Southern Machinery provides professional SMT peripheral equipment.

PCBA Quality Process Audit - Reflow oven

2023-02-09 17:51:23
1. Work Instructions
1.1 Is there a revision controlled Operator Work Instruction which contains set-up information for the specific product being reflowed? (Score 0 if any unsigned/undated handwritten instructions or any handwritten instructions more than 48 hrs old)
1.2 Are Work Instructions readily available to the operator and are they followed at Reflow?
1.3 Is the conveyor speed set point specified on the Work Instruction and is it the same as that specified in the program?
1.4 Are the temperature set points specified on the Work Instruction and are they the same as those specified in the program?
1.5 Do Work instructions indicate if pallets or other tooling are required?
1.6 When center rail support is required, do Work instructions indicate this requirement and is the location specified?
1.7 Is the machine Program Name specified on the Work Instruction or set-up sheets?
2. Machine Capability
2.1 Is the Reflow technology in use suitable for the product being built? Must be full forced Convection with sufficient zone count.
2.2 Are air flow controllers or a centralized control system used to balance exhaust flow rates for each individual exhaust drop?
2.3 Are exhaust flow rate ranges specified and monitored on a regular basis to insure compliance?
2.4 Is the machine Program Name revision controlled to show traceability of program changes?
2.5 Is the machine Program Name traceable to the PWB and PCBA part number?
2.6 Is access to the machine program password protected with restricted access?
2.7 Do program changes to critical parameters during machine control remain unsaved unless approved by a technician/engineer?
3. Temperature Profile
3.1 Is there available a Temperature Profile for the product currently being built?
3.2 Is the Temperature Profile assessable and readily available to operators / technicians as and when required?
3.3 Were the Temperature Set Points and Conveyor Speed logged for that Thermal Profile when it was conducted?
3.4 Do the Temperature Set Points & Conveyor Speed written on the Thermal Profile correspond to the current Program settings?
3.5 Is there available an Engineering based specification to detail the acceptable process window for Temperature Profiles?
3.6 Was the Engineering based spec. derived from the Paste & Component manufacturer’s recommendations but controlled to a narrower window?
3.7 Does the product Temperature Profile fall within the Engineering based specification for the process window?
3.8 Does the product Temperature Profile fall within the Engineering based specification for glass transition temperature requirements?
3.9 Can any excursions outside of the process window be justified and supported with hard evidence and logical analysis?
3.10 Does the product Temperature Profile meet the reflow requirements for the SMT components according to the component manufactures?
3.11 Are the boards used to establish the initial Thermal Profile kept as engineering samples?
3.12 Is there evidence that a once off comparison study been conducted for a loaded versus an unloaded oven?
3.13 Have at least five thermocouples been used at various points on the board to establish the Thermal Profile? Note*
3.14 Is there a documented and systematic approach used to identify the most appropriate locations to attach the thermocouples?
3.15 Can it be demonstrated that a BOM review was conducted to verify that the chosen profile is appropriate for all specific component conditions?
3.16 Is there evidence that each thermocouple ball was bonded to a board joint using Hi Temp. Solder or Conductive Epoxy?
3.17 Is there the capability to detect a temperature zone failure and to trigger an alarm automatically if this occurs?
3.18 Has a Calibration Profile been established in order to detect machine long term performance degradation?
3.19 Is there a documented frequency for running a Calibration Profile and was it established based upon historical performance data?
3.20 Is there evidence to demonstrate that Calibration Profiles are conducted and that records are up-to-date?
3.21 Is the practice of comparing the current Calibration Profile to the Standardized Calibration Profile used to identify changes?
3.22 Is the current Calibration Overlay/Profile used to determine if a variation in the ovens thermal characteristics has occurred?
3.23 Is the current Calibration Overlay/Profile used to determine if a variation in conveyor speed has occurred?
3.24 Is there evidence to demonstrate that action was taken when the Calibration Profile was different to the Standard?
3.25 Is a standardized tool, like an OvenRider, used with a standardized profile to conduct a Calibration Profile?
4. Manual Inspection (NA allowed, for questions in this section if AOI is deployed)
4.1 Are outputted boards at least sample inspected pre reflow for placement, missing components, and solder defects?
4.2 Are Workmanship Standards defined for placement and soldering, and are they accessible and used to determine board acceptability?
4.3 Are Inspection Templates available and used to identify missing & unpopulated components and component polarity post reflow?
4.4 Are Inspection Templates or Visual Aids used to identify ICT not tested components post reflow?
4.5 Are Templates readily accessible for verification purposes?
4.6 Are Inspection Templates revision controlled and traceable to the current product ECO level?
4.7 Is there a point and click software tool post reflow which is linked to CAD or program data to facilitate component identification for rework?
4.8 Is there a documented requirement to conduct at least sampling X-ray inspection for BGA devices, and is there evidence that it is practiced?
5. Automatic Inspection (NA allowed, for the cells indicated)
5.1 Are AOI/AXI complementary methods, which include solder joint inspection, used for all reflowed parts?
5.2 Is the AOI coverage % calculated based on the board OFE for a given side vs the total # of joints/components inspected?
5.3 Are the components/joints not covered by AOI documented and known and targeted for visual inspection?
5.4 Is there evidence that the AOI coverage is verified periodically by using ICT and manual inspection feedback data?
5.5 Can it be demonstrated that the machine calls are reviewed by the operator to determine if real or false?
5.6 Can it be demonstrated that the operator been fully trained and certified to interpolate the AOI images presented?
5.7 Does the ICT pareto of defects suggest that AOI is being 100% deployed and is being effective?
5.8 Can it be demonstrated that AOI detectable ICT failures are feed back to AOI to improve program and operator effectiveness?
5.9 Are rejected boards automatically stopped on the line post operator false call validation?
5.10 Are changes to AOI coverage made based only on performance feedback?
6. Process Control
6.1 Is there evidence that the SPC used to monitor output post reflow, is effective at identifying & correcting process performance issues?
6.2 Is the processes DPMO and the products DPU monitored in real time? (‘real-time’=now)
6.3 Is OFE data readily available and calculated in accordance to documented procedures?
6.4 Is AOI data used to calculate SMT’s DPMO? Score 0 if AOI deployed and not done.
6.5 Are ICT debug results used to re-calculate SMT DPMO as a true measure of SMT DPMO?
6.6 Is the data collected meaningful and can it be demonstrated that it is used to make process control decisions?