Surgeon grade rework and repair, by the book and guaranteed. ®
Newsletter | Contact Us
Phone: 978-374-5000
  
3.2 Bow and Twist Repair More Guides
Outline
Procedure is used to eliminate, or reduce the bow and twist, or warping of circuit boards.

Caution
This repair method is most suitable for FR-4, GE or GF substrate base materials having glass transition temperatures below 125 degrees C (257 degrees F).

Caution
This process uses high temperatures. Some components may be sensitive to high temperature.

Note
Bow and twist should not be repaired unless sighted as a defect.

Minimum Skill Level - Intermediate
Recommended for technicians with skills in basic soldering and component rework, but may be inexperienced in general repair/rework procedures.

Conformance Level - High
This procedure most closely duplicates the physical characteristics of the original, and most probably complies with all the functional, environmental and serviceability factors.

Acceptability References
IPC-A-600 2.0 Externally Observable Characteristics
IPC-A-610 10.0 Laminate Conditions
Procedure References
1.0 Foreword
2.1 Handling Electronic Assemblies
2.5 Baking and Preheating
IPC7721 3.2 Bow and Twist Repair
Tools and Materials
Images and Figures
3.2 Bow and Twist Repair
Figure 1: Check edge deflection for maximum warp
3.2 Bow and Twist Repair
Figure 1: Check edge deflection for maximum warp.
3.2 Bow and Twist Repair
Figure 2: Clamp restraint bars to edge needing rework.

Procedure
  1. Check the deflection to determine if rework is needed. See Figure 1.

    Note
    Bow and twist after soldering shall not exceed 1.5% for through-hole circuit boards and .75% for surface mount circuit boards. The bow and twist shall not be sufficient to cause difficulties during placement, soldering and testing operations. Before dispositioning circuit boards with bow and twist as scrap, keep in mind how the circuit board is mounted in its final destination. Keep in mind "form, fit and function" without jeopardizing reliability.  

  2. Place the restraint bars along the edges that require rework. (See Figure 2)

    Caution
    Components or parts that will interfere with the restraint bars should be removed.

  3. If the circuit board is warped along more than one edge or more than one plane, clamp the entire circuit board to the base plate.

  4. Place the circuit board, restraint bars and base plate into the oven. Bake for 1 hour at 125 degrees C - 257 degrees F.

  5. Remove from the oven and allow to cool to room temperature.

  6. Remove restraint bars.

  7. Check the edges deflection using a caliper or pin gauges.

Evaluation

  1. Check for marks or damage along edges.

  2. Electrical tests as applicable.
Procedure for reference only.
Customer Comments
"We had never considered sending our rework projects until recently. The cost savings since we started using Circuit Technology Center has been significant. I hope we never have such a massive rework project again, but if we, do you'll be the first to get a call"
N.C. Fort Wayne, IN USA
The Toughest Component Rework?
The Toughest Component Rework?
Rework of surface mount and through hole components can be a challenge. Our techs are ready to tackle your toughest rework projects.
Learn more ...
Challenging Surface Mount Pad Repair
Challenging Surface Mount Pad Repair
Surface mount and BGA pad repair are routine operations at Circuit Technology Center. Learn how it's done with absolute precision and reliably.
Learn more ...
BGA Component Rework Simplified
BGA Component Rework Simplified
When you have tough BGA rework, where do you turn to? Discover the nation's #1 contractor for outsourced BGA rework, repair and reballing.
Learn more ...
Can You Repair a Broken Corner?
Can You Repair a Broken Corner?
What happens to an assembled circuit board with a broken corner? Can it be repaired reliably? It can if you have the training and the experience.
Learn more ...
ipc-logo Circuit Technology Center has been an IPC member since 1986
circuitmedic-logo
First-aid Kits for Circuit Boards ®
About Us | Base Board Repair | BGA Reballing | BGA Rework | Coating/Marking | Circuit Repair | Component Salvage | Conflict Minerals | Contact Us | Copyright/Disclaimer | Directions | ECO/Modification | Feature Articles | Frequent Questions | Gold Contacts | Intranet | Inspection | Order Tracking | Newsletter | Plated Hole Repair | Prices, Terms, Delivery | Products | Privacy | REACH | RoHS | Services | SMT/BGA Repair | SMT/PTH Rework | Sitemap

Circuit Technology Center, Inc.
22 Parkridge Road
Haverhill, MA 01835 USA
Copyright © Circuit Technology Center, Inc.. All rights reserved.