Electronics manufacturing services (EMS) providers are frequently asked if they offer "traceability" on the materials they procure. Then there is the follow up question - the one the original equipment manufacturer (OEM) really wants answering – "how far can you go back?"
If the EMS providers you are talking to respond with anything less than "yes, of course" and "back to the original source", you may want to reconsider your list of potential partners.
But have you ever probed them further on these answers? Do you really know what details are being recorded? How confident are you in their systems, procedures and processes? And, therefore, how likely is it that they could provide you with the information should the need ever arise?
The purpose of this blog post is to look at the standard levels of traceability all good EMS providers should be able to offer. By going into some of the detail, we hope to explain which details are being captured and how this data might help you in the long term.
We have all read horror stories over the past few years relating to product recalls, from the horsemeat scandal back in 2013 through to last years "must have" gadget – the exploding hover board. Although I’ll never know if I’ve really eaten a horse burger, I was able to react in time and stop Santa Claus from delivering a potentially lethal product to my child.
So, when it comes to traceability one of the most critical factors is speed; specifically the time it takes the EMS provider to supply the information you need. In order to do this they must have robust processes and procedures in place to record, store and manage the data so they can extract it at the touch of a few buttons.
Purchase order creation
When an EMS provider raises a material purchase order their computer system should create a unique record number. This unique record number should link the material to the purchase order and supplier.
Goods received
When material is received it should be assigned a Goods Received Number (GRN). This number should be automatically assigned by the EMS provider's computer system and must be unique. The GRN links the incoming purchase order and supplier documentation (such as delivery notes and C of C’s) to an internal stock batch number, which is also automatically generated when the material is booked in.
An internal stock batch number might look something like this:
- YYWW/NNRRRR
- YY = Year
- WW = Week
- NN = Number of deliveries made in a specific week
- RRRR = RoHS status of the item
As an example, if an electronic component - i.e. 1N4148 - is delivered on 9 May 2016 and is confirmed by the supplier as being RoHS compliant, its stock batch record number would be 1619/01RoHS. The unique identification therefore ties the two together - i.e. 1N4148 – 1619/01RoHS.
Works order creation
When a works order is raised, another unique record number should be created by the EMS provider's computer system. Each works order should be serialised and the serial number allocated to the product should capture both the works order number and the individual number of units produced within that batch.
A serialised works order number might look something like this:
- XXXXXX/ZZZZ
- XXXXXX = Works order number
- ZZZZ = Number of products built within the batch
As an example, if you were to order a batch of x300 "widgets" in total and the EMS provider's system generated works order number 659800, the 45th product to be built would have a serial number of 659800/0045.
Material allocation
Raw materials should be allocated by the assembly partner to the works order using a first in, first out (FIFO) method. If any specific customer conditions apply - i.e. the supply of non-RoHS material only - the EMS provider will need a process to ensure they can comply with these requests.
In addition to capturing details of the material, a robust works order system will also capture details of each of the production and test operatives assigned to the build. Through the use of bar code scanning the dates and times of each operator’s involvement in assembling the product will be captured.
Works order completion
When a works order is completed into stock, a batch code, similar in structure to the stock batch number (YYWW/NNRRRR), is generated.
Despatch documentation
When completed products ship from the EMS provider their despatch paperwork should reference the works order batch code and, in addition, the assembly partner may list the serialised works order numbers to reflect what has been shipped. This may be part of their standard process or something they will offer as a customer specific instruction.
Customer specific instructions
If you need additional levels of traceability, the EMS provider will need to demonstrate their systems and processes can meet your requirements. For example, you may need the date code of a particular integrated circuit capturing, or the SIM card numbers used in your products recording. This shouldn’t be an issue - however, as these details will be unique to you or your product, the EMS provider will need to either flag these on their computer system as a "customer specific" instruction or reference them somewhere in the build documentation they create.
How far can you go back?
Should the need arise, and providing the above steps are followed, the EMS provider will be able to trace the material back to the original supplier.
Using the unique works order serial number, the EMS provider will be able to find the works order details and highlight which operators were responsible for assembly, as well as the internal stock batch numbers allocated to the build. If there is an issue with a particular item of stock, the EMS provider will be able to identify the batch number of the item and trace this back to its unique GRN. This GRN will link back to the incoming purchase order number and the supplier that delivered the part. From here they will be able to find the supporting supplier documentation - i.e. the incoming despatch paperwork or C of C. If there is a need to go back through the supply chain even further - for instance, to the original device manufacturer - the EMS provider can provide the supplier with their original paperwork and ask them to carry out the same process.
Time to react
So how quickly should they be able to provide this information to you? Well, if you are talking about one product and one device it should only take a matter of minutes to get the raw details - i.e. works order numbers, batch numbers, GRN and purchase order numbers. If you need traceability information spanning multiple products and several different parts then obviously it will take a little longer. But it shouldn’t take weeks, and certainly not months, for your EMS provider to send these details through to you.
Finally, it’s important this process works in reverse too. For example, if an issue is found with a specific piece of material/stock batch number, the EMS provider should be able to quickly tell where this stock has been allocated, if finished product has already shipped out, whether they have any currently allocated to work in progress, and how much they have left as raw material.
We hope that you found this blog post useful. Knowing that your EMS provider has a robust traceability policy in place is much like any other insurance policy you have in place. You hope you’ll never need to use it but if you do, you’ll want the company to react quickly to your needs and make the process as pain free as possible.
Image by Flood G
