How pocket calculators are made
Some cheap calculators have a fake solar panel. It is a plastic decal, and a battery does all the work.
- stations
- 7
- things upstream
- 96
- raw sources
- 27
- steps from the ground
- 10
The short version
A pocket calculator has very few parts. Its whole brain is one bare chip glued to a circuit board and hidden under a black blob of epoxy. A rubber keypad presses carbon pads onto that board, a striped rubber strip links it to a small LCD, and a strip of amorphous silicon solar cell or a button battery powers the lot.
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Glue the bare chip
A single unpackaged silicon die, cut straight from a wafer, is glued directly onto the circuit board. Skipping the usual plastic package makes the calculator cheaper, lighter and thinner.
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Bond the hair-thin wires
A wire bonder welds fine wire leads from each pad on the die to traces on the board. These leads are far too delicate to touch afterward.
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Drip on the epoxy blob
A drop of epoxy is dispensed over the die and its wires and cured hard. That black bump is what you see if you open a cheap calculator, and it keeps out moisture and fingerprints.
Goes in -
Mold the rubber keypad
Silicone rubber is compression molded into a single mat of keys, each on a thin flexing web. A conductive carbon pill on the underside of every key touches two interleaved traces on the board when pressed.
Goes in -
Link the display
A small liquid-crystal display is clamped above the board with a rubber connector between them. Its stripes alternate thin conductive and insulating layers, so each pad on the glass finds its matching pad on the board without solder.
1.5 to 2 V
Goes in -
Add the power source
A strip of amorphous silicon solar cell is wired in above the display, a button cell is clipped in below, or both. An LCD and a low-power chip need so little current that indoor light can be enough.
Goes in -
Snap the case together
The keypad, board and display stack into a molded plastic case with printed key legends. The back clips or screws on, and each unit is tested key by key.
Goes in
Worth repeating
- By 1976 the cheapest four-function pocket calculator cost about 1/20 of what it had five years earlier.
- The rubber strip linking a calculator's display to its board was one of the first uses of elastomeric connectors.
- Most pocket calculators work in binary-coded decimal, handling each displayed digit as its own small unit instead of in pure binary.
Back to the ground
Follow every input upstream and pocket calculator starts as these 27 raw sources.
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Sources
These sources say little about the factory steps themselves, so parts of this line are a general description. Treat the details with care, and tell us if you know better.
Cite this page: "How pocket calculators are made." Assembly Line, 2026-11-03. https://assemblyline.org/make/pocket-calculator