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Prepared by Chipsimple Engineering Team, Engineering and technical content review
Published online August 10, 2026 · Reviewed August 10, 2026
ENGINEERING ARTICLE 23 / VOLUME 4
Common Thick Film Circuit Failure Modes and How to Trace Them Back to Process
Failure analysis should begin with a precise symptom and a preserved sample. Cleaning, re-soldering or aggressive probing can erase evidence. Compare failed and good units from the same and adjacent lots, then build a timeline: when the characteristic was first known good, what thermal or mechanical steps followed, and whether the failure is permanent, intermittent or environment-dependent.
Separate Electrical Failure Modes
Process capability follows from the mechanism: Open, high resistance, leakage and drift point toward different physical paths. The direct implication is that one label such as circuit failure delays localisation. This makes the topic a design input, not merely a factory setting adjusted after the drawing is complete.
A practical release action is to record value, polarity, temperature, humidity and intermittency. The requirement should survive staff changes and future lot reviews because it is recorded with the controlled construction.
Use four-wire, insulation and thermal-stimulus measurements to demonstrate margin. When feasible, compare the result before and after the operation most likely to disturb it.
Pay attention to repairing a conductor when leakage actually runs across contaminated dielectric. A corrective action is credible only when it changes that physical mechanism and the follow-up data confirm the change.
Use Location as Process Evidence
Repeated failure at an edge, neck, via, trim tip or pad implicates local geometry and stress. The consequence is that random-looking lot data can contain a strong spatial pattern. In a thick film circuit failure analysis review, this relationship deserves an explicit decision rather than an assumption copied from a previous drawing.
The practical control is to map failures on a common artwork coordinate system. That instruction should be linked to the layer, material system or feature it governs so that production and inspection read it in the same way.
Verification should include overlay of defect maps with screen, furnace and fixture positions. If the evidence is collected only after final assembly, the team loses the ability to separate printing, firing, trimming and assembly effects.
A common warning sign is averaging data and losing the positional cause. Treat that symptom as a request to examine the process chain, not simply as a reason to widen the final tolerance.
Read the Failure Timeline
The first operation after a known-good test narrows the suspect window. The consequence is practical: assembly heat, cleaning, trimming and environmental exposure can each create similar final symptoms. This is one reason thick film circuit failure analysis cannot be reduced to a single catalogue value.
During design review, retain stage-by-stage records and samples. The objective is not to freeze every process setting on the customer drawing, but to define the functional boundary that the manufacturer must protect.
A useful evidence package contains reproduction trials that add one operation at a time. Comparing those records with the approved construction is more informative than judging an isolated photograph or one resistance reading.
Watch for attributing every field failure to the last visible process. It often indicates that two individually acceptable variables have combined at the edge of their windows.
Preserve and Section the Right Sample
Cross-section location determines whether the defect is found. Consequently, a section beside rather than through the failure can appear normal. The engineering value comes from understanding the direction and sensitivity of the effect, not from memorising a nominal number.
A robust drawing or process plan will localise electrically or optically before destructive preparation. This makes the design intent visible and gives the supplier room to use a qualified material set without changing the function.
The result can be checked through documented cut plan and sequential images. Where possible, keep readings before and after the next thermal or mechanical operation; the delta often reveals more than the final value.
The failure pattern to investigate is destroying the only evidence without crossing the active defect. Before changing materials, confirm orientation, lot history, measurement method and acceptance limits.
Convert Cause into a Control
The physical starting point is straightforward: A corrective action must change a measurable input or detection gate. From there, training reminders alone do not prove recurrence prevention. For thick film circuit failure analysis, the important issue is the amount of process margin left after normal variation is included.
On the drawing and in the review record, update drawing, process window, fixture, test or maintenance criterion. Keep the requirement functional wherever possible, while making any safety- or interface-critical boundary unambiguous.
A production trial should capture capability and stress evidence from post-action lots. Record the condition of the specimen and the next operation so that a later change can be traced to a specific stage.
If the team sees closing analysis after one good sample, pause before adding inspection or rework. First check whether the layout and the qualified process window are asking for contradictory outcomes.
A Worked Engineering Review
A resistor network drifts after humidity bias. Map which resistors move and whether the change follows voltage polarity or surface spacing. Inspect for contamination and dielectric edge coverage before destructive cleaning. Compare insulation resistance and ionic-cleanliness evidence from good and failed lots. If the pattern follows a rinse or handling change, reproduce it on coupons. The corrective action may be improved cleaning and protected storage plus a biased-humidity monitor coupon—not a wider room-temperature resistor tolerance.
Design Review Checklist
- Define symptom and test condition precisely.
- Preserve failed and good controls.
- Map location and process timeline.
- Localise before sectioning.
- Verify corrective action on stressed lots.
Questions Engineers Commonly Ask
Should a failed part be cleaned before analysis?
Usually not until surface evidence is documented. Cleaning can remove residues or alter leakage paths.
Why compare adjacent lots?
They help distinguish a one-time event from a process trend and identify the change boundary.
What makes a root cause credible?
A physical mechanism supported by evidence, reproducible influence and a corrective control that prevents recurrence.
Related Engineering Resources
Closing Note
The strongest failure analysis connects symptom, location, timeline and mechanism. Its final product is a measurable prevention or detection control, not simply a photograph of damage.