How pacemakers are made

A pacemaker battery's cathode is poured in molten, then hardens inside a cell sealed against moisture.

stations: 7
things upstream: 72
raw sources: 24
steps from the ground: 9

The short version

Three parts are built separately, often with help from outside suppliers: a lithium-iodine battery, insulated metal leads and a circuit board smaller than a postage stamp. Workers join battery and board, close them in a titanium case made in pieces, and add a fitting where the leads connect. Each device is tested repeatedly, including under humidity and stress.

Pour the battery

Iodine and a polymer are heated into a molten blend and poured into a half-moon cell that already holds the lithium anode and a collector screen. It solidifies into the cathode, and the cell is sealed airtight.
Extrude the lead wires

Molten metal alloy is pushed through a small opening to make wire. Many wires are bundled and insulated with a polymer such as polyurethane, then one end gets a shaped tip and the other a connector.

Goes in
Polyurethane
Build the circuit board

Semiconductor chips, resistors and capacitors are placed on a tiny mapped board and fixed with as few solder joints as possible, forming one complex circuit.

under 2 sq cm

Goes in
Printed circuit board Microchip Solder
Form the shell pieces

The case is typically titanium or a titanium alloy, made in several pieces so the parts can go in before it closes.

Goes in
Titanium
Join battery and circuit

With every component ready, battery and circuit are wired together and set into the metal case.
Seal and add fitting

The case pieces are sealed together around the electronics, and a fitting is attached to give the leads a place to connect.
Test and pack

Visual and electrical checks run through the whole line. Finished devices are tested again, some under high humidity and stress, and packed with their accessories.

End of the linePacemaker

Worth repeating

In the late 1960s some pacemakers were powered by heat from plutonium-238 inside a titanium case, until the lithium iodide cell arrived in 1971.
Early pacemakers failed because water vapor from body fluids diffused through their epoxy coating, which is why makers moved to hermetically sealed metal cases.
In 1932, American physiologist Albert Hyman described a pacing instrument driven by a hand-cranked, spring-wound motor.