World Class Custom Prototype PCB Assembly Manufacturer in China
PCBMay is a Professional Prototype PCB Assembly Manufacturer in China,Who Provides Many Different Kinds of Prototype PCB Assembly.
Only an expert and professional company can accelerate prototype pcb assembly process, easier, and better. The use of stencils for PCB assembly is becoming an increasingly common approach with the transition to SMT components and the ever-growing number of components used.
Main Advantages of Prototype PCB Assembly
Lead-free PCB Assembly
PCBMay doesn’t only build lead-free circuit boards but also provide RoHS Compliant PCB assembly services:lead-free material analysis,single and double-sided assemblies,wave soldering of lead-free,lead-free circuit board rework,lead-free selective soldering and much more.
Consignment PCB Assembly
The client provides the necessary components in the consignment PCB assembly process.It seems reasonable to go with the consignment PCB assembly process if you manufacture expensive products having exclusive parts. This will ensure that your product is not replicated and yet the manufacturing process stays cost-effective.
Mixed Signal PCB Assembly
Mixed signal PCB assembly is now very popular because using this design of the PCB board(hybrid PCB) actually reduces the cost in the long run. Thus mixed-signal IC’s are actually a staple in consumer electronics. Thus mixed-signal print circuit boards are great for prototyping and for low volume production as well. This board is best to incorporate custom designs efficiently.
What is Prototype PCB Assembly Process
A prototype of a printed circuit board is its technological model,created as a result of design and construction,but has not yet been put into mass production.
Further testing and examination of the prototype allows developers to:
- Identify and eliminate inaccuracies
- Design errors
- Defects in the created printed circuit board
Having tested the prototype,the customer can check how functional and efficient the newly designed printed circuit board is.How it meets certain technological requirements?
The direct manufacturer of the future series of printed circuit boards,in turn,having studied the Prototype PCB Assembly,can correlate the actual production capabilities with it,adjust something,improve and rationalize.
Why a Prototype is Important before Mass Production
In the process of designing a printed circuit board,it is almost impossible to avoid mistakes and inaccuracies.This is why starting mass production without testing a prototype is likely to result in a large number of defective items.As a result,the project as a whole will receive a significant but senseless rise in price.Its implementation will stretch over time.
The process of creating a prototype circuit board involves a fairly large number of stages.This process begins with the:
- Definition of the characteristics of the circuit.
- Then the stage of designing the circuitry of the board
- Then the stages of designing the board at the physical level and its production
The entire process is completed by Prototype PCB Assembly.
Prototype PCB Assembly Process
1,Solder Paste Application
At the beginning of the assembly process,solder paste must be applied to a new,component-free PCB. Solder paste is applied only to those areas of the board where you need to create conductive contact between the component and the metallized mounting pad.
Typically,a soldering stencil is used for this.Moving along the solder mask placed directly on the board and fixed in the desired position,the slider squeezes a small amount of solder paste onto the board through the holes in the mask.
Since the solder mask is formed from data generated during the PCB design process,it has holes where the pads should be.And thus solder is applied only to the pads that are intended for soldering.
There are two basic types of solder stencils:
- Frame stencils for use in soldering equipment
- Without frame stencils for hand-applying solder paste
Component placement can be done either manually or using equipment.In manual placement,the technician uses tweezers to position each component on a specific area of the solder paste.
In machine placement,a special mechanism with components loaded into it grabs the components and places them on the board.The pulling force of the solder paste is usually sufficient to hold the component in position.
Component placement equipment uses component location and orientation data (which is usually stored in Centroid files) as reference information to correctly place components on the board.Centroid files are usually generated from data generated by the CAD system during board development.
3,Reflow Heating and Soldering
After the components are installed on the board,the next step in the Prototype PCB Assembly process is to run the board through the bulk solder.Reflow soldering is the most common method for soldering SMT components,especially for prototypes,although wave soldering equipment is sometimes used.
Functional testing of the board in order to verify its functionality.
As you can see from this sequence of steps,the Prototype PCB Assembly process begins with the application of solder paste.
To securely solder pinned components, the hole in the board must be filled with solder.Another prerequisite for reliable soldering is that there is no solder outside the mounting pads of the SMT component, otherwise short circuits may occur.
5,Benefits of Using Solder Paste
The process of pre-applying solder paste to the board and then placing the components in the solder-paste areas has great advantages.Because the placement quality is improved as the solder paste is evenly distributed under the components before reflow.
The question,however,is how best to apply the solder paste.For this I use a stencil.
To get PCB prototype assembly quote for your custom PCB project, please click the following button and upload your circuit spec and BOM. We will give the PCB Assembly price within 48 hours.
What is a Stencil?
Stencils are specially made in accordance with the requirements of the board on which the components are going to be mounted. Usually the stencil is made from a sheet of hard material (aluminum, copper, or mylar). In most cases, there are two ways to make a stencil: make it yourself or order it from a specialized company.
Buying a Custom Stencil
In the process of buying any fairly serious production equipment for making stencils within the company, it often comes to the expert decision. It is best to use the services of a specialized prototype pcb assembly company to create the stencil that you need. The advantages of a custom stencil from a specialized manufacturer are:
- Speed of manufacture
- The possibility of repeated orders
In addition to using various materials, stencils are available in two basic classes: frame and mock-up. Frame stencils are built on the basis of a special type of mounting hardware (frame) for attaching the stencil to the equipment for applying solder paste.
Dummy stencils are not mounted on the frame. Instead, the three edges of the stencil are usually bent at right angles, creating a notch for the solder paste, stiffening the stencil and allowing the operator to work with it. The dummy stencils are optimized for working with board prototypes. Model stencils have the following properties:
- Actually have the same quality as the production stencils
- They can be made quickly
- Ease of use
- Are used once and are recyclable
When is a Stencil Economically Viable?
It is possible that the Prototype PCB assembly company that assembles the boards is the best fit for you. Or maybe your project is so simple (for example, all components with pins are used). It is best to take a soldering iron and manually unsolder a huge number of components.
How do You Find the Optimal Solution?
The easiest way to use layout stencils is in the following cases.
- A significant number of surface mount components are available.
- Multiple changes are expected, but at this stage the final layout of the components is accepted
- It is necessary to simplify the soldering process (with high quality).
Let’s consider how you can improve the technological route using a stencil. Estimating the time it takes for prototype PCB assembly by hand soldering, we get a pickup / placement / soldering time of 2min 20s per component.
This is on average. It takes less time for passive components. And much longer for large discrete components or connectors.
But if you consider the stage of filling the pads with solder, placing the component using tweezers and soldering the leads, then 2:20 per component looks quite real. Since the technician prepares and solders each component individually, the preparation and reflow time is included in the average estimated time for each component.
A different picture appears when using a soldering stencil for soldering. Unlike manual soldering, when using a stencil, the technician quickly applies a thin layer of solder paste to the entire board.
The time required for the application of the paste becomes fixed, i.e. the application time for a large and complex board is the same for a more compact and simple board. Let’s assume that it takes 2 min 30 s to apply solder paste to the board using a stencil.
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