Quality

Read more

Technical Support Quality Statement

As a family run business, achieving customer satisfaction is close to our hearts.

We continually work to improve the effectiveness of our Quality Management System and to deliver high quality product, on time, with good value.

If a quality issue arises, then we must determine what went wrong and implement changes in our processes or systems to ensure it doesn’t happen again.

We endeavour to achieve this by good communication, ongoing assessment and training, and putting quality ahead of schedule and cost.

About Quality

Electronic Engineering is often a key part of product design and can make or break the success of an otherwise well engineered product.

Quality has many aspects in Electronics, but is embodied in one philosophy; “Do the job well and measure the quality against accepted benchmarks.”

Where we introduce our own benchmarks, they should exceed accepted standards and never undermine them in any way. This is where experience comes in.

In manufacturing, we are expected to adhere closely to agreed standards and deliver product that matches or exceeds client expectations. This includes the appearance of the product, but appearances can be deceptive. There are other less obvious areas that visual inspection can’t detect. These are outlined and discussed in Quality in Manufacturing.

Product is often required on extremely short lead times. This can be a risk area if things are rushed. Although it’s ultimately the job of the QA manager to insist that all procedures are carefully observed under these circumstances, it should really be embedded in company culture.

Since the financial crash of 2008, many PCB assembly businesses have had to cope with lower margins. In order to do well, businesses have had to invest to increase productivity. Businesses with a poor debt to equity ratio were not well equipped to do this. Our family business has steered a safe course. We have greatly improved our productivity with new equipment whilst keeping risk low.

Manufacturing Quality

Systems

Quality starts with good business systems and good attitude.

Recording and signing off the client’s bill of materials is the first crucial step. An attitude of “I think that’s OK” can be disastrous. As an example – some of us may have had the experience of incorrectly specified capacitors exploding. Just one wrong component can cause a very expensive failure; reputation, equipment cost, down-time and call-out expense.

ERP systems don’t always meet the needs of PCB assembly. We chose to build our own Microsoft Access based system which has matured over two decades. It enables us to do accurate costings whilst maintaining good component and process data across different technologies. Purchasing and Goods Received are all tied in. This is the core of our QA and relies on good communication with our clients.

Build Quality

Cleanliness, accurate and neat component placement, and high quality soldering are all required. We have high-end machines and high-end skills in order to do a great job.

Our hand-built prototype PCB assembly is close to production quality.

People

Good training and quality-feedback are are essential. One of downsides of many businesses is staff turnover. Quality can wobble if a person who became familiar with your product leaves and a new person has to gain familiarity. We don’t have staff turnover and we train our people well.

Hidden Problems

The product can look excellent and perform well, but long term reliability can be affected by things that you can’t necessarily see. Some examples…

Static Control

Static control is probably the best known requirement for PCB assembly. Damage can occur with poor handling. High impedance chips are most susceptible – damage is unseen and highly variable. Failure can occur immediately, but worst case, can occur after delivery to the user.

Storage Humidity

If components are to be stored for any length of time, correct storage bags and low humidity are required. Contact oxidation and moisture ingress are the main problems. Incorrectly stored components can fail as a result of damage during the soldering process because of absorbed moisture in even mildly hydroscopic materials. We store your parts correctly.

Temperature Profile

Avoiding thermal shock is a key requirement of soldering. Greater precision has been required since ROHS regulations specified lead free solder in PCB assemblies. Lead free solder has a higher melting point than tin-lead alloys. Plastic components have had to change in their composition to ensure compatibility, but the temperature window for safe operation is now smaller. Good equipment is required. Avoiding thermal shock is all about accurate temperature zoning.

Working Humidity

Static conductive and dissipative work areas are required for safe handling. The risk of static damage increases when the humidity is low. In addition some adhesives require minimum humidity levels to attain hardness.

Experience, training and intelligence are required to implement a good quality environment.

Quality in Circuit Design

Business Philosophy – Quality Design Starts Here

An integrated commercial approach is required. Businesses that make engineering products are often described as market driven or engineering driven. Some think that these two disciplines conflict. They shouldn’t.

All engineering businesses should be market driven, but should have a deep awareness of engineering constraints and possibilities. There needs to be a closeness between the two disciplines so that they work as one. The Italians would call it ‘sympatico’. In this context, the best engineering solution is one that meets or exceeds market requirements. Business approaches have changed and there are many recent successes that have been led by engineers who are very market savvy.

Designing on Budget

Trade-offs sometimes have to be made that can lower reliability. The ideal component may survive extreme conditions – but the need to value engineer may mean that less robust components are used at lower cost. So astute knowledge needs to be gained from the field in order to set priorities.

‘Value’ will vary from application to application. Sometimes the value is perceived only at purchase time.

In ‘mission-critical’ applications, such as life support, value takes on a different perspective, but cost is still important. In some applications, cost of ownership becomes a key factor. For example, if the client is operating the equipment, he’ll want to know that his service team are not called out by unnecessary failures. The same applies when considering the cost of product guarantees. A pound now may save a hundred later.

When starting a project with a manufacturing budget, a spreadsheet or similar is ideal for looking at what-ifs when considering different circuit configurations versus cost. The engineer can then work with a number of scenarios which can be presented to management.

The main cost constraints come from affordability and competition. Innovation, quality and market reputation can help to relieve these constraints.

The Tech Stuff

This may be pretty obvious, but components should be chosen to provide reasonable headroom in areas that could cause failure. Sometimes, the tricky bit is establishing possible causes of failure. It’s worth taking time over this. You might benefit from speaking to service engineers who are familiar with products in your target market.

A common cause of failure has been connecting system components with power on. If a ground pin is last to be connected, a temporary circuit for higher voltages can be made through sensitive pins that would otherwise be ok. Very often, connectors with elongated ground pins are used to avoid this, or the problem can be designed out with protective circuitry.

In a typical industrial control circuit, inputs and outputs are expected to be subject to voltage spikes of varying energy levels. So the microcontroller is ring-fenced with protection circuitry. Schottky clamping diodes on the micro’s I/O can be a good line of defence after dissipating and blocking high energy pulses with limiting resistors or whatever.

So how far do you go in protecting your circuitry? Do you really need to allow for the customer incorrectly connecting 240V mains to your 12V inputs? Maybe you do, but most would think that the guarantee would be invalidated by that action.

Some of the larger MOSFETs can be very robust, can withstand inductive load switching well, and can be driven by 3.3V logic.

Note that an enthusiastic electrician or technician can connect his high current PAT tester to your device. Sacrificial components such as VDRs can be blown unless he switches his tester to IT test mode. Some are not aware of the risks. Many computers died to bring us this information.

Choosing components that work well within their temperature comfort zone is very important for long-term reliability. Heat sinks are often required, but often involve additional PCB assembly techniques and can raise costs. A solution can be to design for lower power or to spread heat dissipation across a number components, or use switching devices for greater efficiency. Just be careful of EMC.

There are many applications where vibration is a factor to consider. For example some small pedestal toll payment machines are subject to vibration from wind and unhappy customers. Electrolytics and other standing components break unless secured very well and connectors need to be the locking variety. It’s good to design on the basis of “If it can happen – it will happen.”

It’s good to visualise all environmental conditions that your product is likely to face. Many environmental hazards can be more severe than anticipated. This includes EM fields and static.

Enclosure design should allow good routing of cables. If your circuit protection is ‘on the edge’ when unexpected surges or voltages occur, well routed cables can be the the factor that makes or breaks reliability. A fold in the metalwork can be used to provide extra screening.

Door panels should be well grounded. Some of the fields that occur in cabinets can be localised and fast-rising. Some manufacturers prefer the use of braided cable to connect doors effectively. The important thing is to shield and provide return paths so that your circuitry isn’t KFC.

Multi-layer ceramic capacitors bring low ESR and compact design. They can often replace the two capacitors that we may have previously used to decouple the power tracks next to a chip. But it’s always a good idea to scope the circuit to make sure there are no nasty oscillations. Some chips such as RS232 interface chips can put some noise on the power line.

Quality in PCB Design

Some of the issues discussed here are dealt with when choosing component package type – in particular, through-hole or surface mount.

When the use of CMOS microprocessors was new in industrial control, engineers had to go through a steep learning curve. Electromechanical control was replaced by circuitry that is very sensitive to external electric or magnetic fields.

Early triac control gained a poor reputation in some industries because fast turn-on could cause voltage spikes that caused the micro to freak out. Design engineers with little or no experience of this kind of thing had to learn fast – this wonderful thing called EMC. They had previously dealt with it, but not like this.

A number of improvements are now commonplace; zero-volt switching, a better knowledge of protection components, surface mount technology, and a greater understanding good PCB layout. Like it or not, the EMC directive has made many of us refine our skills in this area.

PCB tracks have to satisfy a number of requirements. These are mainly…

  • Current carrying ability
  • High voltage creepage and clearance (safety and the Low Voltage Directive)
  • Electromagnetic compatibility
  • Manufacturing tolerances
  • High frequency
  • Analogue and instrumentation

(Notice the ironic use of ‘high’ and ‘low’ voltage with regard to the same thing. This highlights the difference in perspective between Electrical and Electronic engineers.)

The PCB designer needs to be fully aware of the widths and distances required to satisfy all of the above requirements.

If PCB track gaps and widths go much below 6 mil, then PCB costs can rise or reliability can go down. It’s wise to set design rules to remind you of this. Make sure that tracks are designed to take current when a fault condition occurs.

If you’re designing for high frequency, then special rules apply which require expertise. If your design just includes a high frequency component such as an antenna for an RF module, then you’ll probably find that the manufacturer or supplier has guidance available with a suggested PCB layout. This also applies to sensitive analogue.

A four layer PCB with power and ground planes can be very desirable, but it’s quite possible to achieve a good design with ground plane only on a two layer PCB if the design is less dense and not too sensitive. A good ground plane is the minimum requirement for a board with a micro. The great thing about microcontrollers is that they keep fast busses on the chip when you’re controlling low speed apparatus.

Benefits of Surface-Mount Technology

SMT brings many big benefits. Amongst these are…

Durability

Being flat on the PCB and secured with no wobbly leads is an obvious benefit.

EMC

Having no leads to increase inductance, and being small so that a capacitor can be very close to a component pin is an advantage. Compact design can improve EMC.

 

Cost

A smaller PCB along with less drilling mean lower cost. Maybe more important is that more functionality can be squeezed into the same area as a through-hole product. Manufacturing costs are often lower. Not all PCB assemblers have automatic stuffing for through-hole components, but most will have SMT pick-and-place machines.

You may like to come in and see our SMT PCB assembly. We often populate boards on both sides, which is another advantage of the technology.

 

Downsides of SMT

The downsides are generally worth working through because you’ll probably have a better product with SMT.

SMT is more expensive to prototype – although you can always breadboard circuit elements with through-hole components.

 

Rework requires special tools, the most expensive being specialist chip removal heads, but things can get a lot more expensive for reworking BGA components. This requires specialist workstations.

If you see the need to remove and replace chips, such as ROMs or OTP micros, then it may be worth considering PTH socketed chips. Of course, most microcontrollers can now be reprogrammed in-circuit.

 

Contact Technical Support

Want to know more about us? We welcome your enquiry – please give us a call. Contact us on the details below or email us your data and we’ll get back to you to discuss your requirements

Contact us