Unsoldering and reading an EPROM Information Manual Introduction The most used types of EPROM for ECU are: DIL, PLCC, and the last born PSOP. For each Eprom is necessary to apply an unsoldering process totally different, as they have different build-up features, even if the final aim is the same for all the three models: a precise, clean and fast work. In a few simple steps you can get a good result, even if you have never used a welder. All you need is a minimum manual ability and a little bit of care: this manual provides both to beginners than to experienced an accurate and clear technique in line with the one used by Alientech. The following rules suit for all the three models of Eprom: 1. Before unsoldering, take note of the orientation of the Eprom focusing on the side where the pin 1 is turned. 2. Avoid soiling the ECU with shaving, scraps of tin or any other thing that may cause a short circuits: work on a clear surface, uncluttered with other metal objects. 3. Flux is a valuable aid to unsolder but if used in excessive dose or not properly removed it may create malfunctions even after days or weeks. Clean very carefully with a good cleansing agent (e.g. trichloroethylene) and a clean brush to remove excess of flux from the components. Clean and brush always in the same direction. 4. Always make sure to properly orient the components in the adapters. 5. Always control the connection wires of the programmer including those to the electricity network 1. Eprom 32 pin DIL 2. Eprom 28 pin DIL 3. Eprom 44 pin PSOP 4. Eprom 44 pin PLCC 5. Eprom 32 pin PLCC
At the beginning there was only this type of Eprom, but then with the need to add even more information Dil Eproms have been replaced by more capable models, even if DIL Eproms are still installed on the ECUs of cars which do not have to manage a very complex electronics. The Dil Eprom are parallelepipedal with two rows of pins arranged on the longer sides (See fig. 1) Chapter 1 DIL Eprom (Dual In Line) DIL Epron are soldered like most of the discrete components through a hole on the ECU. The welding is applied on the opposite surface to the one of the component. The unsoldering of these components is quite difficult unless using suitable tools, but whit a minimum of patience anyone can do it. Basic tools needed: Welder Tin Unsoldering pump or unsoldering suction station Pliers to extract DIL memories First step is to identify the pins connected to ground and work on these at the end (These pins are connected to a wider area then a normal pad so more difficult to heat with a soldering iron). For the other pins the process is easy: 1. Heat the pad with the soldering iron (350 C) and lead the tin of the pin to melting, then remove the tin with the unsoldering pump, standing as close as possible to the tip of the soldering iron. If you have an unsoldering suction station proceed in the same way without the soldering iron, and take care that the tin is melting before activating the suction pump. 2. Proceed with the same technique for all the pins, except those to ground. Whether the tin do not come off at first attempt do not further heat the pad or it may be damaged: reapply some tin and repeat again the process, maybe using tin with a lower melting point. 3. For pins connected to ground, the process is the same except for the temperature of the soldering iron, which has to be slightly higher (380-400 C) 4. Also for the pins to ground if they not come off at first attempt, reapply some tin and try again. 5. Once that all the tin has been removed from the pins move the component: the pins which do not move under stress are still welded to the pad by a small part. The rheophore has two different order of size to set on the pad and may stay tied. 6. At this point you must be very careful as there is the risk to take away along the Eprom also a part of the pad, irreparably damaging the printed circuit board. Use carefully a little pliers or a tool to move slightly the pin until it comes out. If there is only a pin left to come off you can heat it with the soldering iron while removing the component. 7. Once removed, the EPROM must be thoroughly cleaned from any excess of tin which could fake the reading.
8. Now you can read the Eprom through an Eprom Reader Device (we recommend Galep-5) following all the operations which may vary from device to device. We wish to point out that, many times, the reading of an Eprom depends on its cleanliness and integrity. Most of the common errors are due to the presence of tin flash or remnants traces of flux on the pins, which fake the result, or pins bent that do not contact the adapter. In this case read the Eprom more than once and if necessary remove and replace the component on the base to be sure that you have correctly read the data. Chapter 2 PLCC Eprom The second most common type of Eprom after Dil Eproms is certainly the PLCC: small, clever, and easily rewritable as the Flash Eprom. The PLCC is like a small square, with pins arranged on all four sides and bent inwards. These Eprom are mounted on SMD (Surface Mounted Device) ECU and this means no through holes on the ECU as for the DIL Eprom. Tools needed to unsolder PLCC Eprom: Unsoldering tweezers (ERSA i-con) with appropriate tips Flux gun Unsoldering plait Trichloroethylene Soldering iron with a 1,8 mm shear tip and a 0,4 mm tip to weld again Bench vise Tin Warning: Take note of how the Eprom is positioned and in case of more than one PLCC (as per TDI ECU and similar) mark the correct location of the component. How to work with the Flux gun: 1. With a paper adhesive tape border all around the Eprom so that the flux will not infiltrate other parts outside of those concerned. (See fig.234) 2. Uniformly spread the Flux on the perimeter of the pins, being careful not to deposit elsewhere. 3. Choose the tips of the tweezers of the unsoldering station according to the component (PLCC32, plcc44, or higher). 4. Adjust the right temperature according to the component (see Table below)
5. When the tweezers are on temperature, gently grasp the component with the ends of the tips and press down so that all the pins of the component are touched by the unsolderer. 6. Move the tweezers in lightly rolling movements to allow the tips to settle down and try to remove the component from the plate in a reasonable time (15 sec. max), thus avoiding damaging and overheating. If within fifteen seconds you have not yet been able to remove the component, pull away the tweezers, wait a few moments and then try again. 7. Once removed, put the PLCC on a heat-resistant surface to cool it down for a few minutes, then take it and hold it up in the vise taking good care not to bend the pins (We suggest you to interpose a rubbery material between the jaws of the vise) 8. Clean the pads and place the unsoldering plait in to the area slightly pressing with the hot soldering iron. Remove the tin in excess. 9. Clean the pads with a clean cloth dampened with trichloroethylene. 10. With the component blocked, proceed as for the pads: place the unsoldering plait over a pin and by slight pressuring with the hot soldering iron pull the plait until every trace of tin has been completely removed, because it may distort the reading. 11. When all the pins are cleaned from tin, remove any trace of flux still present on the Eprom with trichloroethylene. 12. Through the Eprom programmer at your disposal (EMP20, ALL-07/-11 or others) read the contents and verify the accuracy of the result by running a Cheksum after the reading. If the Checksum changes at every reading it means that a pin does not correctly contact: control the orientation of the PLCC in the adapter and if each pin is clean and properly aligned. If necessary perform once again points 9 and 10 to obtain always the same reading even after removing and replacing the component into the adapter several times.
Last born in the field of memories, the PSOP Eprom combines a large capacity of data storage with small dimensions, making more and more popular this type of component. The external appearance is similar to that of DIL, a rectangle with two rows of pins arranged on long sides, but much flatter and with pin at surface assembly (SMD) as the PLCC. Chapert 3 PSOP EPROM Tools needed: Unsoldering tweezers with tips for PSOP44 Soldering iron with a 1,8 mm shear tip and a 0,4mm tip to weld again Tin Unsoldering plait Flux gun Trichloroethylene Bench vise How to proceed: 1. Mark with an indelible pen where the pin #1 is positioned. 2. With a paper adhesive tape border all around the Eprom to prevent flux to spread in the ECU 3. Put the Flux on the two rows of pins. 4. Adjust the right temperature of the tweezers (See Tab.1) 5. Gently place the tweezers along the two rows of pins and slightly press down. 6. Once the tin of all pins is melted, gently lift the Eprom. 7. Clean the pins on the contact surface with the soldering iron and a 1,8 mm tip. 8. Clean the pads on the PCB with the unsoldering plait and remove flux traces with a clean cloth and detergent or trichloroethylene. Reading this Eprom memory may be difficult due to many factors. Follow the suggestions below as a guide to troubleshooting: As there are several type of PSOP memory on the market which are slightly different one from another, be sure to determine which one you have to work on by carefully reading the code on the component and associate it to one of the following items: 28F200 29F200 B 29F200 T 29F400 B 29F400 T 29F800 B
29F800 T In addition to the model (28Fxxx, 29Fxxx etc.) what identifies the type of PSOP is the caption B or T, which is expressed by two letters (AB, BB, BC, CB, AT, BT, CT, TC, XB, XT, etc ) always with the second letter as B or T. In the selection memories menu select the memory according to the caption B or T. Be sure to have the software updated to read that type of Eprom; in case download it from the website of the producer of your programmer (see the address on the box or on the user s handbook) Check more than once that you have correctly inserted the memory into the adapter and the adapter into the base of the programmer In the end check that all the pins of the component are aligned.