IC packaging refers to the process of electrically and mechanically connecting an integrated circuit to external circuits. The purpose is to protect the chip from physical damage and environmental factors while providing electrical interfaces to connect with external circuits. Ball Grid Array (BGA) is one such packaging variant. Known for its high-density pin layout, excellent heat dissipation, and outstanding electrical properties, BGA has become the mainstream packaging technology in modern electronic devices. However, due to frequent use, failure issues are inevitable, and the concealed solder joints design makes rework more technically challenging.
This article systematically explains the key steps and methods for BGA rework, based on the structural characteristics of BGA and practical repair experience. The goal is to provide technicians with a practical and detailed rework guide, effectively addressing common issues encountered during repair and improving work efficiency and rework quality.
Challenges in BGA Rework
As a high-performance, high-density electronic packaging technology, BGA components differ significantly from traditional components. For example, the I/O terminals of BGA packages are typically arranged in round or column-shaped solder joints, distributed in a grid array on the bottom of the package, rather than being connected by two long leads like traditional components.
While this unique design offers higher pin density and improved reliability, it also increases the difficulty of soldering and rework. Since the solder joints in BGA packages are completely hidden at the bottom, operators cannot visually observe the melting and solidification of the solder joints during the process. This poses a challenge for temperature control: if the temperature is too high, it may damage the package, while if it is too low, the solder joints may not melt sufficiently.
Moreover, the hidden nature of the solder joints limits the use of traditional inspection methods, making it harder to assess solder quality, which further raises the technical barrier for BGA rework processes.
Types of BGA Package
Although the general rework process for BGA components is similar, subtle differences may arise due to variations in packaging materials and structures. Therefore, before starting BGA rework, it is crucial to accurately identify its type and match the corresponding process parameters and details. Based on the packaging materials and structures, BGA can be categorized into four types: PBGA (Plastic Ball Grid Array), CBGA (Ceramic Ball Grid Array), CCGA (Column Grid Array), and TBGA (Tape Ball Grid Array). Among these, PBGA and CBGA are more commonly used in modern electronic manufacturing.
PBGA packaging uses plastic as the primary material, and the solder balls are typically made from a 63/37 (lead-based) or 305 (lead-free) alloy, with corresponding melting points of 183°C and 217°C, respectively. Although plastic packaging results in lower costs and simpler processes, it also brings some issues, such as high moisture absorption, which can cause solder joint cracking or component damage. Therefore, prior to PBGA rework, it is essential to properly dry the component to avoid the adverse effects of moisture absorption.
CBGA packaging uses ceramic as the primary material, and the solder balls are generally made from a 90Pb/10Sn alloy, with a higher melting point that makes the solder joints more robust in high-temperature environments, capable of withstanding higher operating temperatures. Because ceramic packaging is sturdier and less prone to moisture absorption, CBGA reduces issues during the rework process. Additionally, the solder joint diameter in CBGA is typically larger than the PCB pad diameter, meaning that when the CBGA chip is removed, the solder does not remain on the PCB pad, reducing the difficulty of cleaning the pads. Therefore, compared to PBGA, CBGA rework is less challenging.
Next, this article will use PBGA as an example to provide a detailed explanation of the rework process and practical techniques.
Complete BGA Rework Process
Step 1: Preparation
- Drying:
During the BGA rework process, drying is often an overlooked detail. As mentioned earlier, PBGA components have a strong hygroscopic nature, and the primary purpose of drying is to remove moisture from the component.
It is important to remove all temperature-sensitive components, such as optical fibers, batteries, and plastic parts (e.g., handles), before drying. This ensures that these components are not damaged by high temperatures.
Additionally, must be desoldered, ball implanted, and re-soldered within 24 hours after drying to ensure the quality and reliability of the solder joints.
- Component Protection:
Although temperature-sensitive components have been removed, this alone is not enough. If there are other components within a 10mm radius of the rework area, such as heat sinks, inserted oscillators, electrolytic capacitors, plastic light guides, low-temperature barcodes, or BGA sockets, high-temperature adhesive tape should be applied in 5 to 6 layers on their surfaces for additional protection.
- Support and Nozzle:
For PCB wider than 100mm, it is recommended to add supports to the workstation heating platform. The support rods should be positioned at the center of the PCB to ensure the board remains flat and prevent contact with sensitive components. For the nozzle, it should be 2 to 5mm larger than the BGA component.
- Desoldering/Soldering Curve:
The actual temperature of the BGA solder balls is influenced by several factors, including the size of the BGA, the packaging material, and the efficiency of the heating system. Therefore, it is best to measure the temperature curve before desoldering/soldering. If the workstation already has stored rework curves, verifying their accuracy is sufficient; otherwise, a new temperature curve must be created.
The method for creating the temperature curve is similar to the reflow temperature curve in SMT: Use a test board identical to the rework PCB, drill holes at the bottom of the BGA component to insert a thermocouple, and use high-temperature solder or epoxy resin to secure it.
Common temperature curves come in two types: platform (soaking) and tent (continuous) temperature curves. The platform curve maintains a constant temperature for a set amount of time, while the tent curve gradually increases in temperature until it reaches the target peak temperature after entering the furnace.
Since the temperature zones of rework stations are limited, a tent-shaped temperature curve is typically preferred. The heating rate should be controlled at or below 3°C/second, and the cooling rate should not exceed 5°C/second to avoid impacting soldering quality. During temperature curve creation, it is crucial to fully preheat the bottom of the PCB to prevent warping caused by uneven heating.
Step 2: Desoldering
Desoldering is the process of removing the BGA component from the PCB board, and it is relatively simple as long as the proper temperature curve is chosen.
Based on the physical properties of BGA packaging, all solder joints are located between the package and the PCB, and the heating and melting of the solder joints mainly rely on the heat transfer between the package and the PCB.
After the desoldering procedure is complete, the equipment will automatically remove the component. If the surface is rough or uneven, tweezers can be used to assist in removal.
When using tweezers to assist with removal, gently lift the component to ensure the solder joints are fully melted before picking it up. Never use excessive force to avoid causing unnecessary damage to the pads.
Step 3: Cleaning the Pads
After desoldering, solder residue and contaminants are often left on the BGA pads and PCB pads, so it is essential to clean these residues thoroughly before re-soldering the BGA. This process is usually done using a flat soldering iron tip and desoldering braid. The cleaning process is as follows:
- Place the desoldering braid on the pad surface and gently press the soldering iron tip onto the braid.
- Heat for 2 to 3 seconds to melt the solder and allow it to be absorbed into the braid.
- After desoldering, avoid dragging the braid; instead, gently lift both the braid and the soldering iron.
- After removing contaminants, use an appropriate solvent to clean the pad area, ensuring the surface is clean and free from contaminants.
Step 4: Ball Placement
Although the BGA component can be reused after desoldering, the solder balls on the bottom of the BGA may be damaged to varying degrees during the desoldering process, so they need to be replaced. It is essential to emphasize the importance of auxiliary materials. While flux paste and solder paste can be used, solder paste is more recommended because it effectively prevents solder ball bridging in a hot air reflow environment.
The choice of solder balls should be based on the component’s datasheet and typically falls into the following categories:
- Composition: Lead-free 305, leaded 63/37, and 90Pb/10Sn for CBGA.
- Size: Common sizes include 0.3mm, 0.4mm, 0.5mm, 0.6mm, and 0.7mm.
When choosing, ensure the composition of the solder paste and solder balls matches, and the diameter of the solder balls should be slightly smaller than the original solder balls so that after merging with the solder paste, they approach the original solder ball size.
There are three methods for ball placement based on tools and materials: multi-purpose ball placement machines, dedicated ball placement machines, and universal ball placement machines. Regardless of the method, the basic process is the same: printing solder paste – ball placement – heating. Below is the detailed process using a multi-purpose ball placement machine:
- Choose a template that fits the ball size and pitch, ensuring the template holes are typically 0.05-0.1mm larger than the solder ball diameter.
- Secure the template to the base, evenly sprinkle the solder balls, and gently shake the ball placement machine to allow excess solder balls to roll into the collection tray, ensuring one solder ball remains in each hole.
- In the rework workstation, secure the BGA pad side of the PCB with the printed solder paste downward and adjust the alignment of the template with the pads using a visual alignment system.
- Use the nozzle to pick up solder balls from the template’s surface and carefully place the component for heating.
Step 5: Solder Paste Printing
When re-soldering the BGA component, you still need to choose auxiliary materials, either flux paste or solder paste.
Flux paste is easy to operate and does not require a stencil, making it suitable for small-scale repairs. However, it is less stable when dealing with larger BGA components. When applying flux paste, it is recommended to use an ESD-safe anti-static brush to apply multiple layers to ensure even coverage with no buildup or debris left behind.
In contrast, solder paste requires the use of a stencil but offers better adhesion, which compensates for PCB warping due to thermal deformation and enhances the soldering process. First, position and tape the stencil to the PCB (to secure the stencil and prevent solder paste spillage). Then, align the stencil openings with the pads without any misalignment. Finally, use a scraper to take an appropriate amount of solder paste and scrape it over the small stencil openings.
Step 6: Visual Alignment
Place the PCB with the applied auxiliary materials onto the workstation and use the workstation’s alignment system to precisely adjust and ensure the component and pad images are perfectly overlapped. If flux paste is used in the previous step, the component can be manually placed, using the silkscreen frame as a reference for alignment. However, if solder paste is used, BGA placement must be done with the equipment, and manual handling is strictly prohibited.
After the component is placed and before the soldering begins, ensure the height of the reworked component is uniform and check for any tilting or height discrepancies.
Step 7: Soldering
Once all the previous steps are confirmed to meet the standards and the component placement is accurate, proceed with the soldering process. Since BGA components are surface-mount devices, reflow soldering is used for soldering.
Choose the appropriate temperature curve program based on the component specifications to heat the BGA, ensuring the temperature variations during the soldering process are within the required limits. After soldering is complete, allow the board to cool naturally before taking it out.
BGA Rework Common Issues Analysis
Warping and Deformation
As mentioned earlier, the BGA rework process involves multiple heating steps, including desoldering, ball placement, and soldering. Each heating phase introduces thermal shock to the chip and PCB, increasing the risk of chip warping and PCB deformation. According to statistical data, after rework, the probability of BGA chips experiencing warping or delamination can be as high as 5%.
Therefore, during all heating processes, it is crucial to strictly control the temperature. The preheating time should be extended, the bottom heating temperature should be increased, and the top heating temperature should be lowered, all while ensuring the maximum temperature and reflow time conditions are met to reduce the risk of thermal damage.
Short Circuits and Open Circuits
There are several reasons for short circuits occurring on reworked circuit boards, such as uneven solder paste application, insufficient drying, or damage to the solder mask when cleaning the pads. Open circuit issues may arise from factors like improper soldering curves, incorrect choice of soldering materials, or failure to perform drying before soldering. Ensuring the accuracy and compliance of each step in the rework process is key to avoiding these problems.
Ending
Although manufacturers continuously enhance training for rework technicians and strive to improve BGA rework technology, no matter how advanced the technology becomes, the life of the chip will still be affected by multiple thermal shocks, leading to a decrease in its stability. Therefore, in addition to improving rework capabilities, optimizing the manufacturing process, managing equipment, and handling materials and personnel are equally important. Ensuring smooth SMT assembly, improving yield rates, and minimizing BGA rework are the most cost-effective strategies!
You Might Be Interested
Master the complete BGA rework process with our detailed guide. Learn step-by-step techniques for safe desoldering, cleaning, ball placement, and re-soldering. Improve your skills and efficiency while overcoming common challenges in BGA repairs.
BGA (Ball Grid Array) packaging revolutionizes chip protection and heat dissipation in electronics. Unlike traditional methods, BGA arranges solder balls in a grid beneath the chip, offering controlled soldering and enhanced stability. Despite challenges, BGA variants cater to diverse applications. Successful BGA PCBA involves strategic design, precise pick-and-place machine placement, reflow soldering, and X-ray inspection for defect identification, ensuring reliable electronic components.
Learn the essential steps in BGA reballing, from material selection to four effective methods. This guide covers everything from desoldering to reflow soldering, helping you restore components for improved performance and cost savings.
Explore the key differences between QFN and BGA packaging technologies. Learn about their unique advantages, applications, and how to choose the right one for your project needs. Ideal for electronics designers and engineers.
Choosing the right partnership model is crucial for effective PCBA project management. Turnkey PCB assembly services offer strategic advantages and insights. In this article, TechSparks explores the benefits and implementation of turnkey, enhancing project management in the PCBA industry.
SMT, or Surface Mount Technology, is a widely adopted assembly technique in the electronics industry. It involves mounting smaller Surface Mount Devices (SMD) directly onto printed circuit boards, offering advantages such as automation, high quality, miniaturization, improved performance, and cost-effectiveness. SMT has become popular due to its ability to optimize production efficiency, enhance product quality, and promote miniaturization trends in electronic devices.
Discover the top 5 SMT PCBA pick and place machines that are revolutionizing electronics manufacturing. Whether you need speed, precision, or versatility, our guide helps you choose the perfect machine for your production needs. Click to explore the best options!
Learn the essential steps and industry standards for performing PCB rework, from inspection and desoldering to cleaning, re-soldering, and final testing. Discover how to ensure high-quality results, minimize rework risks, and extend PCB lifespan with expert techniques.