PCBA Quality Process Audit — Wave soldering machine

1. Work Instructions
1.1 Is there a revision controlled Operator Work Instruction which contains set-up information for the specific product being processed? (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 Wave?
1.3 Do Set-Up Sheets specify the Solder, the Flux, and the thinners (as applicable) to be used?
1.4 Do Set-Up Sheets specify the Spray Flux parameter settings such as delay, duration, traverse speed, pressure, etc?
1.5 Do Set-Up Sheets specify the Pre-Heater set points and the Solder Pot Temperature and are they the same as those on the machine?
1.6 Do Set-Up Sheets specify the Conveyor Speed and is it the same as that in the program?
1.7 Do Set-Up Sheets specify the Lead Clearance and is it the same as that set by the machine?
1.8 Do Set-Up Sheets specify Wave Type (Chip/Lambda/Omega) to be used?
1.9 Do Set-Up sheets specify the Solder Pot Hot Air Knife Pressure and Temperature settings?
1.10 Do Set-Up sheets specify if the Finger Cleaner must be on? No Finger Cleaner = 0
1.11 Is the machine Program Name specified on the Work Instruction or set-up sheets?
1.12 Do the all the above wave parameter settings correspond to those settings on the machine?
1.13 Are Generic Wave Set-Up Parameters documented? These are the parameters which are not changed for product changeovers.
1.14 Do these Generic Wave Set-Up Parameters include, pressure settings, conveyor angle, etc.
2. Machine Capability
2.1 Is the flux application technology in use suitable for the product being built?
2.2 Is the wave technology in use suitable for the product being built in terms of the ability control critical parameters to achieve desired results?
2.3 Does the wave use a top side pre-heater to ensure PTH barrel fill meets IPC 610 specs given the mass of the board, carrier, and the top hat?
2.4 Are air flow controllers or a centralized control system used to balance exhaust flow rates for each individual exhaust drops?
2.5 Are exhaust flow rate ranges specified and monitored on a regular basis to insure compliance?
2.6 Is Automatic Wave Height control installed to control the laminar wave height?
2.7 Is there a Solder Pot Hot Air Knife installed and used on the wave equipment?
2.8 Is there an automatic Finger Cleaner installed and used on the wave equipment with an appropriated cleaning fluid? No FC = 0
2.9 Is the machine Program Name revision controlled to show traceability of program changes?
2.10 Is the machine Program Name traceable to the PCB and PCBA part number?
2.11 Is access to the machine program password protected with restricted access?
2.12 Do program changes to critical parameters during machine control remain unsaved unless approved by a technician/engineer?
2.13 Is the safety equipment and protective clothing provided adequate and are they used? Must include boots, apron, gloves, face shield, etc
3. Flux Application
3.1 Is flux applied using either a fixed nozzle or moving nozzle spray application method? Any other application method = 0
3.2 Can the sequence of; detection, delay, trigger, duration, and stop, be clearly explained by a technician? Other method = 0
3.3 Is the detection, delay, trigger, duration, and stop, controls performing as expected? Other method = 0
3.4 Is there a feedback link between the conveyor speed and the flux applicator to auto-compensate for changes? Other method = 0
3.5 Is there an automatic sensor that indicates when a flux drum is near empty?
3.6 Is there a method to determine if the quantity of flux applied to the board to ensure it adequate? Not too much and not too little.
3.7 Is there a test used to check the coverage of flux applied to the board to ensure it is sufficient?
4. Wave Set-Up
4.1 Has specifying the Solder Pump Speed value been discontinued as a way to achieve the desired Wave Height?
4.2 Is the relationship between Wave Height set-up and Contact Area/Length known for the product being processed?
4.3 Is there a Quartz Plate available to verify Contact Area/Length achieved for the board being processed?
4.4 Is the documented Contact Area/Length being achieved for the Wave Height set-up used?
4.5 Does the shape of the Contact Area indicate parallelism?
4.6 Does the Contact Length coupled with the Conveyor Speed, achieve the documented dwell time requirement?
4.7 Is there evidence that Contact Area/Length and shape verified after Solder Pot removal and replacement, and maintenance?
4.8 Is there evidence that the Contact Area/Length and shape verified on addition of solder or on adjustment of lead clearance?
4.9 Does the board/pallet exit the Solder Pot in the stagnant area for the set conveyor angle and lead clearance?
4.10 Are all conveyor Fingers in a good state of repair?
4.11 Is the quantity, type and spacing of each Finger design defined for the conveyor?
4.12 Has the pot been set up to run with an intermittent wave so as to reduce dross build up? If gap between subsequent PCBAs too small, score 1
4.13 Does the level of Dross in the pot suggest that the pot is dedrossed at least once every 8 hours?
5. Temperature Profile
5.1 Is there available a Temperature Profile for the product currently being built?
5.2 Is the Temperature Profile assessable and readily available to operators / technicians as and when required?
5.3 Were the Pre-Heat Set Points, Conveyor Speed, and Solder Temperature logged for that Thermal Profile when it was conducted?
5.4 Do the Set Points, Conveyor Speed & Solder Temp written on the Thermal Profile correspond to the current Machine settings?
5.5 Is there available an Engineering based specification to detail the acceptable process window for Temperature Profiles?
5.6 Was the Engineering based spec. derived from the Flux manufacturer’s recommendations but controls to a narrower window?
5.7 Does the product Temperature Profile fall within the Engineering based specification for the process window?
5.8 Does the product Temperature Profile fall within the Engineering based specification for glass transition temperature requirements?
5.9 Can any excursions outside of the process window be justified and supported with hard evidence and logical analysis?
5.10 Does the product Temperature Profile meet the requirements of the SMT components already attached to the PCBA?
5.11 Are the boards used to establish the initial Thermal Profile kept as engineering samples?
5.12 Have at least five thermocouples been used at various points on the board to establish the Thermal Profile? Note*
5.13 Is there a documented and systematic approach used to identify the most appropriate locations to attach the thermocouples?
5.14 Is there evidence that each thermocouple ball was bonded to a board joint using Hi Temp. Solder or Conductive Epoxy?
5.15 Is the top side Temperature Profile low enough to prevent secondary reflow? Must be below 160 degrees C.
5.16 Has a Calibration Profile been established in order to detect machine long term performance degradation?
5.17 Is there a documented frequency for running a Calibration Profile and was it established based upon historical performance data?
5.18 Is there evidence to demonstrate that Calibration Profiles are conducted and that records are up-to-date?
5.19 Is the practice of comparing the current Calibration Profile to the Standardized Calibration Profile used to identify changes?
5.20 Is the current Calibration Overlay/Profile used to determine if a variation in the wave’s thermal characteristics has occurred?
5.21 Is the current Calibration Overlay/Profile used to determine if a variation in conveyor speed has occurred?
5.22 Is there evidence to demonstrate that action was taken when the Calibration Profile was different to the Standard?
5.23 Is a standardized tool, like a WaveRider, used with a standardized profile to conduct a Calibration Profile?
6. Solder Analysis
6.1 Is there a documented frequency for conducting Solder Analysis and was this frequency established based upon historical results?
6.2 Is there evidence to demonstrate that Solder Analysis records are up-to-date?
6.3 Does the Solder Analysis results suggest that contaminants in the solder pot are within acceptable levels?
6.4 Is there evidence to demonstrate that action was taken when Solder Analysis results were unsatisfactory?
7. Manual Inspection
7.1 Are outputted boards at least sample inspected post wave for wave solder defects as part of machine performance control?
7.2 Are Workmanship Standards defined for soldering, and are they accessible so that machine performance can be measured accurately?
7.3 Is Defect Density Charting used to identify the common location of defects so that actions may be take to eliminate them? This may include addition of solder thieves, pallet/carrier modification, etc.
7.4 Is there evidence of the use of at least sampling X-ray to ensure via penetration and barrel fill are to acceptable standards?

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