Checking a Selective Flux Pattern Against the Actual Solder Joints

A selective flux program describes where the machine intends to apply material. Qualification must also show where the material reaches the actual board. Compare the physical deposit with the solder joints and neighboring restricted areas before adjusting solder contact time to address a wetting concern.

Separate the flux and solder patterns

Identify the joints to be soldered and the corresponding flux application pattern. Keep solder-nozzle travel separate from flux-nozzle coordinates, even when software derives them from a common drawing. Each physical operation has its own geometry.

Ersa’s POWERFLUX description lists point, line and area application patterns with nozzle monitoring. These functions illustrate why the programmed pattern and the observed deposition should both be part of a process review.

Use a board-coordinate overlay

Mark the intended fluxed region, joint location and any keepout on the assembly drawing. Confirm bottom-side orientation and fixture references. Include component bodies that can obstruct observation or change access beneath the board.

For example, two adjacent connector rows may have similar coordinates but different surrounding components. A pattern copied from one row should be checked on the actual assembly rather than approved because the holes have the same pitch.

Observe deposition using an approved method

1. Identify the flux product and material condition.
2. Confirm the correct nozzle and machine program.
3. Verify deposition location and repeatability.
4. Check the relation to the intended solder contact.
5. Inspect areas where unwanted flux is a concern.

Choose a method appropriate to the material and equipment with the process owner. The visual appearance of one wet spot is not automatically a measure of deposited quantity or active material at the joint.

Preserve the interval and preheat sequence between application and soldering. A trial with immediate solder contact may not represent a production line that includes a longer transfer or hold.

Investigate a local defect with its local history

If one joint wets differently, compare its physical deposit, board condition and thermal history with a relevant good joint. Keep alternative explanations open until evidence distinguishes them. Adding flux everywhere can conceal a targeting problem while changing residue elsewhere.

Record any maintenance or nozzle replacement during the trial. A successful run after replacement should retain the new hardware identity so the result is reproducible.

Release the application pattern with its accepted material, nozzle and monitoring method. If a component changes position, review the flux overlay even when the solder machine still has access to the lead.

The nozzle condition guide addresses solder delivery, while residue-removal qualification supports products that require subsequent cleaning.