AOI Brings Contract Manufacturer Up To Speed

Worthing based Wildtrax provides a flexible contract manufacturing service with an ability to rapidly produce small production runs of sometimes highly specialised PCBs. Over its 15 years of operation, the company has witnessed a steady evolution in board complexity and a corresponding evolution in automated optical inspection, AOI, technology.

As a contract electronics manufacturer, Wildtrax is NASA accredited. As part of its service to the organisation, Wildtrax had to produce and inspect a run of just four or five high value PCBs containing gold impregnated ceramic devices. And for that its AOI system has to provide fast setup and flexible, efficient operation for such small and specialised production runs. But there are other important features too.

Some 15 years ago, Wildtrax started life building electronics for hydraulic power packs in patient bath and bed lift and tilt controls, as well as for rail applications, battery packs, cable assemblies and data leads. The involved circuits were typically rugged and often epoxy encapsulated, and first inspections in production were entirely manual.

Seeing the need for inspection technology, its first foray involved using a slow and inaccurate comparator. It met a need but its customer base was meanwhile growing, meaning a higher throughput and larger production runs, in batches up to 2000/month. Yet demand for prototype and low volume runs remained consistent and in t hat scenario Wildtrax saw the need for a faster and more flexible AOI solution.

Wildtrax upgraded its inspection to its first AOI system around seven years ago, suing a system based on camera, lighting, motor drive and computing hardware. And this was the size of a small car and could only be repositioned by dismantling or manoeuvring with a forklift truck.

Nonetheless the solution enabled inspection on a production basis and continued until round 18 months ago when disaster struck around 18 months ago. A hard disk crashed and of course with kit that old there was no replacement as technology had moved on. A quick eBay purchase of a second hand and subsequently cannibalised machine enabled automated inspection to resume.
However the incident was a wake-up call, highlighting the company’s vulnerability to obsolete equipment and also the slowness of old inspection technology that was increasingly lagging behind the needs of production for fast, accurate and reliable throughput.

Programming set-up time of this old inspection kit was 1.5hr or more, sometimes a day for larger boards. And there were errors too: drive belt slip meant board positioning errors of up to 2mm, enough to signal errors in the machine’s fault reporting. There were also problems from excessively reflective PCB material, as well as reflections from components with glass tubes. And inspection was not made any easier by monochrome images, poor resolution and insufficient contrast.
Above all, the old system’s scanning technology made the throughput too slow for many boards, with too many false positives and missed faults.

So Wildtrax scoured the market for a replacement solution and in tests and assessments plumped for Nordson YESTech’s BX system. Notably this solution was up and running within 30min of arriving on site: it was programmed and then inspecting a simple sample board supplied by Wildtrax. And, as a reflection of the ruggedness of modern technology in cameras, lighting, drives and computing, the unit had been transported in the back of a car and easily carried to a benchtop for the demonstration. In many small CEMs, space is at a premium, and the BX’s benchtop-scale dimensions alone are an important feature.

BX came at a good price too so Wildtrax did the deal and purchased the system, finding training simple and programming easy. The system’s speed was readily demonstrated by the disappearance of Wildtrax’s production board bottleneck and backlog that the previous mach8hne had caused.
“We like the way the BX does what it says it will, and appreciate its simplicity of use,” comments Wildtrax’s Ian Warren. “Additionally, since installation, we’ve been discovering the other ways it can boost our productivity. For example, sometimes our customers have issued us with low cost PCBs where fiducial mark positioning varies across different batches. The BX can store different versions of the board image to match each different fiducial position, then, during inspection, automatically check the board against all stored image versions as necessary. This automates a process where we previously had to keep re-adjusting and running the test again until the false positives were eliminated.”

This flexible automation is also useful for handling further inconsistency problems that arise because a contract manufacturer doesn’t have control over sourcing or quality of the boards being assembled. Boards can be distorted, pads can be oversized or undersized, and components can float from their base positions. Additionally, there can be problems of soldering quality, tombstoning and billboarding, wrong components or wrong orientation, or inconsistencies in component labelling between batches.
In transferring its inspection operations to its new BX AOI, Wildtrax wanted to make use of data for component types, orientation and positioning already held for all the boards it regularly manufactured and inspected. This was achieved without undue delay to production by individually importing CAD files as needed from Wildtrax’s pick&place machines. Nordson YESTech’s universal CAD translator software, along with a little editing to remove information not needed by the BX, solved that problem.
Alternatively, new inspection programs are set up in typically 30~45min. Once stored on the BX, inspection data can be recalled in seconds slashing the time required to inspect diverse, low volume production runs.

Three months down the line after installation, Wildtrax says the advantages of the BX for production inspection and setting up are apparent. The company says it particularly likes the BX’s sharper definition, colour lighting and filtration, which copes well with poor ID markings through bad printing or laser etching. Colour filters allow image enhancement to reduce the incidence of false positives and, similarly, where specific solders are used on some production runs, the refraction characteristic can be optimised by the use of colour filters and contrast. Side view cameras give extra readability from their different positions and can check whether components are firmly down on their pads.
For Wildtrax, the BX has also brought automation to board panelisation. Typically it produces panels containing eight identical boards with PIC microprocessors. On the old AOI, the whole panel had to be programmed as if it contained one large board. The BX, however, only needs the first board need be set up by programming, then the other seven are step & repeat set up. During production, the BX can be instructed to ignore any board within the panel deemed a ‘cross-off’, saving considerable time as the earlier AOI needed to delete every component within a cross-off, subsequently programming it back in for fully populated panels.

“Given the nature of the products we manufacture,” concludes Warren, “QA is critical, so we perform 100% inspection. This includes 100% re-inspection of any boards we find necessary to rework. The BX’s speed of set-up, smart features and production throughput is contributing significantly to our achievement of this, and therefore our business efficiency. And our access to this new level of AOI technology was facilitated by first class service, fast response and an effective training course from YESTech Europe.”