# Semiconductor Tray Stacker Anatomy

How a semiconductor tray stacker peels JEDEC chip trays off one magazine, carries them along belts and builds a new stack\.

By sunny\-koala\-a59769a7

Topic: Machines

[Open the interactive Jig](https://ask.jig.com/j/VvVUDtLpxzmf)

## Transcript

### 1. A machine that moves trays

Computer chips travel through a factory in flat plastic trays\. This tray stacker takes trays one at a time from a stack on the left, sends each along a belt, and builds a new stack on the right\. It never touches the chips themselves, only the trays\. Drag anywhere to turn the machine\.

Machines like this sit between testers and packing stations, so people do not have to handle every tray by hand\.

### 2. Meet the JEDEC tray

Every tray follows one shared size, set by an industry group called JEDEC\. It is about 32 centimetres long, 14 wide and just over 6 millimetres thick\. A grid of small walls makes pockets, and each pocket holds one chip so it cannot slide around\.

Trays are made within about 0\.2 millimetres of the standard size\. A tray only slightly too big could jam a stacker\.

### 3. The input magazine

A magazine is a tall frame that holds a stack of trays\. Its four corner guides keep the stack straight, so every tray sits in exactly the same place\. The trays nest on top of each other, rim on rim\.

Trays usually travel in stacks of about five to seven, often with an empty tray on top as a lid\.

### 4. Fingers peel off one tray

Small fingers, pushed by air cylinders, poke into notches in the side of the bottom tray and hold up the whole stack\. To release one tray, a lift rises underneath, the fingers pull back, and the lift drops by exactly one tray\. Then the fingers slide in again to catch the next tray, and the bottom one is lowered onto the belts\.

The black\-edged parts are the separating fingers\. Everything depends on them moving at the right moment\.

### 5. Along the belts

Two belts run under the long edges of the tray and carry it through the machine\. Halfway, a sensor shines a beam of light down\. When the tray breaks the beam, the machine knows a tray has arrived, and where\.

The red line is the sensor's light beam\. It only appears while the sensor is checking\.

### 6. Building a new stack

The output magazine works the same trick in reverse\. A lift pushes the arriving tray up under the stack, the fingers pull back, and the lift raises everything by one tray\. The fingers slide into the new bottom tray, so the stack grows from underneath\.

Adding trays at the bottom means the machine never has to reach over the top of a tall stack\.

### 7. The brains of the machine

A small computer inside this box, called a controller, times every move\. It reads the sensors, fires the air cylinders and runs the belt motor\. A touch screen lets a person start, stop and check the machine\.

Many stackers also use a simple signal plug, called SMEMA, to tell the machines beside them when a tray is ready\.

### 8. The whole loop

Release, carry, check, stack: the machine repeats the same short cycle again and again\. Each move is simple, but done in the right order, tray after tray, it keeps chips flowing without anyone lifting a tray by hand\.

When the input magazine runs empty, a person loads a new stack and the cycle starts over\.