Indium Blog

Special Cause and Common Cause Variation and Knob Twiddling: continued

  • Indium Corporation
  • Rework
  • Solder
  • Soldering
  • Solderability
  • Soldering Products
  • Wave Solder

  • Folks,

    Let’s see how Pete is handling the wave solder crisis.

    Pete had to admit that he was surprised by the positive outcome of his meeting with Fred Castle.  He had sent Patty a text the day before, after he took the operators to lunch, before meeting Fred.  The text was a little negative.  So he was eager to send her the good news about the surprises in his two meetings with Fred since then.  He was frustrated that he kept on getting her voice mail.  Finally she answered.

    “Advanced Processes,” Patty speaking.

    “Hey, kiddo, it’s your favorite process genius!” Pete responded cheerfully.

    “Oh, this must be Oscar Patterson!” Patty joked, and they both laughed. Patterson was an annoying chap they had to deal with a few years ago.  He topped their list of most annoying people. Pete had almost come to fisticuffs with him.

    “How is it going there?” Patty asked.

    “Shockingly well. My meetings with Fred Castle were very productive” Pete answered.

    “Well, that is shockingly positive news. But I thought he said, ‘I’ve forgotten more about wave soldering than you’ll ever know,’” Patty responded.

    “That’s the first thing he said to me when we shook hands, but he was clearly teasing.  He slapped me on the back at the same time and chuckled. He went on to say that he had worked in wave soldering for over 30 years, typically at companies that had processes that were out of control.  It was clear that he understood a lot about wave.  We talked for 30 minutes about what makes a good wave process. As far as I could tell he was right on in everything he said.  I think the operators didn’t pick up on his teasing, by the way,” Pete elaborated.

    “What about special cause vs common cause?” Patty queried.

    “He didn’t have a clue,” Pete replied.

    Patty was bracing herself.  She was concerned that Pete might have insulted Castle.

    “And you didn’t tell him he was an idiot?’ Patty teased.

    “Patricia! I’m shocked you could even think such a thought,” Pete replied.

    Pete went on, “We bonded, and he admitted that he was frustrated with the yield loss increasing.  He was studying the situation and spending a lot of time trying to figure out the issues.  He said he was having trouble sleeping.  He mentioned that, in his last job, he was responsible for the wave processes at 10 locations.  He was constantly fighting fires and got good at it.  He had never worked at company that performed DOEs and developed optimized processes.”

    “I’m dying to know how this situation worked out,” she interrupted.

    “Patience, patience,” Pete admonished jokingly. He continued, ”It was clear that Fred likes to learn, so  I mentioned that, recently, The Professor had mentioned the importance of understanding the differences between common cause and special cause variation when trouble shooting a process.  I suggested that maybe studying these topics might help. So I gave him a few links to The Professor’s posts on common cause and special cause.” (Dr. Ron note, it will be helpful understanding this story to read The Professor's post, if you are not familiar with common cause and special cause fails.)

    “What happened then?” Patty asked, the impatience in her voice apparent.

    “Remember, this is now the end of my first day. I watched the process in the morning, took Molly and Chuck to lunch, and then met with Fred.  On the second day I had a morning meeting with the quality director, Pam. Then Castle and I went to lunch,” Pete elaborated.

    “And?” Patty asked impatiently.

    “Castle was all excited.  After studying common cause and special cause all night, he realized that he was seeing common cause fails in his detailed scrutiny of the wave line. By adjusting the process parameters slightly when he found a common cause fail, he was moving away from the optimized process settings that were determined by a DOE, so the failure rate got worse.  In his previous job, he was mostly seeing special cause fails, as the processes were not optimized, so he was used to intervening,” Pete explained.

    “It seems like he won’t have enough to do now,” Patty commented.

    “I suggested he help quality.  They are stretched thin and he is a detailed-oriented fellow.  He keeps meticulous Pareto charts of the fails,” Pete said.

    So, where are things now?’ Patty asked.

    “Yesterday and today, first pass yields are at 96%.  Fred also started helping quality today. It felt good to help and not offend,” Pete finished.

    Patty thanked Pete for the great job he did and complimented him strongly for being successful and making friends at the same time.  As she hung up the phone, she saw an email from Pam Olinski in her in box.  It was a kind note thanking her and Pete for his help.  It recounted much of what Pete had said.

    She wistfully looked out her window.  She was happy and grateful for all of her success, but, to be truthful, she missed the action of being out on the shop floor solving these types for problems.

    She was jolted from her chair when she suddenly remembered it was her turn to take her twin sons to karate lessons.  So she packed up quickly to pick them up at her mother-in-law's, to get them to the gym by 5PM.


    Dr. Ron