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May 6, 2014

Challenges with 01005 Components

We are going forward with assemblies that will use 01005 components. We're wondering if anyone on the experts panel would have some input as to what are the most important challenges we are going to face?

T.G.

Experts Comments

Here is a my list of important challenges:
  • Pad design on the board – associated defects: tombstoning, unsoldered parts
  • Stencil design and thickness – paste deposition issues. The population on the boards is also very important – the 01005s in combination with large components on the same board may require stepped stencils
  • Paste selection in combination with stencil – a type IV paste in combination with a nano-coated stencil has shown good results for deposition and paste release from the stencils’ apertures
  • Paste deposition inspection – not enough as well as unbalanced volume can lead towards tombstoning
  • Pick and place repeatability, component placement pressure, total assembly time – placement position (x,y) is critical as well as the placement pressure (the component being “in the paste”). Long assembly time will “dry” your paste
  • Reflow profile – aggressive profiles will increase the tombstoning problems
  • Do not forget to have available tools for rework if necessary – hand soldering tool tips are available for components that small – have them available just in case.
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Georgian Simion
Engineering and Operations Management
Independent Consultant
Georgian Simion is an independent consultant with 20+ years in electronics manufacturing engineering and operations.
Contact me at georgiansimion@yahoo.com.
In general, the miniaturization of components leads tosmaller and smaller pads on the PCB. The printed solder paste will as a result have an increased surface to volume ration. The solder paste will be subject to a higher tendency for oxidization as well as a host of other complications. This leads to more challenging printing and reflow processes.   

You may want to check with both your solder paste and components suppliers to determine what impact your 01005 components will have on their thermal process specs. The odds are that you will face a tighter thermal process window, and you will need to develop a new setup for your reflow oven in order to position the PCB profile within this window. Also, with a smaller process window you will need to check your thermal process more frequently as there will be less room for process drift.
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Bjorn Dahle
President
KIC
Bjorn Dahle is the President of KIC. He has 20 years experience in the electronic manufacturing industry with various manufacturing equipment companies covering pick & place, screen printers and thermal process management.
01005 component size is small and it presents many challenges in its assembly. However, one of the most challenging aspect is solder paste printing process.

The important paste printing process factors are solder paste type, optimum PCB pad and stencil aperture design. Results indicate that stencil thickness is significant factor for solder release characteristics. 0.003" thick stencil provided much superior paste release than 0.004” thick stencil.

You can find more information from these papers/presentations:
  • ASSEMBLY PROCESS CHALLENGES FOR 01005 COMPONENTS                 Authors: Rita Mohanty and Vatsal Shah  Date: 08/17/2008
    Conference: SMTA International (SMTA International Conference Proceedings)
  • 01005 Assembly Process, Materials and Tooling
    Denis Barbini, Universal Instruments Corp
    http://www.smta.org/chapters/files/Oregon_Barbini_SMTA_01005.pdf.
Additional Information:
  1. Printing a sufficient volume of solder paste and having sufficient paste pad coverage are critical both to the  placement process and for proper solder joint formation.

  2. A positional placement accuracy of 0.002 in. is the  placement accuracy neighborhood needed for low ppm defect rates.

  3. A 0.002 in. thick electro-formed stencil provided good results with either type 3 or type 4 paste sphere size.

  4. A 0.004 in. thick laser cut stencil provided acceptable results only with paste made with type 4 powder.

  5. Rapid heating during reflow is important to prevent solder sphere oxidation.  An oven profile that results in a straight, rapid temperature ramp rate of close to 3.0 deg. C per sec. was found to yield good reflow soldering characteristics.

  6. Reflowing in an inert environment (< 10 ppm O2) would widen the reflow process window.

    Source: "Process Characterization of the 01005 (English) Component Package"
    Tom Borkes, The Jefferson Project,Orlando, FL
    Lawrence Groves, Dynatech Samsung, Horsham, PA 
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Santosh Kumar
R&D Manager
MK Electron Co. Ltd
Santosh Kumar is R&D Manager at the MK Electron Co. Ltd., Korea and engaged in the electronic interconnect materials development and technical marketing. His key focus is novel lead-free solder materials, electronics packaging, wire bonding materials and process.
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