Indium Blog

PoP Flux Dipping Process Inspection: Colored Flux

  • PoP Flux

  • I have been receiving some questions recently about colored or dyed PoP Fluxes.  Indium Corporation currently has the following fluxes in production or available for beta site sampling:

    We have received feedback from our customers that different pick and place equipment sets have different capabilities for inspecting the bumps after the dipping process.  Up until fairly recently, all of our PoP Fluxes have been the typical amber flux color, and this seemed to work fine.  However, in an effort to minimize defects, many of the customers using a PoP or dipping process have presented a need to inspect for flux presence on the bumps after dipping the BGA into the flux reservoir.  Other customers don’t have the need to perform 100% inspection of every component for flux after the dipping process but have asked us to offer colored flux so that they can visually inspect the BGAs at the process set-up stage - to ensure that their process is set-up correctly.  They also use the colored flux to visually verify the process set-up at specific time intervals.

    Fast-forward to today; you can pretty much see our new pink flux from outer space. This makes it very easy to visually inspect - to confirm the flux is present while setting up the process or performing a visual process verification.  The other benefit is that the pink dye doesn’t get picked up by the vision system - similar to how highlighter markings on a printed page don't show up when you make a copy on the copy machine. 

    Our new dark-colored fluxes also allow for easy visual inspection at the process set-up stage or when performing visual inspection.  However, with many of the dark blue or black fluxes on the market, such as the 89LV-B, the dark color can confuse the vision system (the vision system can’t decipher between the flux color and the component body - both being similarly colored, black or dark).  This causes the pick and place system to reject the component because it inspects for the balls/bumps and can’t see them (false rejects).

    We have found that there are pick and place equipment sets that have the ability to tune in the gray scale on the vision system to enable it to differentiate and see the ball and the flux uniquely.  In other words, if a black-colored flux is used and the balls are dipped into a black flux, the equipment will pass and place the component - if the gray scale is within a certain color range/contrast.  If it is too dark, the component will be rejected for missing balls/bumps; if it is too light the component will be rejected for missing flux.  I have a feeling that this is a pretty complex process set-up and that it takes some serious time to make sure the gray scale inspection is tuned in properly.

    Other pick and place equipment sets cannot decipher the difference in gray scale with their vision systems, and a black-colored flux is detrimental to the process (all components would be rejected for missing balls/bumps).  The only way around these false rejects, when using a dark-colored flux, is if the vision system aligns the component with the four corners or the four sides instead of using the bumps for alignment.  This alignment technique is typically less accurate and may cause part skewing issues or misalignment in the placement process.  Hence the need for the pink-colored flux. Our 89LV-P still aids in visual inspection but doesn’t cause false rejects on equipment that doesn’t have the ability to decipher gray scale differences.

    Stay tuned for more exciting posts in the near future.