Tag Archives: SMT
We frequently receive inquiries about the moisture sensitivity of our surface mount components.Technically, all of our components are moisture sensitivity level 1 (MSL1) according to the IPC/JEDEC’s J-STD-20, meaning that they can be mounted and reflowed an unlimited amount of time after they are removed from the packaging. This is not the complete story however.
Because of the unique, high frequency construction of our surface mount devices, the lid provided for them is only a dust cover, epoxied on. For this reason it is not sealed against aqueous solutions, and special precautions need to be made.
All sensitive elements inside of the units are sealed independently, and the circuits themselves are not moisture sensitive. However, during the aqueous wash process the solution will penetrate the components and therefore will require some time to dry.
For this reason, Marki Microwave suggests that all surface mount components be subject to a vacuum bake at less than 120° C for one hour.
The important element in this is the vacuum, which will cause the solution inside to evaporate and evacuate the dust cover. A lower temperature or lower vacuum can be used, but it must be subject to the process for a longer time. If the part is tested within 24 hours after an aqueous wash, then the performance will be affected by the solution still inside the dust cover.
Microwave designs are pushing towards an all surface mount future, due to reduced assembly complexity and cost and reduced system size. Marki Microwave is pushing this technology by offering many of our designs in surface mount packages. The main question for a microwave surface mount package is the transition: how do you bring the signals from the board into the component, and back? The component must be on a substrate of some sort, and a straight wire up the side of the substrate will not generally be 50 ohms. The trick is to maintain a broadband 50 ohm impedance through the transition. Marki uses three different techniques to achieve this:
Image of T3A-EZ package
EZ eyelet – The EZ package uses a Marki proprietary technology we call an ‘eyelet’. This is a 50 ohm transition built into a metal carrier to allow a transition to a taller base height for the substrate. A suspended substrate is then attached to the carrier, allowing for surface mount suspended substrate mixers. This is the best method for transitioning to a suspended substrate part available.
Product Lines: Mixers (M1, M3, M4), Amplifiers, Doublers
Carrier Material: Tin/Lead(85/15) plated Brass
Max Recommended Frequency: 20 GHz
Suspended Substrate Compatible: Yes
Lead-Free Option: Because of the construction of the EZ eyelet, it cannot be built with lead free solder. For this reason the M1, M2, and M3 mixers are not available as lead-free surface mount units.
Image of T3-CQ package
CQ and CQG Castellation Via – A castellation via is a method of creating a transition by making a plated through hole in a circuit and cutting the through hole in half. Unlike in an EZ eyelet, it does not have a ground that transitions with it, so the transition appears as an inductive line. Further, it is limited to certain materials that are capable of supporting the construction. It is however very robust and is a visible transition, making it easier to inspect the solder fillets.
Product Lines: T3 Mixers
Carrier Material: FR4
Max Recommended Frequency: 16 GHz
Suspended Substrate Compatible: No
Lead-Free Option: Yes (CQG)
Bias Tee SM Package
Plated Through Hole – This is a standard way to achieve surface mount transitions. It can be performed with a wider variety of materials, including thinner and lower dielectric materials.Because it is used with thinner materials, it is typically only associated with smaller parts, to keep the board flat and prevent it from warping during assembly. Because it is used with thinner materials the transition can appear less inductive, thus performing to higher frequencies.
Product Lines: Bias Tees, Power Dividers, Diplexers
Carrier Material: PTFE
Max Recommended Frequency: 35 GHz
Suspended Substrate Compatible: No
Lead-Free Option: Yes (SMG)