Production of GOODRAM memory modules begins with the automatic transfer of PCBs, also known as multiblocks, to a surface mount line.
There, a Panasonic SPG machine, used for paste printing through a precision screen, applies Alpha OL107F-A solder paste to the board. The printing accuracy is 12.5 µm (CPK = 1.33). For comparison, the finest human hair is 0.2 mm. This is important because the fine passive components and modules will be placed right next to each other.
Specially designed screens in the DEC VECTORGUARD™ system tailored for each type of board are laser-cut, which prevents excessive solder paste consumption and allows the paste to be applied only in designated areas of the board.
However, before the machine begins to apply the paste, the camera scans the wafer and screen looking for reference points on the wafer, known as Fiducials, precisely positioning the screen relative to the wafer. The entire process, from the entry to the exit of the wafer, takes about 15 seconds and is controlled by a computer throughout. A constant temperature and humidity are maintained in the machine, and the screen is systematically cleaned.
PCB multiblocks with solder paste applied, are subjected to inspection in the process of automatic inspection through the SPI machine from the “Solder paste inspection” PARMI SIGMA-X using a fast and precise laser for inspection. The inspection takes a few seconds. The machine is capable of verifying a 60cm2 area in one second with paste printing up to 10 µm x 10 µm. The machine’s task is to verify the precision and correctness of the solder paste application on the PCB. This, after verification, is transferred to the assembly of passive components, which is carried out in Panasonic NPM-D2 machines.
NPM-D2 machines have a modular design. This means that each module has two assembly heads in a configuration selected according to the type of product.
In each of them there are suction nozzles, the so-called “nozzles”, which are used to retrieve components. Each component, which is taken from the rolls placed on the so-called “feeders”, is subjected to a verification process by the machine vision system consisting of 2 cameras and a height sensor. The capacity of the NPM (3 modules) is 360,000 components per hour, which means that the machine needs only 0.01 seconds to apply one element (component). Between 4,500 and 7,000 GOODRAM Industrial modules can be produced daily on the production line.
The same machines are also used to assemble memory chips, so-called “memory dice,” which come in two types of housing: TSOP and BGA. Memory dice can be fed from rolls, as well as from special trays. These components are also 100% inspected by the machine’s vision system.
Surface mount machines are fully safe for operators and the production process itself. A sudden power outage does not damage the workpiece that is currently being assembled, as when the machine resumes operation, it automatically starts from where the outage occurred.
The memory production process ends with the soldering of the assembled packages.
This is done in a special ERSA HotFlow 2/14 SMT production furnace, with 7 top and bottom soldering zones and 2 cooling zones for reflow soldering. During this process, the solder paste, consisting of a suspension of tin balls, silver and copper in flux, under the influence of temperature forms a solid connection between the board and the components, the so-called “solder paste” is formed.
Depending on the solder paste used and the components applied to the board, a special soldering profile is set via a specialized instrument – ECD SUPER MOLE GOLD 2 profilometer. The temperature in the furnace is about 260°C and varies in each zone. The wafers passing through the furnace move at a speed of 60 to 120 cm/minute, after which the wafers go to the buffing machine, from which they are further transported to the process of automated visual inspection AOI from. “Automatic optical inspection.”
Then the panels, via the highly efficient AOI PARMI Xceed machines, are subjected to an automated inspection using a laser, the machine checks the correctness of the soldering and the quality of the welds, as well as the height of the placement of passive components, and the mechanical damage of the PCB soldermask is verified. The machines operate at a very high capacity of 65cm2/s for components with a dimension of 14 µm x14 µm. For BGA bones, modules are checked in an X-ray machine, X-Ray, which works in 3D.
The culmination of the assembly process is the selection conducted by the AOI device via an automated magazine. The AOI separates PCB multiblocks into those without defects, known as PASS, and multiblocks where a non-conformance has been found, known as Fail.
After this stage comes the EEPROM programming, where the SPD program and lot number information is loaded. The next stage is the functional test, where computer operation is simulated on stands specially designed by Wilk Elektronik, and the memory is subjected to dynamic loads. On separate functional workstations, in turn, the compatibility of individual products is tested. The system used in RAM verification was developed from scratch by the company’s Development Department. The developed software is an operating system integrated with network card drivers, communication protocol and memory management system. This solution makes it possible to indicate a possible defect even in a single memory chip. In addition, the software takes full advantage of the test platform’s capabilities, forcing the maximum load on the memory system. The conditions created are designed to test the module under conditions of maximum duty cycle load. On separate functional stations, in turn, the compatibility of individual products is tested.
1. The first step in the inspection of DRAM modules after the SMT assembly process is the OPEN/SHORT test, during which the correctness of the assembly is checked, and their configuration is uploaded to the modules. The test is performed using specialized testers manufactured by CST – one of only a few manufacturers of such devices in the world. These advanced devices in critical situations allow electrical measurements of memory modules and eliminate errors from the process.
2. DRAM modules that have passed the first qualification stage are subjected to another test called the application test, which uses Wilk Elektronik’s proprietary test program. Just like a typical operating system, the test program manages the memory and the tasks involved in the write/read process, as well as the verification of master data. These are built to simulate intensive operation of modules in a computer such as image or sound processing or multi-threaded applications. When the program detects a misrepresentation of the master data, an error is signaled. Thanks to the algorithms specially built at Wilk Elektronik, the program makes it possible to locate the faulty memory chip. It should be noted that the construction of test algorithms needs to be updated to ensure maximum diagnostic efficiency for each new memory chip introduced into the production process. Similarly, the expansion of test benches to include new PC motherboard models requires updating the test program to add new algorithms to indicate the location of the damage. These algorithms are created using a unique method developed at Wilk Elektronik. Software changes and updates are developed and implemented by Wilk Elektronik’s Laboratory department.
3. The operation of the test program is controlled over the LAN. The program downloads the test settings from the server and compares them with the memory module under test. If, for example, the speed or capacity of the memory is different from that set by the test bench configuration, an error is signaled. This is an additional check step to confirm the correctness of the uploaded configuration. At this stage, the program records in the server logs the result of the test when it indicates a failure, also storing the list of tests that detected the failure. In this way, statistics are created that allow improving test procedures and raising the quality of Wilk Elektronik’s memory products. Associated with the process of quality improvement are the procedures of conduct, according to which, on a quarterly basis, the statistics of complaints are analyzed and the catalog of test procedures is updated. Thus, the process implements the Deming cycle, which includes planning, implementing, checking, correcting test procedures.
4. Product identification is provided by a unique test number stored by the test program in the EEPROM and a serial number on the label. This makes it possible to link the memory module to information about the testing process and the production order, and further to the BOM and suppliers. The overriding goal of this procedure is to ensure the traceability of products required by a wide range of contractors.
5. The final step in the testing methodology adopted by Wilk Elektronik is the evaluation of the results obtained from the testing process. This is done in the quality control department, which decides on the release of the product for sale. This is assisted by a catalog of test procedures, in which waste thresholds are defined, the so-called “re-test thresholds”, beyond which the test procedure is repeated. This procedure is related to the so-called “bathtub curve,” according to which damage that occurs during the first period of use can be stimulated by means of tests in the application. Following the definition of the curve, decreasing waste in successive repeated test cycles indicates that the product has reached the “life” period, during which damage should only arise due to improper operation or damage of a random nature.
6. Complementing the diagnostic capabilities of memories on test benches is their validation in a climate chamber. Validation in the chamber allows you to confirm the correct design and construction of the memory, the selection of components, the assembly process and provides confirmation of the ability to operate within the specified parameters. Validation in a climate chamber is carried out in accordance with customer specifications or the worldwide standard from the IEC60068 family. Validation in the thermal chamber can take place at temperatures from -70ºC all the way up to 180ºC and humidity up to 95% at 95ºC. Wilk Elektronik’s methods of conducting validation, developed by Wilk Elektronik, have made it possible to replace explosive glycol at negative temperatures with water, which is successfully used at -45ºC. Moreover, methods of sealing the climate chamber, i.e. protection against moisture penetration, were developed for the process by Wilk Elektronik. The validation process is adapted to the current needs of customers, i.e. it requires procedures for preparing the equipment and the process flow. The same applies to the software used to verify the correctness of operation under climatic conditions. The procedures adopted at Wilk Elektronik allow the use of customer-supplied equipment.
