Electronic Manufacturing PCBA Quality Process Audit – Solder Paste Printing

1. Work Instructions
1.1 Is there a revision controlled Operator Work Instruction which contains unique details for the specific product being built? (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 Paste Print?
1.3 Is the Solder Paste specified in the Paste Printing program or on Work Instructions?
1.4 Is the Solder Paste manufacturer, number, & mesh defined in the Paste Print Program or on Work Instructions?
1.5 Is the Stencil’s identification specified in the Paste Printing program or on Work Instructions?
1.6 Is the Stencil’s identification traceable to a specific PWB part number, revision level and board side?
1.7 Is the Stencil loading orientation specified on the Stencil or on Work Instructions?
1.8 Is the Squeegee in use specified in the Paste Print program or Work Instructions?
1.9 Is the number, location, type and height of the Support Blocks/Pins specified on Work Instructions?
1.10 Are all hand tools needed by the operator listed with their descriptions on Work Instructions?
1.11 Has the use of metal tools for the application and/or removal of paste been specifically disallowed?
1.12 Is the PWB part number and Revision specified on the Work Instruction or line set-up instructions?
1.13 Is the PWB orientation to the Stencil identified in the Work Instructions or line set-up instructions?
1.14 Is the machine Program Name specified on the Work Instruction or line set-up instructions?
2. Solder Paste
2.1 Is there a Standard Operating Procedure for the cold storage of solder paste?
2.2 Is the cold storage temperature within the manufacturers’ recommended range for all solder paste in cold storage?
2.3 Is the Solder Paste FIFO controlled while in cold storage? A gravity feed rack is preferred.
2.4 Does the cold storage unit have a temperature recorder, which can be read without opening the unit, to record temperature over time?
2.5 Is there a documented requirement to periodically check that the recorded temperature is within the required storage limits?
2.6 Is there evidence to demonstrate that action was taken when the temperature was outside the defined storage limits?
2.7 Is the cold storage expiration date of the Solder Paste specified on the Solder Paste container?
2.8 Is the date and time that the Solder Paste has been removed from cold storage specified on its container?
2.9 Is the date and time that the Solder Paste is available for use, after removal from cold storage, specified on its container?
2.10 Is the date and time that the Solder Paste expires at ambient temperature with its ‘seal broken’ documented and known?
2.11 Is the date and time that the Solder Paste expires at ambient temperature with its ‘seal in place’ documented and known?
2.12 Is there evidence to demonstrate that this information has been correctly completed and that this process is fully understood by users?
2.13 Are Screen Print Operators required to wear gloves when handling Solder Paste?
2.14 Is there a specification readily available for the Solder Paste?
2.15 Is the mesh for the Solder Paste used suitable for the pitch technology on the board being built?
2.16 Is the maximum time that the Solder Paste is allowed to remain on a board prior to reflow documented, known, & followed?
2.17 Is the Solder Paste lot code recorded and fully and easily traceable to the individual product serial number product?
3. Stencil
3.1 Are all Stencils adequately stored in a manner to avoid potential damage and to keep out foreign or airborne materials?
3.2 Are all Stencils identified with process proof labels or plates which are visible when the stencil is in its rack or mounted in the Printer?
3.3 Is the Stencil cleaned in a automatic stencil cleaner at the end of a production run or after a fixed time has elapsed?
3.4 Is there a documented requirement to inspect a Stencil for damage once cleaned?
3.5 Is the evidence of cleaning and inspection documented?
3.6 Is there a documented Stencil Cleaning process which identifies the chemicals, wash times, dry times, & consumables to be used?
3.7 Is there a documented Stencil Cleaner maintenance procedure which defines frequency for checking filters and solution levels?
3.8 Is there evidence to demonstrate that the Stencil Cleaner’s Maintenance procedure and records are adequate and up-to-date?
3.9 Is there a documented requirement to periodically check the Stencil tension and is there evidence that this is done?
3.10 Is there a document which specifies Stencil ordering requirements with respect to size, thickness, ratio, orientation, identification, etc.?
3.11 Is there a document which specifies the conditions for when Laser vs. Chemical Etched vs. Electroformed Nickel, should be used?
3.12 Is there evidence to demonstrate that the Stencil ordering requirements are followed?
3.13 Is there a documented Stencil First Article procedure which checks, tension, thickness, aperture sizes and design, first print, etc.?
3.14 Is there evidence to demonstrate that the Stencil First Article procedure and records are adequate and up-to-date?
4. Squeegee
4.1 Are the Squeegees length, angle, style/durometer, defined to ensure correct Squeegee selection?
4.2 Is there evidence to demonstrate that the Squeegee used is correct and is fully and easily traceable to the product and stencil?
4.3 Are all Squeegees adequately stored in a manner to avoid potential damage?
4.4 Is there evidence that Squeegees inspected for damage prior to use and prior to storage?
4.5 Is there a requirement to ensure the Squeegee is leveled either automatically or manually documented, prior to use?
5. Vacuum Blocks and Tooling
5.1 Is there a documented requirement to indicate that Blocks, Support Pins or Vacuum Blocks are needed for specific products?
5.2 Are all Vacuum Blocks identified with a name or tooling number that is fully and easily traceable to the product and board side?
5.3 Are all Vacuum Blocks clean and adequately stored in a manner to avoid potential damage?
6. PCB
6.1 Are there satisfactory methods in place to control PCB handling and exposure?
6.2 Does the PWB part number and Revision cross-reference to the PCBA part number and Revision?
6.3 Is a unique tracking label or PPID label placed on the PWB for tracking purposes at Paste Print? Score NA if Dell Assy Dwg does not require.
6.4 Does the unique tracking label or PPID label date code specify the date the PWB was paste printed?
6.5 Are misprinted PWBs cleaned in an automatic board cleaner using appropriate fixturing?
6.6 Is there a documented Board Cleaning process which identifies the chemicals, wash times, dry times, & consumables to be used?
7. Machine Capability
7.1 Is the Paste Printing technology suitable for the product being built?
7.2 Is the Paste Printing operation automated with fiducial camera alignment?
7.3 Is contact printing with stainless steel stencils and squeegees being used?
7.4 Does the Printing machine have the capability to automatically wet and dry wipe the Stencil?
7.5 Does the Printing machine use the automatic wet and dry wipe capability?
7.6 Does the Printing machine have Vacuum Stencil clean capability?
7.7 Does the Printing machine use Vacuum Stencil clean?
7.8 Is there a documented minimum frequency for stencil clean specified based on the technology used on the board?
7.9 Are stencil wet and/or dry automatic clean rates specified for each product and shown in the program?
7.10 Are all materials used to wipe the stencil specified as low lint or preferably lint free?
7.11 Are changes to clean rates approved based only upon performance feedback?
7.12 Does the Printing machine have the capability to automatically dispense Solder Paste?
7.13 Does the Printing machine use automatic Solder Paste dispense?
7.14 Does the Printing machine flag when the Solder Paste container is near empty?
7.15 Are all Printers enclosed in order to keep out foreign or airborne materials?
7.16 Are localized climate control units installed and in use on all Paste Printers?
7.17 Is the Printing machine programmable? If not score 0 for next 4 questions.
7.18 Is the machine Program Name revision controlled to show traceability of program changes?
7.19 Is the machine Program Name traceable to the PCB and PCBA part number?
7.20 Is access to the machine program password protected with restricted access?
7.21 Do program changes to critical parameters during machine control remain unsaved unless approved by a technician/engineer?
8. Solder Paste
8.1 Is automatic 2D or 3D solder paste inspection deployed and effective? Review ICT or AOI/AXI results to determine effectiveness.
8.2 Can it be demonstrated that the machine calls are reviewed by the operator to determine if real or false?
8.3 Is the 2D or 3D coverage % calculated based on the total # of pads with 2D or 3D vs the total # of apertures on the stencil?
8.4 Does the exit conveyor from the API Equipment, stop to allow for verification of defects so that defective boards may be captured?
8.5 Are rejected boards automatically stopped on this conveyer for operator false call validation?
8.6 Are changes to 2D or 3D coverage made based only on performance feedback? Is this reflected in the Program Revision?
8.7 Is there a document which defines the effect of changing critical Paste Printing parameters on the quality of the output?
9. PCBA
9.1 Are outputted boards at least sample inspected for print quality to ensure process control?
9.2 Is there a documented frequency for checking print quality?
9.3 Is there evidence to demonstrate that this print quality inspection is conducted?
9.4 Is there a specification that defines acceptability of paste printing, available and used at the Paste Printer?

Write a Comment

Your email address will not be published. Required fields are marked *