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Corporate Improvement
Wave Solder Defect Reduc1on Chris Ballou
January 24, 2013
Business Case • Since the beginning of Q3 in 2011, the PCB team has seen an increase in
assembly solder joint defects stemming from the wave soldering process.
Business Case
• PCB Team uses two soldering techniques – Wave Soldering – Hand Soldering
Advantages Disadvantages Advantages DisadvantagesAllows for mass soldering of assemblies in a very short period of time.
Equipment and materials are expensive.
Better control of soldering process at specific solder joints.
Solder joint quality can be inconsistent due to human factor.
Quality of a joint is very consistent from board to board.
Process consumes a sizeable footprint within production space.
Can consume a much smaller production footprint.
Generally requires a large number of human resources and is very inefficient (labor intensive).
Wave Soldering Hand Soldering
Business Case • Based on the complexity of our board designs, the wide range of components
used in each design, and the size of many of our assemblies, wave soldering is a highly complex process. Due to the complexity of this process, many of our assemblies require addi1onal hand soldering rework to correct soldering defects caused by wave soldering.
• By reducing the amount of defects present on our assemblies, improvements
will be made in the following areas: – Reduc1on in Opera1ng Cost
• Less rework on each assembly will decrease resource requirements and cycle 1me.
– Reduc1on/Elimina1on of 3 of the 7 Wastes • Inventory – With less rework being required, assemblies will travel through our value
stream faster thus reducing the amount of WIP on the floor. • Over Processing – Addi1onal rework leads to over processing of assemblies. In regards to
soldering, over processing assemblies will decrease the overall quality and integrity of our product.
• Defects – Reducing the amount of rework required on our assemblies is directly related to a reduc1on of the number of defects present on each assembly. This reduc1on will improve the overall efficiency of our process.
A good Problem Statement contains:
q What? q Where? q When? q To What Extent? q How Do I Know?
Problem Statement (remove/hide for presentation)
Problem Statement
• “In April, May, and June of 2012, an analysis of Pareto data collected at Post Wave shows excessive soldering defects being generated at the Wave Soldering Machines. An average of nearly 385 recorded defects per week are resul1ng in excessive assembly rework and an average weekly DPMO of 2471.”
Business Case • Nearly 385 defects per week is very good considering our average
opportuni1es for defects per week are in the range of 163,000! Despite this, the PCB team strives to minimize non-‐value added ac1vity.
• Many contract manufacturers (CMs) accept a certain amount of touch up and rework for several reasons: – CMs produce assemblies for mul1ple customers, not just one. – There is addi1onal costs to dedica1ng resources to op1mize processes.
Touch Up and Rework = Non Value Added
A good Project Objective is:
q Specific q Measurable q Achievable q Relevant q Time Bound
Project Objectives (remove/hide for presentation)
Project Objec;ve
• “Reduce the weekly DPMO of 2471 by 50% at Wave Soldering on the assemblies that make up “the top 90%” by October 2012.”
Value Stream Map
Wave Soldering Process
Assembly Travels into the Wave Machine
Flux the Assembly
Preheat the Assembly
Wave Solder the Assembly
Assembly Travels out of the
Wave Machine
Wave Solder Fishbone Diagram
• Used to iden1fy where process gaps may be present within the Wave Soldering Process.
Wave Recipe Op;miza;on
• Op1mizing tools used to refine wave recipes.
• Assemblies that had low or no DPMO average during the data collec1on phase were not op1mized.
• Eliminates the gap of incorrectly wrijen wave recipes.
Wave Recipe Op;miza;on Observa;ons
• Many recipes had conveyor speeds that were far too slow.
• Wave height levels were not within specifica1ons.
• Several recipes had preheat temperatures that were too warm.
Wave Recipe Op;miza;on Results
• 10 of 15 wave solder recipes were op1mized. • Many of the new recipe parameters are iden1cal or very
close to one another.
Transfer of Automa;c Solder Feeder
• Automa1c Solder Feeder is used to fill the solder pot.
• Eliminates two separate gaps iden1fied in the Fishbone: – Solder pot not filled to required level. – Not filling the solder pot when required.
Transfer of Automa;c Solder Feeder Observa;ons
• ECO was required to convert all material to required bar stock sizes.
• Aler the transfer, it was observed that the Automa1c Solder Feeder was not being lel on during opera1on.
Transfer of Automa;c Solder Feeder Results
• The Lead-‐Free solder pot now stays at the op1mal level whenever the wave soldering machine is in use.
• The Automa1c Solder Feeder has been password
protected in the “ON” state.
Defect Iden;fica;on Training
• Eliminate the gap of improper training. • Can reduce the amount of over processing that is
occurring. • Can reduce the number of falsely iden1fied defects at
inspec1on. • Increases the quality of our assemblies by minimizing the
effects of thermal cycling on solder joints which occurs during rework.
Defect Iden;fica;on Training Observa;ons
• Many assemblers were not following the IPC guidelines for iden1fying defects in regards to solder joint forma1on.
• Most assemblies require only class 2 requirements be met.
• Many assemblers were building to class 3 requirements.
Defect Iden;fica;on Training Results
• Assemblers are now aware of the appropriate IPC requirements.
• Assemblers know where to find any informa1on if they have ques1ons.
• Assemblers have shown they can correctly describe IPC requirements for par1cular classes during random audi1ng.
ECO Work
• Revisions to bare boards helped reduce defects – Increased lead pitch to minimize/eliminate shorts – More components now machine placed. This minimizes component movement which will affect soldering.
Results
• Aler op1mizing wave solder recipes, transferring the automa1c solder feeder, providing addi1onal training to our assemblers, and ECO work, our DPMO has improved from the baseline by 75.93%!
1st Eight Week Period 2nd Eight Week Period
Results
• The improvement in DPMO translate directly to a reduc1on in rework 1me. This reduc1on also translates to an average annual cost savings.
Nearly Two (2) full weeks of continuous rework eliminated!