• All the BGA soldering problems you want to know are here


BGA is a type of chip package, the abbreviation of English (Ball Grid Array), the package pin is a ball grid array at the bottom of the package, the pins are all spherical and arranged in a pattern similar to a grid, hence the name BGA.

Many motherboard control chips use this kind of packaging technology. The memory packaged with BGA technology can increase the capacity by 2-3 times without changing the volume. Compared with TSOP, BGA has smaller volume, better heat dissipation and electrical performance.

BGA package pad routing design

1. Traces between BGA pads

When designing, when the spacing between the BGA pads is less than 10mil, no wires can be routed between the two BGA pads, because the line width and spacing of the wires exceed the production process capability, unless the BGA pads are reduced, and the spacing is guaranteed when making the production draft It is enough, but when the pad is shaved into a special shape, it may lead to inaccurate soldering position.

2. Resin plug hole electroplating filling in the hole in the plate

When the spacing between the pads of the BGA package is too small to be able to go out, it is necessary to design the hole in the pad, punch the hole on the pad, and route the wires from the inner layer or the bottom layer. At this time, the hole in the pad needs to be filled with resin plug hole electroplating , If the hole in the pad does not adopt the resin plug hole process, it will lead to poor soldering during welding, because the hole in the middle of the pad has a small welding area, and there will be tin leakage in the hole.

3. Via plug hole in BGA area

The via holes in the BGA pad area generally need to be plugged. However, considering the cost and production difficulty of the sample, the basic via holes are covered with oil. The plug hole method is ink plug holes. There are foreign objects or protect the service life of the vias, and when the SMT patch is reflowed, tin leaking from the vias will cause the other side to open and short.
4. Hole in PAD, HDI design

For BGA chips with small pin spacing, when the pin pads cannot be routed out of the process, it is recommended to directly design the hole in the pad. For example, the BGA chip of the mobile phone board is relatively small and has many pins. If the wiring is routed from the middle of the pins, the PCB can only be designed with the HDI blind buried hole wiring method. The middle hole is drilled on the BGA pad, the buried hole is drilled in the inner layer, and the inner layer wiring is conducted.

BGA soldering process

1. Printing tin height

The purpose of solder paste printing is to apply an appropriate amount of solder paste evenly on the PCB pad to ensure good electrical connection and sufficient mechanical strength when the SMD component and the corresponding pad of the PCB are reflow soldered. , Printing solder paste needs to make a stencil, and the solder paste passes through the corresponding openings of each pad on the stencil, and under the action of a scraper, the tin is evenly coated on each pad to achieve good soldering.

2. Component placement

Component placement is chip placement. Use a placement machine to accurately mount chip components to the corresponding positions on the PCB surface printed with solder paste or adhesive. The high-speed placement machine is suitable for mounting small and large quantities of components, such as Capacitors, resistors, etc., can also mount some IC components; general-purpose placement machine, suitable for mounting heterogeneous or high-precision components, such as QFP, BGA, SOT, SOP, PLCC, etc.

3. Reflow soldering

Reflow soldering is to melt the solder paste on the pad of the circuit board to realize the mechanical and electrical connection between the solder end of the surface mount component and the PCB pad to form an electrical circuit. As a key process in SMT production, reflow soldering requires a reasonable temperature Curve setting is the key to ensure the quality of reflow soldering. An inappropriate temperature curve will cause soldering defects on the PCB board such as incomplete soldering, virtual soldering, component lifting, and excessive solder balls, which will affect product quality.

4. X-Ray inspection

X-Ray can check almost all process defects. Through its perspective characteristics, check the shape of solder joints and compare them with the standard shapes in the computer library to judge the quality of solder joints, especially for BGA and DCA component solder joint inspection. Irreplaceable, no need to test the mold, the disadvantage is that the price is currently quite expensive.

Causes of bad BGA soldering

1. BGA pad holes are not processed

There are holes on the pads of BGA soldering, and the solder balls will be lost together with the solder during the soldering process. Due to the lack of resistance welding process in PCB production, the solder and solder balls will be lost through the holes close to the solder plate, resulting in the loss of solder balls.

2. Different pad sizes

The size of the pads for BGA welding is different, which will affect the quality and yield of the soldering. The outgoing wire of the BGA pad should not exceed 50% of the diameter of the pad. The outgoing wire of the power pad should not be less than 0.1mm, and can be thickened. In order to prevent the deformation of the soldering pad, the soldering blocking window should not be larger than 0.05mm, and the window on the copper surface should be as large as the line PAD, otherwise the BGA pads are made of different sizes.

Quickly Solve BGA Soldering Problems

It is not uncommon for related problems to be caused in production due to improper design in the early stage. So is there any way to solve production problems in advance once and for all? Here I have to mention a software that can perfectly avoid production risks: Huaqiu DFM.

1. Hole-in-Package

Use the Beton DFM one-key analysis function to detect whether there are holes in the plate in the design file, and prompt the design engineer whether there is a hole in the plate and whether the file needs to be modified. The hole is changed to a normal hole, which can reduce the cost of the product. At the same time, it also reminds the manufacturing board factory to design the hole in the plate, and needs to do the production process of the resin plug hole and the hole in the plate.

2. Pad to Pin Ratio

Use the Beton DFM assembly analysis function to detect the size ratio of the BGA pad in the design file to the actual device pin. If the pad diameter is less than 20% of the BGA pin, there may be poor soldering. If it is greater than 25%, the wiring space will become smaller. , at this time, the design engineer needs to adjust the ratio of the pad to the diameter of the BGA pin.

Beton has detailed solderability solutions for BGA pads and other issues. It helps users review the solderability of BGA design files before production, avoids solderability problems of BGA chips during assembly, and prompts that BGA chips have solderability problems. Solderability quality yield, etc.

At present, Beton engineers can realize the synchronization of manufacturing and design processes, and simulate the entire production process of selected PCB products from design, manufacturing to assembly.

Beton DFM makes the four modules of BOM arrangement, component matching, bare board analysis and assembly analysis interconnected, and work together to complete a complete DFM analysis!