Table of cont ent 1. Introduction 2. The logic board 2.1 The circuit 2.2 Ground 2.3 IC’s 2.4 Connectors 2.5 Additional components 3. Tools 3.1. Main tools 3.2. Knowledge sources sources 3.3.. Furth 3.3 F urther er necessary too ls 4. Defects Defects 4.1. Water damage 4.2. Repair damage 4.3. Falling 4.4. Wrong charge c hargerr 4.5. Bendin Bending. g. 4.6. Lo Long ng screw damage 4.7 The most comm c ommon on repairs repairs 5. Repair Repair practice 5.1. No power 5.2. Speci Specific fic proble problem m 5.3 Further reading reading
Table of cont ent 1. Introduction 2. The logic board 2.1 The circuit 2.2 Ground 2.3 IC’s 2.4 Connectors 2.5 Additional components 3. Tools 3.1. Main tools 3.2. Knowledge sources sources 3.3.. Furth 3.3 F urther er necessary too ls 4. Defects Defects 4.1. Water damage 4.2. Repair damage 4.3. Falling 4.4. Wrong charge c hargerr 4.5. Bendin Bending. g. 4.6. Lo Long ng screw damage 4.7 The most comm c ommon on repairs repairs 5. Repair Repair practice 5.1. No power 5.2. Speci Specific fic proble problem m 5.3 Further reading reading
1. Introduction
What is logic board repair and when is it necessary? The logic board of a iPhone is the like the organs inside a human body. It contains most of the hardware needed for a IPhone to function. Ironically enough most repair shops lack the knowledge to perform logic boards repairs. They focus on the most common repairs: screen and batt ery replacements. Even Apple doesn’t do t his kind of repairs. When a iPhone get s water damaged or suffers a hard drop changes are that the logic boards needs repair. So there seems to be a business opport unity here. Asides from the addicting thrill of repairing a iPhone logic board of course. But what does it take to start repairing logic boards? Basically three things: Tools, knowledge and experience. Let’s start with the tools: The smallest repairable parts on a logic board are hardly seen with the naked eye. So what you need is good microscope. They range in price from 200 dollars minimum to a couple of thousand. Personally i use a 200 dollar microscope and doing fine. But if you want to do all kinds of logic board repairs you’ll need a 500 dollar minimum microscope. Secondly what you need is a soldering- and hot air station for removing and replacing parts. Thirdly what you need is a multimeter to test parts and circuit lines. Finally you’ll need a DC power supply to see the board powering on, and for testing short circuits. These are the main tools. Of course you need some extra tools for running the repair process like a tweezers and heat resistant tape. But where to get t he know-how? With this book you have a good start and overview of what is needed for logic board repair. I will further guide you to other sources of knowledge. Most important: the iPhone schematics and the repair solutions offered by Filip Pusca of Itelsa Solutions. Schematics give you a blueprint of the logic board is build. It shows the components, their values, and how they are connected. It’s like a city map with roads, bridges and houses. The official iPhone schematics are not publicly made available by Apple, and the ones on the internet are leaked . personally i avoid them and use a Chinese tool with operates just like the schematics instead. The ZXW to ol. The tool comes with some great extras: as well. The tool shows how each component on a circuit line is connected, and it also show the value components, and the positioning of IC’s. In this work i will lay out the basics of iPhone logic board repair.
2. The logic board
In this chapter I will discuss how a logic boards works and how its main components operate .
2.1 The circuit
All iPhone logic boards have basically the same layout. There is a battery that provides current that flows through the board which provides energy and data to the components to function. You can compare this to the blood flow inside a body threw veins, in order to feed the organs. The current flows through so called traces inside the board. These traces sometimes reach the surface. The point where a trace reached the surface is called a pad . The components are soldered onto these pads. If a component or trace gets damaged the current flow stops, or is (partly) blocked, and needs repair.
2.2 Ground
Another part of the logic board is called ground (GND). This is the metallic part of the board that isn’t supposed to carry current. Most GND is. If a current flow accidentally contacts GND you have a short and loss of energy. This normally creates heat , and causes malfunctions.
2.3 IC’s
The most important parts of the board are the IC’s. You can compare them to the organs inside a body and they provide the functions needed for a iPhone to operate. They work in concert with other components like filters, capacitors, resistors, diode’s and coils. Some of the most important IC’s in logic board repair are: the Power Management IC (PMIC), the NAND Flash IC, the Processor IC, the charge IC, the touch IC’s and the backlight driver IC. See the following picture for these IC’s on the iPhone 6.
2.4 Connectors
The place where the logic board can connect to extern hardware is called the connecter . It transports current form and unto the extern hardware. They are a common cause of malfunction. I consider CyberDocLLC the expert in the art of repairing iPhone connectors. Therefore i would recommend his video’s for learning this discipline.
2.5 Additional components
The additional components are for altering the current flow. I will next discuss their main function and I will provide pictures for their recognition.
Filters The main purpose of a filter is filtering the current flow. Most of the times it is located near to a connector. They are the ones which often get damaged first. They also provide protection (like a fuse) against current spikes to other parts on the same circuit line like IC’s.
Capacitors The purpose of a capacitor is to store electronic energy for a certain amount of time. They have one side on a line pad and the other on a GND pad. If they somehow get damaged they can short the line to GND and cause little or bigger malfunctions.
Resistors The purpose of a resistor is to diminish current flow or voltages on a line.
Diode’s The purpose of a diode is to pass current in one a way and to block it in the other way. Like a valve.
Coils The purpose of a coil is to amplify or diminish voltage. It is needed for creating high voltages like for powering the backlight.
3. Tools
In chapter 2 I have pointed out how a logic boards works and how its main components operate .In this chapter I will discuss the tools needed for fault finding and repair.
3.1. Main tools
Microscope As I said before: the smallest repairable logic board components can hardly be seen with t he naked eye. So a good microscope is essential. Perso nally i use a microscope with 10X magnification for most repairs, and 20X magnification for things like t race repair link. If you have a good budget i would advise a better one: link With this one you have a proper tool for all kinds of logic board repairs. For myself: I love to find items that are the best value for the money .
Soldering station All components are attached on the board with solder. So to replace a small component a soldering iron is needed. This one works fine for me: link. Many repair shops use a Hakko soldering station like the FM-202. A nice extra about some Hakko stations is that on some of them you can use soldering tweezers. It makes it easier to replace both sides of small components in one try.
Hot air station To replace an IC a normal soldering won’t do the trick. IC’s are attached onto board with soldering balls. That ’s why you can only replace them with a hot air st ation. I use the following hot air st ation: link. Many repair shops use a Hakko hot air station like this one: link. In chapter 5 i will explain some basics of how to replace an IC using a hot air. DC Power Supply To see if a board powers on properly (boots), and to see if there is a short to GND somewhere, a DC Powers Supply (DCPS) is a valuable tool. This is mine: link A DC power supply acts the same as a a battery. It provides current. It has a display that shows volts and amps and comes with two probes. A red probe for the positive (+) side. And a black probe for the negative (-) side. These probes need to be connected to a capacitor on a shorted line to detect heat and to find the damaged component. It can also act as a battery. There are special cables for that. In t hat case you can see how the board boots and if there is a short on important circuit lines. When a board consumes energy without having it powered it means a big short somewhere. When a powered on iPhone consumes Amps in standby mode that
means there is a smaller short somewhere. These smaller shorts are not easy find in my experience. Multimeter To measure faulty components, continuity in lines, and short s a multimeter is an absolute necessity. In chapter 5 i will explain how to measure these things with a multimeter.
3.2. Knowledge sources
Schematics Schematics provide a blueprint of how the boards is build. It shows it’s components and value’s, t he way components and lines are connected and t heir functions. The official iPhone schematics are not publicly made available by Apple, and the ones one the internet are leaked . Personally i avoid them and use a Chinese tool with operates ust like the schematics instead. The ZXW tool. The tool comes with some great extras: as well. The tool shows how each component on a circuit line is connected, and it also shows the value of components, and the positioning of IC’s. Itesla Solutions Another great source of information are the step-by-step solutions provided by https://itesla.solutions/ The site provides, among ot her things, step-by-step solutions for most defects. The site charges a subscription fee which I find absolutely worth the money. In chapter 5 i will explain how to use these solutions.
3.3. Further necessary tools
Next I will give a list of some other tools needed for iPhone logic board repair. For these i normally choose the best quality items. I have listed them in the working routine order. The rest of the needed items are common household items like scissors, a toothbrush, needles etc. For removing and replacing the logic board from a iPhone: •
iPhone screwdrivers
•
Scalpel (for removing standoff screws + ot her purposes)
•
Magnetic mat
For testing logic board before and after repair: •
Working housing + lcd
For working on t he logic board in general: •
HAKKO Precision Tweezers
•
Silicon mat (to work on)
•
PCB Circuit Board Holder (especially for shield removal)
For testing parts: •
Freeze spray
•
Ultra fine probes for the multimeter
•
DCPS cables specially for IPhone
For repairing the board: •
Donor boards
•
CyberDoc Liquid Flux
•
Kapton Tape
•
Desolder Braid Wick
•
Reballing stencils
•
CyberDoc Desoldering Alloy
•
Solder bal’ls
•
Cyberdoc insulated jumper wire
•
Copper soldering iron tip
•
Solder
•
Solder Iro n Tip Cleaning Tool
For cleaning board during and after repair: •
50x Double Tip Foam Swabs
•
Alcohol
For sourcing parts: www.mouser.com https://microsolderingsupply.com http://stores.ebay.nl/inrem-UK
4. Defects
In the former chapters i have told how a the logic board works, the functions of its main components and the tools needed for repair. In this chapter I will move on discussing the most common reasons for damage, and the most common defects resulting from that damage. The kind of defects can be numerous. From a less dramatic defect like a not working compass, to more devastating defects, like a short ed processor unit. The most common forms of damage are: Water damage, repair damage, a fall, a wrong charger and bending.
4.1. Water damage
When a powered on logic board gets wet the water can act as a bridge conducting current t o places where it shouldn’t go. It creates heat and components can get burnt. This way water damage can cause permanent shorts to GND. The iPhone can lose functions, or decide to not turn on at all. A water damaged iPhone not powering on mostly happens when one of the two most import ant lines: BATT_VCC or VVC_MAIN, is affected. When able to locate and relieve a short on 1 of these lines the iPhone normally will return back functioning. There are different methods for detecting a short to GND. Abnormal power usage can be seen using a DC power supply and is indicative of a short. A short also creates heat. This can be felt with your lips. When a line is short ed the capacitors on that line will beep on bot h sides. But most of the time there is only one component the culprit. Your task it to find that “sucker”. For this you power the shorted line with a DCPS. The voltage must match the normal voltage of the shorted line . And with things like freeze spray and your lips you try to find and replace the short ed component. The ZWX-tool shows you which components are on a the shorted line.
Liquids can also cause residue and corrosion on the board. Proper clearing is mandatory. For cleaning: alcohol and a brush can be used. Water damaged iPhone can have invisible damage and can there for be pot entially be unstable. Many repairs shops do water damage repair fo r data recovery only.
4.2. Repair damage
Repair damage can happen during a “normal” iPhone repair like a lcd or battery replacement. This can cause defects like no more backlight or no boot at all. Repair damage can be detected using a microscope. When uncertain if a small component is effected one can try pinching it a little with a needle to see if it moves or test it with a multimeter. The ZXW t ool can help you determine which functions are affected. video
4.3. Falling
When a iPhone drops hard, changes are that a IC loses full contact with the board (cold solder), or that for example a glass IC breaks. These kind of problems can be harder to detect. If possible you can try get into DFU mode and see what error pops ups. The error code can indicate where the problem is. Many times a reflow of the effected IC helps out. A reflow is heating a IC until t he solder under it melts. When there is epoxy under a IC t hen a replacement is a saver option. replacement. Anot her method is pressing the suspected IC while boo ting. Subspecies IC’s are the Power Management IC (PMIC), the NAND Flash IC and the Processor IC.
4.4. Wrong charger
Using a non-official iPhone charger can damage the charge IC. In that case the Iphone wont charge or wont boot at all. It can also show with other symptoms like the message: "The accessory may not be certified” when inserting the charge cable. The only remedy is replacing this IC.
4.5. Bending
Bending can also be a cause of cold solder under IC’s. The IPhone 6 and 6 plus are notorious for this problem. The infamous “ Touch disease” .The reason for this seems to be a design flaw. The housing is prone to bending. And no epoxy is used under the two Touch IC’S. Replacement is of the IC’s the only remedy.
4.6. Long screw damage
As told you before: current through so called “traces” inside and on top of the logic board. And these traces follow a path and connect the components. When a trace or a component gets damaged it is possible that the flow in that line is blocked. The blockage needs to be removed or the trace reconnected. A special case of trace damages is the so-called “long screw damage”. This can happen when a long screw is used in a small screw bracket. The screw then can pierce some traces. As a result all kind of malfunctions can occur. These repairs are high skill. The ZXW tool shows which lines are involved.
4.7 The most common repairs
As a result of the damages described in this chapter the 4 of the most common repairs are: 1.
Defected touchscreen
2.
Defect ed backlight
3.
Defected charging
4.
No power
5. Repair practice
In the former chapters i have told how a the logic board works, the functions of its main components and the tools needed for repair and discussed the most common reasons for damage and defects. In this last chapter i would like to show defect assessment and repair in practice. When a customer shows up with a defected iPhone t he first question is ask myself is: Is this really a logic board issue or is it maybe something else? Therefore i first ask what happened just the before t he malfunction occurred, and let the customer describe the problem. The history of t he defect can you point you in the right direction. “No touch” can mean logic board issues, or a just a faulty lcd screen. Therefore I first check the motherboard in a “known good housing”, with a “known good battery” (or the DCPS) and with a “known good screen”. If the problem persists than you can assume it is indeed logic board failure. So: 1. Check history 2. Test in a known good housing, with a known good battery (or the DCPS) and with a known good screen. The board problem can be a clear problem (like no touch) or a general problem (like no boot). For each I follow different approaches. I always first remove the shielding with hot air.
5.1. No power
If the board doesn’t power on I start with connecting the DCPS to see if it draws any energy (Amps) before trying to power it on. If it indeed consumes Amps at that point i know there is a major short probably on VCC_MAIN. In this case i follow the procedure described in 4.1. On the iPhone 6 many times the capacitor next to the WiFi IC is to blame. If there is no history of water damage, than probably the board suffered a fall resulting in cold solder under a IC. In this case i follow the procedure described in 4.3. I also inspect the board for cracked components or other (repair) damage. As a last resort i replace the charge IC. There are more troubleshooting methods but those are lengthy and complicated. I believe these other methods are economically feasible for data recovery purposes only.
5.2. Specific problem
If the iPhone powers on normally, but (also) shows other malfunctions, I follow a different approach. If the problem is common like “no t ouch” or “no charge”. I replace the responsible IC for t hat function. Most of t he times that solves the issue. If the problem is less common I start inspecting the board. If there is visible damage I just replace the damaged component. I also check the screw brackets for long screw damage. If a component needs to be replaced you have two options. First find a part supplier to order the component. The values are shown in the ZXW tool. Second: take components of a donerboard (a board beyond repair). If I can’t locate t he reason for the malfunction I start consulting the step by step solutions provided by https://itesla.solutions. These contain a screenshot (part) of the logic board with a step by step approach to test the components on the line(s) responsible for a specific function. For example for “no backlight” .The solutions start with t he most easy t o repair failing component s, and move on t o end with the hardest to repair components. I will conclude this e-book with outlining how to perform each of these tests. Most of the solutions take the following approach: 1. 2. 3. 4. 5. 6. 7. 8.
Test these filters Test these capacitors Test these resistors Test the diode and/or the coil Test these lines Test these voltage Replace these I C’s Replace the PMIC
For testing filters and capacitors you set the multimeter to “continuity testing” (diode mode), usually it is pictured as follows. See the position of the knob. It is important to disconnect all power sources before try any testing as readings would not be correct. (Only for voltage testing the board needs to be powered on). To make reaching the smallest part easier I solder needles to the end of the two probes. One probe is negative (black) the ot her positive (red).
1. Testing filters A good filter beeps (has cont inuity) when holding each probe simultaneously on each side of the filter. If it doesn’t beep it is faulty and needs to be replaced. If replacement isn’t possible the line needs to be jumped. This means a piece of (insulated) wire is attached from one point of the line to another to make the current in the line flow again. See this video for a example. 2. Testing capacitors If a capacitor beeps when holding each probe simultaneously on each side of the filter capacitor it can mean two things: the capacitor is faulty, or the line on which the capacitor seats is shorted GND. To find out you'll need remove the capacitor and test if it still beeps when it is removed. If it doesn’t beep it still can be faulty. But it doesn’t have to cause a malfunction. I keep it to this level of inspection. A good capacitor shouldn't beep. 3. Testing resistors For t esting a filter you set the multimeter to Ohm-mode . For t esting hold each probe simultaneously on each side of the resistor. The value shown on t he multimeter should approach the value of the resistor. It is recommended to remove the resistor of board before testing. I do it while onboard.
4. Testing diodes and/or coils
/
This it often an important part for testing "no backlight". Diode testing: put the multimeter to diode-mode
.
Put black probe on the negative side of diode and red probe on the positive side .
The multimeter should show the letters OL, if you test the black probe to the positive side of diode and red probe to the negative side of the diode it should have the value for the diode(usually between 200-400 Ohm). This type of component must be soldered in the correct way, that is positive side of diode t o the positive side of the line, and negative the same way. Coil testing: put the multimeter to continuity-mode each probe simultaneously on each side of the coil.
. It should beep when holding
5. Testing lines For testing lines you have to put the multimeter to continuity -mode . For this test I put one probe on a the active side of a capacitor (the opposite one of GND), and the other one on another active part of the line. You can see the connected components on the line using the ZXW tool.
6. Testing voltages For testing a voltages you set the multimeter to Voltage-mode . For this test the IPhone needs to be turned on. One probe needs to put on the active side of a voltage carrying capacitor, and the other probe on GND. The voltage should have the indicated value.
7. Replacing a IC For replacing a IC a hot air station is needed. A complicating factor is that some IC’s have epoxy under fill and ripping off pads under a IC sometimes happens. If the missing pad is active you have to find a way to jump it. It can also be a NON CONNECTED pad (NC). In that case you can go without. The ZXW tool can be used to determine if the pad needs to be jumped. Jumping the pad involves most of the time trace repair. These repairs demand high skill.
For removing the IC hot air is blown onto the ic. Personally I use 380 ° Celsius with a light air flow. It s surrounding often need be prot ected against t he heat. Best practice is heat resistant tape and some coins used as heat sinks. T here is a danger of accidently moving other components causing new malfunctions. This mostly happens in the direct surroundings of the ic or on the opposite side of the ic on the ot her side of the board. After lifting the IC old solder on the pads on the board, and on IC itself needs to be removed. When using braid there is a danger of accidently ripping of pads. The best way to remove old solder is using a royally tinned well heated soldering iron. In most cases t he IC can be reused. Then it needs t o reballed. For reballing a stencil and solder paste is used. See this video fo r t he reaballing process. The IC needs to be replaced in the same position it came off. The ZXW tool is able to show the right position. For replacing the IC some flux is needed. Then the IC to is heated until the solder balls melt. Most of times you can see the IC falling nicely in to place when the melted
balls the solder of the board pads. A little tap on the side of the IC when the solder is still liquid confirms proper positioning. See this video. The PMIC ic is a little harder to reinstall because of it’s size and it’s tricky position on some boards.
