An OEM submitted a sample to Nortra that their previous cable shop was having trouble soldering. The OEM was late on their deliveries and needed a quick solution. The assembly consisted of a thick brass ring that required soldering hooks to the top outer edge and connecting wires to small solder cups in a tight circular pattern in the center of the ring. The sample supplied had charred wire and cold solder joints.
IPC Workmanship standard
The basic fundamentals of soldering presented in the IPC/WHMA A-620 standard is based on the concept of having the correct solder tip that matches the wire and terminal to be soldered; the correct type of solder for the application; the correct temperature of the solder iron; Using clean parts free from contamination and the right timing the solder tip is placed on the terminal/wire.
The first thing that was noticed was the wire used had a low temperature rating. Nortra tried a different type of wire with a higher rating but was still very difficult to solder. The brass ring was acting like a heat sink. We conferred with an IPC Master Solderer and he reviewed the assembly and offered suggestions. He suggested using a hot plate to heat up the brass ring before we attempt to make our solder connections. He also suggested cleaning the parts to remove any contamination before we begin the solder process. The solder operation also required a higher power solder iron with a fine tip. Nortra also determined the order in which each wire was to be soldered to the ring to prevent burning the insulation of an adjacent wire.
After the changes had been enacted, the result was clean and consistent solder joint throughout the entire assembly. The customer received their parts and met their delivery obligations.
Through a referral, Nortra received a request for quote from a Medical Device Manufacturer. The OEM had a cable shop but was having quality and delivery issues and they needed to find another shop to build their cable harness assemblies. The Customer needed the cables quick and provided a document package for quote. Nortra reviewed the documents and found several errors. We informed the Customer and they provided a sample cable for quote and needed a quick turn. The customer was pleased with the results and requested help in updating their documents.
IPC Workmanship standard
The IPC standard requires that all products meet the requirements of the assembly drawing / documentation. The basic fundamentals of making a quality connection, presented in the standard, require a focus on the correct terminal matched with the correct wire size; the correct strip length of the wire, the correct tool and personal who are trained in proper workmanship.
A comparison of the sample provided and the assembly drawing identified errors. The errors found included missing dimensions; incorrect connection details; using a wire type not in the assembly BOM; mismatched wire AWG to terminals and confusing and conflicting drawing notes. Nortra typically finds 15% of drawings submitted for quote are not ready for production.
Nortra worked with the customer to clean up the drawing to match the sample. The red line was approved and the drawing was changed.
One area that is critical in making a good connection is the use of proper tooling. A review of articles on crimping is provided.
IPC Workmanship standard
The IPC/WHMA A-620 standard requires the selection of tools shall be appropriate to the intended function. They shall be clean, properly maintained and free from physical damage. Unauthorized, un-calibrated and defective tools shall not be used in production of any crimp connection.
A review of the literature revealed common crimp issues.
- From IAEI magazine, “How common are bad crimps anyway? A recent Consumer Product Safety Commission (CPSC) investigation on Fixed Position Electric Heaters (S-00-5262) had an annex that evaluated this in ten off-the-shelf samples of fixed position heaters that were manufactured by three different manufacturers. In that study, there were a total of seventy-one current-carrying crimp terminals. Of the seventy-one connections, a significant number (>10%) had various manufacturing errors that were classified bad crimping.” IAEI Article
- From Circuits Assembly, “Crimping is a reliable process, provided design and process engineers follow the crimp supplier’s guidelines on crimp wire capacity and the crimp tool settings. Both of these points would have prevented these horror stories. In recent years, good inspection and in-process control of the wire and cable preparation has been enhanced with the launch of IPC/WHMA-620, “Requirements and Acceptance for Cable and Wire Harness Assemblies.” Examples of crimp defects are shown. Circuits Assembly Article
- From EDN: J. Duncan Glover, PhD gave a presentation on connector reliability. He investigated electrical failures on heating and cooling unit that would occasionally catch fire. It was traced to the power-cord connections. Glover found that improper crimping was the root cause of the problem. The assembly was produced in China. The factory was not using the specified AMP crimping machine. The factory used a knockoff crimp machine resulting in defective crimps. EDN Article
The articles presented demonstrate how critical it can be to use the specified tooling when making a crimp connection. With over 30 years in business, Nortra has acquired the tooling for our Customers crimping needs. We are continually updating our tools list to meet the current connection requirements of our industry.