Our Services
Call Us: +44 (0) 1252 333 444
E-mail Us: sales@geminitec.co.uk

At Gemini Tec, we believe in a culture of continuous improvement and have during our four decades in business been at the leading edge of innovative and technically advanced developments. Through our investment in the latest processes, training of our staff and state of the art software and machinery we have been able to offer the very best quality service to our clients.

PCBA Assembly Services at Gemini Tec with Solder Jet Printing


Gemini Tec Timeline – Key Achievements:    

In 1978, Gemini Tec was founded as a PCB design company 

In 1986, Gemini Tec opened a PCB fabrication facility to manufacture a range of PCBs 

In, 2004, Gemini Tec commenced its assembly operation, providing a fast turn prototype service

In 2006, Gemini Tec installed its first Mydata pick and place machine supporting small volume orders

In 2007, Gemini Tec were the first UK CEM to adopt solder jet printing technology, to provide unrivalled product quality and reliability

In 2008, Gemini Tec installed a fully automated SMT line from Mydata/Mycronic, comprising of 2 x SMT machines for small to medium volume orders

In 2009, Gemini Tec installed its 2nd solder jet printing platform MY600

In 2010, Gemini Tec installed a further SMT machine from Mycronic, along with a 4th solder jet printing platform MY600 JP/JD

In 2016, Gemini Tec installed a second fully automated SMT line from Mycronic, comprising of 2 x SMT machines

In 2017, Gemini Tec installed its 3rd jet printing platform from Mycronic MY700 

In 2018, Gemini Tec were the first UK CEM to adopt Asscon's fully in-line vapour phase reflow soldering technology to further support complex product manufacturing

In 2020, Gemini Tec increased its operation to 30,000 sqft, adding 3D AOI inspection capability and advanced X-Ray inspection with Scienscope

In 2021, Gemini Tec installed its seventh Mycronic SMT line, complimented with Nitrogen (N2) reflow to increase capability in complex SMT production 

Leading Edge N2 Reflow Soldering for High Reliability PCBAs


Contact us in confidence to discuss your requirements in more detail, or arrange a visit to our production facility. Tel +44 (0) 1252 333 444

Or download our company overview here: G-Tec Company Profile

G-Tec Engineering & Operations CentreThe preparation of our customers data is a key element of our process to ensure the success of all subsequent production operations. Our experienced data engineering department has two key elements, covering the blank PCB substrate and the various data sets and drawings required for the production process. 


Blank PCB engineering 'Front end tooling'

As the blank PCB is the foundation of the product, its essential our engineering department work to help customers validate the PCB layout. Our aim is to identify potential issues from the processing of the data and support customers to apply best practices. Using Ucamco tools we complete a series of DFM, DRC and netlist connectivity checks, reporting back any issues, such as solder mask and via tenting, layer stack conflicts and impedance calculations.

Once the data has passed our checks, we supply the digital data directly to the PCB fabricator for use. This ensures all the requirements have been fully considered and risk removed.  Areas include; The correct step and panelisation for board transport, suitable fiducial marks for SMT placement, board panel routing, all IPC specifications and UL requirements. Our process ensures that all blank PCB's will be manufactured in accordance IPC standards and the follow-on build process. 


Data Engineering    

Using Aegis FLX software tools, we create our machine data, programs and drawing sets directly from your ODB++, ensuring a higher level of accuracy is attained. Not only does this remove the risks associated with using X&Y or pick and place files, it removes valuable down time during production with the need to 'Teach' our machines how and where to place components.Fully engineered production PCBA on SMT line 1

The ODB++ data contains all the required data, including the correct digital rotations and center points, further removing the need to rely on ambiguous PCB ident information for important build decisions. Using advanced tools reveals the granular level of detail required construct and output issue-controlled data sets.

Outputs include the required data for boards transportation, placement data, package data for placement configuration, AOI data for inspection and jet printing data from our fully tested paste typologies. A full set of build drawings are produced to capture information for production engineers, such as odd form component processing, obscure orientations, build directions, fitted parts, build order and even where to locate serial numbers. 

Our engineering department are on hand to deliver accurate data to the production process. To help customers provide the relevant data for engineering, please download our guide



To find out more about our CEM services, contact us for more assistance. Tel +44 (0) 1252 333 444

Gemini Tec Ltd - Privacy Policy Notice & GDPR Policy

This document concerns private information collected and stored by Gemini Tec Ltd from its customers, suppliers and professional service providers. We only collect basic personal data comprising of name, email addresses, phone numbers and who employs you. Personal data is data related to an identifiable individual and not to the company or organisation they represent.

Why we need your data.
We need to collect this data to be able to process customer orders for products and services provided by Gemini Tec Ltd and to comply with legal requirements to retain details of financial transactions. Our dominant business is relationship based and our customers typically place repeat orders for products or services many times and on trade credit terms. We need to be able to contact customers to discuss their orders to provide a high quality efficient and responsive service without the need to repeatedly input and process the same contact information.

From time to time we need to send important information concerning our holidays, those of our key suppliers or major changes in the marketplace which are likely to impact our business with you (for example changes in exchange rates which affect the prices of our products and services).

We may also need to contact you to invite you to subscribe to new information services we may provide in the future, for instance a technical blog which offers technical advice in the preparation of electronic and PCB designs.

How we store your personal data.
Personal data is held in encrypted databases with blue-chip service providers within the EU and also
held in backups at our own premises as well as stored securely offsite. The principal communications channel used by our customers and suppliers is unencrypted email and we are not able to protect personal information sent by these means.

What we won't do with your data.
We do not share personal data with third parties except as is necessary to fulfil orders for products or services purchased from us. We may share personal data with our trusted providers of professional services for example book-keepers, accountants and legal advisers or where it is necessary for you to interact directly with a partner business to successfully execute an order. We never sell or release bulk private data to any outside organisations.

How long we keep your data.
We are required under UK tax law to keep your basic personal data (name, address, contact details) for a minimum of 6 years following any financial transaction after which time it will be destroyed. If you have agreed to receive information circulars we will keep basic contact information until you notify us that you no longer wish to receive this information.

What are your rights.
If at any point you believe the information we process on you is incorrect you can request to see this information and have it corrected or deleted. If you wish to raise a complaint on how we have handled your personal data, you can contact us to have the matter investigated using any of our published communications channels.

To comply with GDPR, a Subject Access Request can be requested via email, addressed to the company (This email address is being protected from spambots. You need JavaScript enabled to view it.). These requests will be charged per subject access request. Gemini Tec Ltd will aim to provide the relevant data within 14 days of receiving the request.

Gemini Tec will always verify the identity of anyone making a subject access request, prior to handing over any information.

If you are not satisfied with our response or believe we are processing your personal data not in accordance with the law you can complain to the Information Commissioner’s Office https://ico.org.uk/

G-Tec 3D AOI Department

Our QA assessment team is equipped with the very latest 3D AOI inspection equipment for advanced process control and defect detection. 

Mirtec are the market leaders and award winners in 3D AOI technology. The OMNI Vision 3D machines are equipped with world class Moire 3D projector technology and lighting systems for a precise measurement using advanced analysis algorithms. The system combines 3D, 2D and lateral inspection to build a full picture of each device and accurately identify any failure modes.

Higher levels of inspection are achieved by referencing the physical pad data and simultaneously inspecting the multiple surfaces of each component, including J-Lead, No-Lead and the bottom solder of coil type parts for acceptability. FOD located outside of the typical inspection area can now be included within the inspection process. 

3D AOI inspection of a typical SMT connector provides a full 3D image of the placement with accurate measurements of the physical features for the correct validation process.    




 3D AOI Offline Programming

Technical benefits translate into superior quality products:

Advancements in 3D AOI inspection technology has reduced both downtime and false errors within our inspection process. The benefits provide direct benefit to our customers product quality:

  • Increased efficiency with fast offline programming 
  • Off line and real time de-bug
  • Fault verification with serial number tracking
  • Improved inspection process with deep learning AI and auto-teaching
  • Vastly reduced 'false calls' removing operator dependency
  • Higher downstream productivity
  • Higher yields at functional test/ICT/flying probe
  • Granular levels of details checked on all PCBA applications
  • True co-planarity and solder volume inspection, back to our customers design



Complementary Processes:

AOI inspection is a standard process applied to all products we manufacture at G Tec, regardless of quantity and technology.  

We also use additional inspection tools for product and process validation including regular microscopes, Ersascope fibre optic cameras and X-Ray inspection. We currently have two X-Ray platforms (X-Tek and Scienscope) providing the widest range of inspection capability which includes automatic void detection and PTH barrel fill inspection.G-Tec Auto Void Detection X-Ray


Our passionate teams deliver a world class service, are committed to providing the highest quality products and put our customers at the heart of everything we do. We support our customers with PCBA applications, working from concept to completion starting with the PCB design layout, through to NPI and finally production.

To find out more about our CEM service, including 3D AOI inspection or arrange a visit to our plant, please contact the commercial team on +44 (0)1252 333 444



Gemini Tec use the very latest processing technology available to manufacture customer PCBA products. We operate with two Asscon vapour phase reflow ovens, providing customers with seamless PCBA processing from early prototype through to batch production. Gemini Tec are the first UK CEM to operate the latest in-line vapour phase reflow oven, manufactured by Asscon of Germany.

We have listed out some of the FAQ's about this technology:


Why use vapour phase reflow, instead of other popular reflow methods? 

Assemblers in progressive companies such as Gemini Tec recognise the advantages of this soldering method as the simplest and most reliable method of soldering. It allows for the processing of ALL types of components and PCBA's without many hours of complicated calculations to create thermal profiles, which are often a compromise between the solder paste and the component make up.

Vapour phase reflow is a repeatable process, without external factors that drive the process window. 


How does it work? 

A Galden liquid boils to deliver a layer of saturated vapour which contains no oxygen or other gasses. As the PCBA is immersed into the vapour zone, the vapour condenses onto the PCBA and transfers its corresponding heat in a linear method. 


Vapour phase reflow was popular in the 80’s, but went out of favour due to chemicals that contained CFC’s, is this still the case? 

The fluid used in today’s vapour phase machines do not contain any harmful CFC’s. The chemical is environmentally compatible, non-corrosive and extremely stable.


Are vapour phase machines expensive to run, which pushes up manufacturing costs? 

No, the chemical running costs of a typical machine is around 70p an hour or a little over 1p a minute. Our Asscon vapour phase oven also consumes much less power, running at at 2.5kW p/h VS the equivalent convection oven running at 20kW p/h. The investment into the process is alot higher than a typical convection reflow oven, but ROI is seen very quickly through finished yields and removal of other hidden costs.  


Is condensation soldering different to vapour phase soldering? 

No, they are the same. The same fluids are used and heated to their boiling point to create a vapour, which allows the solder to reflow in an inert atmosphere. The only differences are to the individual manufacturer’s machine design.


Can PCBA products be overheated, much like a convection oven? 

No, the maximum board temperature is equal to the boiling temperature of the liquid used, i.e.200ºC. for SnPb or 230ºC for lead-free materials. Irrespective of how long the PCBA and solder material remains in the vapour, irrespective of board thickness the temperature can never exceed that of the relative vapour. 

So if your PCBA is 0.5mm thick or at 2.4 thick with 18 layers using 2oz copper ground planes, both will get the sufficient heat required and neither will overheat. The laws of physics dictates the process is impossible to overheat the PCBA.


What about oxidation? 

Vapour phase reflow produces a 100% inert/oxygen free soldering environment that eliminates oxidation problems. The vapour is heavy (in comparison to steam or air) and therefore displaces lighter gases, which are found above the vapour. In this method, the vapour creates a protective gas atmosphere even without the use of nitrogen, which is a highly expensive soldering process. 


Does vapour phase reflow cause tomb-stoning? 

The ability to completely pre-heat the board, according to the material/component requirements (see previous answer), and create a very gradual temperature rise will help avoid thermal stress and tomb-stoning.


Higher technology boards are high in mix and use components with small process windows, such as µBGAs, CSPs and flipchips. A uniform reflow is crucial, so how can vapour phase provide this? 

During conventional reflow to ensure any hidden central joints are heated sufficiently, the temperature may have to be raised as much as 50ºC above the melting point of the alloy. Overheating of the external solder connections causing permanent heat related damage. With vapour phase the heat is drawn by conduction from a saturated vapour onto the PCB. The heat is distributed evenly throughout, irrespective of whether components have a high or low thermal mass. Reflow temperature differentials across the assembly are always less than 5ºC, as the delta T of vapour phase is only 5°C


How does vapour phase cope with lead free solder paste? 

The temperatures that is required for lead free materials are more extreme. Typically this is +10% for wave soldering and +20% for reflow, these additional temperatures add even further risk of damage by excessive heat. Vapour phase is the only reflow process that allows you to change to lead free (for example: SnAg 3,5 with a melting point of 221ºC) without any danger of overheating the board or its components by using a liquid with a boiling point of 230ºC.


Is the solder wetting of lead free materials a concern? 

Lead free alloys do not wet as well as SnPb, an inert atmosphere will be more important to employ the best possible soldering conditions to help overcome this problem. When using convection reflow the use of a nitrogen atmosphere will improve solder joints, but this adds excessive cost and is a process that is not widely adopted in the UK over concerns with the long-term reliability.  

Vapour phase reflow soldering automatically provides a 100% inert atmosphere, without adding nitrogen (and without adding additional cost), to guarantee the best possible soldering conditions along with the best possible long term reliability with every use.


What about the problem of pop-corning during production? 

As plastics are hygroscopic, humidity will get into the body of these components (e.g. BGAs). When reflow soldering this can lead to high pressure of the moisture trapped inside the components which is converted into steam and forced out under pressure during reflow. This can cause delamination of the substrate or 'pop-corning'.

The higher the reflow temperature needed for lead free alloys results in a greater the risk of pop-corning, therefore a maximum reflow temperature of 230ºC is the optimum process. And with no risk of heating the PCBa's above a maximum of 230ºC, vapour phase reflow provides a vastly reduced risk of pop-corning. All MSL related materials used at Gemini Tec are subject to baking prior to use, when required. We also have in house vacuum sealing machines and automated control over exposure time and labelling materials.  


Gemini Tec support a wide range of customers and applications from prototype to medium volume production, our investment in processing technology, allows us to support complex and demanding PCBA products where reliability and conformance is essential.


If we can help you with more technical questions or if you need our expertise, please contact us to arrange a site visit. +44 (0) 1252 333 444