Sourcing contacts and coils from India: capability, silver and export

A specialist market, not one market

India is often described as a single sourcing destination, which is unhelpful for contacts and coils. The companies that make contact rivets, welded contact assemblies, coil bobbins and wound coils are a small, specialised group. Many of them sit near switchgear, relay and appliance manufacturers, and their process depth varies more than their addresses suggest.

A general sheet metal stamper can produce a contact carrier. It is unlikely to have the silver handling, the welding control and the inspection needed for the contact face. In the same way, a motor winding shop may have excellent layer winding equipment and no experience of an encapsulated relay coil with a thermal cut-out.

The first sourcing question is process, not region. That changes the way a buyer builds a shortlist. Instead of asking for a country capability, ask for the specific process: rivet heading, contact welding, brazing, coil winding, encapsulation, plating and assembly. Then check that the supplier performs that process in house, or has a stable partner it controls.

Contact capability

The contact supply chain in India covers stamped contact springs and carriers, solid and composite rivets, tips and pads, welded buttons and brazed assemblies. The stronger shops tend to be the ones that combine stamping with an in house joining process, because the joint is where most contact failures begin. A shop that stamps the carrier and sends it out for welding adds a transport step and a second process owner.

Ask to see the welding or brazing area, the electrode maintenance record and the way the joint is checked. A contact weld is a short, high current process, and the variables that matter are current, time, force and electrode condition. A supplier that tracks those variables can hold a joint; one that relies on the operator's eye cannot.

Silver content, oxide distribution and hardness are the material calls. For a composite contact, the drawing should state the face material, the backing material and the joint. The supplier should be able to show a material certificate for each lot and a hardness or shear result at a stated frequency. Without those, a certificate of conformity is only a statement of intent.

Coil capability

Coil winding is a different supply base from contact making. The equipment decides what a shop can do: a layer winder with a controlled traverse produces a predictable build, a wild winder fills a bobbin quickly at a lower cost, and a toroidal winder handles a closed core that neither of the others can touch. Encapsulation, varnish and potting add another process and another set of equipment.

Ask for the winding method used on a comparable part, the wire range, the maximum build diameter and the way resistance is measured and recorded. A shop that winds to a resistance target and records the value at a stated temperature is easier to audit than one that winds to a turn count and measures later. If the coil has a bobbin, ask whether the bobbin is moulded in house or bought, and who owns the tool.

Termination is the second half of coil capability. Pins, tags, flying leads, connectors and welded lead exits each need a different station. A shop that is strong on PCB pins may have little experience of a flying lead with a sleeve and a ferrule. Send a drawing with the termination fully defined and ask for a sample before the volume is discussed.

Silver handling and the metal account

Silver is the largest material cost in many contact programmes, and it is volatile. A quote that fixes the silver price for twelve months carries a risk premium. A quote that treats silver as a pass through is more transparent, but it needs a clear basis: which price, which source, which purity and which date.

Ask how the supplier buys silver, how it accounts for scrap and how it returns the value. Contact making produces scrap in the form of trimming, rejected parts and spent solutions from plating. A supplier that recovers that value and credits it is behaving like a metal business. A supplier that ignores it is likely to recover the cost somewhere else in the price.

The same logic applies to the contact face. If the drawing calls for a silver tungsten or silver tin oxide face, the supplier needs a source for the material and a way to verify it. Ask for the material certificate and the lot traceability from the face material to the finished contact. A price that looks low on a composite contact often reflects a thinner face or a different oxide system, neither of which shows in a visual check.

Qualification before volume

A new contact or coil supplier should be qualified on the process and the part. Start with a process audit that covers the equipment, the calibration, the material control and the traceability. Then ask for a first article that includes every drawing dimension, the material certificates, the joint test and the electrical results. For a contact, add a shear or pull test on the joint. For a coil, add resistance, inductance where relevant and a dielectric test.

The life test is the part that separates a supplier that can make a sample from one that can make a product. A contact that switches a few hundred times on a bench proves very little. Ask for an endurance test at the rated load, with the contact resistance and the erosion measured at defined intervals, and compare the result with the design expectation.

Certification helps, but it is not a substitute for the process audit. An ISO 9001 certificate says that a system exists. It does not say that the welding electrodes are dressed on a schedule or that the silver lot is traced to the finished part. Use the certificate to open the conversation and the audit to close it.

Export, packing and logistics

Contacts and coils are light, high value parts, so air freight is common for urgent releases and sea freight for repeat volume. The packing has to protect the contact face and the coil build. A contact that arrives with a damaged face is scrap, and a coil that has been compressed in transit may have a shifted winding or a cracked bobbin.

Agree the Incoterm, the port or airport, the packaging specification and the documents before the first shipment. A commercial invoice, a packing list, a certificate of origin and the material certificates are the usual minimum. If the part attracts a preferential rate under an agreement, the origin evidence has to be right, not retrofitted.

Build a buffer for the first shipments. A new supplier needs time to settle the process, and a programme that plans to the day will feel every delay. A small safety stock and an agreed review cadence are cheaper than expedited freight.

What to verify, by supplier type

The table below maps the main supplier types to the evidence that matters. It is a starting point for a video audit or a site visit, not a replacement for either.