The SCAR Design Engineers Must Have

Everyone makes mistakes. When we do, we all swallow our pride, get past the embarrassment, learn, and move on. But what happens if the same mistake is made over and over again or goes unrecognized? We move into a cycle of perpetual failure, with the associated corrective action and lost opportunity costs. That's why you need best-practices for handling process, procedure, and people failures.

About a year ago, I bought several thousand dollars worth of bare printed circuit boards (PCBs). I requested the fab house to forward them to an assembler as part of a consignment kit for an assembly that added about $250 in component costs to each stuffed board's value. When I received the completed assemblies back for testing prior to system level assembly, not one of the boards was fully functional.

There did not seem to be a pattern in the failure modes from board to board. Upon closer inspection with the aid of a stereo microscope, it was discovered that the copper trace widths seemed unusually thin in some places, and downright raggedy-edged in others. We were looking at boards that had been seriously over-etched. The proper calls were made. The proper apologies were given and received, and discussions about the proper reparations ensued. I should state that we had been using the same fab house for years without experiencing any difficulties.

Part of our standard operating procedure was to have the boards electrically tested and visually inspected prior to shipment from the PCB fab house. Also, as part of the procedure, we would test one solder sample that we could “ohm out” to make sure that power was not shorted to ground prior to stuffing any components. What went wrong? I needed to know, and, more importantly, I had to guarantee this would never happen again. Enter the Supplier Corrective Action Request (SCAR) and internal Corrective Action Request (CAR) procedures and forms.

The SCAR is one procedure that is aptly named. When you receive a wound and it heals, sometimes there is an ugly scar that reminds you that you should not play Superman and jump off your roof with just a bath towel cape wrapped around your neck for extra lift — speaking from experience here. In the same manner, having a SCAR report form on file that details your supplier's mistakes will remind both you and the supplier that errant actions won't “fly” with your company. For too many companies, here is how things work without a SCAR procedure:

  1. The problem happens
  2. The problem is recognized by the victim of the problem
  3. The source of the problem is investigated
  4. The party responsible takes full ownership of the problem or loses his or her job and all respect
  5. The responsible party promises it will never happen again
  6. he problem happens again
  7. Return to step 2 and repeat steps 1 to 6 until the company initiates a formal SCAR/CAR procedure.

The value of the SCAR or CAR is that it is not only used to pinpoint the true nature of the problem, but it requires the person behind the problem to state the actions taken to guarantee the problem will never happen again, and to identify the cause of the problem using Root Cause Analysis (RCA) techniques. The remedies may include the supplier modifying materials, documents, procedures, processes, and employee training and certification programs.

As it turned out, after initiating the SCAR procedure, the fab house reported that the over-etching occurred because our boards were panelized with another company's boards to save FR4 material waste. But the etching process for our boards was different than the company's boards on the same panel. The operator put all the boards through the same etch process, and we got the thin end of the deal. On the SCAR returned to us with this explanation was also a corrective action statement that included an extra inspection step for the etching work station.

That procedure required a signature verifying that the etch instructions had been read for each unique board prior to beginning the etch process. We modified the instruction to include a copy of the etch station signature being sent to us on every board fabrication. Why didn’t the electrical test catch the problem? Because the boards were batched together and only the company's boards were tested.

Also, in our own CAR was a statement that required an internal procedural change: Prior to any shipment from the fab house to the assembler, the solder sample board would need to be sent to us for electrical testing and visual inspection. We also stated that our boards were never to be put on panels with any other company's boards. We never had another problem.

In summary, be sure to verify the solution is in place and that it's effective. If necessary, visit the supplier and see how readily available the modified process or procedure is to the individual or team responsible for the operation. The modified procedures should be part of the training certifications on file.

Because we were trying to save time and additional freight costs by having the fab house send the bare boards directly to the assembly facility, we paid a heavy price. But because we instituted the SCAR/CAR procedures and changed how things were done, we probably saved even more money than we had lost through cost avoidance savings on future builds.

The SCAR form and instructions on completing it are available here. You can also share this information on SCAR and CAR procedures with key players in your company.

12 comments on “The SCAR Design Engineers Must Have

  1. CurlyHarry
    March 14, 2012

    We had  this problem a long time ago and it cost us $80K worth of parts that were placed on the PCB's. The Supplier replaced his $4K PCB's but we were left with the cost of the parts gone. This was unfair so we went to suppliers and required them to have insurance against the parts contained on the PCB's. PCB supplier must insure themselves as they are the only ones that could collect as they are the ones neglegent. This is a problem with insurance, we cannot insure against someone elses neglegence. Since then we collected once $120K from their insurance company.

    I think all PCB suppliers should consider insurance because it is not costly at all. Our PCB pricing did not change at all. 

  2. bolaji ojo
    March 15, 2012

    CurlyHarry, How does this type of insurance work and what can be covered? As you noted, how do you insure yourself against the negligence of a partner?

  3. CurlyHarry
    March 15, 2012

    With insurance you can only insure for you own negligence not others. For example, If you ran over the PCB's with a forklift this can be insured against because it was your fault. In the case of the PCB's you cannot insure against the PCB manufacturers mistake, he must insure for his mistakes that cause subsequent damage. 

    It is like liability insurance that everyone has, My company has this type of insurance for things that happen on our premises. It will not cost me substantially more for the insurance if I want to cover Customers material on my premises against my negligence. If the material is stolen his insurance must pay for it unless it can be proven it was my fault and then my insurance would pay. Only one insurance will pay. 

    Back to the PCB manufacturers responsibility, if he specifically insures his goods being the PCB's he is supplying against consequential damages it would only cost him a minor amount on top of the premiums he already pays per year so the cost per PCB suppplied is negligable. He simply has to establish this line of insurance at his end. I cannot insure against things he may do wrong, he must.

    At our company we will not purchase from PCB suppliers that do not have this type of insurance. We have collected off the insurance companies as well so it does work. More importantly it focuses the PCB supplier on our material because if something goes wrong his insurance premiums will go up. Because the additional premiums is spread out over ll customers then the cost per PCB is minor.

    We have done this for 4 years now without problems and collected twice totalling $135K from insurance. This does not help the fact that my customer does not get his assemblies on time but at least I am not out of pocket.

  4. Barbara Jorgensen
    March 15, 2012

    CurlyHarry: I started to write on supply chain insurance but couldn't figure out how it works. Thanks for the description. It is as I suspected: you can recoup some of your losses, but it doesn't do your customers any good. And, becuase the supply chain is so interdependent, I couldn't figure out how liability is assessed. It sounds for from ideal, but at least I understand it better.

  5. Barbara Jorgensen
    March 15, 2012

    Douglas: As much as I am assigning blame this week (to Apple for missing forecasts) I really don't think most people in your position with the PCBs are really looking for heads to roll. All we want is corrective action and for it not to happen again. The error you described seems faily straightforward and the company took action. You can even see how it happened. Kudos to you for following through on behalf of your client–everybody needs an ally now and again.

    I also try to admit when I am wrong. Apple may have still missed its forecasts, but it turns out there's a supply chain problem with its displays. (I doubt Apple is sitting around waiting for a mea culpa.) But I very much doubt Apple's display makers will miss the mark a second time. I wonder what their SCAR process looks like?

  6. ProcurementEtc
    March 15, 2012

    i agree -assigning liability could get ugly and drag on in litigation.

    even so, as part of due diligence (audit, financials, references, etc.) with critical suppliers i would recommend obtaining a certificate of insurance and detailed description of what is covered.  it's reasonable to request a new supplier have a 1yr rider added for special circumstances at the supplier's expense. after a year with no SCARs the rider can be dropped.  you'll have to give something in return like a prepayment, guarantee supplier is sole sourced for specific time period, etc.

    the certificate is also a requirement for workforce providers and independent contractors to protect IP and any physical work product.   sadly in a past life we had an IC go off the deep end.  It was truly tragic but from a business perspective we lost significant data and dollars to get back on track with a project.   it took 1.5yrs but we received compensation to recoup much of the loss.

    Thanks to Douglas for the reminder on the importance of SCARs and internal CARs.  Yes, they can be time consuming and cumbersome but oh so worth it on many levels.

  7. Clairvoyant
    March 16, 2012

    Great article, Douglas. Corrective action reports are an exellent way to prevent future mistakes from happening. Mistakes are bound to happen, so correcting processes for less mistakes to happen can save a company a lot of time and money in the long run. These processes should be part of every successful company.

  8. stochastic excursion
    March 16, 2012

    This is a great methodology and it's true that every company should strive to implement it where needed.

    Human factors may make the source of costly process flaws hard to determine.  Often a depth of business administration knowledge and technical expertise are needed.  This points to the need for professionals at high levels in the organization to participate in analysis and corrective action.

  9. Brian775137
    March 17, 2012

    SCARs & CARs


    Not coming from the commercial market, I didn't realize how little some companies protect themselves.  My experiences with this sort of thing happening within the aerospace industry is very limited, because the Government and most Aerospace manufacturers require that problems associated with poor product being delivered, is anathema because there is, most often, human life associated with it.


    Witness the explosion of Apollo 13.  The failure of a set of relay contacts, costing under two dollars (unusual within Aerospace) fused together in a heater circuit of the oxygen tank, thus causing the tank to keep on heating up until the oxygen pressure was so high that the tank ruptured.  Were it not for the investigation as to the cause of the failure, initiated by a CAR (and probably a SCAR too) no one would have figured out how the explosion happened and how to prevent another one from happening again.  


    This points out two very important things in my mind:

    (1)     You must have all you processes under control, and

    (2)     You must know what is to be done to eliminate the problem from ever happening again if a problem occurs.

    Assuring that your manufacturer's processes are all under control is just a subset of controlling your own processes and SCARs and CARs are an effective means of doing this within and without of you plant.  Audits and source inspections can be effective in accomplishing this.


    With a form such as a SCAR, there is little doubt as to (a) what the problem is, (b) how long has it existed, (c) what was the cause of the problem, (d) what will be an effective remedy to the problem, and (e) when will the corrective action be implemented.  A SCAR is not designed to cast blame (that does nothing to solve the problem) it is designed to detect and remedy the problem so that it does not happen again.


    Insurance against having problems, is merely applying a Band-Aid (even though it recoups lost dollars).  The main idea, is to find out how and why the failure occurred and what can be done to prevent the problem from ever happening again.  This will save money in the long run – you probably won't lose your customer's business, your reputation may be tarnished, but it won't be bad, and you won't, hopefully, see the same problem again and lose more money. 


    I leave you with this thought   – Einstein's definition of insanity is to do the same thing over and over again, and expect that there will a change to the outcome of whatever you're doing.  Assure yourself that you know exactly what's happening at all times, by whatever means, and use documentation such as CARs and SCARS and others as necessary to return to the “straight & narrow”.  It's cheaper in the long run.

  10. elctrnx_lyf
    March 17, 2012

    The kind of mistakes that could happen in PCB fabrication or Board assembly will be mostly due to not following the instructions. All the manufacturers should learn to respect their customers data and shouldn't try unnecessary experiments unless approved by the customer.

  11. Brian775137
    March 17, 2012

    I couldn't agree with you more.  When in doubt, don't punt, follow the insructions.  Remember, instructions are written to tell you how to do something correctly, be it how to make a product or how to use your new cell phone.  Instructions are written for a purpose.

  12. t.alex
    March 18, 2012

    Yes, this is so scary. Will we come back to the same vendor again?

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