High Density Advances
As electronics become smaller and faster, supporting components must first be developed to achieve a smaller footprint. Increased density and reduced size give manufacturers less room for error, and better machining methods must be developed.
Handling higher density connectors on printed circuit board assemblies creates complex issues that must be addressed. Designers must consider the processing temperature, producibility and solder joint integrity of each component. The increased density is due to the need for higher I/O connectors in the same space that used to be occupied by much lower I/O connectors.
Traditional through-hole or surface mount connectors have reached the limit of the number of signals (pins per square inch) that can be effectively used in these applications. This is where connector manufacturers consider utilizing BGA, solder crimp and solder charge designs to reduce component footprint.
Solderability
Solderability issues are usually easy to fix with double row connectors. Not to mention, if there is a problem, it can be fixed with rework by using a simple soldering iron to correct the solder joints. On multi-row connectors, however, the process becomes more complicated and it becomes more and more important to get the connector right the first time.
Some Common Problems That Can Cause Bad Solder Joints Are：
Solder paste volume
Template size
Incorrect oven temperature curve
PCB flatness
There is no one-size-fits-all solution to the problems listed above, as each manufacturing setup is unique. Some of the differences that must be considered are the equipment being used, the solder paste (brand and chemistry) and the application (board design, component density, etc.).
Connector Solutions for High Density I/O Needs
One of the solutions connector manufacturers use for high-density applications is the BGA setup. BGA applications use ball solder balls attached to component leads to provide more solder without heavy solder paste.
Another unique difference in SEARAY™ 0.8mm (SEAF8/SEAM8 series) solder charge is the alternating pitch of 0.80mm and 1.20mm. This design can provide the board designer with additional row-to-row trace routing.
Alternate spacing of SEAF8 / SEAM8
The key to better solder joints during machining
In general, it is best to follow the manufacturer’s machining guidelines for maximum soldering of the part to the PCB. Some manufacturers provide PCB footprint, stencil layout and thickness, solder screen printing process, component placement, proper oven outlines, and even rework considerations.
Footprints and Templates
Connector manufacturers often offer PCB designers the ability to download PCB footprints along with stencil layouts and thicknesses. Samtec offers over 200,000 symbols and footprints for download in popular EDA tools like Altium, Circuit Studio, Eagle, Fusion 360 and more.
By utilizing the provided package and stencil layouts, the PCB designer has a higher chance of achieving correct solder joints.
Solder Screen Printing Process
Pad coverage is critical for proper solder joints and should cover the pads completely. For this reason, the aperture size in the stencil is intentionally larger than the pads on the PCB. This is to ensure that the solder on the SEAF8 (or the connector) is in contact with the solder paste, as shown in Figure 4.
The solder position is relative to the solder printing, and the contact between the solder paste and the solder is good.
If the solder paste does not cover the solder properly, proper wetting cannot be achieved. Automatic detection is used to ensure correct solder coverage on the PCB. It is recommended to reject, clean and reprint any incompletely covered pad components.
Place Components
Automatic pick and place equipment will ensure the correct placement of components. For proper solder wetting, it is important that the Z-axis dimension fully fixes the solder on the PCB surface.
When the solder is reflowed in the oven, the weight of the connector will cause the connector to settle on or near the board after handling. This phenomenon helps reduce any coplanarity in the connector.
Correct Oven Analysis
At this point, most surface mount components should be able to handle the lead-free reflow profile described in IPC/JEDEC J-STD-020. The specification requires that components must be able to withstand peak temperatures of 260°C and 30 seconds above 255°C.
During reflow, a low oxygen environment, usually achieved by injecting nitrogen, will help improve the wettability of the solder surface. For high density connectors like SEAF8/SEAM8, it is recommended that the soldering process be done only in nitrogen rich environments.
Proper analysis of fully populated PCB assemblies is critical. The reflow process that forms solder joints is often overlooked, but it is critical to ensure that solder joints are formed correctly.
To ensure the solder reaches the desired temperature, it is recommended to place the thermocouple through the back of the board into the center of the connector and on the outer edge. This will ensure that the solder paste manufacturer’s reflow profile parameters are met.
The Growing Importance of Getting It Right
While no process is ever without defects, using the proper processing settings will eliminate the need for rework, scrap, and reduced profits. This importance will continue to increase as electronics become smaller and their components become denser.
About Wonderful
Shenzhen Wonderful Technology Co., Ltd. is China’s top model and small batch circuit board manufacturer.
The company targets precision circuit board samples and small batches as the main target market. Since its establishment, it has adhered to the development concept of good quality and important reputation.
Invest huge sums of money to introduce advanced equipment, strictly regulate the operating standards and QC standards for incoming and outgoing materials, to ensure that the shipped products reach Seiko quality.
The self-developed ERP management system can realize the whole process of paperless operations such as online ordering, online payment, online production progress query, online logistics tracking, and online statistical report production, which greatly improves work efficiency.
It ensures that each order can be shipped quickly. After more than ten years of development, the company’s products and services have been well received by the market.
As well as the opening of an electronic component mall, integrated circuits, semiconductors, resistors, capacitors and other products are sold.
The company’s scale is developing rapidly, and the sample and small batch shipment capacity reaches 500 models/day.
The products are widely used in communications, medical equipment, industrial control products, aviation, military products, testing instruments,Automotive, computers and other peripheral products.
We will continue to pay attention to customers, with efficient delivery speed and perfect after-sales service, to become the most trusted brand supplier in the PCB industry.
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