Case Study: Stamped Copper Busbars for an EV Battery Pack…

Case Snapshot

A Tier 1 battery pack integrator was launching a new cell-to-pack architecture for an EV platform and needed laminated copper busbars plus a family of thinner interconnect terminals from a single supplier. The program carried a hard date: sample lots had to qualify before the pack's cell line was frozen. ISTAMPING took the program from DFM to PPAP with in-house progressive tooling, C10200 oxygen-free copper, managed selective plating, and a single quality system covering both the busbars and their smaller stamped siblings.

Parameter	Value
Part	Laminated copper busbars and interconnect terminals for a cell-to-pack battery
Material	C10200 oxygen-free copper strip, 0.05 to 3.0 mm thick, up to 650 mm wide
Die	In-house progressive dies, piloted to ±0.005 mm
Press	New-energy 45-110T presses for busbars; Aida 25-80T high-speed line for terminals
Plating	Selective gold 2-8 µm on contact zones; tin on weld pads
Quality	IATF 16949:2016, CMM first article + in-line vision, PPAP Level 3

Why the Customer Came to ISTAMPING

The integrator had been buying busbars from a stamping house and terminals from a second supplier, with plating farmed out to a third. Three handoffs meant three tolerance stacks, two plating windows, and one recurring argument about which supplier owned a contact-resistance failure found at pack assembly. The audit trail was the real problem: when a lot of plated busbars drifted out of the resistance window, nobody could produce the process data to show where the drift started.

They came to ISTAMPING because the entire chain runs under one roof on 10,000 m² of floor: coil in, stamped, plated, inspected, and packed with one quality system and one set of records. The busbars stamp on our new-energy 45-110T presses while the thin interconnects run on the Aida high-speed line, but both share the same tool room, the same plating program and partner lines, and the same CMM and in-line vision gates. For a program where every lot carries a resistance traceability requirement, that single-chain structure was the deciding factor.

The DFM Review

The DFM review started from the print, not from the die. The busbar's critical features were the flatness across the laminate stack, the edge condition at the weld tabs, and the plated contact window on the cell-end surface. C10200 was specified for the conducting layers: oxygen-free copper keeps weld porosity out of the stack-up joints, and its conductivity lets the pack current flow without forcing an oversized cross-section. The review also covered the tolerance stack between the busbar hole pattern and the terminal pads, because a cell-to-pack architecture lives or dies on the position of every hole relative to every cell post.

Three findings from that review changed the print before tooling started. First, the weld-tab edges were re-specified with a burr-direction callout, because burr on a laser-weld surface creates spatter and porosity in the joint. Second, the plating window on the cell-end contact zone was locked to the hole pattern with a registration tolerance, so selective plating lands in exactly the same place on every part. Third, the interconnect terminals were consolidated from two alloys to one C10200 family so both part groups share a material certificate and a plating lot. Each change reduced a handoff that had been costing the customer time across three suppliers.

The Engineering Approach

The die work began in our own tool room, where wire EDM and CNC machining centers cut the progressive tooling, and the dies were tried out and qualified on our own presses before the first production lot. Piloting holds strip registration to ±0.005 mm, which matters twice in this part family: once for the hole pattern that locates the busbar on the cell posts, and again for the plating window, because selective plating only lands where the mask says it lands. The laminate stack-up is produced with controlled burr direction and deburring stations in the die, so the weld tabs present a clean edge to the pack's laser weld.

The strip stock runs from 0.05 to 3.0 mm thick and up to 650 mm wide, which gives the layout room for multiple cavities across the coil. The heavier busbar sections run on the new-energy 45-110T presses, where the tooling carries the forming loads of the thicker copper without sacrificing the registration between stations. Interconnect terminals in the same program run multi-up on the Aida line at up to 300 SPM, with in-die forming and coining to hold the terminal geometry across the whole reel. Because both lines sit in the same facility, the two part groups are released against the same lot structure and the same quality records.

Production Results

Metric	Result
Strip width	Up to 650 mm coil, 0.05 to 3.0 mm thick
Positioning tolerance	±0.005 mm (piloted progressive dies)
Plating	Selective gold 2-8 µm on contact zones, XRF verified per lot
Terminal line speed	Aida 25-80T presses at up to 300 SPM, multi-up tooling
Quality system	IATF 16949:2016, ISO 14001:2015, CMM + in-line vision
First article	PPAP Level 3 approved ahead of the pack cell line freeze

Quality gates run at every step of the chain. The busbar lots are dimensioned on the CMM against the full print, and the terminal strips pass through in-line vision on the press, which catches dimensional drift before it becomes a lot-level issue. Plating thickness is verified by X-ray fluorescence on a per-lot basis for both part groups, and the results ride in the same lot record as the stamping data, so the resistance traceability the customer needed exists as a single file per lot instead of three files from three companies.

First-article inspection covered every dimension on the print, and the customer's pack integration team signed off on the flatness and weld-edge condition in the first PPAP submission. Production has since run in synchronized batches, with the busbar lots and terminal lots released under one part-number set so the pack line receives a complete interconnect kit, not two shipments from two suppliers.

What Made the Difference

Three structural choices carried this program, and each one is worth naming because they are the same choices any battery program will face. First, the tooling was built in the same building that runs it, which compressed the tryout loop from weeks of shipping to days of walking. Second, the plating window was treated as a tooling tolerance, not a process afterthought, so the selective gold at 2-8 µm lands on the same spot on every part out of every cavity. Third, the quality records were structured around the lot, not the operation: one lot file holds the strip certificate, the stamping SPC data, the CMM first article, and the XRF plating report, which is exactly what the customer's traceability requirement needed.

The environmental side deserves a line too. ISTAMPING runs ISO 14001:2015, and the copper scrap from the busbar and terminal lines goes back into the alloy supply chain rather than to landfill. For an EV program whose customers audit the carbon story of the battery, a stamping partner with a certified environmental system and a closed scrap loop closes a question that would otherwise come up at the annual audit.

Why This Case Matters for Your Program

If your battery program joins high-current copper with a critical plated surface, the supplier decision is really a process-chain decision. Ask the questions this customer asked: Is the tooling built and proven in-house? Does plating run in the same chain as stamping? Is the strip flat and burr-controlled through the die, or patched up after? Can one supplier ship the busbars and the terminals against one release? The answers decide whether your pack line starts on schedule or spends a quarter chasing a resistance failure across three suppliers.

Send us the drawing and your annual volume. We will run the same DFM review for your busbar or interconnect program and return a tooling price with the piece-cost curve at three volumes, so the decision is visible before you sign.

Case Study: Stamped Copper Busbars for an EV Battery Pack Program