the contacts, rinse them, and then allow them to dry. Repeat this process with the nickel and gold solutions.

    Plating rework is very demanding from a time and labor perspective. Designers must carefully review design rules to ensure compliance and promote manufacturing excellence that ideally reduces the need for connector repair in the first place.

    Prepare Instead of Repair with Cadence Solutions

    PCB connector repair is unavoidable during PCB manufacturing and regular service life operation, but it's possible to minimize its occurrence by adhering to a proper DFM methodology. Designers should carefully consider the impact of design rules and work alongside production to ensure the fabrication and assembly are in lock-step with the board layout. Conforming to design rules as agreed upon between the designer and manufacturer ideally limits the number of revisions necessary to bridge from design documents to the final board, accelerating the time-to-market. Cadence’s PCB Design and Analysis Software suite assists product development with an easily-configured and highly modular Constraint Manager that allows layout designers to focus on what they do best. Alongside the powerful and easy-to-use OrCAD PCB Designer, board layout – even in the era of HDI – has never been easier.

    Leading electronics providers rely on Cadence products to optimize power, space, and energy needs for a wide variety of market applications. To learn more about our innovative solutions, talk to our team of experts or subscribe to our YouTube channel.