Surface mount technology is known for its efficiency when it comes to electronic packages. One aspect that makes for an excellent surface-mount packaging is the Ball Grid Array, popularly known as BGA.
BGA package
Simply put a Ball Grid Array is a Surface Mount Component, which is an array of small conductor balls that come without leads. It is the solder balls that are responsible for passing the electricity from the package to the circuit board. Additionally, the BGA connects to the substrate which connects through wire bonding to the die. Electric signals are thus passed between the balls & the base.
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BGA offers many advantages that include:
- It is quite compact & does not occupy much board space. In a scenario where miniaturization of boards is an increasing trend, its advantage cannot be overstated.
- On account of its shape, it displays adhesion properties.
- It is known for its heat dissipation properties
- It is a good conductor of electricity
- It is known for its cost-effectiveness
Some aspects to remember while using BGA packages, however, are that:
- It requires extremely careful handling
- Post soldering, it is difficult to inspect the solder balls
Types of BGA Packages
There are broadly 3 main types of BGA Packages, as below:
1. Ceramic BGA Package
Here the substrate is made of ceramic. Typically, the solder balls composition includes 90% lead and 10% tin. This kind of package scores in terms of its coefficient of thermal expansion. It has a very high melting point and is known for its thermal conductivity & electrical performance.
2. Plastic Laminate BGA
It was first invented by Motorola and is extremely popular when it comes to double-sided PCBs. Here the substrate is made up of plastic. The other materials involved include Polyimides, dry clad, Bismaleimide triazine epoxy glass. In terms of solder ball composition, it is 63% tin & 37% eutestic lead.
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3. Tape BGA
The advantages that this array offers are multiple:
- The solder balls have fine lines with a flexible interconnect
- The chip and heat sink can face downwards. If you choose to do that you need to go with the flip-chip technology. If chips are facing up, wire bond is recommended.
- It typically works well for thin packages.
- It is known for its heat dissipation & electrical conductivity.
4. Enhanced Ball Grid Array
Essentially this contains an added heat sink which improved thermal performance. Chips always face down here & wire bond is used for conduction.
5. Flip Chip BGA
The substrate material in this case is BT resin. This kind of array is known for its electrical performance as well as its cost-efficiency.
Typically, the lead:tin ratio here is 63:37, that offers improved surface tension in the melting state.
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6. Metal Ball Grid Array
The substrate used in this array, is aluminum. It is known for both its thermal & electrical performance.
7. Micro BGA
As its name suggests this array is known for its small size & it therefore finds usage in several compact applications. The substrate in this case is packaging tape. It also has an elastomer layer that ensures that there addresses the stress between the tape & the chip.
BGA Package Sizes
Here are some best practices to follow when it comes to BGA package sizes:
- It is recommended that you use an NSMD pad size when it comes to BGA PCB designs of 0.4mm pitch.
- If you are using ball sizes of 0.5 mm pitch or less, remember not to reduce BGA pad sizes.
- When you are using ball pitches less than 0.4 mm, you need to create a bridging between NSMD pads
- With small pad sizes, solder mask webbings aren’t good enough as adhesive strength is compromised.
- There should be no traces on the external layers when it comes to BGA pads. On the internal layers, it is recommended to have one trace.
To Sum Up
The advantages of ball grid array for surface mount technology are immense. It is important that you take into account aspects such as weight of the product, heat generated and more, in making the right choice.
Hiring the right PCB manufacturer is also important. Contact Mer-Mar Electronics who have 40 years of experience in the PCB industry, Mer-Mar Electronics Provides PCB assembly, PCB design, and PCB fabrication services under one roof. Fill out the form below request a free quote or send us mail at sales@mermarinc.com.
