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Reflow Solder Defects

Summarized below are some typical reflow / solder defects along with recommended corrections or preventative actions to improve your PCBA process and product quality. At Optima Technology Associates, Inc. we have over 25 years of experience manufacturing PCBs, PCBAs and providing engineering services to help you meet your quality standards and expectations. Contact us today to learn more about working together on your next project.

Defect Cause Action
Insufficient Solder or Dry Joint Insufficient Solder Via placed within pad causing solder paste to flow away from pad and through hole during reflow. Revise design to either reposition via outside of component footprint or employ plug via
Unsoldered Round SMD Device Unsoldered Round PCB surface finish not flat (HASL), component misplaced, not enough solder paste printed using flat surface finish such as ENIG, check component parameters in placement machine, use enough solder paste or increase thickness
Delamination of PCB Delamination of PCB Contamination under solder mask layer, moisture trapped within FR4 material expanding as PCB is heated. Pre-bake PCB's before use to remove any excess moisture, consider using material with higher Tg rating, store PCB's in moisture cabinet.
PCB Measling PCB Measling Component flipped over in feeder during index function causing part to be picked and placed upside down. Consider alternative PCB supplier, pre-bake PCB's before use and consider using material with higher Tg rating, store PCB's in moisture cabinet.
Cracked SMD Capacitor Cracked SMD Capacitor Heating rate of reflow profile set too high causing moisture trapped within component to expand during soldering Store components within humidity cabinet or pre-bake before use, reduce heating rate within reflow profile.
Thermal Component Damaged Thermal Component Damaged Temperature profile incorrect during reflow Verify peak temperature and time above liquidus during reflow.
Solder Balls around SMD Components Solder Balls around Heating rate of reflow profile too high causing flux within solder paste to splatter Reduce heating rate of reflow profile to no more than 2ºC/second
Graping Graping Too much heat applied during preheat and soak causing flux to become exhausted before reflow Reduce time and/or temperature during preheat and soak stage of profile
Head-in-Pillow (HIP) Head in Pillow Excessive heat during preheat and soak causing flux to become exhausted before entering reflow stage, oxidized solder connections Reduce time and/or temperature during preheat and soak stage of profile, consider using nitrogen or higher activity solder paste
Open BGA Joint Open BGA Joint Insufficient solder paste applied, poor PCB surface finish, component defect, PCB warped. Check height and volume of paste deposit using 3D SPI before component placement, check PCB solderability, check quality of component, check PCB for bow and twist.
Low Reflow Temp Low Reflow Temp Insufficient temperature during reflow Increase temp and / or time at reflow stage
Solder Ball, Mid Chip Solder Ball Stencil design causes solder to separate during placement and reflow. Incorrect PCB component footprint Revise stencil aperatures, modify PCB footprint
Tombstone Components Tombstone Components Thermal imbalance due to copper difference/component misplacement Balance copper in PCB design. Revise reflow profile to reduce change in temp. Improve accuracy of placement
Poor Solderability Poor Solderability Poor PCB quality or surface finish quality New PCB supplier, alternate PCB surface finish, or storage procedure for PCBs
Component "Popcorning" Component Popcorning Entrapped moisture within components which expands / outgasses during reflow Storage of components in humidity cabinets or pre-bake prior to usage
Solder Voids under Components Solder Voids Volatile elements from solder past entrapped by component or vias within pads creating air pockets Increase time during reflow stage for volatile elements to escape. Revise stencil design to all volatiles to escape. Use low-voiding past and plug vias
Lifted Lead – Coplanarity Lifted Lead Coplanarity Component damage, vision system miss Verify coplanarity check in software for bent leads
PCB Bow or Twist PCB Bow Twist PCB manufacturing defect – copper imbalance between sides, or poor support during reflow Employ copper balancing for PCBs to even heating and cooling during reflow. Improve PCB support with center support during reflow
No Visible Fillet No Visible Fillet PCB footprint same size as component so AOI unable to identify fillet Revise PCB footprint design based on Mfgr’s recommendation or IPC 7351
Insufficient Solder Wetting Insufficient Solder Wetting Component or PCB contamination, poor quality paste, poor reflow profile Verify PCB and component condition, solder past and reflow profile
No Intermetallic Formation No Intermetallic Formation Poor component solderability, poor quality solder paste, incorrect reflow profile, poor compatibility of PCB finish, solder type, and component termination material. Check PCB and component solderability, check quality of solder paste, check reflow profile to solder paste datasheet
Billboard Parts Billboard Parts Pickup error during component placement process quite often caused by feeder problems Check feeders on component placement machine are indexing smoothly so parts are not flipped onto their side, adjust vision system on placement machine library to detect parts picked up on their side and reject
Insufficient or No Solder Insufficient or No Solder Error during solder paste printing process caused by insufficient solder paste on the stencil or blocked aperture Ensure enough solder paste is applied to the stencil and is frequently replenished, set printer to clean stencil with appropriate chemical and vacuum, inspect solder paste print before placement.
Solder Short on Fine Pitch QFP Solder Short Component misplaced, component disturbed before reflow process, misaligned solder paste print. Check component height, vision parameters and placement speed for component package to ensure accurate placement, ensure good solder paste print using 3D SPI.
Solder Short to Unmasked Via Solder Short one PCB unmasked via positioned very close to surface mount component footprint, inaccurate solder paste print. Ideally reposition via further away from component footprint, apply solder mask to via to remove risk of short occurring.
Solder Short – IC Pads Joined Solder Short IC Pads Joined PCB design had two pads of an IC footprint joined together as electrically were the same point Recommend changing PCB design to always have separate pads for all component leads even if are
RoHS Component Failure RoHS Component Failure Rohs compliant component not compatible with reflow process temperature for SAC lead-free solder. Use low temperature lead-free solder, use alternative Rohs compliant component that is compatible with SAC reflow process temperatures.
Cracked Solder Joint Cracked Solder Joint Poor solderability of component, poor quality solder paste, incorrect reflow profile - incorrect rate of cooling Check component solderability, check quality of solder paste, check reflow profile to solder paste datasheet.
Solder Short, Top of Chip Capacitor Solder Short Top of Chip Capacitor Solder paste contamination of component during placement process Discard any misplaced components or ensure cleaned of any solder paste before reuse.
Partial Solder Joint Partial Solder Joint Silk print on component footprint pads stopping complete formation of solder joint Ensure PCB supplier clips away any silk screen from component footprint pads.