Risk to Shelf-Life of Epoxy during Shipping

The sin­gle biggest risk asso­ci­at­ed with stor­age at high­er than the rec­om­mend­ed stor­age con­di­tions is a reduc­tion of flow rate. Epoxy mold­ing com­pounds when blend­ed already have the resin/hardener com­bi­na­tion into one blend — and this is what we call a “B‑stage” epoxy mold­ing com­pound. B‑stage refers to a stage between the unmixed (A‑stage) and the cured (C‑stage) of the cur­ing cycle.

Final Epoxy Properties Unaffected by Shorter Flow

In its B‑stage, it is there­fore impor­tant to keep the mate­r­i­al refrig­er­at­ed to slow down the cur­ing process. The cold­er the mate­r­i­al is kept, the slow­er the process takes place.

The most impor­tant rea­son to slow down this process is to be able to ensure that the mate­r­i­al can be processed at the cus­tomer loca­tion. If the mate­r­i­al is not kept under prop­er stor­age con­di­tions, the flow rate of the mate­r­i­al will decrease and there is a risk that the mate­r­i­al does not fill into the cav­i­ties of the mold prop­er­ly result­ing in a defect known as “incom­plete fill”.

What is very impor­tant to note is that regard­less of the flow rate of the mate­r­i­al, for all intents and pur­pos­es the final prop­er­ties of the cured mate­r­i­al are unaf­fect­ed. This means that whether the flow rate is still at 100% of its ini­tial val­ue, or at 50% if the mate­r­i­al is then post-mold cured, the Tg, CTE, mois­ture resis­tance, and all oth­er crit­i­cal prop­er­ties remain the same.

flow retention and shelf-life of epoxy mold compound

This being said, “incom­plete fill” is also a defect, so the shelf-life of the mate­r­i­al is giv­en such that the epoxy mold com­pound is with­in the flow rate spec­i­fi­ca­tion right until the end of the shelf-life. The way we mea­sure this shelf life is to keep mate­ri­als stored at var­i­ous tem­per­a­tures and then we test the flow rate over a peri­od of many days to see the effect on the flow rate.

As you can see in the attached chart for a “tem­per­a­ture-sen­si­tive epoxy”, as expect­ed, the flow rate data drops dras­ti­cal­ly at room tem­per­a­ture (23C). At 5C how­ev­er, we have a sig­nif­i­cant­ly improved shelf life — and have less than a 20% reduc­tion even after 50 days. At ‑10C stor­age, we appear to have almost no reac­tion tak­ing place, though we need more data to be able to com­ment more accurately.

Please vis­it us at www.caplinq.com to learn more about our whole range of mold­ing com­pounds includ­ing our semi­con­duc­tor-grade epoxy mold­ing com­pounds, our fiber­glass-rein­forced indus­tri­al mold­ing com­pounds, and our opti­cal­ly clear epoxy mold com­pounds (CMC). If you have any oth­er ques­tions about B‑stage or shelf-life or UL-approvals for epoxy mold com­pounds, please feel free to leave a com­ment below or don’t hes­i­tate to con­tact us.

About Chris Perabo

Chris is an energetic and enthusiastic engineer and entrepreneur. He is always interested in taking highly technical subjects and distilling these to their essence so that even the layman can understand. He loves to get into the technical details of an issue and then understand how it can be useful for specific customers and applications. Chris is currently the Director of Business Development at CAPLINQ.

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