PCB Finishes – Hot Air Solder Leveling

mwcms on October 12, 2020

If you are involved in the PCB – “printed circuit board” industry, you must already understand that these boards have copper finished surfaces. In case if they are left unprotected, the copper will start oxidizing and deteriorating, making your circuit board unusable. 

The surface finish helps form an interface between the PCB and the component. This finish has two significant functions – the protection of exposed copper-based circuitry and providing a solderable surface during the assembling of the components to the PCB. 

What is Hot Air Solder Leveling?

Hot Air Solder Leveling or HASL was once hailed as a tried, tested, and true way to produce consistent and quality PCB assembly results. That said, the ever-evolving and increasing circuit board complexity and density of components have pushed the capabilities of all horizontal soldering systems to their maximum limits. 

HASL is probably the most common type of printed circuit board surface finish used within the industry in the modern era. The Hot Air Solder Leveling finish composition is in the proportions of 37 percent lead and 63 percent tin. However, you can also use HASL for a lead-free finish; all it takes is a minor tweak to the entire process. 

HASL Process

This type of PCB surface finish is applicable by first dipping your circuit board into a pot of molten lead/tin alloy after the application of the solder mask. The next step is the removal of excess solder via Hot Air Leveler (HAL) using hot-air knives that results in leaving behind a thinnest possible layer. 

The job of this remaining thin solder layer is to protect underneath traces from corrosion. The finish also facilitates the activity of soldering your components to the circuit board during the printed circuit board assembling process via pre-tinning the pads on your board. 

Hot Air Solder Leveling is one of the most cost-effective PCB surface finishes compared to other finishes types available in the market. Therefore, it is a recommended and preferred choice of surface finish for general purpose PCBs. 

Although considered a separate type of surface finish in its own right, we can discuss a little about Lead-Free HASL. It is identical to HASL in both usage and appearance; however, the solder in LF-HASL contains a mix of 0.6 percent copper and 99.3 percent tin. 

This alloy has a higher melting point for lead-free soldering in comparison to leaded soldering. This raises the need for a slight modification to the reflow soldering operation in your printed circuit board assembly solution. 

Lead-Free HASL is a viable replacement for the traditional lead sourced soldering process but only used when you require a RoHS compliant circuit board. You must also remember that you will need a laminate material with a high temperature to apply this type of finish. Otherwise, the rest of the soldering process is similar to HASL.

In the past years, Hot Air Solder Leveling was the most in-demand and popular PCB surface finish. It was due to two main qualities, i.e., robust solution, and low cost. 

However, the recent evolution and fundamental changes to the printed circuit board industry introduced more complex and advanced surface mount technology (SMT), which exposed the shortcomings of HASL.

You cannot use HASL with fine pitch SMT circuit assembly because of the incompatibility between the uneven surfaces and fine pitch components. Although a lead-free HASL solution is not available in the market, there are several other options that you can use to achieve highly reliable products. 

Pros & Cons of HASL

There are certain advantages and disadvantages to using HASL, and they are:

Advantages

  • Widely available
  • Low cost
  • Excellent shelf-life
  • Easily re-worked

Disadvantages

  • It produces uneven surfaces
  • Not an ideal solution for fine pitch components
  • Poor wetting
  • Not ideal for PTH or Plated Through-Hole
  • Thermal shock

Still Worth it

HASL still stays relevant, and one of the lesser-known and unintended benefits of HASL is the exposure of your PCB to higher temperatures of up to 265⁰C. This will help identify potential delamination problems before you attach any expensive components to the board. 

How to Panelize your Boards for Assembly

mwcms on September 21, 2020

So you have managed to sketch the perfect printed circuit board (PCB) assembly design. You cautiously created a layout of your components and respective traces for optimal thermal and EMC/EMI considerations. You even ensured that your PCB fits perfectly and conveniently within the secure socket of your product. 

However, there is just one issue. You contact your regular fabrication house only to find out, the transfer conveyors they have on their production machinery cannot process single boards. They inform you that your conveyor width has to be 2 inches or more. 

Eager to get your order, chances are their sales liaison will recommend you to make your design bigger or try PCB panelization. 

However, the designed enclosure on your product does not have ample margin for expansion of the width of your PCB. Even if it could, the price to do so for a single board will be too steep. PCB panelization is an ideal solution for such situations. 

Let us find out what PCB panelization is and how it can be helpful for your manufacturing needs. 

What is PCB Panelization?

It is a technique used in the manufacturing process. This process enables smaller manufactured boards connected en-masse as a single array. The whole exercise makes it easier to transition through the assembly line. 

There is another term used for PCB panelization known as “Array.” In other words, it is a process of combining your single printed circuit board multiple times to create a larger array of boards connected together. It is also known as “stepping out.” 

The whole process of PCB panelization is reversible; hence you can easily remove or de-panelize boards individually from the array for installation or packing into a product. Alternatively, you can also use panelization to create an edge around an individual board to increase the width that fits the assembly line. 

Factors to Consider

If you wish to reap the benefits of panelization in a mass production environment, it is essential to embed the following design considerations in your PCB assembly. 

PCB-Array Strength

There is a tradeoff when it comes to the array’s integrity and ease of de-panelization during the product. Increasing your per array board count can also increase the strength while reducing the vibration. 

Component Layout

Placement of all the connectors and components, especially the ones hanging off the board’s edge, can limit panelization options. Be thoughtful of where you locate the sensitive SMT components on the edges.

PCB Shape

The board’s shape can cause complications in the panelization process. Rectangles are ideal; however, if your board’s shape is complex, using a CAD program can help you fit an unusually shaped PCB into the desired array. 

Tooling Holes

Breakaway process edges and arrays can provide you spaces for tooling holes. It will help you run automated testing on your PCB assembly line. 

How to Panelize Your PCBs for Assembly

There are two ways to panelize your PCB for assembly.

V-Groove

Using V-groove panelization, you use a triangular saw to cut approximately one-third into each side of your PCB panel. It leaves you with a thin sector for FR4 that holds PCBs together, so you can separate them using a simple tool.

You can only use this panelization process on designs with straight lines separating all the PCBs. But you cannot use the v-groove technique if PCB components are hanging over the edges of any of the boards. Using V-groove panelization would damage your board. 

However, V-groove is a faster route to panelize your boards, plus it adds little space to the overall size of your panel, reducing the costs. 

Tab-Route Panelization

For boards that are inseparable by straight, simple lines or if a PCB design involves multiple boards with various designs, tab-route panelization is the solution. It is a far more flexible strategy for board panelization. 

In this process, you use a router for cutting through FR4 between PCBs. It leaves small tabs to hold all the boards together when going through the assembly. You can break these tabs apart by hand or using de-panelization tools 

Tab-route allows your boards to have components overhanging from the edges. Typically, a tab-routed PCB has a series of holes, making the separation of the boards easier.

At Nova Engineering, we are ready to help you with any PCB orders or issues you may have. Contact us today!

Common Mistakes When Placing a PCB Assembly Order

mwcms on August 27, 2020

PCB assembly is one of the major components on your purchase list if you are an owner of a company that manufactures or produces electronics products. Outsourcing some of your electronic components can turn out to be your worst nightmare if not handled correctly. 

If you choose the wrong contract manufacturer (CM) for purchasing printed circuit boards assembly (PCBA), you may end up shipping a product that does not work at all or works incorrectly or sporadically. It can damage your reputation for being non-compliant with the industry’s standards. 

Hence, you must find the right contract manufacturer to give your business a competitive edge over others in your niche. For that, you will have to steer clear of some of the common mistakes most companies make. 

Five Common Mistakes to Avoid When Placing A PCB Assembly Order 

Here are five mistakes you must never make when you place an order for PCB assemblies. Avoiding these blunders will help you garner the most out of a CM partnership. 

Rushing CM Decision

If you are in the manufacturing business and produce original equipment, looking to hire a contract manufacturer, you must be vigilant and thorough in your search. Take your time to weigh in all the options, along with their benefits as well as drawbacks. 

Do not rush and make a precise list of what you need. You can schedule interviews with all prospective CMs and evaluate them to determine which PCB will work best for you. Be as detail-oriented during the interview as you can, and take your time. It will help you spot any red flags before you enter into a contractual relationship. 

Failing to Clearly State Your Project Objectives 

As you may already know, communication is vital for a profitable CM partnership. Failing to state or conveying your project’s objective with clarity to your contractual manufacturer can sink your business. Too often, OEMs suffer because they either give out confusing or vague project plans or descriptions. 

It results in a product with inconsistencies or errors in specs, colors, and materials. Therefore, save yourself from the pain of wasting your precious time and money by clearly expressing what you need in the first interaction with the CM. 

If you choose a professional and the best contract manufacturer to place your PCB assembly orders, they will carefully review your documentation prior to starting the project. 

Having Little Trust in Your CM

In order to outsource your PCB assembly from a CM, you will need to demonstrate a certain degree of trust in them. Of course, it is critical as you hand over your blueprints, plans, and ideas to a third party so they can produce a PCB assembly according to your desired specifications. 

To establish a fruitful partnership, you must feel confident and comfortable to hand over some control to the CM. Giving some freedom to your contractual manufacturer can pave the way for unusual ideas and innovations to boost your brand. 

However, if you believe you cannot trust the CM you are working with, it is time to switch. 

Opting for the Lowest Rates

Always looking for the best bargain is not a wise thing to do when placing an order for your PCB assembly. The lowest rates often fail to translate into exceptional quality; be aware of contractual manufacturers offering lower prices. 

If it seems too good to be true, it is because it probably is. Instead of choosing a CM based on the prices, look for someone who can ensure long-term profitability. Good prices come with consistent, high-quality PCB assemblies.

It is unwise to compromise quality and jeopardize your reputation just to save a few bucks. 

Outsourcing Overseas

Do not commit the mistake of outsourcing your PCB assembly from overseas just to save money. Not all overseas CMs offer low or bad quality PCB assemblies, but it is alarming if they offer cheaper rates. 

Additionally, sending your sensitive product plans and personal information oversea can leak your intellectual property. Therefore, do not risk it and trust a local U.S. based contract manufacturer to place your PCB assembly order for a reliable supply chain.