BGA Substrate: The Ultimate FAQ Guide

Choosing a suitable BGA substrate requires in-depth knowledge.

In this guide, you will find all information you need to know about BGA substrate.

So, keep reading to learn more.

What Is A BGA Substrate?

A BGA substrate is a carrier that you will use with several versions of BGA packages.

Complex devices such as microprocessors require that the BGA substrate offer several varying interconnections pins.

Besides, the design process of the pins and their integrations into the BGA substrate package can be tasking.

BGA substrate

BGA substrate

What Substance Will You Use When Making A BGA Substrate?

BGA packages use organic substrates and not lead frames in their construction.

The material that makes up the BGA substrate can either be:

  • Polyimide

Polyimide

polyimide

  • Bismaleimide

Bismaleimide

Bismaleimide

Why Is It Necessary To Design A BGA Substrate Automatically?

Most of the designs about BGA substrates happen through the use of an automatic device.

This is because of the following reasons:

  • The design entails the use of numerous pins
  • It is simple for computerized systems to determine the shortest route for each pin

Besides, the automatic process happens via EDA design software.

Also, there is some form of human interaction during the editing process of high-density designs.

However, modern BGA substrate designs happen mainly through the use of software and computer systems.

What Should You Consider When Designing A BGA Substrate Design?

Some considerations when it comes to designing BGA substrates entail the following:

  • Using shorter leads
  • Signal integrality
  • Power planes
  • RF performance

What Is Ball Pitch In A BGA Substrate?

The ball pitch is the distance that sits between the center parts of a single BGA ball to the other.

For instance, the space can be as small as 0.2 mm.

ball pitch

ball pitch

What Are Some Features Of A BGA Substrate?

Some of the features you may find entail the following:

  • Takes up less space on boards
  • Low inductance
  • No presence of leads to bend
  • The high amount of lead count
  • It self-centers when conducting reflow processes, hence minimizes issues relating to placement during surface-mount soldering
  • A low thermal inhibition between printed circuit boards and BGA packages enhances the cooling process and prevents overheating

What Challenges Will You Encounter While Conducting BGA Substrate Routing?

Routing BGA substrates have complex challenges that are worth considering when designing your printed circuit boards.

Some of these challenges entail the following:

Manufacturability

Some certain limitations and rules depend on how you route the BGA substrate connection with one another, and externally.

Some limitations depending on the manufacturers’ capacity include:

  1. Number of layers
  2. Size of vias
  3. Angle of pitch
  4. Drilling hole type, etc.

Signal Integrity

One of the main issues about signal integrity is the control of impedance.

This tends to affect reflections and transmission.

Some processes you can use to control impedance include the following:

  1. Employing the right thickness of the dielectrics
  2. Matching the width traces between the return lines and the forward lines
  3. Installation of plane references between the signal layers

Besides, you can effectively lower crosstalk when you install ground or reference planes between signal traces adjacent to one another.

It is important to maintain the space between the traces when signals originate from similar layers.

Reliability

How reliable your circuit board is relies on its quality of construction and how you synchronize your design with the capacity of the fabricator.

If you fail to synchronize the board, you can have a board that is limited in its functionality as per the design.

Also, the board may malfunction once you start using it.

Examples of material problems that may cause it to fail during operation include:

  1. Weight of copper
  2. Structure of copper grain
  3. The thickness of the solder mask
  4. Ionic contamination
  5. Trace routing
  6. Type of via

What Are Some Types Substrates You Can Use To Make BGA Packages?

BGA packages are of varying subtypes and this relies on the materials and other substrates in them.

Besides, all these types will employ solder joints that connect the BGA package substrates to the printed circuit board.

These packages can be found in the following categories:

  • Ceramic BGA

tape BGA

Tape BGA

  • Plastic laminate BGA

plastic laminate BGA

plastic laminate BGA

The composition of soldiers is important when reballing the various types of BGA substrates.

To ensure suitable levels of conductivity, you should ensure you balance the metals within the solder.

Besides, a suitable solder structure makes sure the reballing work is durable.

Ceramic BGA

This BGA package will use a ceramic substrate material.

Several varieties within the ceramic BGA entail LGA and CCGA.

Each pin in ceramic BGA costs more than those of plastic BGA packages.

However, some applications need ceramic BGA.

For instance, devices that need more pins on the flip-chip designs will employ this package style.

Besides, plastic BGA is not able to achieve the pin density for these applications.

Also, the ceramic BGA operates favorably with the flip-chip designs.

The solder balls contain 10% of tin and 90% of lead.

This enhances the reliability of ceramic BGA.

It will also assist in overcoming the coefficient of thermal expansion differences that occurs between the circuit board and the BGA substrate.

Besides, you can also locate ceramic column grid array [CCGA].

This BGA package employs twice the available contact points compared to the basic BGA.

Besides, CGA solder joints last almost three times that of BGA.

Plastic Laminate BGA

This type of BGA uses plastic as the substrate material.

The solder balls in plastic laminate BGA occupy 63% tin and eutectic lead occupies 37%.

Plastic laminate BGA substrate can withstand temperature ranges that reach up to 150 °C.

The material choice for plastic laminate BGA substrate include the following:

  1. Polyimide is a form of laminate plastic
  2. Dry-clad which is a laminate that is epoxy-based, proprietary from IBM
  3. Bismaleimide triazine epoxy glass which is also known as BT epoxy glass

Besides, you can include flip-chip designs with plastic laminate BGA to enhance connectivity between printed circuit boards and the package

Tape BGA

This BGA employs flexible interconnections that form fine lines within the solder balls.

Besides, tape BGA performs better in matters thermal.

Another BGA that relates to tape BGA is metal BGA.

This version of the BGA package entails the use of a simple form design comprising of aluminum substrate.

The design of metal BGA offers the same outcome even though it lacks flexible layers of tapes that tape BGAs use.

To connect the aluminum base to solder mask, metal BGA employs thin films and microchip module technologies.

Besides, the thermal performance and electrical performance of tape BGA and metal BGA are outstanding.

LGA Type Package

This type of package stands for land grid array.

Besides, LGA leads to the introduction of the BGA substrate package in the 90s.

This is because it uses solder balls that connect the circuit board and the package.

LGAs that employ sockets have pins that will connect the circuit board to the socket.

Some LGAs contain direct connections to the printed circuit board via the use of solder and not a socket.

Similar to the BGA substrate package, the LGA substrate package does not contain balls, but rather contains flat solder contacts.

PoP Type Package

The PoP represents a package-on-package and represents double-stack designs.

Besides, the upper chip contains the random access memory [RAM] whereas the lower chip contains the CPU.

The design of the PoP type package enables you to fit several packages in small configurations on the PCB.

Flip-chip

The design placement of this version will face downwards.

Besides, any of the flip-chip surfaces may contain connections through the joints of the solder ball.

The benefit of this design is the short distance and lowering inductance.

QFN type of package falls under the category of QFP that lacks lead.

This is because QFN represents a quad flat pack with no pins of leads.

QFN Type Package

This stands for a quad flat pack.

It is a version of a surface-mounted chip that will use the entire four sides to relay the lead.

Besides, since it uses all four sides, it gives this BGA package its quad name.

They comprise ceramic and plastic substrate materials.

Ceramic QFP lacks gull-wing leads whereas plastic QFP contains them.

What Precautions Should You Follow To Ensure You Perform A Good Soldering Process On A BGA Substrate?

These include:

  • The use of ample heat make sure all balls within the grid sufficiently melt to form strong bonds on all BGA solder joints
  • Surface tension ensures the balls remain in place till the solder cools and solidifies.

Ensure correct temperature during BGA soldering to ensure a solid solder joint and minimize short-circuit

  • Ensure the composition of solder alloy and temperature are correct so that the solder remains semi-solid and does not melt away.

This allows the balls in the grid to stay in separate areas.

Which Method Will You Use To Inspect Solder Joints Within A BGA Substrate?

It is impossible to employ optical methods to inspect BGA substrates since solder joints are out of sight below the BGA parts.

Also, you cannot use electrical tests since they are less reliable as they show the electrical conductivity of BGA substrates instantly.

The test does not indicate how long the solder will last as it may fail at some moment in time.

Therefore, the suitable method to inspect these joints is using X-ray tests.

This is because the X-ray penetrates the components and allows you to view the joints hiding beneath.

For this reason, automatic X-ray inspection is the most widely used method to inspect the BGA substrates.

Can You Rework A Faulty BGA Substrate?

Yes, you can repair a faulty BGA substrate when you find that components are faulty.

To perform this task, you begin by applying heat to the solder joint to melt it away.

This process happens by locally heating the faulty BGA substrate part, causing the solder to melt.

During the reworking process, you will heat the component in special reworking units.

This unit has the following constituents:

  • Infrared heaters
  • Thermocouple that will monitor the level of temperature
  • Vacuum system that raises the BGA packages

Besides, ensure that you carefully heat the only faulty component without causing damage to other surrounding parts on the circuit board.

What Are The Benefits Of Using A BGA Substrate?

There are numerous reasons why the BGA substrates are popular in several modern applications.

These entail the following:

High Pin Density

To enhance the price, performance, or features of packages, manufacturers will increase the pins.

Concurrently, they would lower the quality of the package as the pins are close together and lead to weak solder joints.

However, BGA substrates contain multiple pins which maintain the integrity of solder joints and the reliability of the package.

Low Inductance

The connecting conductors in BGA substrates are short thereby lowering the signal inductance,

This in turn enhances electrical performance while minimizing inductance.

Suitable Heat Conduction

The short distance and lower inductance between the printed circuit board and BGA substrate are beneficial.

They lead to low thermal resistance between two parts thereby enabling ample heat flow via the circuit board.

Also, they have a lid that enhances heat dissipation thereby lowering overheating of the chips and chances of thermal degradation.

Performs Better At High Speeds

Several benefits of BGA substrates increase their electrical performance than other IC package types.

Since BGA substrates have connections at the lower part of the chip, it means they are short.

Thereby, the BGA substrate will perform at high rapid speeds and perform exceptionally.

High Reliability

The pins present in quad flat packages are thin and fragile.

This means that damages are likely to occur in these setups and when it happens, it is nearly impossible to repair them.

However, the connection solder pads in BGA substrates are sturdy, allowing you to achieve reliable connections.

What Are The Limitations Of A BGA Substrate?

Some of these drawbacks include the following:

Costly

BGA substrate packages cost more than the standard IC packages.

Some of the elements that add to the cost include the substrate and the bumping technique.

Difficult To Inspect

The soldering process enhances the performance of BGA substrates and the entire circuit.

However, it comes with some drawbacks such as not being able to inspect the package after soldering on the printed circuit board.

This means it is tasking to check for potential issues that need immediate repair.

Therefore, you need to use X-ray inspection to check the internal parts of the BGA substrate.

However, this process is costly.

How Does An LGA And BGA Substrate Compare?

LGA stands for land grid array while BGA stands for ball grid array.

Besides, you will solder BGA substrates on the circuit board meaning you cannot plug them out or replace them.

LGA sustrate

LGA substrate

However, you can plug and unplug LGA and even replace it from the motherboard.

BGA substrates contain round contacts which you will solder on the circuit board.

LGA has flat surfaces that contact the circuit board’s socket containing many pins.

Can You Perform Reflow Soldering On A BGA Substrate?

Yes, reflow soldering is used when soldering BGA substrates as it assists the whole system to attain a standard temperature.

This temperature melts the solder balls beneath the BGA substrate components.

BGA substrate

 BGA substrate

When soldering the BGA substrate, solder balls have a specific solder quantity.

After placing, in the reflow oven, the board with solder balls on the BGA substrate melts due to the heat.

Surface tension will cause molten solder to hold the BGA substrate in the right place on the circuit board.

Besides, ensure the solder has the right composition that will allow it to maintain a semi-solid state.

What Is The Future Of BGA Substrate?

BGA substrate is gaining popularity and will continue being used even in the future years.

Besides, with new technological advancements, there are new variations of BGA substrates.

Also, these BGA packages are affordable and offer impressive electrical performance standards.

The main types that will influence the future of BGA substrate include the following:

eWBL

This stands for embedded wafer level BGA and it contains an interposer within a bumped die.

It offers several benefits like high current carrying capability, better electrical performance, affordability, small configuration, etc.

WLCSP

This stands for a wafer level chip scale package which is a version of a bumped die.

Besides, this package is small and has great thermal and electrical characteristics.

Also, it offers excellent connectivity that assists in maintaining low inductance and resistance.

They are common in everyday gadgets such as smartphones which experience frequent vibration, stress, and drops.

What Are The Applications Of A BGA Substrate?

BGA substrates are gaining popularity with time as they offer several benefits.

Some of the areas which employ BGA substrates include:

  • Graphic processors
  • ASIC for routers and servers
  • MPUs that find their use in highly tuned game consoles
  • The automotive industry requires high reliability
  • Image sensors
  • Chipsets

What Should You Consider When Placing Components On A BGA Substrate?

If you are working with complex components, you need to plan how to route every part successfully.

BGAs with high pin-count require meticulous planning during the design process as it needs to design escape routing patterns for each net.

This requires you to plan on how to place parts before you start routing the traces.

Begin the placement floorplan with fixed parts like IO, switch, connectors, etc.

Ensure you consider thermal management of the board to ensure the BGAs receive constant airflow to remain cool.

Place the memory chips and processors close to their respective off-board connections.

This means you will avoid using long trace lengths along the whole board.

Also, ensure all components fit cleanly with traces not wandering far from reach.

When beginning the placement process, ensure the BGA parts have enough room to cater for routing.

Ensure they contain ample bypass capacitors next to their associated pins.

Also, sequentially place signal path components between the signal load and source.

This process may be tasking, hence prepare to be interactive when finalizing component placement.

Another factor to consider is that you need to make the design with suitable power integrity besides good signal integrity.

This entails placing power supplies near areas that they are supplying without mixing the circuitry with sensitive parts of the BGA.

After placing the components optimally, you can begin the routing of the BGA substrate nets.

What Tips Are Important When Routing Traces That Connect BGA Substrates?

Begin by panning escape routing from the surface-mount fine-pitch parts, such as the BGA substrate components.

Ensure you plan the escape routing by considering the following:

  • Layer stack up
  • Routing density
  • Signal integrity requirements
  • Placement of components

Besides, you require high-density interconnect and layer boards for BGA substrates with high pin-count.

However, confirm with our PCB fabricator the cost and their capacity to construct the HDI board.

When routing vias and escape traces out of the BGA substrate, begin with the extreme rows.

Then continue operating inwardly through the pin rows.

Some vias you can operate with during this process include the following:

  • Blind and buried vias which penetrate a portion of the substrate
  • Thru-hole vias which you create using mechanical drills and drill through the board
  • Micro vias which you will drill using a laser as they are small

I know you may be interested in:

SMT Assembly

Through-Hole Assembly

For all your questions on BGA substrate, contact us now.

Scroll to Top