Introduction

We had the opportunity of visiting Kingmax’s factory in Hsin Chu, Taiwan. This is a great opportunity for you to learn how memories are manufactured, since Kingmax manufactures both memory chips and memory modules.
 
We were excited because this was the first time we’ve seen a chip manufacturing facility from inside. On other memory manufacturing facilities we’ve been to so far from Kingston, Corsair, OCZ and PDP Systems they only manufactured memory modules, so the memory chips came to the factory already as a final product.

There are many steps involved in the memory module manufacturing:

• Wafer manufacturing
• Memory chip manufacturing
• PCB manufacturing
• Memory module manufacturing

In summary, Kingmax gets the wafer from their wafer vendor (which they don’t disclose), cuts and packs it as memory chips and put the chips together in a memory module, buying the printed circuit boards from Brain Power, a company specialized in PCB manufacturing and very well known among memory enthusiasts.

The memory chip manufacturing or “packing” as it is also called is done by a sister company called Kingpak. After being manufactured, the memory chips go still untested and unmarked (or UTT in the industry lingo) to Kingmax’s facilities (which are located in a different place) for testing and labeling. After that, memory modules are manufactured.

Kingpak factory also manufactures optical sensors for cameras, and both Kingpak and Kingmax also manufacture memory cards. We’ll concentrate our tour on describing how memory modules are manufactured.

Kinpak Factory Tour

As we’ve explained, Kinpak is Kingmax’s sister company specialized in packing, i.e., cutting the memory wafer and adding a packing and pins to the memory silicon.

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Figure 1: Arrival at Kingpak.

Memory packing process is divided into two big steps: front-end and back-end. In Figure 2, you can see the steps inside the front-end process, while in Figure 3 you can see the steps inside the back-end process.

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Figure 2: Front-end steps for memory packing.

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Figure 3: Back-end steps for memory packing.

The whole process isn’t fast. For BGA memory chips the front-end process takes 5 days, while the back-end process takes 4.5 or 5.5 days.

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Figure 4: Some stats from the packing process.

Kinpak Factory Tour (Cont’d)

In Figure 5, you can see a chart with the anatomy of a memory chip.

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Figure 5: Anatomy of a memory chip.

The packing is a very delicate process. All machinery and people work in a clean environment and that’s why we couldn’t go inside the memory chip manufacturing facility – a single dust particle could ruin the whole process –, but we could see it through a glass window.

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Figure 6: Overall view from the machinery used.

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Figure 7: Here an employee is performing the wire bond process, i.e., adding wires to the silicon chip (the golden wire in Figure 5).

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Figure 8: These ladies are working on quality control.

This is pretty much of it, since we couldn’t step inside and take pictures of all steps in the memory chip manufacturing. After finishing the process in this factory, the chips are all black (unlabeled) and untested or UTT as called by the industry experts. From here the memory chips go to Kingmax’s factory where they will be tested, labeled and assembled on a memory module.

Chip Testing

We left Kingpak and headed to Kingmax.

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Figure 9: Arriving at Kingmax factory.

After the chips arrive at Kingmax, they go to the testing and labeling facility.

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Figure 10: How the chips look like when they arrive at Kingmax. These are the so-called UTT chips.

The chips are loaded into a tester, which is the machine shown in Figure 11. This machine has several bins, which one in programmed according to the chip speed and timings the manufacturer want to test the chip for. The machine in Figure 11 has nine bins. Some of the bins are used to store the rejected memory chips. In Figure 13 you can understand how this process works. On the machine in front of us bin1 was being tested for DDR433 CL 2.5, bin2 was being tested for DDR400 CL 2.5 and so forth. Bins 6 to 9 were reserved for rejected chips, which are separated according to the reason they were rejected.

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Figure 11: Memory chip tester.

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Figure 12: Memory chip tester in action.

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Figure 13: Memory chip tester configuration.

Chip Testing (Cont’d)

After the chips are speed-graded and tested, they go to environmental testing. They are put in a big tray that goes into a kind of oven that simulates different environmental conditions (i.e., different temperatures and humidity levels) and tests if the chips work correctly under all environmental conditions set by the manufacturer.

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Figure 14: Tray where the memory chips are installed for environmental tests.

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Figure 15: Machine for environmental conditions testing.

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Figure 16: The same machine in action.

Chip Labeling

After they are tested, the chips are laser-marked, i.e., labeled. Here the manufacturer can print anything on the memory chip. In Figure 18 we can see what was being printed on the memory chips inside the machine on the moment we were visiting the factory.

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Figure 17: Laser marking machine.

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Figure 18: Screen of the laser marking machine.

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Figure 19: Status screen of the machine.

After this step the memory chip is done and ready to be installed on a PCB and sold as a memory module. At this stage the memory manufacturer has two options: sell the memory chips to memory module manufacturer or send them to their own memory module production line, if they have one. Kingmax is on the second case.

Memory Module Manufacturing

Memory module manufacturing is quite simple:

• Solder paste is added to the PCB;
• Memory chips and other components (little capacitors and SPD chip) are put on the PCB;
• The module enters an oven where the solder paste will be melt thus soldering the memory chip to the PCB;
• The modules are cut from the panel;
• The memory module is then tested;
• The memory module is packed and shipped to costumers.

As we mentioned, Kingmax buys the printed circuit boards (PCB) from another company, called Brain Power. The PCB comes in a panel, with several modules attached together (see Figure 20). In the case of the modules being manufactured, each panel had nine modules.

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Figure 20: PCBs on their original package.

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Figure 21: They came from Brain Power.

After being unpacked, solder paste (grey stuff in Figure 22) is applied to the PCB. A stencil is used in order to allow the solder paste to be applied only on the exact spots were the manufacturer wants to solder something.

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Figure 22: Solder paste being applied to the PCB.

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Figure 23: PCBs after applying the solder paste.

Soldering the Components

After applying solder paste, the panel enters into a SMD machine, process also known as “pick-and-place”, where memory chips are picked by the machine and placed on the spots were they will be soldered. This machine also adds other components to the PCB, like small capacitors and the SPD chip.

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Figure 24: SMD machine.

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Figure 25: SMD machine adding components to the modules.

With the components added, the panel enters a big oven where the components will be soldered to the modules.

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Figure 26: Oven.

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Figure 27: Modules entering the oven.

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Figure 28: Modules exiting the oven.

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Figure 29: Quality control check.

Then the modules are cut from the panel and tested.

Memory Module Testing

First the modules are tested and, at the same time, their SPD chips are programmed. SPD (Serial Presence Detect) chips hold all info about the memory module, like its speed and timings.

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Figure 30: Memory module initial testing and SPD programming.

After the SPD is programmed, the modules are tested in another station to make sure that the SPD was correctly programmed.

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Figure 31: SPD check.

After that the modules go to compatibility testing, which is a huge lab with hundreds of motherboards from several different manufacturers to be tested for compatibility with several different platforms.

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Figure 32: Compatibility testing.

After that the module is ready to be marketed, so the modules are labeled, packed and shipped to Kingmax’s costumers.

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Figure 33: Modules being packed.

• For more information: http://www.kingmax.com