Surgeon grade rework and repair, by the book and guaranteed.®
Newsletter | Contact Us
Phone: 978-374-5000
  

3.2 Bow and Twist Repair

  • This procedure is used to eliminate, or reduce the bow and twist, or warping of circuit boards.
  • Check the edge deflection to see if it exceeds the maximum warp.
  • Clamp restraint bars to edge needing rework. Bake the circuit board or assembly for 1 hour at 125 degrees C - 257 degrees F.
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.

Proprietary Information Proprietary
This guide may contain proprietary or copyright-protected information for access by authorized persons only.

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  Proprietary
IPC-A-610 10.0 Laminate Conditions  Proprietary
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
Pin Gauges
Pin Gauges
Use to provide accurate measurements for thickness and hole diameters.
Bars
Restraint Bars and Clamps
Steel bars and clamps to restrain warped circuit boards during rework.
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.
Questions / Comments?
Call 978-374-5000 or submit your questions, comments and requests using the form below.

Your Name


Your E-mail


Your Phone


Your Company


Your Country


Send us a file

Maximum file size 4 megabytes.

Questions/Comments



Customer Comments
We just received our repair circuit boards. They look great. Nice job!!"
J.M. Wilmington, MA USA
Robotic BGA Solder Ball Removal
Robotic BGA Solder Ball Removal
Watch a video that shows robotic BGA component deballing. This precision process is highly reliable when preparing BGA components for reballing.
Learn more ...
BGA Component Reball Video
BGA Component Reball Video
Video demonstrates robotic BGA component deballing. This precision process is highly reliable when preparing BGA components for reballing.
Learn more ...
Tough Engineering Changes?
Tough Engineering Changes?
Engineering changes are a reality that need to be dealt with. Do you have qualified rework technicians to do the job efficiently and reliably?
Learn more ...
Epoxy Packs Eliminate Measuring
Epoxy Packs Eliminate Measuring
This unique kit contains 10 packages of super strength epoxy, precisely measured out into two-compartment plastic packages.
Learn more ...
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 | 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.